Replacing a motor on a pump, and getting the correct size for your pool?

I've got a bad motor (smoking when running) and am ready to order up a new motor and stick it on the existing pump (see sig below.) It seems as if this would be a good opportunity to upgrade to a bigger motor, as there was once a 1.5 HP pump installed before we (possibly wrongly) put a new pump with a smaller (1 HP) motor in last year.

Just curious how one would calculate how much power a motor would need for a given size pool? I've got a 26,000 gallon in ground rectangular pool, with an outlet to the pool in the shallow end, a skimmer in the middle, and a return port in the deep end (all piped together with 1 1/2" PVC.)

Changing just the motor on a pump does not change the performance of the pump. It is the impeller and wet end that determines performance of the pump. The motor is just there to turn the impeller but must be sized correctly for the impeller. If you don't change the impeller, the motor size should not change.

But when it comes to circulation and filtering, even the smallest pump is usually sufficient for the largest pool and usually the best choice. Larger pumps require larger filters and just use more energy without much benefit. I have a 1/2 HP pump on a 20k pool and it is more than sufficient for cleaning the pool.

But lets start with why you think you need a larger pump.

Ok, two threads on the same topic is a no-no. Don't do that.

Sorry, posted the other topic in the wrong spot, and what I'm after has changed. I think this is probably the thread to use, and the other should be locked or deleted. My bad.

I assumed that since the previous owners of the house (my in-laws) had a 1.5 HP motor in there previously, that what we should have replaced the old pump with the same size. I don't know if that is a correct assumption, now that I've been doing some digging on the topic. It seems as if 1.5" PVC pipe is going to be the limiting factor, and that anything over 1 HP could well be doing more harm to the motor than good?

Does this sound correct, that 1.5" pipe is going to allow for the maximum flow rate of 44 gpm, while my pool probably needs a minimum flow of about 54 gpm (26,000 g/8 hrs, and then divided by 60 min to get the max flow rate.) From what I'm seeing, it sounds like a 1 HP motor would put me in the ballpark of 40 gpm, depending on which motor I get.

As far as the current motor, smoke was emanating from this hole near where the wire enter the back of the motor. I don't see any scorching on the wires, I've tested for voltage on both legs of the wiring (it's 230v), and the motor is set to 230v.

Attachment 945

While we're at it, my pump runs 24/7. Does that change the calculation for how many gallons need to be filtered per 8 hours? We don't really use it that often to need it to be cleaned 3x per day... or does that mean we probably ought to consider putting in a timer to limit how much it runs?

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Originally Posted by CarlD

A 1HP IG pump should be fine, but not a 1HP AG pump.

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Are they constructed differently for each type of pool? I guess I'm potentially not following what you mean by this statement.

Smoking motor is not good.
AG pumps are designed to run with the pool water higher up so there is gravity pressure. An IG pump is able to pump from the surface and pump the water up.

Further, most AG pumps are "up-rated" while IG pumps tend to be "full-rated". To super-simplify, it means that an AG pump rated at 1.5HP may have the same flow rate as a 3/4HP IP pump.

Re-read mas985's post above.

OK, re-reading mas985's post. I think I understand it a bit more now that I did before... and now I think I might just benefit from going to a SMALLER motor and impeller after looking at the spec sheet for my pump. To answer his original question though, I thought I might need a bigger motor because I was seeing debris just float by my skimmer, so I thought maybe there wasn't enough suction to properly skim the pool?

To the specs: http://www.waterwayplastics.com/prod...d-pumps/smf-2/

According to their flow rate chart, the 1 HP motor I've had might just be too big. 40 ft of head for the skimmer line = 75 gpm flow rate, and that's higher than the rating on my filter. FWIW, I've got 25 feet of head to the other suction line.

I guess I'd be looking more at the 3/4 HP pump now, based on the flow rate chart. This is all assuming that I'm calculation my GPM's correctly (54 gpm to turn over the pool in 8 hours, 60 gpm flow rate of the filter, 44 gpm per suction line x2) Based on all of that, would I be correct in choosing a 3/4 HP pump instead? If I were to get a replacement 3/4 HP motor, would I also need to get a different impeller as well?

