thinking of switching to heat pump - looking for advice

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dleclair

Member
Jun 24, 2019
17
Ottawa, ON
Hi all,

My Raypak nat. gas heater bit it last summer due to heavy corrosion. I suspect its early death (~ 4-5 years) was due to pool chemistry and/or the electrical grounding. I'll make sure both of those are done better with the next appliance no matter what technology I choose to go with.

As we look ahead to spring I'm doing homework on what kind of heater to put in next. One option I'm considering is going with a heat pump, mostly to reduce my household carbon footprint and if I can get lower operating costs then bonus. We live in Eastern Ontario, Canada so one obvious consideration is the heat pump's ability to hold the desired water temperature in our cooler climate. One Raypak model I'm looking at has an AHRI rating of 50K BTUH @ 50 deg F. ambient (low-temp) going up to 80K BTUH @ 80 deg. F. so if I'm understanding it right, it will be roughly 1/3 as fast as my 150K BTU gas heater on 50 deg ambient days and roughly 1/2 as fast on warmer 80 deg days. We usually like to keep the pool water in the 88 deg - 90 deg range. Based on that, the heat pump will surely be slower than what we had before but I'm not seeing it as a show-stopper unless I'm missing something in how I'm looking at it.

The other consideration is that the heat pump is rated for an upper limit of 40 GPM flow rate. I'm finding it surprisingly difficult to find a simple spec or way of calculating what my current flow rate is with my pump and filter setup. My hunch is that my system is running closer to 70 GPM but again, I'm not sure. If anyone can help me figure out my current flow rate based on my system setup and ways to control it to bring it inline with the heater's flow rate specs that would be great.

Any other thoughts or considerations I should think about before making my choice?

I'm running a 21' round aboveground pool with SWG, Hayward cartridge filter, and Hayward Matrix pump.
 
Based on the couple of posts I've read about heat pumps vs gas is that they are not made for instantaneous heating like gas models are. From what I understand but don't have any experience with heating a pool, gas heaters can warm the water somewhat quickly, that may be a consideration if you don't keep the water heated 24/7. Operating costs may be a factor as well, here in NJ it is much cheaper to run gas vs electric.
 
dleclair said:
Hi all,

My Raypak nat. gas heater bit it last summer due to heavy corrosion. I suspect its early death (~ 4-5 years) was due to pool chemistry and/or the electrical grounding. I'll make sure both of those are done better with the next appliance no matter what technology I choose to go with.

As we look ahead to spring I'm doing homework on what kind of heater to put in next. One option I'm considering is going with a heat pump, mostly to reduce my household carbon footprint and if I can get lower operating costs then bonus. We live in Eastern Ontario, Canada so one obvious consideration is the heat pump's ability to hold the desired water temperature in our cooler climate. One Raypak model I'm looking at has an AHRI rating of 50K BTUH @ 50 deg F. ambient (low-temp) going up to 80K BTUH @ 80 deg. F. so if I'm understanding it right, it will be roughly 1/3 as fast as my 150K BTU gas heater on 50 deg ambient days and roughly 1/2 as fast on warmer 80 deg days. We usually like to keep the pool water in the 88 deg - 90 deg range. Based on that, the heat pump will surely be slower than what we had before but I'm not seeing it as a show-stopper unless I'm missing something in how I'm looking at it.

The other consideration is that the heat pump is rated for an upper limit of 40 GPM flow rate. I'm finding it surprisingly difficult to find a simple spec or way of calculating what my current flow rate is with my pump and filter setup. My hunch is that my system is running closer to 70 GPM but again, I'm not sure. If anyone can help me figure out my current flow rate based on my system setup and ways to control it to bring it inline with the heater's flow rate specs that would be great.

Any other thoughts or considerations I should think about before making my choice?

I'm running a 21' round aboveground pool with SWG, Hayward cartridge filter, and Hayward Matrix pump.
Click to expand...

What do you do now? Do you heat your water to a certain temp (88-90F - wow) and keep it there all season, or do you let it drop down and then heat it only when you want to swim?

This is a site where you can run the number on how many BTUs it takes to heat up various sizes of pools given the air vs. water temp. - Swimming Pool Heaters

You can run some comparisons and see if they results are acceptable to you.
 
phonedave said:
What do you do now? Do you heat your water to a certain temp (88-90F - wow) and keep it there all season, or do you let it drop down and then heat it only when you want to swim?

This is a site where you can run the number on how many BTUs it takes to heat up various sizes of pools given the air vs. water temp. - Swimming Pool Heaters

You can run some comparisons and see if they results are acceptable to you.
Click to expand...
For the peak season (mid-June to late-Aug) we hold it more often than cycle it up and down. Outside of the peak season we cycle it more - higher on weekends, lower on weekdays. Thanks for the link. I’ll check it out.
 
I see you are in Ontario - I would not recommend a heat pump for anybody in the north. Heat pumps work best and are most efficient when the ambient temperature is above 70 F. My first pool was in Michigan, and a heat pump will struggle to get you anywhere near the temps you want for swimming. I was also in Georgia for 10 years, and I had a heat pump there - it struggled in late spring, early fall to keep up. It may work from late June through August, but that's it. You need a gas heater where you are.
 
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Heat pumps excel at warming an already warm pool, when the ambient air temps are also warm and preferably humid.

Gas pumps excel at overcoming a larger temperature difference, or for heating quickly with up to 3X the BTUs.

Plenty of things skew the principle. PV solar for example on the house may erase most of the usage costs. Or it might be too expensive to run gas lines to the location. Or if NG isn't available and propane is ridiculously expensive in that area. But in those times, folks feel better about the HPs limitations.
 
