1. ## Cost to run pump for freeze protection

How do you get to \$.40? A 1.5 HP Jandy pump uses about 2.2 kw per hour so how much do you pay per kwh? Even at \$0.05 / kwh, that is \$0.88 for 8 hours of run time.

2. ## Re: How to manage pool during freezes

I guess the biggest thing is that we are not below 32* for eight hours in Houston.
Kw=(motor hp)*(efficiency)*(power factor)
For a typical 1.5hp pump the efficiency is 0.78 and power factor is 0.81.
I pay \$0.08/kW.
So \$0.46=(1.4kw)*(\$0.08/kW)*(4 hours)

I only run it when it's 32* or below.

I am using typical motor data as I have clamped an amp meter on my new pump yet.

3. ## Re: How to manage pool during freezes

No, that is not the correct equation.

First, based upon actual measurements, the power draw for a typical 1.5 HP pump is 2.2 kw not 1.4 kw.

Second power factor is only used when calculating power with RMS volts times amps so it should not be used in the equation you showed.

Third, you should divide by efficiency to get power draw, not multiply.

The correct equation is:

Electrical Power (kw) = Label HP * Service Factor / Motor Efficiency * 0.7457 kw / HP

1.5 HP * 1.65 SF / 0.78 * 0.7457 = 2.37 kw

But that is at service factor load. Nearly all pump motors run below full load which is why the measurement shows 2.2 kw.

5. ## Re: How to manage pool during freezes

It is not derived but a rating that is listed on the motor label. A typical 1.5 HP full rated pump has as a motor service factor of 1.65. An up rated pump is around 1.1.

BTW, if you tell me which pump model you have, I can tell you more accurately what the power draw actually is from APSP measurement data.

6. ## Re: How to manage pool during freezes

So using your number, 4 hours, \$0.08/kW it's \$0.70.

7. ## Re: How to manage pool during freezes

So do you manually turn off your pump after 4 hours or have automatic freeze protection?

8. ## Re: How to manage pool during freezes

I have been checking the weather each night and looking at when it is 32* or less. The last few times it I have only had the pump on from 1am to 5am.

9. ## Re: Cost to run pump for freeze protection

I don't know about freeze protection, but a little math like previously mentioned will get you in the ballpark. My pump costs almost \$.21 per hour that it runs. That's around \$5 a day if it ran 24 hours a day, which it did when I bought it.

10. ## Re: Cost to run pump for freeze protection

What is your electric rate?

\$.10078/kWh

12. ## Re: Cost to run pump for freeze protection

Whatever it costs, it's going to be less than a new pump housing.

13. ## Re: Cost to run pump for freeze protection

Originally Posted by Richard320
Whatever it costs, it's going to be less than a new pump housing.
That's very true

14. ## Re: Cost to run pump for freeze protection

A pump housing has far more volume per surface area than the piping so will take much longer to freeze and much less likely to freeze. A 5" diameter pump basket in a 15 MPH wind will take over 50 hours to freeze at an average temperature of 25F and 30 hours at an average temperature of 20F. A 2" pipe will freeze in half that time.

15. ## Re: Cost to run pump for freeze protection

Originally Posted by mas985
A pump housing has far more volume per surface area than the piping so will take much longer to freeze and much less likely to freeze. A 5" diameter pump basket in a 15 MPH wind will take over 50 hours to freeze at an average temperature of 25F and 30 hours at an average temperature of 20F. A 2" pipe will freeze in half that time.
I stand corrected.

Let me rephrase that: Whatever it costs to run the pump overnight, it's going to be less than the cost of the PVC fittings to repair a broken pipe.

16. ## Re: Cost to run pump for freeze protection

Seems a like such a hassle to have actual weather....

17. ## Re: Cost to run pump for freeze protection

Risk assessment isn't just about a single event or a single night of running a pump. It is about the probability of the event occurring vs the recurring cost of risk mitigation. So if you turn on your pump every time it gets below 32F even though there is zero probability of a freeze event occurring, that is simply a waste of money without any benefit. As temperatures drop and/or duration of time below 32F lengthen, the probability of freezing increases so the benefit of running the pump might increase. However, not every freeze event results in a damage event either.

For example, if the probability of freezing when temperatures drop below 32F is 10% and the probability of damage is 10% of that, the probability of damage is only 1% of the below 32F events. So 1 out of 100 days there is damage. If it costs \$1 per night of running the pump, the actual cost of the insurance is \$100, not \$1. But in many cases, the probability is far less than that even when temperature get down to the low teens which means the cost of the insurance is much higher.

In 2012 we got down to 13F and there was no damage to my equipment even without running the pump. But I knew ahead of time there wouldn't be any freezing of my equipment. Time to freeze was 14 hours under those conditions, and we never have freezing temps longer than about 6 hours.

All I am suggesting is that it can be an waste of money to blindly run the pump the moment temperatures drop below freezing. With little effort, you can reserve running the pump for those conditions where there is actually a probability of freezing. At that point, it might make sense although the probability of damage is still fairly low.

18. ## Re: Cost to run pump for freeze protection

True, but I sleep better.

If it's 1:100 then I don't mind spending my \$100 over the many years it will take me to get 100 nights at 32 or less.

19. ## Re: How to manage pool during freezes

Originally Posted by Jabooh1
I have been checking the weather each night and looking at when it is 32* or less. The last few times it I have only had the pump on from 1am to 5am.
That doesn't sound like sleeping better to me.

20. ## Re: Cost to run pump for freeze protection

I don't stay up checking it. That would suck!

I check it at 10 or so before bed.

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