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

[mitchryan912]

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!

[CarlD]

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

[mitchryan912]

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...)

[mitchryan912]

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.

[mas985]

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.

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

That is impossible. You filter gauge is broken.

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

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

[CarlD]

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.

[mas985]

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.

[mitchryan912]

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?

[mitchryan912]

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.

[mitchryan912]

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?