Geek out on me! Let's talk about the best way to maximize heat pump with autocover...

[Suz.E.Q]

I want to know if there are any super geeks out there who have done the work to figure out the best way to efficiently heat up a pool without overspending! Specifically, I would like to hear from those who have electric heat pumps and autocovers.

My old findings (from my last pool that only had a solar bubble cover and no heater): the heat was maintained in the pool a bit better when the pump was left to circulate all night long when nights were cool.

My new pool is "sealed" with an autocover, so would the same apply (when the heat pump is off during cool nights because of minimal heat gain cost/benefit at that time), or would the pool water being exposed through above ground pipes be marginally cooled down? Does an autocover have more insulation power than those solar bubble covers? (Seems like it to me!).

Am I making sense? Ultimately - should I keep circulating the water all night with the heat pump off, or turn off circulation for best results and electrical bill benefits?
Thanks!

 

[1poolman1]

I want to know if there are any super geeks out there who have done the work to figure out the best way to efficiently heat up a pool without overspending! Specifically, I would like to hear from those who have electric heat pumps and autocovers.

My old findings (from my last pool that only had a solar bubble cover and no heater): the heat was maintained in the pool a bit better when the pump was left to circulate all night long when nights were cool.

My new pool is "sealed" with an autocover, so would the same apply (when the heat pump is off during cool nights because of minimal heat gain cost/benefit at that time), or would the pool water being exposed through above ground pipes be marginally cooled down? Does an autocover have more insulation power than those solar bubble covers? (Seems like it to me!).

Am I making sense? Ultimately - should I keep circulating the water all night with the heat pump off, or turn off circulation for best results and electrical bill benefits?
Thanks!

Many with a VSP run their pumps 24/7. If you do that at night at a speed that will allow the heat pump to operate, it will maintain the temperature it is set to (within its ability due to climate changes). Keeping the cover closed will insulate and the heat pump will maintain. There is very little water in the pipes above ground, so heat loss would be very minimal. A plus would be that any concerns over freeze damage would be very greatly diminished. Don't know if you close the pool in the winter, but an occasional Spring freeze can happen.

 

[jakeblat]

I'm interested in this but haven't fully got into the detail yet. I've been recording enough data to start to analyse and model it as I heat my pool for the start of the season. My key drivers for heat pump efficiency might be different to yours. I have a solar pv array on the roof and generate enough excess power to run the heat pump for ~7 hours per day during sunlight hours.

I'm currently collecting data on

• Water temperature
• Outdoor air temperature
• Indoor air temperature (my pool is enclosed in a separate glass structure)
• Solar irradiance
• Heat Pump power usage
• Pump power usage

The last week of data looks like this:



My pool is in an enclosed space so not open to the wind and somewhat insulated from the outside air. I keep a solar heat retention cover (Heat Retention Pool Cover - RaeGuard™ - With GeoBubble™ Technology) on it almost all of the time while I'm waiting for it to get up to temperature.

I may be a bit optimistic trying to open with such low outdoor temperatures but as the power is "free" from the solar I might as well try. My priority is to only use solar backed power where possible as I pay £0.3418/kWh (~ $0.43/kWh) for electricity so running costs could add up very fast otherwise.

Using the data I've collected I've started to build a simple model in a spreadsheet to calculate heating and cooling effects based on conductive heat loss through the sides of the pool and cover based on some approximated R values for insulation.



Once I've got some more data I'll be able to check the fit of my calculations. They don't seem too far off but it looks like I need to take into account the additional heating effects on radiation on the cover when the sun irradiation is high. Blue line in this chart is my model estimation of expected temperature, red is actual measured temperature.



Will update if I get any further with this.

 

[treyrich]

I'm interested in this but haven't fully got into the detail yet.

Hahaha seems like you've gotten into quite a bit of detail.

I'll be following this conversation closely, I'm still waiting for my pool to be plastered/filled (hopefully happening tomorrow if there's not too much water seeping through the shell), but I've got an Autocover as well as a Pentair Ultratemp Heat Pump that I can't wait to fire up after my plaster startup. I've also got a Solar PV system which I'm adding additional panels to in anticipation of keeping the pool open year round (and warm enough through the winter that people want to keep swimming).

Would love to get as much information as I can get about how well the autocover holds in the heat over night, as well as ambient temperatures where I'm just wasting my time with the heat pump. I'm sure that I'll figure out a lot of this in a few weeks as I'm able to start my heater up and experiment, but it's fun to get as much knowledge as possible in advance.