Convert single speed pump to 2-speed?

[y_not]

I'm pondering as to whether it's possible to convert a single speed pump to a 2-speed without replacing the whole motor /w a 2-speed model.

Are the motor manufacturers using a simple 2-mode VFD or variable frequency driver design in their 2-speed motors, say 30/60Hz off of a rectifier+pwm?

Here's a VFD, same style of circuitry design concept as they use in the VS pumps such as the IntelliFlo or the VS Pump controller: AccuDriveXS. But this one, unlike a 2-speed pump, is actually variable, not just dual mode.
http://www.ebay.com/itm/140969496835?ss ... 1438.l2649
Of course its amperage is too low, but this is just a lower cost one I grabbed the link on.

Or do you suppose the motor manufacturers such as AO-Smith/Century are using the age-old "2 separate windings with a different number of poles" and simply switching between them through the terminal board?

I almost think they're doing the latter. If so, well, a VFD would be in order.
I get the idea it's the latter from here: http://www.pumped101.com/vf101.pdf
Some fun stuff on the subject.

As for VFD's, are there any that are as power efficient as the native 2-speed pump design? Or are they all power hogs?

I look forward to your thoughts, DIY success stories, or hair brained ideas on the matter.
Cheers!!

EDIT: Changed from "stationary switch" to "terminal board". Still understanding pump terminology.

 

[mas985]

A typical two speed motor has two sets of independent winding's for both speeds. The low speed winding is wound over the high speed winding using a much smaller wire which is why low speed has such poor power efficiency although the overall efficiency of low speed is still better than high speed.

As for building your own VS pump from a VFD:

First, you need an inverter duty motor. Most single speed motors are not inverter duty so this is an extra cost. You can get VFDs that would work with single phase motors but they are a bit more and more prone to failure. Also, you can't just hook up a VFD to a motor using any cable, it must be inverter duty matched cables to prevent arcing and reflections which can damage the VFD. Next, you need a NEMA housing to put the VFD into unless it comes with it or you can install the VFD in a garage or other building. However, the longer the connection cable, the more critical the cable design and performance needs to be and the higher the cost. This is why most solutions put the drive directly on the motor. Hayward is the only one I know who offers a short cable to mount the drive on the wall. Also, the VS pumps/motors by main manufactures use permanent magnet 3-phase motors to increase the efficiency.

The total cost of all this equipment tends to be more than if you just went out a got one of the cheaper VS for ~$900.

BTW, you are not the only one who has considered this:

variable-speed-pumps-cheaper-better-alternatives-t33726.html
homemade-variable-speed-pump-t36097.html

 

[y_not]

A typical two speed motor has two sets of independent winding's for both speeds. The low speed winding is wound over the high speed winding using a much smaller wire which is why low speed has such poor power efficiency although the overall efficiency of low speed is still better than high speed.

Makes perfect sense.

First, you need an inverter duty motor. Most single speed motors are not inverter duty so this is an extra cost. You can get VFDs that would work with single phase motors but they are a bit more and more prone to failure.

Meaning that you then would not need an "inverter duty" motor?

Also, you can't just hook up a VFD to a motor using any cable, it must be inverter duty matched cables to prevent arcing and reflections which can damage the VFD. Next, you need a NEMA housing to put the VFD into unless it comes with it or you can install the VFD in a garage or other building. However, the longer the connection cable, the more critical the cable design and performance needs to be and the higher the cost.

On eBay I can get a large VFD that can do the job for about $150. A new 2-speed motor is going to cost me roughly $300, but if I went the new motor route, I still would be stuck with only 2-speed efficiency. The other route makes much more sense, as I get to take advantage of a wide range of speeds. But only if the inverter is power efficient enough, otherwise it defeats the whole purpose.
Since this is a 3-phase inverter, I'd be "de-rating" it by aprox. 33.3% if I ran it on single phase. Thus a 12amp unit would become 8amps.
So that may kill power efficiency. They're supposed to be something like 97% efficient or so according to the talk here: Machinist's Workshop - VFD Efficiency

According to this user, it uses about 2amps over what the pump requires. So in his case, it's roughly a 57% loss in energy, or only a 43% efficiency level.
Instructables - Variable Speed Mod To Your Pool Pump
That's my concern with it.

I did find this wonderful product from Ausland, which they say works on 97% of all single speed motors. It sounds like they made it a direct mains prong plug-in design to avoid the problems of impedance matched wire. Also it has a true single phase design, so no derating (overbuying in amps/hp) necessary for the VFD.
http://ecocontrollers.com/

About 1/2 way down the pg on the following link, user: "trhought" poses some interesting information. In fact, you even participated in that very thread.
http://ths.gardenweb.com/forums/load/po ... 97501.html
It's interesting to note the information provided in the discussion as to remotely mounted VFDs, vs. the big 3 manufacturer's on-pump vfd designs. This gets it away from the pump vibrations and out of the sun. Both being failure points.
Also peaking my interest are the supposed myths of permanent magnet motors vs. psc motors and their actual end efficiency and failure points vs. total overall cost increase of the PMC design, over PSC.
One user in that thread did in fact buy a rather large VFD unit, he even listed current draw, but only on the output side at the pump. He intended to, but never posted as to the numbers measured on the wall current side of the VFD. So I have no idea how efficient it is in the end.

The total cost of all this equipment tends to be more than if you just went out a got one of the cheaper VS for ~$900.

BTW, you are not the only one who has considered this:

variable-speed-pumps-cheaper-better-alternatives-t33726.html
homemade-variable-speed-pump-t36097.html

Drat, really? Bad, bad search engine. LOL
Well, then again I looked for "converting single speed pump to 2 speed". I didn't look for the VFD stuff. So my bad.

Even with possibly being able to get a cheapo one on eBay. How much per foot is that wire?
I'd be mounting the thing indoors in my garage, right by the panel. So then it'd be easy to do 220v if need be. I'd definitely have to do a conduit burry, but I'll have to do that to a degree anyway.

