New Pump Advice

[USFishin]

I’m looking at replacing my existing 1 ½ HP single speed pump with a 2 speed. I just need a little help on calculating what size I should get and the total head of my system.

I have a 15,000 gallon in ground pool with spillover spa and 1.5” piping. I calculated that I need a 30 GPM pump for a full turnover in 8 hours. My problem is I’m not sure how much head I have in my system. I can fairly easily calculate it out but I’m not sure what some of the check valves in my system are adding. I currently have 2 spring check valves in the system and then another one in my heat pump (which I could put in a bypass valve to completely bypass it since it’s only used when using the spa). One of the two is after my filter because I have a solar system on my 1 story patio roof (about 10’ up) and the 2nd is on the spa return line so the spa doesn’t drain down to the level of that return when the pump is turned off. I can replace the one at the pump with a flapper type if I need to but the one for the spa is in a vertical position and would need to stay as a spring type.

In doing the reading I’ve done so far on 2 speed pumps, I’m thinking I might be able to get away with running my new 2 speed pump on low all the time, and then flip it to high when running the spa. This situation would be ideal because I wouldn’t have to add any additional controls for the pump. I have a Zodiac MX8 cleaner which says it can run on as low as 20 GPM, which is well under my required 30 for my water turnover. So based on whatever my total head is, if I could find a pump that met that requirement at 30 GPM on low speed I’d be a happy camper.

It also appears as though since the solar system is only on the 1st story that a pump on low speed should have enough power to purge the panels.

Am I headed down the right path or totally crazy? What should I add for the spring check valves in my system? Would running the pool cleaner on low be effective and is it doable?

Here's a picture of my system if that helps...

 

[Smykowski]

I'm sure someone will be along shortly to help with your question. While we're waiting, can you put your city and state in your profile?

 

[Kiss4aFrog]

Since we're just sitting here might as well ask him to fill out his signature too (please).


If you're about ready to post and ask some questions, you will first need to help us and yourself by getting some basics out of the way.

Profile
Please put the city and state in which you live in your profile. Your climate is important to the advice you receive.

Signature
Please put the following information in your signature.

The size of your pool in gallons
If your pool is an AG (above ground) or IG (in ground)
If it's IG, tell us if it's vinyl, plaster/pebble, or fiberglass
The type of filter you have (sand, DE, cartridge) and, if you know, the brand and model of the filter.
If you know, please tell us the brand and model of the pump, and mention if is it a two speed or variable speed pump.
Date of pool build/install, particularly important if less then a year old.
What kind/model of water test kit you are using
Other significant accessories or options, such as a spa , SWG, or cleaner

 

[mas985]

With a SPA, I would not change the "Size" of the pump or risk poor spa jet performance. So you have two options:

1) Change the pump motor to a two speed.

2) Purchase a new pump of similar "size".


That is obviously a Sta-Rite pump. Do you know the model#?

But one red flag for me is the size of your filter. It is way to small for the high flow rates normally required in a spa. How many jets do you have in the spa and what size pipes is feeding them?

 

[USFishin]

Alright, I updated my signature with my pool information.

Mas985, I am planning on replacing it with a motor or motor/pump of similar size, but would like to go with a 2 speed so I can take advantage of the energy savings.

Here is the info on my motor http://www.marathon-motors.com/C1246-5KC39UN6086X-1-1-2-Hp-115-230-56Y-FR-1-PH-3600-Rpm-C1246.htm. I'm not sure what the model is of my current whole pump/motor assembly.

I think I have a total of 4 or 5 jets in the spa with 1.5 piping.

 

[bignick]

A 2-speed motor replacement to the motor you linked is a Century/AO Smith B2982. I put one in earlier this year. You will need 230V power and a way to switch speeds (control panel or separate switch). One thing though...check the frame size of your existing motor. The one you linked is a 56Y (approx. 6.5" diameter), but the picture looks like a 48Y (5.5" diameter).

 

[USFishin]

The link to the motor I posted above is the exact model number pulled off of the label from the motor. The label does list it as a "56Z" though and not a "56Y". The motor you referenced above is a 1HP. I need a 1.5HP. I'm still wondering if I can fully function on the low speed of a 2 speed motor. That would be my ideal situation. Then I wouldn't have to worry about automatic control of the motor between speeds. I have no problem adding a switch for manual switching when I want to run the spa but would prefer not to change out my timer.

 

[bignick]

The total brake horsepower is the listed horsepower times the service factor. So your existing motor is 1.5 x 1.1 = 1.65hp. The B2982 is 1.0 x 1.65 = 1.65hp. One is just uprated; it's a numbers game. Strange about the 56Z/56Y labels. The pictures I found of a 56Z is just a motor with a shaft sticking out. Maybe a 56Y is just a 56Z with the mounting plate? Dunno. I can't help on your flow because I don't have a spa, but I will add that I haven't had any luck priming my solar panels on low speed (panels on roof of single story home). So what I've been doing is running on high speed in the summer and low speed in the winter. I see dramatically reduced energy costs in the winter.