I'm in Mi, Detroit Metro area. I have a heat pump and it's great.
There is a couple ways to use them, most common would be have your pump timer shut off at night and turn on during the day. Then your heat pump will only run during the day when it is most efficient. Or if you are not using the pool that much, say only on the weekends shut the heater off and turn it on a day or 2 before you use it. You can heat the pool in a day during summer, gets a bit tougher in fall. We keep it pretty close to a constant 80*.

Mine is a Aquacal Tropical T90, 96k btu so pretty big. As far too much pump pressure that is not a concern because you will be putting in a 1 way bypass valve at the heat pump. This will tie the heater intake into the heater return and any extra pressure opens that valve releasing the extra pressure.

Additional info on heat pumps. I run one to heat and cool a 1000sq ft garage. Its an older one and is rated to work down to 5*, it definitely works decent in anything above single digits. Newer top dog ones work to -15*
 
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I lived in MI for 48 years. I don't see any way a 96k BTU heater (by the way, that's actually pretty small) can keep a pool like that much warmer than 80 and that would be running all day long. Average temp in MI at night, even in July is not much more than 60. A 96K BTU heater would have to run about 10 hours to get it back up to 80. And the pool would be much colder than 80 all day while getting it back to 60. Once it's at 80, the pool might only drop to 70 overnight, then you're looking at min 5 hours run time to get it back to 80. I keep my pool at 89 - this would never work. In MI, I had a 400K BTU gas heater for a 42K gallon pool, and it had to run quite a bit to maintain temp.
 
Two questions -

1. Do you already have the electrical service close to your equipment capable of handling a heat pump? Most need their own dedicated, 50amp 240V breaker.

2. Do you plan to use a pool cover when not swimming and during overnight hours? Pools lose most of their heat through evaporative cooling. If you don’t cover it, the heater will struggle and you’ll lose a lot of the heat you added overnight.
 

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And another very important question - who will service this heat pump when it breaks? It is the experience of some here on TFP that many pool service shops are happy to sell you a heat pump and install but they know next to nothing about diagnosing and fixing them. Most residential HVAC companies won’t touch pool equipment. That leaves you at the mercy of tracking down someone capable of dealing with problems and the equipment manufacturers are often very little help in that regard.
 
My HP efficiency dropped off a cliff at about 70 degrees and I quickly lost what I gained, or more than i gained at times. Yes it technically worked but It didn't extend the season by much and I often had to keep it running just in case things warmed up in a week or two. I wouldn't have been able to overcome the temp differences if I lost the warmer water.

It stung to pay for the HP to run constantly with lackluster results. But again, if I was looking to blow through PV solar gains instead of selling them back at pennies on the dollar, it would have stung alot less both financially and in principle. Or if propane was outrageous, I'd be happy I was only spending several hundred with the HP.
 
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PoolBrews said:
I lived in MI for 48 years. I don't see any way a 96k BTU heater (by the way, that's actually pretty small) can keep a pool like that much warmer than 80 and that would be running all day long. Average temp in MI at night, even in July is not much more than 60. A 96K BTU heater would have to run about 10 hours to get it back up to 80. And the pool would be much colder than 80 all day while getting it back to 60. Once it's at 80, the pool might only drop to 70 overnight, then you're looking at min 5 hours run time to get it back to 80. I keep my pool at 89 - this would never work. In MI, I had a 400K BTU gas heater for a 42K gallon pool, and it had to run quite a bit to maintain temp.
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96k is small? I keep my pool at 90* too. I can get 90* in October with the heatpump. It also only costs me less than $50 a month to operate.

I'm not sure where you get your calculations from but I'm actually using a heat pump in Michigan and it is way better then you are saying. This is the AGP section these pool average 12000-22000 gallons. You are mentioning 42k gallons so maybe that's the issue. My pool 15000 gallons.

I also have a 36k heatpump for my 1000 Sq ft garage and that heats until single digits and I've never seen it too hot to AC.
 
Trick said:
I also have a 36k heatpump for my 1000 Sq ft garage and that heats until single digits and I've never seen it too hot to AC.
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Not really a fair comparison. Air-sourced heat pumps heating a volume of air operate very differently than air-sourced heat pumps heating water. For one thing, water has 6X the heat capacity of dry air. So a heat pump heating water will have to deliver roughly 6X the output to get the same temperature rise for a given mass. It’s not uncommon to see pool heat pump compressors turn into blocks of ice when trying to keep a large volume of water warm. At that point it’s very inefficient.
 
Trick said:
96k is small? I keep my pool at 90* too. I can get 90* in October with the heatpump. It also only costs me less than $50 a month to operate.

I'm not sure where you get your calculations from but I'm actually using a heat pump in Michigan and it is way better then you are saying. This is the AGP section these pool average 12000-22000 gallons. You are mentioning 42k gallons so maybe that's the issue. My pool 15000 gallons.

I also have a 36k heatpump for my 1000 Sq ft garage and that heats until single digits and I've never seen it too hot to AC.
Click to expand...
I'm only relating my real life experience with heat pumps. In Georgia, I had a 140K heat pump and an in ground 18K gallon pool, and couldn't hit 90 in October without running the heat pump for a significant amount of time (most of the day, 10-12 hours). By the time the temp would get to where we would actually get in, the day was gone. The temp drops at night means the heater had to run every single day, and I used a solar cover at night. I had to close the pool in December through March because the heater couldn't keep up.

Night temps in Michigan are far worse than Georgia. Your experience is far outside the norm, and I don't want folks getting the wrong expectations and wasting $$$ on an iffy solution.

In addition to the size of the heat pump, the temps late in the season in Michigan will decrease the efficiency of the heat pump significantly to the point where it doesn't matter what size heat pump you have, it may not be able to attain the desired temp in the pool.
 
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