In the end, all I'm really after is the most energy efficiency I can get. Without spending so much on a true variable speed pump that it ends up not being a good ROI.

The dilemas....
- Do I keep my 1.5HP Pentair Dynamo's wet head and just swap the motor with a more energy efficient 2-speed Century Flex 48 Lasar Line, or do I go for the Century/AO 2Green line. Or replace the whole thing?
- I have toyed with even doing a 220v pump, as from my understanding they're more power efficient on current draw than a ~115v motor. But then I took those seemingly lower amp ratings, multiplied them by the voltage to get the watts and to my surprise it came out to more total current consumption.
- In the end, I'll need a pump that can backwash the Tagelus 100D I can pick up used for 100 bones.
But I want the lowest daily run current consumption that I can, while still getting an ROI. Cause, as you said in the link above, pumps don't last 20yrs.
used-sand-filter-avail-options-your-recommendations-t56734-40.html
Just jump to pg. 3 that I linked to, skip the 1st post there by me and you'll see the meat of what I'm currently trying to figure out and what others have discussed on the matter.
Or, you can skip all the way to the last post, which happens to be my most recent post to the thread. Where it's all distilled down pretty good and gets to the point. There is stuff above that pulls some of your words of wisdom into it.

Thanks a bunch Mark!!
I know you're a busy guy, so take your time on this as you need. I'm not in a major hurry. None of this will likely happen before a few mo. out at least. Still have to excavate, burry conduit, pipe.... OH BOY!!

EDIT: I have some figures I have run on the cost of power consumption on some of these pumps/motors I have been looking at. But I'm not quite done with them.
BTW, cost /KWh including all the lovely taxes and minus their whatever credits, comes to: 0.16898c/KWh (17c). Here in my part of Central Oregon.

 

[mas985]

The single phase VFDs would also need an inverter duty motor. You always need an inverter duty motor when using a VFD or the motor and drive will not last very long.

I don't believe you can use a three phase VFD on a single phase motor since the phasing is not correct. Single phase is split-phase, 180 degrees apart, while two arms of a three phase supply is 120 degrees apart. Plus in a three phase VFD, all three arms must be balanced or it will fry the VFD. Plus, I doubt a $150 VFD is very high quality and would last that long. Do you have a link so I can take a look at it?

Even with possibly being able to get a cheapo one on eBay. How much per foot is that wire?

I have seen pricing around $100/ft. But you can get it cheaper on ebay.

In the end, all I'm really after is the most energy efficiency I can get. Without spending so much on a true variable speed pump that it ends up not being a good ROI.

There is diminishing return with efficiency so it won't matter much after a certain point. This is the primary reason that a two speed pump can have a lower lifetime cost than a VS pump. The upfront cost can end up dominating any cost savings from energy at a certain point.

- Do I keep my 1.5HP Pentair Dynamo's wet head and just swap the motor with a more energy efficient 2-speed Century Flex 48 Lasar Line, or do I go for the Century/AO 2Green line. Or replace the whole thing?

Despite the label, that is actually a very small pump and has a very high energy factor (gallons/watt-hr). So it would end up being most economical to just put a two speed motor on that pump.

I have toyed with even doing a 220v pump, as from my understanding they're more power efficient on current draw than a ~115v motor.

Not true. 220v motor has identical efficiency to a 115v motor. The only difference is the power feed to the motor. But if larger wire is used on the 115v side, which you should, there really is no difference.


I also have a spreadsheet (see pump spreadsheets below) that you can download to compare the cost of running different pumps. The database doesn't have all pumps but it has quite a few.

 

[y_not]

The single phase VFDs would also need an inverter duty motor. You always need an inverter duty motor when using a VFD or the motor and drive will not last very long.

Hmmm, OK. Understood. It's all so very misleading. Care to enlighten me as to the difference in the motor design? It doesn't need to be anything gory or lengthy.

I don't believe you can use a three phase VFD on a single phase motor since the phasing is not correct. Single phase is split-phase, 180 degrees apart, while two arms of a three phase supply is 120 degrees apart. Plus in a three phase VFD, all three arms must be balanced or it will fry the VFD.

Check out the link I posted to the machinist's workshop forum, look at the post that has the rectifier graphic in it. That's where I got the idea from.

Plus, I doubt a $150 VFD is very high quality and would last that long. Do you have a link so I can take a look at it?

Haha, yeah, probably wouldn't.
4HP 3.0KW 13A 220-250V VFD INVERTER

Even with possibly being able to get a cheapo one on eBay. How much per foot is that wire?

I have seen pricing around $100/ft. But you can get it cheaper on ebay.

OUUUUCH!!! That pretty much cancels it all out right there. Impedence matched simply means that each wire is a different gauge, required to speed or slow the electrons to compensate for the greater or lesser amp draw of each leg, compared to the other. Yeah?

There is diminishing return with efficiency so it won't matter much after a certain point. This is the primary reason that a two speed pump can have a lower lifetime cost than a VS pump. The upfront cost can end up dominating any cost savings from energy at a certain point.

Yeah, I have heard you preach that practice many times here @ TFP. I fully believe it too. I was just trying to figure out where I fit in. Of course, Pentair has a PDF, which I'm sure you have seen, on how inefficient 2-speed motors are compared to their VFD motors. How they really save very little energy and can cost you more in the end. Blah blah! I think it's all marketing hype personally. They say the avg. pool pump costs around $1,000/yr to run.
Where's that, with electric rates at a remote island science station??? On the island "Lost"? :lol:
Surely Faraday, much like the Prof. on Gilligan, could fix that and wouldn't need Pentair's help.

Le' Article: Pentair - The Truth About 2 Speed Pumps

Do I keep my 1.5HP Pentair Dynamo's wet head and just swap the motor with a more energy efficient 2-speed Century Flex 48 Lasar Line, or do I go for the Century/AO 2Green line. Or replace the whole thing?

Despite the label, that is actually a very small pump and has a very high energy factor (gallons/watt-hr). So it would end up being most economical to just put a two speed motor on that pump.

More marketing lies huh?
I presume you're referring to the Century 2Green line??

