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Bert teaches the Kalos techs a bit more about pool heat pumps. He expands upon the pool heat pump components that we don’t see on A/C systems, especially heat exchangers.
Heat pump pool heaters operate on a refrigeration circuit, just like A/C units. They work like normal A/C heat pumps running in heat mode. Inside your pool heater, you have a heat exchanger with water coming in and going out. There are also two copper lines going in.
Superheated, cool refrigerant gas goes into the compressor. After it’s compressed, it goes through the heat exchanger and heats the water. The heat rejection to the water causes the refrigerant to desuperheat and liquefy. Then, it goes through the liquid line (½”, not ⅜”) and into the TXV. After the TXV, the cool liquid refrigerant goes into the evaporator, where the cycle continues afterward.
As with A/C systems, TXV replacement is a common issue on pool heat pumps.
Every pool heater has a heat exchanger. Some heat exchangers have water hookups going in and out with refrigerant lines running within. Regardless of the form, heat exchangers all have the same function: to reject heat to the water and act as a condensing unit.
Heat exchangers can crack and leak water. In those cases, you can expect the culprit to be severe versions of water flow issues, high pressure, the safeties malfunctioning, or high-temperature conditions. Water can only get into the copper lines through a heat exchanger crack (with blown-out copper). However, heat exchangers are pretty durable, so cracks are rare problems.
When heat exchanger cracks do happen, the repair project is usually very labor-intensive. You may be better off quoting for the entire heater. If you quote only the heat exchanger, you will want to test the entire system; you will want to find out what happened to cause the heat exchanger to crack.
Pool heaters also have thermostats, thermostat probes, water temperature, and pressure switches. Water pressure switches are very similar to float switches in their wiring; if 24v comes in and 24v goes out, the heater will know that it’s okay to run. If there is a flow issue that prevents the heater from running, you will see an error code like LO or FLO. Some older heaters may have float switches and pressure switches in the same circuit, and you can figure out if something’s wrong because the pressure switch can open and kill the power. You can ohm the components out with the power off. Clogged filters can also trip pressure switches. (You will also want to install pressure switches after the filter.)
You’ll likely be replacing low and high-pressure switches more often on pool heat pumps than normal A/C heat pumps. It’s also poor practice to quote a switch without finding the issue that caused it to open. R-22 switches and R-410A switches have different pressure limits, so you will want to make sure you read the pressure ratings on the switches.
When you have a pressure issue on a pool heater, it should NOT be your first instinct to add refrigerant right away. Pressure can fluctuate a lot with temperature differences between the pool and spa, and pool heaters tend to be sensitive to refrigerant charge levels. Try to find out why your pressures are high or low; if your pool temperature is cool but you have high pressures, then the pool heater might be overcharged.
A heater will have two thermostats: one for water, one for defrost. The only defrost function is to shut the compressor down but leave the fan on when enough ice builds up. Defrosts tend to be quite long and inefficient, and pool heat pumps don’t generally work very well in ambient conditions below 50 degrees Fahrenheit.
If you need to check your water temperature split, keep in mind that the bottom of the pool is cooler than the surface. You’ll want to read the temperature as close to the base of the pool as possible.
Also, be sure to check the pump timers. The timers may not be running long enough to heat the pool sufficiently.
Read all the tech tips, take the quizzes, and find our handy calculators at
Learn more about the 2022 HVACR Training Symposium at

Okay, so nathan all wrote this helpful, full heater service manual - okay, so just you can print this out. If you want it's fine, it's only a few pages. It's actually something that you can read in like 20 minutes just read through and then make a mental note of the different topics. So when you run into something like that on a call you know you can.

Oh, i actually that's in that service manual and so when you're doing service or install there's some things in here. That could both be helpful for that keep this source. It helped me a lot when i was going through pool heaters. I would just simply scroll through and i was trying to figure out - maybe a specific thing.

We got limit switches here. I was trying to figure out something with the limit switches high limit switches. It talks about them how you're going to find them failed and how to diagnose them and what type of heater they're on and there's even pictures so props to nathan. For writing that everybody make sure you use that at least read through it.

So you know what's in there and then, if i get a call about something that's really specifically on here, then i will yell at you about that. Okay, all right so uh heat pump, pool heaters here is a nice beautiful diagram of the refrigerant circuit. So is there anybody that doesn't understand the refrigerant circuit or the pool heater in here heat pump, pool heater great, we'll, go really quick on this, then that's well. I figure because i mean it's - it's very, very similar to an ac, so you got all your components that you would with the ac.

