How do you calculate head?

[Rangeball]

Looks like 60 gpm, turnover in a bit under 6 hours. I run my pump 24/7. I'm contemplating cutting that in half, but the pool is spotless, so it may be cheap insurance

[mas985]

If you do go with a new pump, it will be probably more powerful than the one you have so a 3/4 HP is probably more than enough for you. Your head will likely increase as well as your flow rate.

[Rangeball]

When I talked to Pentair last year after I discovered I had an AG pump, they suggested a 3/4 hp whisperflow.

From what I've been able to tell, I don't know how much it would save me in electricity. The 1 hp dynamo pump I have is rated at 12 amps. I believe the 3/4 whisperflow is 11 amps. Am I missing something? This is all new to me.

[mas985]

I think both of those are at 115v if I am not mistaken so the power usage will be slightly lower for the new pump as well as your turnover allowing you to run the pump for a shorter period of time saving even more.

Have you considered a two speed pump? The low speed will save you even more. Even with doubling the turnover for low speed, you will still save ~30% in energy costs over the 1 speed pump. The extra $100 for the 2 speed would be paid off in a few months.

[cygnusecks]

Wouldn't it be most accurate to mount a vacuum gauge just before the pump inlet, and a pressure gauge just after the pump outlet? Also, I assume that you want the solar ON (i.e. not bypassed) when taking the readings, as this will slow the pump down the most.

[mas985]

Yes it would be more accurate but not many people have the extra guages at hand nor feel comfortable doing the measurements so I was giving him an approximation from calibrations on my pool (i.e. suction 40% of return).

As for the solar, the head approximation of 3.2 * filter PSI breaks down so a direct measurement would be best. The pressure rises on the retun side but the suction side tends to drop a bit as the flow is reduced. Suction then becomes less of a percentage of the return side. The problem is this varies widely with the type of solar panels. I have seen PSI rises from 3 PSI to 10 PSI depending on the panels. It is very difficult to come up with a rule of thumb with solar. However, given the PSI with and without solar, a better calibration can be done with head equations to give a more reasonable number.

[Rangeball]

I think both of those are at 115v if I am not mistaken so the power usage will be slightly lower for the new pump as well as your turnover allowing you to run the pump for a shorter period of time saving even more.

Have you considered a two speed pump? The low speed will save you even more. Even with doubling the turnover for low speed, you will still save ~30% in energy costs over the 1 speed pump. The extra $100 for the 2 speed would be paid off in a few months.

Thanks.

Yes, both have 115v motors.

I currently run my pump 24/7, so I'm getting 4 turnovers a day. I could cut my use by 50% going to 12 hours

I'd really like to try doing so, but I'm having the most trouble free year ever since owning the pool, and am afraid to fix it if it ain't broke.

Even though my pump is AG, I'll use it until it dies, as it's doing a fine job on my pool. Just trying to be prepared for that day, cause, you never know

[mas985]

Well, if it helps any, I was running my pump for a 1/2 turnover during the winter and now I am runing it a 1 1/2 turnovers per day and the water is crystal clear. However, my bather load is light.

One thing you might want to try, is to lower the run time gradually. Drop a few hours each day until you hit 12 hours so you can monitor any changes.

[Rangeball]

I may do that. I think there's an intermatic timer at my in-laws that they use for Christmas lights, I'll see if I can borrow it and do some playing around.

We're coming into the hottest weather, so it should be a good test

[Rangeball]

By filter PSI I assume you mean what my filter gauge reads? Normal operation is 10 psi. So 3.2 x 10 psi = 32 head?

And right now my filter psi is 14 (lot's of cottonwood lately), so head has increased to 44.8?

Is that right?

Mark, on the bold-

Is that right? And if head has increase, why am I getting less flow at the return?

Thanks