Can I go bigger/smaller in motor HP on that wet end, what happens when I do? Same concept of torque as gearing an engine, bicycle, or anything else that uses any sort of gearing ratio, or is it something else?

I have toyed with even doing a 220v pump, as from my understanding they're more power efficient on current draw than a ~115v motor.

Not true. 220v motor has identical efficiency to a 115v motor. The only difference is the power feed to the motor. But if larger wire is used on the 115v side, which you should, there really is no difference.

Just to clarify, I wasn't so much saying at all in fact, that the motor design of a 220v unit was better or more efficient. But that 220 vs. 110 supply is more efficient in general when it comes to high current draw devices. That was all. Just in case you thought I meant the former.
So larger gauge copper line from the electrical panel to the pump. Check!
I presume it's just whatever is to code for the given number of amps for that direct circuit, or do you overspec the wire gauge for higher current transfer efficiency? Size gauge?

I also have a spreadsheet (see pump spreadsheets below) that you can download to compare the cost of running different pumps. The database doesn't have all pumps but it has quite a few.

I did see that on your website, haven't even looked at it. My attention span runs away with me when I read your pump articles. Not for lack of interest, but soooooo maaannnnnyyy numbers. Me no wikey math! :?
That and ADHD to the n'th degree.

I'll check it out though, since it sounds like it'll help.
I have faced a rather annoying problem when doing these calculations and that is.... how much runtime should I key in for low speed, then comparing to how much for high speed?
I have seen you recommend 3-4hrs on low speed, as you run your pool for 2hrs on high & 2 on low, iirc.
I presume the high is for the solar and such.
So I just went with 4hrs on my calculations, as I'll have about the same size pool as yours, even if I have to compromise a little on the deep end.
But what do I do for high speed comparison and making it fair?

 

[mas985]

Hmmm, OK. Understood. It's all so very misleading. Care to enlighten me as to the difference in the motor design? It doesn't need to be anything gory or lengthy.

It is basically in the insulation and bearing design but you might want to read this for a more detailed description:
http://www1.eere.energy.gov/manufacturi ... heet14.pdf

Check out the link I posted to the machinist's workshop forum, look at the post that has the rectifier graphic in it. That's where I got the idea from.

Ok, that is a 3-phase input to a 1-phase output and the discussion was on using the input as single phase. What I was referring to was the output of the drive. If the drive has a 3-phase output, as most do, then you cannot use that for a single phase motor.

Impedence matched simply means that each wire is a different gauge, required to speed or slow the electrons to compensate for the greater or lesser amp draw of each leg, compared to the other. Yeah?

A VFD generates a wide spectrum of frequency components because it is using square waves. So this can set up standing waves on the cable if there cable is not impedance matched. So what they are talking about is the complex impedance (resistive and reactive) are matched to the drive and to the motor to limit the reflections along the cable and prevent reflected waves from hitting the VFD. It isn't using different gauge but it is the design of the cables, dielectric and shielding together which creates a matched cable. This gives a good description of the design elements:
http://www.newark.com/pdfs/techarticles ... EVFDCP.pdf

Le' Article: Pentair - The Truth About 2 Speed Pumps

The Pentair article leaves out a lot of truths as well but you will notice that they don't actually compare the lifetime costs of the VS with the two speed. There is good reason for that as it diminishes the attractiveness of the VS.

I presume you're referring to the Century 2Green line??

Not really. That will give you about 20% more efficiency on low speed than standard 2 speed so it is an option. However, to put things in perspective, if the two speed is using 250 watts on low speed, saving another 50 watts may not pay for the extra cost of the motor. So keep that in mind.

Can I go bigger/smaller in motor HP on that wet end, what happens when I do? Same concept of torque as gearing an engine, bicycle, or anything else that uses any sort of gearing ratio, or is it something else?

The impeller determines the load for the motor and thus what power the motor will need to supply to the shaft. So if you put a smaller rated motor on the same impeller, the current draw from the motor will be about the same as before and may exceed the new motor's rating and it will most likely overheat and shut down. Putting a larger motor on the same impeller is fine the same reasons. The motor will be under-loaded so it is not an issue. However, efficiency may get effected if the motor is significantly under-loaded (i.e. < 25% load).

I presume it's just whatever is to code for the given number of amps for that direct circuit, or do you overspec the wire gauge for higher current transfer efficiency? Size gauge?

Exactly and over-sizing the supply line doesn't buy you much.

I have faced a rather annoying problem when doing these calculations and that is.... how much runtime should I key in for low speed, then comparing to how much for high speed?
I have seen you recommend 3-4hrs on low speed, as you run your pool for 2hrs on high & 2 on low, iirc.
I presume the high is for the solar and such.
So I just went with 4hrs on my calculations, as I'll have about the same size pool as yours, even if I have to compromise a little on the deep end.
But what do I do for high speed comparison and making it fair?

You have hit on a very key point that sometimes gets lost in these discussions and it is difficult to give you a definitive answer because there are so many variables. However, to do a far comparison between the pumps, I think it is reasonable to assume one turnover total per day. My pool only needs about a 1/2 turnover but to be somewhat conservative, a single turnover is probably a good choice.

However, because your pool is so small and turnover would be very short with a very short run time, I can tell you with some certainty that a VS would probably not pay for itself. A new two speed pump would probably not pay for itself either. I would go with a low cost two speed motor replacement. BTW, what is your electrical cost?

 

[y_not]

It is basically in the insulation and bearing design but you might want to read this for a more detailed description:
http://www1.eere.energy.gov/manufacturi ... heet14.pdf

A doc I had read and linked to earlier, pretty much gave me that impression. Where it can actually cause arcing in the bearings and damage them, pitting, splits, etc...
I'll have to read your link soon.

Ok, that is a 3-phase input to a 1-phase output and the discussion was on using the input as single phase. What I was referring to was the output of the drive. If the drive has a 3-phase output, as most do, then you cannot use that for a single phase motor.

Good point, this young grasshopper thanks you.