Where is the condenser wrong? Nope the condenser? What is the function of the condenser in a refrigerant circuit? It rejects heat condenses what refrigerant yep it is on the left so on a pool heater we're using water to condense our refrigerant, so our outdoor condenser fan is on top of our evaporator, which is the coils outside and so basically you're an ac heat pump running In heat mode, is your pool heater and so inside your pool, heater you're, going to have a heat exchanger that has water coming in water going out and both copper line, two copper lines going in. So what happens here is that from our compressor, gas comes in superheated cool gas, low pressure gets smashed, it's really hot goes into the heat exchanger, and then it transfers the heat into the water, and then it comes out as cooled liquid refrigerant and comes into our Txv, so we are going to have pretty much every time. Very rarely are you going to see a piston you're going to have a txv on your pool, heaters pool heater txv replacement is one of your most common projects on there and um. They can be tricky.

They're, like a lot larger and connection points, are really close to the txv. You got to keep it safe, but if you're ever quoting a project with refrigerant on your pool heaters just a side note your liquid line. Dryer is a half inch. It's not 3.

8. It's not your typical liquid line size. The liquid line is larger. It's a half inch.

So when whoever is ordering or doing the project needs to know, like you tell tim or whoever you're having ordering parts, also order a half inch liquid line dryer for this project, because we don't always have one just sitting at our shop, they're kind of an odd Size, so just keep that in mind, that's off topic, but keep that in mind. Let's see this is a heat exchanger, so every pool system, whether it's gas or refrigerant, will have some system like this and that's what you see here doing the condensing job right. So some system, where you can see you, have a water hookup coming in water, hookup going out and your refrigerant lines which in here they just circle through the middle of that water, pipe as you can see on here. So this is another common style.

This is a heat exchanger, and so this is basically the only element that's going to be different than your typical ac system. This is your outdoor unit function on an ac sense of the condenser and then all the other components in there electrically are going to be pretty much the same. Some issues, common issues, common problems with heat exchangers. You can have them crack where they will actually leak.

Water, so that usually means something pretty severe happened to the heater, like you had a high temperature situations, your safeties weren't working properly, some sort of water flow issue, and you got up to a really high pressure inside the heat exchanger and it actually cracked, the copper And in that blowout scenario, you knocked a hole somewhere in your heat exchanger. They are pretty tough. That is a rare problem. But if you come up to a system and you go to hook up your gauges and water starts spilling out of the lines the only way water could have gotten into the copper is inside of this guy.

You have your copper lines going in, so you immediately know you have a heat exchanger that has blown out a copper line has blown outside the heat exchanger. It's got to be replaced, so i mean, unless you have a pretty new heater, that is likely under warranty. Heat exchanger is a pretty extensive project. You got more work than a compressor, so you have two lines like you would on a compressor, but you also have water lines and then to get it in and out you have to take apart that whole heater.

Sometimes you have to move a compressor to try to get the project done so you're doing a compressor and a heat exchanger, so the labor just suddenly becomes a lot, maybe more than replacing the whole pool heater or close enough that at least you have that conversation. Where it's like, we can do this, but you know you're almost playing the price of a whole new heater, not a good option for you here and for property managers you're going to run into a lot of older heaters. If it's a heat, exchanger blowout, we just quote a heater: we don't want to be trying to do a really expensive project for a property manager that can't see how poorly how how his heater is in such poor condition, and he shouldn't be making that decision. Anyway.

You don't always have to give that option, use your judgment on that, but when you do have a newer heater, i've done several of these for aqua cal. The other thing that can happen with heat exchangers is they will sometimes have the temperature probes go straight into there or the water pressure hookup come out of there and both of those have ports and areas that are more sensitive to water cracking. So you get a call out that my pool heater is leaking water, oftentimes uh where's that leak gon na be be found on your heater. Anybody close connection, yep uh, what yeah the water, sensors, yeah, your water pressure, switches, connection points, and sometimes that's right.

In the heat exchanger and you can have an easy repair, and sometimes the heat exchanger has cracked in that area, because that's a weak point, that's a point that it actually goes into the water system. Anytime, a heat exchanger has cracked you need to think about. This happened for a reason, something's wrong here: something's wrong with my water flow something's wrong with my safeties, not turning off my heater. Maybe my water pressure switch is failed, so my heater keeps trying to run at night after the pump shuts off i'm going.

To quote a heat exchanger, but i'm going to put in the notes - and i'm going to have a conversation with the customer that, after we put this new element in, we can test this and likely there's something that caused this failure that we're going to run into That we need to diagnose so you've prepared the customer and also the returning technician, doesn't just replace a part and not pay attention to what might have caused that like testing when they shut off the pump, does the heater actually shut off, replace the part leave the Customer with the same problem, eventually, the new part is going to have the same same issue. Some other elements that you have on your pool heater are your thermostats thermostat probes, water temperature and your pressure switch. I just have a little kit in my van that i carry the extra parts for my pool heaters. Here's a water pressure switch so you're going to see some version of this on your pool, heater every pool heater has one and it's just wire in wire out.

