Another pump question...

[onewomanarmy]

I apologize if this information is already in the forum somewhere, I don't seem to be hitting upon the correct combination of words to find it if so. We have been running an autopilot SWCG with a 1HP Pentair Superflo (single speed) pump. Pool is about 28-30,000 gallons and we use the SWCG brains to control the pump which we run (probably longer than needed) about 12 hours a day. I've always left the prime protection at 2 mins thinking it would be enough to save the pump if something happened and we lost prime somehow.

A couple of days before we returned from vacation, something happened and it appeared that the system lost prime. So when we got home, the system was down and had been down for a couple of days by the looks of it. I assumed it did what it was supposed to and shut down 2 mins after it registered lost prime. It sure works when I'm trying to pump down the water level! Whatever happened, upon regaining prime and restarting, the pump sounded slightly different as it was running than it had in the past. About 3 weeks later, it's making a much louder sound and has been shut down until we can close the pool for the season. Of course temps have shot up into the 80s this week..

Anyway. Our options as I see them - replace the motor, replace the bearings (which I assume are the problem), or replace the whole thing. I don't have the tools to replace the bearings, so we'd need to have someone else do that. Looking at motors (quick glance) appears that the motor would be over half the price of replacing with the same pump. The option that's getting the loudest vote is to just replace the whole thing and at some point, take this one somewhere to see if it's worth trying to rebuild and/or hang on to it for parts/back up.

My question is, if we do go the route of getting a new pump, is there a better pump to buy in our situation? From what I can tell, we wouldn't really gain the benefits of a variable speed pump while using the autopilot controller to handle pump off/on. I've also seen some concerns with the flow not being high enough on the 2 speed pumps to trigger the "flow ok" switch on the SWCG. Even though it doesn't appear that it saved my pump this time, I'm not completely sure what exactly happened and would like to continue to use the prime protection setting on the autopilot in case it would save the pump from burning up.

Is a single speed still our best option? Is there another pump you'd recommend? This is an unexpected expense, so wasn't really looking to sink a lot of dough into this, but want to make a smart decision and will spend more if it makes sense.

Thanks!

 

[xyz]

I would think you WOULD get benefit from a two speed pump.

Here is why. True 1/2 HP is approximate 0.375 kw.

Also, my guess [and maybe someone can verify] the way the motor cuts it's power is by cutting it's RPM.

Bottom line, my 28k gal pool normally runs on 160 watts all day every day. Even when I had overly restrictive plumbing, and a higher back pressure filter, it still would run reliabily at 1800 RPM which happens to be about 0.4 kw.

So if you have a reasonably free-flowing system, it should be no worries; if you have a highly restrictive system, you still are likely to be OK, but need to do a little more measurements.

What is your maximum filter pressure? Give us some idea of the head pressure you are dealing with.

 

[mas985]

I would just replace your current motor with a two speed. A B2980 (230V) is what you want. On low speed it saves over 75% in energy costs.

True 1/2 HP is approximate 0.375 kw

Not exactly. I think you are just doing a HP to kw conversion but that is the output power of the motor shaft and not the actual electrical power necessary to drive the motor. Plus it doesn't take into account the service factor. Most 1/2 HP pumps will use 1200-1400 watts of energy (e.g. Whisperflo).

 

[xyz]

I would just replace your current motor with a two speed. A B2980 (230V) is what you want. On low speed it saves over 75% in energy costs.



Not exactly. I think you are just doing a HP to kw conversion but that is the output power of the motor shaft and not the actual electrical power necessary to drive the motor. Plus it doesn't take into account the service factor. Most 1/2 HP pumps will use 1200-1400 watts of energy (e.g. Whisperflo).

If 1/2 HP PM motor is that inefficient (is using 1400 watts), 1) your system has high flow friction, and 2) it is a poorly designed or poorly built motor.

Since neither of of these should be true, or even close to true, a 1/2 HP Motot (if that is the lower rating of the 2 settings), should deliver most of the power given it. It also has the advantage of far Lower I^2r, since it is really a 1 HP motor running at 1/2 power. Half the current and twice the copper to cunduct more efficiently. Said another way, energy in = energy out. So if the motor was using 1400 watts to create 400 wats of power, that means it would be making 1000 watts of heat. That motor would be cooking itself to death. Imagine pointing a blow dryer all day at your motor.

my motor at 400 watts is barely even warm.

Anyway, if there was so mush head loss and this were a constant displacement pump (like a gear pump), maybe you could overload it and then get little work and lost of heat. That is not the case here.

So, if you have a decent or good flowing system 1/2 HP will likely be more than plenty to get your SWG flow switch to trigger. If you have high back pressure, you may want to get the 2 speed even if you can't use it at first. You could slowly improve (lower) your head pressure, and before you know it, you are saving lots of coin on power.

Also, I've come to realize salt pools are better at lower flow rates, with the added benefit of far lower power bills.