A VFD generates a wide spectrum of frequency components because it is using square waves.

Just like a UPS, battery backup unit. All square wave, so you can't use the common ones for medical, life dependant systems.

So this can set up standing waves on the cable if there cable is not impedance matched. So what they are talking about is the complex impedance (resistive and reactive) are matched to the drive and to the motor to limit the reflections along the cable and prevent reflected waves from hitting the VFD.

Cool! Same concept as with broadcast towers, RF antennas, WiFi, etc... RF is RF.

It isn't using different gauge but it is the design of the cables, dielectric and shielding together which creates a matched cable.

Aaah, OK. Inductance, noise cancellation, crosstalk, just like /w RF cables & data cables.
I may read the link at some point, certainly has piqued my interest. Belden!! The Creme de La Creme of cable manufacturers. Not to be confused with Belkin. Shudders!....

The Pentair article leaves out a lot of truths as well but you will notice that they don't actually compare the lifetime costs of the VS with the two speed. There is good reason for that as it diminishes the attractiveness of the VS.

Well of course, only tell as much truth as you have to. Still makes it being deceptive and filled with lies, but hey. It's a business lie after all.
Those were my thoughts exactly, they're just stinkin' expensive!! YIKES!

I presume you're referring to the Century 2Green line??

Not really. That will give you about 20% more efficiency on low speed than standard 2 speed so it is an option. However, to put things in perspective, if the two speed is using 250 watts on low speed, saving another 50 watts may not pay for the extra cost of the motor. So keep that in mind.

Good point, wise words & duly noted. So which one were you referring to that was a very weak motor? I presume then it's the Pentair Dynamo 1.5HP motor that I'll be acquiring?

Can I go bigger/smaller in motor HP on that wet end, what happens when I do? Same concept of torque as gearing an engine, bicycle, or anything else that uses any sort of gearing ratio, or is it something else?

The impeller determines the load for the motor and thus what power the motor will need to supply to the shaft. So if you put a smaller rated motor on the same impeller, the current draw from the motor will be about the same as before and may exceed the new motor's rating and it will most likely overheat and shut down. Putting a larger motor on the same impeller is fine the same reasons. The motor will be under-loaded so it is not an issue. However, efficiency may get effected if the motor is significantly under-loaded (i.e. < 25% load).

Small motor on big impeller = overdriven motor.
Big motor on small impeller = Better energy efficiency for the same pumping power so long as the motor is within it's efficiency duty cycle range?

What was it that you said you did with your pump? You did something like a different motor & wet head, like you mixed and matched some things. I can't find the post anymore.

I presume it's just whatever is to code for the given number of amps for that direct circuit, or do you overspec the wire gauge for higher current transfer efficiency? Size gauge?

Exactly and over-sizing the supply line doesn't buy you much.

OK, so it sounds like so as long as I stick to code, I'm OK for efficiency sake.

I have faced a rather annoying problem when doing these calculations and that is.... how much runtime should I key in for low speed, then comparing to how much for high speed?.....

You have hit on a very key point that sometimes gets lost in these discussions and it is difficult to give you a definitive answer because there are so many variables. However, to do a fair comparison between the pumps, I think it is reasonable to assume one turnover total per day. My pool only needs about a 1/2 turnover but to be somewhat conservative, a single turnover is probably a good choice.

Thanks, I have been watching your posts and absorbing it when I can. Do you suppose a 20k-22k gal pool can be turned over in about 8hrs, or more like 4-6? Your pool, you said you run it @ full speed for about 2hrs, then 1/2 speed for another 1-2hrs. Why is that? Solar and/or, heater?
I believe I have read on here that some people can get away with as low as 1/4 turn-over per day. And yes, wonderful information you provide here, that a full turn over is a waste.

However, because your pool is so small and turnover would be very short with a very short run time, I can tell you with some certainty that a VS would probably not pay for itself. A new two speed pump would probably not pay for itself either. I would go with a low cost two speed motor replacement. BTW, what is your electrical cost?

Yeah, I have gathered as much and already knew that if I had to go out and buy a brand new variable speed pump, it'd be a waste of money. I just figured if I could do it for cheap on the pump I'll have, then hey, why not. But after talking to you about it... meh, scrap it.
A new AO Smith/Century Flex 48 Lasar @ 1.5HP - BN50V1 & new shaft seal is going to run me $251 including freight cost. Then I still don't have a 2-speed switch to control it with. So I'd have to figure that out, I have seen it mentioned you can use a toggle of sorts. So maybe that'll be a std. cheapo toggle switch, I haven't looked on here for the answer though.
A whole brand new pump will actually be cheaper, assuming it meets my needs from the other thread. Unless replacing the motor on this Dynamo will yield a considerably higher GPM increase at X head, then this may be the better option.

I should add that a 2HP motor will only consume another 8WHrs. Whooptie dooo! LOL

Regarding that, aside from the answer, look at my other thread on the filter for the new pump cost options I tracked down and flow rates it looks like I'll require and all that jazz.

Oh, energy cost is: 0.16898c/KWh
Yeah, you can round it, but then it makes calculations not as accurate. Sat on the phone for a while going through every silly dam removal fee, wind credit thing and rate schedule junk /w the power co. UGH!! Good thing I did, as I thought it was waaaayyyyy higher /KWh than that.

 

[mas985]

Good point, wise words & duly noted. So which one were you referring to that was a very weak motor? I presume then it's the Pentair Dynamo 1.5HP motor that I'll be acquiring?

I think what I was referring to was that even though the Dynamo has a 1.5 HP label, the pump is actually quite small. It is SPL (special rated) which basically means it is double up rated or the equivalent of a 3/4 HP full rated pump. So the label is somewhat deceiving and it really doesn't represent the true pump "size".

Small motor on big impeller = overdriven motor.
Big motor on small impeller = Better energy efficiency for the same pumping power so long as the motor is within it's efficiency duty cycle range?