Like a float switch, and so the design function is that, if 24 volts comes in and 24 volts comes back out, the heater's gon na know that it's okay to run. So what will happen is if you have enough water pressure, it'll push up into here and actually close the connection between here and here and it's that simple and then your anytime, the pump runs. There should be enough pressure to close that connection. Your heater should be able to run if not your heater is going to say something like lo.

If it's a gas heater or maybe flow f, l o like for water flow, we got a flow issue or it could be one of the older style heaters that have the rheostats. So there's no digital display anywhere on that and they have the float, switch pressure switches, all tied, usually into the same circuit, and it just kills power. So you just go through and you're owning out pressure switch pressure, switch water pressure, switch and you're trying to figure out. Where do i have an open circuit on that style, but that's all it does.

It just opens a circuit somewhere. Once you have an open, though, if you're testing it with a flow off or not, so you wouldn't test it with the flow off. You could test it with the power off right, so you can omen out with the power off, but you would want to test your water pressure switch by turning your pump on making sure your pump's actually running yeah yeah. So the other thing that can set off the water pressure switch is a clogged filter.

Your pool heater should always be installed after the filter, so if the filter is clogged or if anything's going through the water, it's been caught by the filter before it goes through. Your pool heater, but it should always be installed after the filter, so in that situation, filter gets clogged. Now the pressure coming out of the filter is really low and your pool heater is going to be going off on low low flow. That's usually a pretty extreme filter issue a lot of times.

What will happen? Is you actually have a high pressure error before a low flow when you have a clog filter, and why would you have high pressure, like a high high pressure error code, refrigerant error code? If you have a clogged filter yep and what why what's the connection there, yeah water cools the refrigerant, so you don't have that good water flow you're going to go up on high pressure. You do find that you're going to be replacing low pressure. High pressure switches. More commonly on pool heaters than i would say on acs because there are just a lot more situations where they're going out on on their pressure switches.

So those pressure switches are being used a lot more often anytime. You actually show up, and your issue is a failed pressure, switch like a failed high pressure, switch again, stop and realize. I can't just replace the switch or quote the switch until i find out what was causing that switch to open so many times that eventually it just stayed open and that'll. Be the situation quick note on that when you're doing a pressure switch, i have a couple in here this one says it opens at 600 psi and then once the pressure comes down to around 475, so they're listed right on here, it'll close.

What type of refrigerant would that be for 410 yep, and then i have another one over here that actually opens at 4 25 and then it'll close again at 3 25. So that would be r22. You don't put the r22 on the 410a system they're both labeled high pressure switch, but whenever you're installing a switch, especially if it's a truck stock, look at the labels make sure. And then this is a low pressure, switch make sure that you're actually reading those pressures because you install r22 switch and it opens at four something there's going to be situations where they're going to be running the spa that water temperature is going to be 102 coming Into that pool heater that pool heater is trying to get rid of heat into 102 degree.

Water you're going to have really high pressure couple notes on high and low pressure issues, because the water temperature changes so dramatically from maybe 60 degree pool to 102 spa you're going to see a huge range in pressures. Don't just jump to adding refrigerant to pull heaters. Pull heaters can be pretty sensitive in charge. It's just a little bit smaller of a refrigerant circuit, a lot of times, not all pool heaters, but some of them are smaller, and so you find really high pressure.

Try to figure out. Why is my pool hot? Is my incoming water hot and is it pretty hot outside? That's why i have a really high pressure. Do i have uh 400 psi on my discharge line, but my pool temperature is 72, then i'm probably overcharged. Now i need to quote the customer to remove the refrigerant and weigh it back in, so we actually have the correct amount of charge for this pool heater and so um same situation.

You're going to run into a lot of extreme temperatures where your water temperature is really low. Outdoor temperature is really low, you're going to have very low pressures. You can't just show up and start adding refrigerant get familiar with the concept that low water pressure. I mean low water temperature, low outdoor temperature, you're going to see really extreme low pressure and that's why they all have some sort of defrost mechanism in them.

So a um, a heater is going to have typically two thermostats one for water, one for defrost, connected to the board connected to the board, and it's going to have on the defrost. The only function is it shuts. Your fan off, i'm sorry, shut your compressor off and just leaves the fan on. So you know like on a heat pump system.