Oh, and by service factor I think you meant power factor? Again, watts is watts. Energy can neither created nor destroyed. So,if you put in 1000 watts into a system, 1000 watts are coming out. Unless you are a large industrial user, PF fees are not applied, so the only thing a "poor" power factor could do is deliver more rotational power than you get charged for.

Anyway, bottom line, if he has reasonably low flow restrictions, a 2 speed will be a really nice upgrade, and will probably pay for itself quickly, especially given his long run times.

 

[GaryT58]

I upgraded my 19,000 gallon pool to an AutoPilot SWG. I also replaced my Pentair 1HP SuperFlo with a Pentair SuperFlo VS. With the variable speed I am able to dial down pump speed to 600 RPM before the Autopilot signaled a flow error. So currently use a minimum of 850 RPM, to allow for the sand filter to get dirty.

A 2 speed will work for you, and be less expensive to purchase. But depending upon your electricity costs and how you want to run your pump, a VS can make sense. For me, in the peak swimming time, I like the pump running 24/7 - to keep clean, and at night when really hot, to run fountains to cool off pool. I do not have firm #s until next year, but should save me about $100/month for electricity (again because of how I like to run). Also with longer run times, I am running my AutoPilot at the lowest power setting (of 3) and currently at 15% (getting cooler).

A great thing as well about the SuperFlo VS, is that its a drop in replacement for the SuperFlo. So no need to adjust plumbing. This would be the same with the SuperFlo 2 speed.

As for power, the 2 speed SuperFlo (SF-N2-1A) uses 1276 W at 3450RPM, and 312W at 1725RPM, so you can see the major power savings. With the VS (342001), if you would use 130W at 1100 RPM, or 95W at 850RPM. So for me, these savings made sense for me to go with the VS.

[EDIT] There was nothing wrong with my 1HP SuperFlo. Just wanted to replace with VS to save money.

 

[xyz]

As for power, the 2 speed SuperFlo (SF-N2-1A) uses 1276 W at 3450RPM, and 312W at 1725RPM, so you can see the major power savings. With the VS (342001), if you would use 130W at 1100 RPM, or 95W at 850RPM. So for me, these savings made sense for me to go with the VS.

[EDIT] There was nothing wrong with my 1HP SuperFlo. Just wanted to replace with VS to save money.

Ah. Cool. More info. So it is half speed not half power. That should save even more power. 2 speed looks like a no brainer if you can swing the up front coin.

So @ 1276w*0.15$*8hrs*30d=46 bucks/mo. 312 yields 11 b/mo. Saves~33 bucks. So if the pump costs more by 250 bucks, that pays for itself in 8 months, and then keeps paying. That seems like a darn good deal.

And the silent operation is going to be an added benefit you didn't know you couldn't do without.

 

[GaryT58]

Ah. Cool. More info.

Here is link to thread (see 2nd post) that shows a great table that compares cost of ownership for various pumps. You can download the excel spreadsheet from the 3rd posting, with link next to "Pool Pump Tools*". You can edit this worksheet (must enable macros) to change the various things to your case, like electric power cost, run times, product cost, run speeds, ....

There are other spreadsheets included which can provide some great info.

I used the "Energy Cost" sheet to verify in my case that the 5-year cost of ownership of the Pentair SuperFlo VS was much better than a 2-speed pump for how I plan to run (low speed 24/7). Also, with the "Energy Cost" worksheet, you can select the pumps you want to compare by entering the "Pump Model" value for the column and it will fill in the data for the pump from the "PumpData" sheet (where you can get the Pump Model values. I edited sheet with my local power $, run times, rates, current pump costs, and compared the couple models I was looking at. Very helpful in selecting my new pump. Thanks to mas985 for setting this up.

 

[xyz]

Here is link to thread (see 2nd post) that shows a great table that compares cost of ownership for various pumps. You can download the excel spreadsheet from the 3rd posting, with link next to "Pool Pump Tools*". You can edit this worksheet (must enable macros) to change the various things to your case, like electric power cost, run times, product cost, run speeds, ....

There are other spreadsheets included which can provide some great info.

I used the "Energy Cost" sheet to verify in my case that the 5-year cost of ownership of the Pentair SuperFlo VS was much better than a 2-speed pump for how I plan to run (low speed 24/7). Also, with the "Energy Cost" worksheet, you can select the pumps you want to compare by entering the "Pump Model" value for the column and it will fill in the data for the pump from the "PumpData" sheet (where you can get the Pump Model values. I edited sheet with my local power $, run times, rates, current pump costs, and compared the couple models I was looking at. Very helpful in selecting my new pump. Thanks to mas985 for setting this us.

Cool!

 

[mas985]

If 1/2 HP PM motor is that inefficient (is using 1400 watts), 1) your system has high flow friction, and 2) it is a poorly designed or poorly built motor.