Thanks for all the help on this, BTW. Last year I got a crash course on chemicals, and now I'm getting a crash course on the mechanical aspects of pool ownership!

mas985 is far better at figuring the mathematics of head to gpm to filter rate than I am.

Hopefully mas985 reads this and can give some suggestions. I'm not sure how long I can let the pool go without circulation, as it's been since late Friday night that it died. I'm keeping the chlorine high to make sure stagnant water doesn't help lead to any funkiness going on in the water. Obviously manually skimming much more often than I usually do as well.

Here's some info on my filter. The pressure gauge on it seems to be broken, as there's no pressure currently, and it's reading 30 psi. When the pump is running, it typically reads 55-60 psi, so I'm assuming it's actually about 25 psi most of the time. I'm not sure if that pressure reading matters, but I'd seen some sites that used that to calculate the head (I don't have a way to check the suction pressure before the pump, at least not yet...)

I'm leaning towards buying this replacement motor, an AO Smith USQ1102: http://www.amazon.com/Smith-USQ1102-.../dp/B007ATO2SK

It seems like it's direct replacement for the US Motors 1081 that was part of the Waterway pump we have.

First the whole concept of turnover for residential pools is flawed (see pump run time study in my sig). There is no minimum turnover required for a residential pool so minimum flow rates are really only important for things such as heaters and SWGs and SPAs so you really don't need to bother trying to figure it out unless you have one of these features.

But if you are going to the trouble of replacing a motor, I would get a two speed. Assuming you have a 48Y square flange motor, then you could use a UQS1102R motor but you will need to buy a 3/4 HP full rated impeller for the pump.

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When the pump is running, it typically reads 55-60 psi,

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That is impossible. You filter gauge is broken.

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While we're at it, my pump runs 24/7.

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No need to. A pool can get by with as little as 2 hours of run time (see study).

I run my pool 12hrs/day at low speed (about 1/4hp) for two reasons:
1) I have an SWCG
2) I have solar panels that are also the decking and when the pump is running it keeps the decking cool while it heats the water.

O/W I'd run it just enough to keep it skimmed and clean.

I too have solar and an SWG but run for only 4 hours per day. I could drop it to 2 hours per day if I didn't need to run solar because the SWG is large enough to do that. In fact, in the winter, that is exactly what I do.

Well, my solar is decking so it's more to keep the deck cool than to heat the water.
In the winter, my pool can have 12-18" of ice in one giant berg!

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Originally Posted by mas985

But if you are going to the trouble of replacing a motor, I would get a two speed. Assuming you have a 48Y square flange motor, then you could use a UQS1102R motor but you will need to buy a 3/4 HP full rated impeller for the pump.

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Would this be it? http://www.amazon.com/Smith-SQS1102R...ao+smith+1102R

It's a 1/.166 HP 2 speed motor. Since the full speed of 1 HP is the same as the impeller I have, would I be able to keep that the same?

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Originally Posted by mas985

That is impossible. You filter gauge is broken.

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Yep, I noted where it is when there's no pressure, and subtracted that from what it reads when there is full pressure (about 25 psi.) Since the system is down, I'll take the time to replace that.

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Originally Posted by mas985

No need to. A pool can get by with as little as 2 hours of run time (see study).

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If I were to go with a single speed motor like I linked above, could I install a timer inline with the motor and still see energy savings?

Also: is the wiring different on a two-speed motor? How do you control the speeds? I don't see any switches or controls on the motor.

The SQS1102R is a full rated 1 HP and larger than you need. You need a 1 HP up rated motor (UQS1102R) OR a 3/4 HP full rated motor (SQS1072R) which have an identical 1.25 THP rating.

Yes, you could just get a single speed and run it shorter to save energy but a two speed will save more over the life of the pump and motor. To control a two speed, you can use a manual switch or a two speed timer. Which option you go with depends on how much money you want to spend up front but no matter what, you will make that money back with energy savings.