 

[USFishin]

You're right, I forgot to look at the SF of that pump you mentioned. I'm assuming there aren't any head to GPM curves for existing pumps with upgraded 2 speed motors? That's one downside I'm thinking there might be for just replacing the motor and not the whole pump. If I replace the whole pump I can select one that has a curve that would fit my situation better. On your solar panels, are they on a sloped roof of your house or flat? Mine are just on the flat roof of my patio which is about 10' up. So the highest point the pump would need to move the water would be 10'.

 

[mas985]

Can you post a picture of the motor label? Just want to make sure but the B2982 is probably the correct motor.

I'm still wondering if I can fully function on the low speed of a 2 speed motor.

I am not sure what you mean by this but many POs with 2 speed pumps find they need a little high speed time for skimmers and cleaners but every pool is different.

 

[bignick]

On your solar panels, are they on a sloped roof of your house or flat? Mine are just on the flat roof of my patio which is about 10' up. So the highest point the pump would need to move the water would be 10'.

My solar panels are higher than yours. From the pump, it goes up about 14 feet to the sloped roof. Then it's another 10-15 feet to some panels and then up and over a ridge to more panels. So definitely more demanding of the pump than your system.

 

[USFishin]

Can you post a picture of the motor label? Just want to make sure but the B2982 is probably the correct motor.

I am not sure what you mean by this but many POs with 2 speed pumps find they need a little high speed time for skimmers and cleaners but every pool is different.

The reason I'm thinking I might be able to run the pump on low all the time except for running the spa is that the pool cleaner only needs 20 GPM. I figured I need a pump with a low speed of around 30 GPM, to meet my turnover in 8 hours requirement, so that should be enough to handle the cleaner. That is assuming that I don't have enough head loss to drop the GPM too low on low speed. That is really the big IF in my situation. Also, being that my pump is probably about 15 years old (not sure if it's the original or the previous homeowner replaced it), would it make sense to replace the whole thing or just the motor? Here are some pics of the pump:

 

[mas985]

I figured I need a pump with a low speed of around 30 GPM, to meet my turnover in 8 hours requirement, so that should be enough to handle the cleaner.

There is no such turnover requirement. Turnover means nothing and has very little to do with pump run time. Please read the run time article in my signature.

As for the cleaner, 30 GPM might be enough for just the cleaner but no skimming. If you want to do both, you might need some high speed run time or be able to change the valve settings dynamically. It is difficult to run everything at the same time on such a low flow rate.

 

[USFishin]

That was a very interesting article. Thanks for the link! I don't plan on running the skimmer and cleaner at the same time. The pool doesn't need skimming too often because I have a screen over the pool. Pollen season is really the only time when a lot of skimming is required. Do you think a motor replacement like the one Bignick suggested, and it running on low, would be able to supply enough GPM in my system for the cleaner to run by itself? Are there any curves available for these retrofit situations? If the wet end of my pump is fully functional, would it make sense to just do a motor replacement instead of a whole pump replacement or should I go ahead and replace the whole thing because of its age?

 

[Brentr]

USfishin, we have a similar set up minus the spa. I would be very interested to see what you end up with as I would like to replace my pump with an more efficient pump. I am wondering if the 2 speed pump running on low speed would be sufficient to run solar.

 

[mas985]

If you run the cleaner by itself, then it should be ok as long as you can isolate cleaner (i.e. turn everything else off).

Also, replacing the motor saves the hassle of having to replace everything. However, it might end up costing the same as a new pump. You just need to shop around.

 

[USFishin]

mas985, do you know how much head the spring check valves add to the system? I'd hate to swap out the motor and end up with issues of it running on low. There's no way to know what the actual GPM flow is on one of these motor swaps is there? All of the motor curves I've seen are for whole new units. If I get the pump mentioned by bignick I can pick it up for $246 shipped. I figure that's probably about 1/2 of what a new motor/pump assembly would cost.

 

[mas985]

Why do you need to know the flow rate? If the cleaner requires 20 GPM, the pump will easily produce that. Give the pump size and your plumbing layout, that pump should produce at least 80 GPM on high and 40 GPM on low speed.


Don't forget that you need to get a new seal kit.

 

[USFishin]

I'm still questioning the GPM I'm going to get on low speed. My exact pump is obviously not made anymore so I looked for the equivalent pump to my current pump and that seems to be the Max-E-Pro P6EA6F-206L (1.5HP single speed). The pump I have with a 2-speed motor on it (assuming I just do the motor swap) would be the Max-E-Pro P6RA6YF-206L. When you look at the curves on those two pumps, they both have the same high speed curve (curve E). The 2-speed version has the "A" curve for the low speed. On that curve 20 GPM (my absolute minimum, although higher would be better) can only do approx 15 feet of head. I figure I probably have closer to 30' of head (unless I'm going about calculating it wrong) when you factor in my pipe runs, 90's, check valves, etc.

http://www.pentairpool.com/products/pumps-inground-max-e-pro-high-efficiency-pool-spa-pumps-96.htm

 

[mas985]

Head loss is not a constant and is dependent on flow rate which is dependent on the pump head curve, pump RPM AND plumbing setup. Low speed is about 1/2 the flow rate as full speed but it has 1/4th the head loss. So if you have 50' of head loss @ 80 GPM at high speed, low speed is 12.5' @ 40 GPM.