No, I think you need to better understand how pump motors are rated. Just because a label says a motor is 1/2 HP does not actually mean the peak rating is 1/2 HP. The service factor determines the true rating of a pump motor. The Whisperflo WFE-2 has a 1/2 HP label but it also has a 1.9 Service Factor so the total HP (THP) is actually 0.95. An induction motor has an efficiency of 60-85%. At lower HP, the efficiency is lower because the winding wire diameter is smaller. So a 1/2 HP motor (0.95 THP) operating at 60% motor efficiency would use about 1200 watts. It would be creating about 700 watts of shaft power.

Also, I am not making these numbers up. The Energy Star publishes these numbers. They are the same numbers that my spreadsheets use (mentioned above).

Oh, and by service factor I think you meant power factor? Again, watts is watts

No, I meant service factor. Again, you need to study up on pump motors. The Pump 101 link in my sig is a good place to start.

Also, as was mentioned by Gary, 50% RPM <> 50% power. The pump affinity laws come into play. 50% RPM is actually 12.5% pump power (not motor power). However, a two speed motor uses a separate winding for low speed with thinner wire so while the shaft power decreases by 87.5%, the energy use of the motor decreases by only 75-80%. The winding efficiency decreases by about 50%.

 

[onewomanarmy]

Thanks for all the information and discussion, it's helpful as I try to sort through this. So, with a 2 speed pump and the control unit of the AutoPilot Total Control system, the pump would actually run all the time, correct? Would run at high speed for any programmed time and then drop down into low speed when it hit the end of that programmed "run" time? So the only way to turn off the pump is to cut power either by installing a switch or flipping the breaker? This wouldn't be a problem as the breaker is easily accessed right by the equipment. This would also mean that the "prime protect" option would no longer be effective because all it would do is kick the pump down into the lower speed...? I guess I've been stubbornly holding onto that as being a bit of insurance, but it doesn't seem to have saved the motor with whatever happened a few weeks ago so probably not as big a deal as I was thinking.

I had tossed around the idea of going to a 2 speed without doing the math, assuming that running the pump 24/7 wouldn't save me that much money overall, but it sounds like that may not be the case. I was also concerned about the lower flow triggering the low flow sensor as well as the fact that the cell would be generating around the clock. It doesn't sound like the flow will be too low based on your comments, is there any downside to running the SWCG 24/7? I realize that means I could run it at an even lower setting, so I'm guessing it wouldn't really be a big deal. A quieter system would also be nice as the pool equipment is right beside our screened in porch.

This discussion has been interesting, I've never gotten too deep into the pump/plumbing details before so always good to learn a bit!

 

[mas985]

Or you can add a two speed timer:

Amazon.com : Intermatic T10604R Pool/Spa Control Center T106M and T104M : Electrical Timers : Patio, Lawn Garden

 

[GaryT58]

Note - I have a variable speed pump, so while I will talk to the 2-speed options, I have not personally used these.

I would not think you would have a flow issue in the lower power setting, but every pool is different - piping, run lengths, water features, ... So while I am able to run at 650RPM and have no issues, I have read others that are around 1000 RPM.

There are many ways to connect and run the systems.

1) Connect both the autopilot and pump to a timer. You use toggle switch to control the pump speed. This would assure that both the salt water generator (SWG) and pump run at the same time. This lets you select a run time for both the pump and the swg which you can adjust as needed. It does not use the autopilot's timer or pump control. You lose the freeze protect feature of the autopilot since it can not turn on the pump.

2) Connect autopilot to power, and connect pump in 2-speed mode as shown in autopilot manual. You can program the pump speed in menu, and can override speed with the PUMP buttons on panel. Pump is always powered on. You can add an optional kill switch between the pump and the autopilot if you want to be able to shut off.

2a) #2 + You "could" even use a timer switch to turn on/off before/after SWG program has run, or just use a timer to control the pump and internal timer for autopilot - but this would lose the freeze protect since it would not be able to turn on pump if it were turned off externally. Also, you have a danger of the timers getting out of sync - especially on a power outage. A simple external timer does not have a clock with battery backup, like the autopilot, so if your power goes off for an hour, now the pump timer will trigger 1 hour later than the SWG. So while the flow sensor will disable the generator, this is not a good-use practice. There are more expensive timers which have clocks and battery backups.

3) Connect the autopilot to power, connect the pump to autopilot as 1 speed pump - connecting the line inputs and leaving the toggle switch connected to control the speed manually. This would allow the autopilot program to control the pump on/off. This would allow the autofreeze protection to still work and assure (in theory) that the pump will run with the SWG. HOWEVER, the two speed pumps do state that it should be on high speed to prime. So if for some reason the pump would need primed and you have it set with toggle to low, then it may not prime. With this method you do lose the ability to change pump speed via the autopilot panel.

Hope this helps and not too confusing. I went with a variable speed pump (vs) so my hookup is going to be different.