Replace motor or motor& pump?

[jtcaputo]

I have a Pentair WFE-3 (3/4 HP) pump. I would like to upgrade to a WFE-4 (1 HP) pump. There is nothing wrong with my present pump. Can I just order a WFE-4 motor and change out motors? The pump housings look the same. That would save me a lot of money if the pumps are the same.

[mas985]

No, just replacing the motor will do nothing. You need to change both the impeller and the motor. But I have to ask why? You will lose some efficiency going with a larger pump.

[jtcaputo]

Thank you for your reply.

I had assumed it was just a matter of impeller rpm. The reason I suspect I need a bigger pump is this. The suction line from the pump is split by a Jandy valve into a pool cleaner line and a skimmer line. The only time I can balance the two lines to get adequate performance is the first few weeks after the filter (Pentair Quad cartridge DE 60) is cleaned. Most of the time I have to run 85% of the suction to the cleaner and the skimmer hardly works.

Do you think a bigger pump would solve my problem? I was thinking of going to a Pentair WFE - 4.

[mas985]

I had assumed it was just a matter of impeller rpm.
All induction pool motors spin at around 3450 RPM on full speed. A two speed motor will spin at 1725 RPM on low speed. A pump's head curve is determined by the impeller so a larger pump will have a larger impeller. Either in diameter, width or both. However, increasing the size of the impeller increases the load on the motor which is why a larger motor is needed too.

But back to your problem. This is basically one of the downsides of a suction cleaner. Some cleaners will work with less flow rate such as ThePoolCleaner so that is another option. Also, you could automate the valve so part of the run time is on the cleaner and part is on the skimmer.

But up sizing the motor generally doesn't get you much. Maybe 5% additional flow rate for each 1/2 HP. But that extra 5% in flow rate costs you an extra 20% in energy. I would focus on another solution such as the valve automation.

[waterbear]

A bigger pump will probably not solve the problem. You have encountered one of the main problems with suction side cleaners--when the cleaner is operating the skimmer is not (or is operating at reduced efficiency). This is actually pretty common and is generally accepted at normal. Do you also have a main drain in your pool or only a skimmer? Are you breaking down the filter and cleaning the grids manually or just backwashing? IF you are just backwashing try breaking down the filter and see if that give you a longer time that the cleaner will operate correctly. (IMHO, when you backwash a DE filter you really don't know how much DE you remove so you really don't know how much to recharge with and usually end up either overcharging or undercharging the filter and this leads to reduced filtration and shorter run times. IF you want to see some photos to prove this here are some on a different forum (that I am a moderator on) that were just posted! (http://www.poolspaforum.com/forum/index.php?showtopic=37289&hl=&fromsearch=1).

[jtcaputo]

Thank you both for your expert advice. I will not be changing pumps. That Quad DE filter is a real pain to clean. The band requires three hands to put back on and the procedure requires constant tightening, then tapping the band with a mallet to seat it. And your chances of getting perfect are 1 in 3.

[PoolDoc]

membership upgraded. -ben