More or less. Once the motor gets below 25% load the efficiency really starts to fall off quickly. However, under loading a motor between 100%-25% also loses a little efficiency so the larger motor at 50% load may be about the same efficiency as the smaller motor at 100% load. So it may not make much of a difference.

What was it that you said you did with your pump? You did something like a different motor & wet head, like you mixed and matched some things. I can't find the post anymore.

I used a Northstar wet end and changed the impeller to a 1/2 HP and I replaced the motor with 1 HP Superpump 2 speed motor. The Superpump motor is just about the right size for the Northstar 1/2 HP impeller although you wouldn't guess that from the labeling. But believe it or not, my 1/2 HP pump would produce about the same flow rate as your 1.5 HP Dynamo on the same plumbing system.

 

[y_not]

Mark, can you enlighten me as to this business of pump up rating?

I've done some reading on it here and there, read some post that you made, etc.. But no serious hardcore research on it or anything.

I get the general gist of it, but there are still some confusion points. I think it'd be easier to get the crash explanation of it and then let you know what parts I may still be confused on. Rather than making a long post detailing what I think it is and what my questions are.

Make sense? Less time reading my long drawn out post.

Thank you so much for all your help. I really appreciate it.

 

[mas985]

Keep in mind that a residential pool pump is actually made up of two machines, the pump (i.e. wet end) and the motor. In the water distribution industry, the two are actually sold separately and paired by the plant engineer. The engineer will also trim the impeller to get the exact flow rate and pressure needed for the application but I digress.

Anyway, up rating is more about the motor than the pump. The rating of the motor is basically determined by the service factor:

Full Rated Service Factor > 1.3
Up Rated Service Factor 1< SF< 1.3
Special Service Factor <1

The label HP times the service factor is the service factor horse power (SFHP) rating or sometimes called total HP (THP) rating and it determines the true maximum load rating for the motor. However, one of the problems for pumps has been that people tend to size pumps by the label HP which is not a very accurate way of sizing.

The service factor rating originated a long time ago when motors were first being used in industrial applications. In some applications, the load on the induction motor could vary considerably over a short period of time so the service factor was used to determine the amount of excess short term overload that a motor could carry. So a motor with a SF of 1.2 could be overloaded by 20% (1.2x) for a few seconds at a time without any issues. This was mainly because of thermal constraints on the motor insulation and the fact that more heat is generated with a varying load (i.e. changes in torque).

However, for pumps, since the load is more or less fairly constant over the short term, the motor can be loaded all the way up to the SFHP continuously. Unfortunately, the industry still uses the concept of service factor more or less for marketing than anything else. So if a customer really wants a high HP pump but the installer thinks that would be a mistake, they can simply install an up rated pump and both the customer and the installer are happy. To me it is more about deception than anything else.

Often times you will see two versions of the same pump in a pump line. For example, the Whisperflo WFDS-3 and the WFDS-24 are identical pumps and motors but the motor labels are different:

WFDS-3: 3/4 HP with 1.67 SF or 1.25 SFHP
WFDS-24: 1 HP with a 1.25 SF or 1.25 SFHP

It creates a lot of confusion in the industry not to mention a lot of sizing errors. If I had my way all pool pump motors would have a service factor of 1 so the label HP was the total HP.

 

[scooperhsd]

The gist of Mark's last post for shopping for pumps / motors - do your comparisions based on the SFHP , not anything else listed on the label.

As far as turnover - my sand filter says it can handle up to 50-60 Gallons / minutes - using 60 - this means it could put 3600 gallons per hour though it. since I have a 19,000 gallon pool, a turn over will take 19,000 / 3600 = 5.27 hours - or just over 5 hours 15 minutes (assuming the pump is up to the 60 GPM).

I'm using a single speed 1.5 HP (SFHP of 1.65) Pentair Superflo Energy effiecent series pump. Typically takes about 1kw - 1.2kw to run it. I also have a Hayward Powerflo II 3/4 HP (sfhp of .75) that I could put in place - this powerflo is probably pretty comparable to your Pentair Dynamo 1.5 HP pump, actually. I have used this powerflo when I was inbetween inground pumps and it worked just fine. It's power use is also about 1000-1200 watts.

 

[mas985]

The gist of Mark's last post for shopping for pumps / motors - do your comparisions based on the SFHP , not anything else listed on the label.

Actually, that is not a good idea either. SFHP is better than the label HP but it can still lead to the wrong conclusion. Motor labels only show the maximum operation conditions for just the motor. It tells you nothing about the wet end. The only way to compare pumps is by comparing head curves.

 

[y_not]

Hi Mark!

I'm finally getting back to doing something about my pump situation. Just so you know for the other thread, I lost out on the GIANT Tagelus filter I was looking at. I'll explain over there in that thread later.
Basically I'll be using the little dippy 150lb filter on my 3.3k gal pool for now and I'll need a 2-speed to drive it on filtration. The Dynamo paired with it is horribly over mismatched and channels like a giant sand dune.
I'll upgrade to a big filter down the road, before the new big pool (20k+gal) is complete.

I was originally thinking I'd save the wet end of this Dynamo pump & just replace the motor /w a 2 speed. But then I still have a 7-8yr. old wet end that's been used with tremendously corrosive pucks in the skimmer 6 feet from its intake. Correct me if I'm wrong, but that seems like a recipe for trouble to me. Yeah?

So what do you think would be a better, more energy efficient route to go. A new Hayward Power-Flo Matrix 2-speed 1HP, or replacing the motor on this one?

The brand new Hayward & a new motor for this one+seal & freight comes out to right about the same. I'm really leaning toward the new hayward, as at least I'll have a complete, fully working Dynamo pump that I can sell on the used market to help recoup some of my expenditures.

Here are some notes/add tos.

So which one were you referring to that was a very weak motor?

I think what I was referring to was that even though the Dynamo has a 1.5 HP label, the pump is actually quite small. It is SPL (special rated) which basically means it is double up rated or the equivalent of a 3/4 HP full rated pump. So the label is somewhat deceiving and it really doesn't represent the true pump "size".

What's the best match to its impeller for efficiency sake...
Do I replace it with a 3/4HP AO Smith 2-speed motor?