It'll actually reverse the refrigerant, so you got hot gas flowing through the coils and you can melt your ice real quickly. But if it's 45 degrees outside you're trying to run a heat pump already, your saturation is going to be below freezing. So as soon as it starts running, it's going to start freezing once the ice builds up to a certain point. Your defrost sensor is going to go off your compressor shuts out.

Your fan just keeps spinning, but it's 45 degrees outside that ice doesn't melt super fast. It's going to be in defrost for a really long time that ice melts system comes back on, immediately, starts freezing again and that's why a lot of times you're going to have to be able to tell customers under 50 degrees, this thing's almost useless, and that's just A realistic fact if your pool is already warm, it has a heat blanket across it to hold in the heat and it's you know: 50 degrees outside yeah, you're, probably going to be able to switch over into spa and slowly heat up your spa, but you're not Going to be able to change the pool temperature that much in that kind of situation, so you'll run into that, and just be aware of that be able to tell customers that, even in installing you guys are going to find that you're put in a new heater. You call the customer new heaters in okay turn it on guests are coming in tomorrow. We need that pool heated.

It's like well, it's 42 degrees right now and i'll turn. This heater on it'll run for like four hours until your pump timer shuts off and then in the morning. That'll come back on, but it's probably going to be two days before your pool gets warm like this kind of weather. They need to know they just got a brand new heater set, the expectation straight.

You know just because it's brand new doesn't mean it's not that it's gon na heat really fast as a heat pump on a cold day. So - and i think i mentioned before - but you this is what i use for testing the the water temperature difference. So if you're going to check your split, it's a water split, we're trying to change the temperature of the water, so you have uh. I just use this right here.

It comes with your meters, plug it into here and drop it in the water in the pool, and you know from swimming in a pool that the water on the bottom of that pool is a lot colder than on the surface. Try to get it as deep as you can and then you're, probably about two two degrees off from the very base where some of your water is going to be drawing your pool pulls in water from the base. And then you take your other. Your other piece - and you can just stick it straight into a jet somewhere when the pool heater is running so the pool here is running.

You should see a three degree difference typically depending upon weather outside. It could be like three to seven degree difference. If you have great weather outside and it's picking up a lot of heat and your pool's colder, you're gon na see more of a extreme difference. Uh temperature split so but if you're getting a three degree difference.

You're gon na have full confidence that your heater is doing its job, even if it looks low in refrigerant, because it's a colder day or whatever you can have confidence to tell the customer that a lot of customers are just like three degrees. Are you kidding me? That's all it'll do yeah that that's that's design like that's all it'll do the only other thing i was going to say is check your pump timers. When customers are having problems heating up the pool, they might have a timer. That's only on for a few hours.

In the day - and so you can talk to them about it, we can run your pool pump timer longer and then you can actually heat so get your supplies. If you're a service truck for servicing full heaters, make sure you have your your uh pressure switches. Your flow switch, your temperature sensor, your saddleback, thanks for watching our video, if you enjoyed it and got something out of it, if you wouldn't mind hitting the thumbs up button to like the video subscribe to the channel and click, the notifications bell to be notified when New videos come out, hvac school is far more than a youtube channel. You can find out more by going to, which is our website and hub for all of our content, including tech tips, videos, podcasts and so much more.

You can also subscribe to the podcast on any podcast app of your choosing. You can also join our facebook group if you want to weigh in on the conversation yourself thanks again for watching you.

7 thoughts on “Pool heat pump kalos meeting w/ bert”
  1. Avataaar/Circle Created with python_avatars Everything HVACR says:

    Well done Bert! Keep up the good work 💪 Service area Nepean??

  2. Avataaar/Circle Created with python_avatars H-H Hidalgo says:

    You guys are good at explaining everything ill start soon my GED to become an HVAC technician

  3. Avataaar/Circle Created with python_avatars ET Lawson says:

    How is low pressure gas coming out of the compressor?

  4. Avataaar/Circle Created with python_avatars Andrew Callaway says:

    Thank you for the info. The company that I do service work for just to picked up aquacal warranty work, and I have just started dabbling my way into pool heaters. This is definitely an area where I just don't know what I don't know! Good stuff.

  5. Avataaar/Circle Created with python_avatars Eassyheat/ Cooling says:

    Anything extensive, it will be a quote for a new heater !
    Stay safe.
    Retired (werk'n)keyboard super tech. Wear your safety glasses!

  6. Avataaar/Circle Created with python_avatars Jay Duffy says:

    Good information. I am a service technician in the pool industry. I have installed a few heat pumps but have not had many opportunities to service or troubleshoot them. Thank you for thus information!

  7. Avataaar/Circle Created with python_avatars Christopher Smith says:

    Hope he's not emo this time 😄

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