- Nov 23, 2014
- 222
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
Back in 2021 @Chuck_Davis asked for anyone with experience with inverter technology heat pumps (HERE) He got one reply, suggesting they are smoke and mirrors. Lately it seems many brands are flooding the market and making some interesting claims – of COP up to to 15, even 30, etc. Some argue that you can efficiently heat a pool in 40 degreeF weather.
One can read more about how it works, but simply stated they use variable speed compressors and fans together with controls to achieve energy savings. There is more detail offered in an HPAC article here. Rectify the incoming AC voltage, invert it to 3 phase variable frequency and you have continuously variable compressors and fans that claim to save energy like a variable speed or two-speed pool pump achieves. I even had a recent refrigerator using the technology – but it averaged similar efficiency to the 15 year old fridge I have in my garage.
Still, we all know we get great energy savings from the variable speed and two speed pool pumps. Since the pumps use far more energy at the higher speeds we save substantially even if we run the pumps for far longer periods, even 7x24 at lower speed saves substantially. For example I save about $40/month running my 2 speed on low for 11 hours/day, versus the old 1 speed at 8 hours. All that is fine and dandy, and so obvious that local governments often mandate use of two-speed or VS pumps when replacing a pool pump.
So, can you get that kind of savings on the pool heaters that consume tons of energy? Or even on heat pumps used for residential HVAC? We might think so, given the continuously variable speed compressor (and evap fans, condenser fans, etc) running on lower speeds. But pool water pumps are not prone to massive efficiency variations based on weather – i.e. ambient air temperature and humidity, whereas heat pumps are dramatically affected by air temp, humidity, etc.
Some or all of these newer inverter technology heat pumps offer control in two modes: “Turbo” aka Maxx” heating mode, and “Silent” aka “Efficient” mode. One provider claims you use max mode to get the pool to temperature, then run the heater more constantly at the far lower speed to maintain temperature. At some point, of course heat losses limit the extent of that ability, but we get the crux of the claim. Is it more efficient overall, even if the heat pump is far less efficient running during the cooler nights? Even most COP ratings reflect the lower COP running at lower temps, often half the COP at 50F vs 80F. But if it used less than half the energy doing so, it might still net out to be more efficient.
Does it net out savings? If anyone has one, I suggest a simple test, perhaps in a more reasonable climate (not 40F) wherein daytime temps rise to 75 or 80F, and nightly they dip to 50’s. Select a 6 day interval. First get the pool to desired swim temp, eg 85. Run for 3 days in max mode, heating as we might usually do, for 6-8 hours per day or whatever it takes to recover the nighttime losses to get back to the desired temp of 85. Record total pool heater energy consumed. Repeat the test over the next 3 days running the heater (and pump) 7x24 or as needed in silent / slow heat mode. Record energy consumed and compare. Best to leave the extra pump run time & energy out of it for now, but cannot ignore it totally.
Any thoughts? If there is much savings, there would seem to be a more widespread market for it in home HVAC. Run your summer cooling on low speed constantly and save $$ ?? As noted my kitchen fridge used inverter technology but wasn’t any more efficient. Then the VFD blew and I found it not worth repair.
One can read more about how it works, but simply stated they use variable speed compressors and fans together with controls to achieve energy savings. There is more detail offered in an HPAC article here. Rectify the incoming AC voltage, invert it to 3 phase variable frequency and you have continuously variable compressors and fans that claim to save energy like a variable speed or two-speed pool pump achieves. I even had a recent refrigerator using the technology – but it averaged similar efficiency to the 15 year old fridge I have in my garage.
Still, we all know we get great energy savings from the variable speed and two speed pool pumps. Since the pumps use far more energy at the higher speeds we save substantially even if we run the pumps for far longer periods, even 7x24 at lower speed saves substantially. For example I save about $40/month running my 2 speed on low for 11 hours/day, versus the old 1 speed at 8 hours. All that is fine and dandy, and so obvious that local governments often mandate use of two-speed or VS pumps when replacing a pool pump.
So, can you get that kind of savings on the pool heaters that consume tons of energy? Or even on heat pumps used for residential HVAC? We might think so, given the continuously variable speed compressor (and evap fans, condenser fans, etc) running on lower speeds. But pool water pumps are not prone to massive efficiency variations based on weather – i.e. ambient air temperature and humidity, whereas heat pumps are dramatically affected by air temp, humidity, etc.
Some or all of these newer inverter technology heat pumps offer control in two modes: “Turbo” aka Maxx” heating mode, and “Silent” aka “Efficient” mode. One provider claims you use max mode to get the pool to temperature, then run the heater more constantly at the far lower speed to maintain temperature. At some point, of course heat losses limit the extent of that ability, but we get the crux of the claim. Is it more efficient overall, even if the heat pump is far less efficient running during the cooler nights? Even most COP ratings reflect the lower COP running at lower temps, often half the COP at 50F vs 80F. But if it used less than half the energy doing so, it might still net out to be more efficient.
Does it net out savings? If anyone has one, I suggest a simple test, perhaps in a more reasonable climate (not 40F) wherein daytime temps rise to 75 or 80F, and nightly they dip to 50’s. Select a 6 day interval. First get the pool to desired swim temp, eg 85. Run for 3 days in max mode, heating as we might usually do, for 6-8 hours per day or whatever it takes to recover the nighttime losses to get back to the desired temp of 85. Record total pool heater energy consumed. Repeat the test over the next 3 days running the heater (and pump) 7x24 or as needed in silent / slow heat mode. Record energy consumed and compare. Best to leave the extra pump run time & energy out of it for now, but cannot ignore it totally.
Any thoughts? If there is much savings, there would seem to be a more widespread market for it in home HVAC. Run your summer cooling on low speed constantly and save $$ ?? As noted my kitchen fridge used inverter technology but wasn’t any more efficient. Then the VFD blew and I found it not worth repair.