What was it that you said you did with your pump? You did something like a different motor & wet head, like you mixed and matched some things. I can't find the post anymore.

I used a Northstar wet end and changed the impeller to a 1/2 HP and I replaced the motor with 1 HP Superpump 2 speed motor. The Superpump motor is just about the right size for the Northstar 1/2 HP impeller although you wouldn't guess that from the labeling. But believe it or not, my 1/2 HP pump would produce about the same flow rate as your 1.5 HP Dynamo on the same plumbing system.

If I have the opportunity to accomplish something like this, that level of efficiency that you have achieved, with what I have to work with. That's what I want to do if it makes good economical sense both in cost & efficiency, not to mention that I'm working with an 8yr old wet end.

PS. I'll get back to the talk on pump motor ratings later on when I get time.

 

[mas985]

I was originally thinking I'd save the wet end of this Dynamo pump & just replace the motor /w a 2 speed. But then I still have a 7-8yr. old wet end that's been used with tremendously corrosive pucks in the skimmer 6 feet from its intake. Correct me if I'm wrong, but that seems like a recipe for trouble to me. Yeah?

Maybe corrosive to metal but a pump housing is usually made of fiberglass so it should be fairly resistant to chlorine. About the only thing that can go wrong with the housing is that it can develop a crack. Everything else can be replaced.

So what do you think would be a better, more energy efficient route to go. A new Hayward Power-Flo Matrix 2-speed 1HP, or replacing the motor on this one?

The matrix is slightly bigger than your current pump so it will most likely use more energy to deliver the higher rate although it is probably not much more. The 3/4 HP Matrix is slightly smaller than your pump but not by much. The 3/4 Dynamo, would be much smaller.

This chart is in the Hydraulics 101 sticky but is shows the relative size of some of the smallish pumps. Your current pump isn't really that big compared to other AG pumps.

 

[y_not]

You wouldn't think it'd be, but the guy's side wall skimmer looked like he poured acid in the thing. Well, a plastic eating acid. All he used were HTH 'orange bucket lid' pucks.

That was my only concern with reusing this one. So are you saying that they use a little half horse motor and stick a big slow moving, geared down impeller on it to achieve the higher gpm?
What size motor do I need to swap it for, keeping the same wet head? A 3/4hp 2-speed, 1/2hp...?

Thanks for all your help Mike and for putting up with my pump cluelessness.

 

[mas985]

Mike?

Skimmers are not made of the same material as a pump. Pump housings are usually fiberglass while some skimmers are PVC and PVC is susceptible to acid degradation.

Your current motor is a 1.5 HP SPL rated motor which is the same as a 1 HP up rated motor. But you will not find an SPL rated replacement motor so you can look for either a 1 HP up rated or a 3.4 HP full rated instead.

If you down size the motor, you will need to downsize the impeller (smaller) as well. So a 3/4 HP up rated impeller would be matched with a 3/4 HP up rated motor.

Don't forget to get a seal kit too.

 

[y_not]

Ooops!!
Mike, Mark, Mel, Mitch..... my brain is weird that way. I have name dyslexia. LOL
So sorry about that buddy, I really truly am.
Have a cold soda on me.

So are you saying I'd have to change the impeller if I can't find a 1HP up rated motor?
So I can't use either the BN36 or the BN37V1 listed here? 48Y Frame AO Smith Motors
Since I tried putting off class... guess I have to ask ya teach...
How do they achieve a "special/up rating" on a motor? I'm gathering it's not so much the impeller as they possibly just over drive the motor? IE. Like hot rodding an engine, or overclocking a CPU. except something tells me it isn't as low impact on the motor as it is for those other applications when done right. IE. Doesn't last as long and burns out quicker?

If tis the case, I really don't want to have to go buy a new impeller too. Seems aaaawwwffully silly considering the cost of a new pump unit is the same as a new motor+shaft seal, let alone before even replacing the impeller.
Is there a reason I shouldn't do this?

*It might seem like I'm waffling, where I said I wanted to do what you had done /w yours, where in I hadn't fully understood what you really did and why. Which I think I understand now more with what I have learned since (from you). It's all about the game of energy efficiency both in electrical consumption and water flow/watt, vs. money spent. Your route in your case worked out better than a new pump it seems.
That, and I like to explore things so I don't beat myself up later. I have never been the type to go into anything lightly, let alone live with my decision if I didn't research it to my satisfaction. :blah:

Poking around the above site, I see Waterway pumps for an incredibly low price. IE they didn't mark them up by 2-2.5x their cost.
The head curve on those is AMAZING!! At least it looks like it to me.
[attachment=1:31j2xp9z]waterway head curve - chart_pump_hiflo_sidedischarge48.jpg[/attachment:31j2xp9z]
For the 1HP 2-speed pump (3/4hp is nowhere to be found @ those prices)
That shows about 70GPM @ 10ft on low / 160GPM @ 10ft on high.
That means its low speed moves 63% more water @ 10ft head vs. the Hayward. YIKES!!!
I call that efficiency!!

Add to that being that the Waterway has what basically sounds like a 3/4HP motor on it @ 8.8/2.6A vs. the Hayward @ 11.0/2.9A because you can't get the Hayward in a 2-speed @ 3/4HP. Kinda a no-brainer on energy.

Here's the Hayward's pump "not curve" 'chart'.
The SP1591 = 3/4hp / SP1592 = 1hp / SP1593 = 1.5hp
[attachment=0:31j2xp9z]Hayward PowerFlo Matrix Head Curve Chart.png[/attachment:31j2xp9z]

When you go comparing the Waterway to the Pentair Whisperflow for example, it's closer to an in ground pump than any agp pump I have ever run across. It only drops below their 1HP full rated pump after you go above 30ft head at a mere fraction of the price. Sure, it doesn't hold up under 40ft+ of head, but still. Not that I'm considering a whisperflow anymore after you talked more about it. But just for comparison sake is all.

