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

[mitchryan912]

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.)

[mas985]

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.

[CarlD]

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

[mitchryan912]

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.

IMG_1366.jpg

[mitchryan912]

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?

[mitchryan912]

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

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