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Originally Posted by mas985

The SQS1102R is a full rated 1 HP and larger than you need. You need a 1 HP up rated motor (UQS1102R) OR a 3/4 HP full rated motor (SQS1072R) which have an identical 1.25 THP rating.

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OK, I think I get it now. I think I'm leaning toward the SQS1072R, as I'm seeing some places say the UQS1102R has been discontinued (looks like HSQ125 is the replacement?) If I went with the SQS1072R, would I need a new impeller and/or diffuser? What about with the UQS1102R or HSQ125?

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Originally Posted by mas985

Yes, you could just get a single speed and run it shorter to save energy but a two speed will save more over the life of the pump and motor. To control a two speed, you can use a manual switch or a two speed timer. Which option you go with depends on how much money you want to spend up front but no matter what, you will make that money back with energy savings.

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Any recommendations on two speed timers, or could something be built from standard electrical parts? I'm a former electrician, so I can wrap my head around the electrical side of things.

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If I went with the SQS1072R, would I need a new impeller and/or diffuser? What about with the UQS1102R or HSQ125?

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HSQ125 may be an issue because of the back end. I can't guarantee that would fit on the motor support.

As for the impeller, it depends on the service factor of your current pump motor. If the current service factor is 1.25 or lower, then the impeller is fine. Diffuser would not change either way.

Timer:

http://www.amazon.com/Intermatic-T10...W61QF3SM3H6H1T

http://www.amazon.com/Intermatic-PE1...BXFB6W5PGHAXZ5

According to the label on the current pump, it's a USQ1102 equivalent, with a SF of 1.25.
Attachment 948

Thanks for all the help! I think I'm going to get or order the SQS1072 after checking with my local pool warehouse.

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Originally Posted by mas985

Intermatic T10604R Control Center

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Am I understanding this right... could this be used to program when the pump is on while also putting a timer on when the pump is switched to a certain speed? Would the main on/off timer feed the switch that determines when the pump is on full speed? That's the sort of thing I'd find handy to have, with manual overrides (if possible.)

Never mind the previous post. I found the wiring diagram on how it works.

Thanks for the help! I ordered up the SQS1072R pump and the T10604 yesterday, and they should arrive tomorrow evening. Since everything was down, I went ahead and replaced the faulty pressure gauge on the filter too.

I just hope I can piece everything back together with the motor when it arrives. Any videos/tips on putting a motor back together? Anything that I need to be aware of?

Fired it up for about a half hour late tonight. Found I had a multiport valve leak and still haven't finished rebuilding the filter yet, so I'm leaving it off until tomorrow when I'll have time to monitor it to make sure everything is working.

Been running for a while, and it's fairly hot to the touch, and I'm only seeing 12 psi at the filter. However, the skimmer is sucking things in at a rate like I've never seen before, so I guess the suction seems to be working well there. Should I be worried about the pump being too hot, or is that pretty normal?

Pump motors can get pretty hot but unless it is shutting off, it is probably ok. One reason to run on low most of time.

After being down for a week, I wanted to get it going. I have an Intermatic T10604R timer to control it, but it's not hooked up yet. Probably should have the electrical ready for it by tomorrow (there was NO timer control whatsoever prior to this whole ordeal.)

I'll probably have it on low most of the time, shutting it down for about 6-10 hours a day at first, until I figure out how much I actually need to run it to keep it clean. Our yard has arbor vitae trees as a privacy fence around our whole yard, so the debris from them lands in the pool all the time. Probably can't shut the pump off completely for very long.

...and the SQS1072 is smoking. Could this still be too large of a pump, or not large enough? The pump is having problems priming, and is overheating right about where it's getting close to being fully primed. Im at a loss as to what's going on...

The motor is the same size as the old motor so should be fine.

But make sure everything was installed properly (impeller ring, diffuser, seal, etc). Any misalignment can cause overloading in the motor. Otherwise, you might just have a bad motor. I can happen sometimes.