 

[mas985]

It is the impeller that primarily determines how much energy is drawn by the motor. So if you downsize the motor without downsizing the impeller, the motor will likely draw more power than it's rating and can be damaged. However, if you put a larger motor on the impeller, the motor will draw less power than it's rating which is ok.

Pump motors will generally come in three different ratings:

Full Rated: Service Factor > 1.3
Up Rated: 1.0 < Service Factor < 1.3
SPL Rated: Service Factor < 1.0

The total HP (THP) is the product of the label HP times the service factor (SF). This is the true HP rating of the motor. Label HP is meaningless without the service factor.

So the same motor, can potentially have three different motor labels even though it is exactly the same motor.

For example, in your case, these three motors are exactly the same but would have different labels:

3/4 Full Rated HP; SF=1.5 (THP = 1.0)
1 Up Rated HP; SF=1.0 (THP=1.0)
1.5 SPL HP; SF=0.75 (THP=1.0)

Notice that the THP for all three of these motors is exactly the same even though the labels are different so all three of these motors have the same maximum rating.

So when replacing a motor, you will need to find a motor with a THP that is at least as big as the old motor. The BN37V1 is a 1 HP 1 SF motor so this would work for your current impeller. However, the BN36 would only work if you downsized the impeller to the 3/4 HP Dynamo impeller.

http://www.amazon.com/Impeller-Pentair- ... B00546YMX6

For the 1HP 2-speed pump (3/4hp is nowhere to be found @ those prices)
That shows about 70GPM @ 10ft on low / 160GPM @ 10ft on high.
That means its low speed moves 63% more water @ 10ft head vs. the Hayward. YIKES!!!
I call that efficiency!!

Unfortunately, it doesn't work that way. Head loss in a plumbing system is dependent on flow rate and low speed of a two speed pump will deliver about 1/2 the flow rate of high speed and head loss on low speed will be about 1/4th the head loss of high speed.

So if you look at the graph I posted earlier, the SP1591 will deliver about 48 GPM @ 38' of head on a 1.5" plumbing system. On low speed, this will be about 24 GPM @ 9.5' of head. Also, low speed will have about 1/4th the power draw as high speed so the net change in energy factor (gallons/watt-hr) is about a factor of 2x.

So you really can't compare pump and/or speed at the same head loss. Head loss changes with pump model, size and RPM setting. The proper way to compare pumps is by using the same plumbing curve which simulates how the pumps would perform on the same plumbing. This is what I did in the graph above.

 

[y_not]

It is the impeller that primarily determines how much energy is drawn by the motor. So if you downsize the motor without downsizing the impeller, the motor will likely draw more power than it's rating and can be damaged. However, if you put a larger motor on the impeller, the motor will draw less power than it's rating which is ok.

Is there any beneficial reason to do this? Putting a smaller impeller on a bigger pump?

Full Rated: Service Factor > 1.3
Up Rated: 1.0 < Service Factor < 1.3
SPL Rated: Service Factor < 1.0

To be sure I'm reading this right.
Full rated has an SF of greater than 1.3, or less?
Up rated has an SF of more than 1.0, but less than 1.3?
SPL rated has an SF of less than 1.0?
Am I understanding it correctly?

What is it that truly determines its "rating"?
In other words, how do they use a little motor on a wet end and call it a higher HP than the motor really is? Is there some sort of gearing system to change its torque, either in the motor or the wet end? Does it have to do with the impeller, as above?
I'm just not seeing it... sowwy. :?
A motor is a motor, it turns at a certain speed and torque based on its design. It's not a transmission. Then again, the impeller does become somewhat like a gear, or a torque converter I suppose. So maybe that's it?
I'm uncertain, as I thought I'd asked that before and the question was dodged. Leading me to assume I was way off base.

The total HP (THP) is the product of the label HP times the service factor (SF). This is the true HP rating of the motor. Label HP is meaningless without the service factor.

So the same motor, can potentially have three different motor labels even though it is exactly the same motor.

Why do they do this?
Intel does something similar to this, at least it sounds that way. Where they make an ultra high end processor "CPU" and sell it for $1,000. But they also take the EXACT SAME processor and sell it from $200 on up, only forcing it to run at a slower speed. Inside, it's the same $1,000 part, they just cripple it so they can sell it for less to meet demand. Also, some may only run at the slower speed due to manufacturing variances in that piece of silicon. They call it "binning" for the lower end parts which have a higher yield than the higher end parts. Also, they sell less of the higher end parts because they cost more. So it all works out.
Is this sort of what the pump manufacturers & designers are doing?

3/4 Full Rated HP; SF=1.5 (THP = 1.0)
1 Up Rated HP; SF=1.0 (THP=1.0)
1.5 SPL HP; SF=0.75 (THP=1.0)

Notice that the THP for all three of these motors is exactly the same even though the labels are different so all three of these motors have the same maximum rating.

If I'm doing the math right, 0.75 x 1.5 = 1.125 HP. No? Or do they round it?

]For the 1HP 2-speed pump (3/4hp is nowhere to be found @ those prices)
That shows about 70GPM @ 10ft on low / 160GPM @ 10ft on high.
That means its low speed moves 63% more water @ 10ft head vs. the Hayward. YIKES!!!
I call that efficiency!!

Unfortunately, it doesn't work that way. Head loss in a plumbing system is dependent on flow rate and low speed of a two speed pump will deliver about 1/2 the flow rate of high speed and head loss on low speed will be about 1/4th the head loss of high speed.

Before I go any further, just to clarify. You didn't potentially mistake the "slash" I put in between the low & high speed values as a slash indicating algebraic division, right?

I'll admit, I had to read this a few times to get it. I think I got it.
So if your whole setup with all your piping, skimmers, jets, drains, valves, elbows, filters... on and on. Causes X resistance in the pipe at the impeller of the pump, giving you X ammt. of head, when you drop down the rotation speed of the impeller, due to the laws of friction "layman term", the amount of force, or pressure required to move the water at the same rate reduces. Thus a lower number in ft. of head. IE. if the system when fully operational requires 40ft of head to move the water, when you switch to low speed, it's not 40ft of head anymore, it's 10ft. Correct?

So you really can't compare pump and/or speed at the same head loss. Head loss changes with pump model, size and RPM setting. The proper way to compare pumps is by using the same plumbing curve which simulates how the pumps would perform on the same plumbing. This is what I did in the graph above.

Surely you can compare at the same speed, no?
IE. Speaking hypothetically, if we know our pool needs 40ft of head at full pumping speed, we can compare pumps in your chart above by looking at how their GPM flow rates line up to the 40ft hd bar on the right. From that, we can ascertain and say, based on the chart, that the pumps on the left will move more water at a higher rate of flow than pumps on the right side of the chart.
Is that right, or am I not getting something?
Are you saying that manufacturers pump performance curves are totally worthless?

 

[mas985]

Is there any beneficial reason to do this? Putting a smaller impeller on a bigger pump?

I assume you mean putting a smaller impeller on a bigger motor. The motor is technically not part of the "pump". The motor drives the pump but really they are two separate machines that are connected by the motor shaft. The actual pump is just the wet end. Residential pools pumps come with motors attached but in the water distribution industry, the pump is sold separate from the motor.

But the only reason to put a smaller impeller on a larger motor is because you cannot find a motor small enough for the impeller. This happens with small pumps like mine where they do not make a 1/2 HP two speed motor so I used a 1 HP up rated motor which is close enough.

Full Rated: Service Factor > 1.3
Up Rated: 1.0 < Service Factor < 1.3
SPL Rated: Service Factor < 1.0

To be sure I'm reading this right.
Full rated has an SF of greater than 1.3, or less?
Up rated has an SF of more than 1.0, but less than 1.3?
SPL rated has an SF of less than 1.0?
Am I understanding it correctly?

Yes, that is correct.

What is it that truly determines its "rating"?
In other words, how do they use a little motor on a wet end and call it a higher HP than the motor really is? Is there some sort of gearing system to change its torque, either in the motor or the wet end? Does it have to do with the impeller, as above?
I'm just not seeing it... sowwy. :?
A motor is a motor, it turns at a certain speed and torque based on its design. It's not a transmission. Then again, the impeller does become somewhat like a gear, or a torque converter I suppose. So maybe that's it?
I'm uncertain, as I thought I'd asked that before and the question was dodged. Leading me to assume I was way off base.

First, a motor rating simply determines the maximum load a motor can support. But an induction motor can support any load below it's maximum load (0%-100%). It is basically a variable load motor. This is why the label HP and even the THP does not give an accurate picture of the pump's performance. The designer may have put an impeller on a motor so the motor is only 80% loaded at it's maximum. The pump's head curve is a much better indicator of pump performance.

Next, total HP (THP) and maximum amps are probably the two most important ratings for the motor. If the motor operates above the rated amps, the motor is likely to overheat and shut down due to the thermal limiter switch. The THP is more useful when sizing a motor for a particular impeller.

So the same motor, can potentially have three different motor labels even though it is exactly the same motor.

Why do they do this?

Good question. There is some history behind motor ratings but it is mostly marketing and to give the tech some wiggle room when the pool owner may insist on a certain "size" but the tech knows that another size would be better.

3/4 Full Rated HP; SF=1.5 (THP = 1.0)
1 Up Rated HP; SF=1.0 (THP=1.0)
1.5 SPL HP; SF=0.75 (THP=1.0)

Notice that the THP for all three of these motors is exactly the same even though the labels are different so all three of these motors have the same maximum rating.

If I'm doing the math right, 0.75 x 1.5 = 1.125 HP. No? Or do they round it?

They do round off but I should of had 0.66 instead of 0.75.

Before I go any further, just to clarify. You didn't potentially mistake the "slash" I put in between the low & high speed values as a slash indicating algebraic division, right?

No, I didn't think it was division. My main objection is that you cannot have the same head loss for both RPM values. It doesn't work that way as I explained.

So if your whole setup with all your piping, skimmers, jets, drains, valves, elbows, filters... on and on. Causes X resistance in the pipe at the impeller of the pump, giving you X ammt. of head, when you drop down the rotation speed of the impeller, due to the laws of friction "layman term", the amount of force, or pressure required to move the water at the same rate reduces. Thus a lower number in ft. of head. IE. if the system when fully operational requires 40ft of head to move the water, when you switch to low speed, it's not 40ft of head anymore, it's 10ft. Correct?

When you drop the rotation speed of the impeller, it reduces the flow rate. This reduction in flow rate is what reduces the head loss in the plumbing. Head loss is proportion to the square of the flow rate so when the RPM is halved, GPM is halved, and head loss is a quarter. This is referred to as the pump affinity law.

Surely you can compare at the same speed, no?
IE. Speaking hypothetically, if we know our pool needs 40ft of head at full pumping speed, we can compare pumps in your chart above by looking at how their GPM flow rates line up to the 40ft hd bar on the right. From that, we can ascertain and say, based on the chart, that the pumps on the left will move more water at a higher rate of flow than pumps on the right side of the chart.
Is that right, or am I not getting something?
Are you saying that manufacturers pump performance curves are totally worthless?

The performance curves are not worthless but you have to know how to use them. You cannot compare two pumps at the same head loss because the head loss might be different on the same plumbing. In other words, when comparing two pumps, you need to compare them for the same plumbing curve which may not result in the same head loss. If you look at the chart I posted above, there are two plumbing curves shown. But you will notice that the head loss (black markers) are not the same for every pump.

The pump has a head curve and the plumbing also has a head curve. Where these two curves meet is the operating point. However, for the same plumbing curve, there is a different operating point for each pump and for each speed of each pump.

The best way to show this is with the following graph which shows several pump head curves with four different plumbing curves. Each intersection of the plumbing curve with a head curve is a unique head loss and flow rate (i.e. operating point). So you can easily see why you cannot use the same head loss for all the pumps when you compare them. However, for a given plumbing curve, all the intersecting head curves can be compared to each other since it is on the same plumbing curve.