I installed a vacuum gauge on the basket side today, and on its own, it wasn't able to get much more than 1 mm Hg. Later in the day, I stuck a drain king into the skimmer and had it blasting water towards the pump, and only then did it shoot up to 20+ mm Hg. The motor still kept shutting itself off before it was able to get full prime though.

It ran just fine for a week before I changed some of the plumbing around. It would be easy to say THAT is the problem, but since we've owned the house, THREE motors in three different plumbing configurations have had problems that caused a motor to stop working. The pump that came with the house worked in the fall we bought the house, but then didn't start up the spring after. The replacement pump worked for a year, but then that motor failed. Now the new replacement motor that we bought on July 20th has died.

I've emailed the company I bought it from in hopes there is at least a 30 day warranty on it.

Unfortunately it seems that one of two things is very wrong, possibly both.
First: there's got to be a problem with your plumbing, somewhere. But it's beyond me--I can handle the simple stuff and I always keep it simple.
Second: You may have a wiring problem, possibly trying to run a 220v pump at 110v or something more subtle.

I doubt it's the pump/motor itself. Not sure what, if any, guidance I can give you. You'll have to rely on Mark for that.

Could the suction line simply be too high up for 1.5" flex PVC running back to the pool? I installed these 2" lines with the ability (hopefully) to hook them up to new 2" hard PVC when the next time we have to do major upgrades to the pool.

http://images.yuku.com.s3.amazonaws....fa1cc1aa31.jpg

Or could a 70' 12 gauge run to the pump not be enough wire? Everything I'm seeing says that it is sufficient, but there's part of me that thinks it's just not enough.

The former is a PITA repair, but one that can be done. I pretty much have to trash everything I did, or use the inside 1.5" slips on the 3-way diverter valves I just bought. The latter is a $4000+ repair, as the main panel in the house needs to be upgraded before any electrician is going to run anything to the shed/pool.

Could the previous motor failure have gotten the wet end hot enough to melt/deform it? I noticed last night that I could still see a small gap between the flange that's inbetween the suction side of the pump and the motor:

http://ecx.images-amazon.com/images/...L._SL1000_.jpg

I poured water over it while it was running, but that didn't seem to do anything. I didn't feel any air being pushed out of the cavity either.

I cannot answer your questions but when I had my pool pump wiring installed, it was 10 gauge wire. And when I extended it, I used 10ga as well with no problems.

I borrowed an ammeter today, and measured a draw of 19A on high and 4-5 on low, on each leg. I don't know much about motors, but that seems excessive. I could see a startup draw spiking really high like that, but not a sustained draw 3x higher than the motor rating.

Yes that is excessive and likely due to interference somewhere in the wet end. If the pump was run without water flowing through it for too long, the water can heat up and deform the wet end causing an interference issue with the impeller. But usually you will hear that when running the pump.

http://www.troublefreepool.com/attac...2&d=1439482338
I did just take everything apart to get things ready for a warranty replacement motor to arrive tomorrow. I did notice the above, that this seal was slightly crooked. Could this cause a major problem?

I never noticed any odd sound until just after I hooked up the pump to some plumbing I re-did (took out two shutoff a and replaced them with a pair of 3-way valves.) Everything seemed fine until a few minutes after running the pump. It was struggling to reach full prime, and it might have been because the water level was too low (pulled all the water out of the skimmer), so I shut it off and filled the pool up a few extra inches over the course of 3 hours. Turned it back on later that night and it sounded really funny, with a sort of him to it like it was seizing up.

FWIW, the pump had run fine for a full week up until I decided to change up the plumbing in an attempt to convert a vac line to an either/or line (vac or return.) There may have been a problem in the height of the new plumbing to the first valve, which was about 8-10" above the pump intake port.

I think you may have the seal in backwards. The ceramic end (white) goes into the motor mounting plate with the ceramic facing towards the impeller. The carbon side (black) faces the ceramic on the impeller side.

And yes, the surfaces must be perfectly parallel and flush or it will ruin the seal and cause friction issues.