So video about heat pumps specifically: Defrost and Heat Pumps. How to test it How it works. We've done some similar videos in the past, but this one's just going to be better. Yeah, because it's because it's Bert and I right? We're uh, we're good at this kind of thing.

I think I Think we're probably the best at Defrost. Yeah, uh. Heat pumps. They have to operate basically in cooling mode in the middle of a heat pump cycle in order to melt the ice off.

That's essentially what we're doing. So you're reversing valve shifts. We're not going to get into reversing valves if you want to know about reversing valves. Oh hey, look, here's a quick clip of our 3D video of how reversing valves look.

Watch. This isn't this cool. Um, so sorry. what is he talking about? See, it's right there.

Um, no. So you know we have the reversing valve. Reversing about shifts between heat and cool. makes the outside coil either a condenser or an evaporator coil.

And in heating mode, it is an evaporator coil. and we're actually extracting heat out of the outside air. Isn't that right? Bird That's right. So that means that our coil has to be actually colder than the outside heat.

Like, significantly colder. And there's often moisture on the coil. because, uh, when when you when you drop the temperature that much below the outside air, you hit dew point, start condensing. Do So.

what happens to that moisture? If the coil temperature goes below 32 degrees, Brian turns into iceberg. That sounds like a problem. I Learned everything I knew from you. Yeah, and um, a little bit of frost is actually going to be normal.

This is one of the first things that comes up a lot is that people imagine that a heat pump is never going to have any frost on it. and that's not true. A little bit of frost is going to form and that comes down to how the Defrost control works. Which actually is pretty logical because let's say the outside air is oh I don't know.

20 degrees outside. Okay, so we got to get heat out of that outside air into the coil. which means the coil has to be below 20 degrees. So if every time the coil got below 32 degrees, it went into Defrost, it would be defrost all the time.

And of course that wouldn't work. So it's got to run the majority of the time in heat mode. And so that means that if it is running for however long, we'll say 90 minutes or whatever the case may be, it needs to still run in heat mode even if a little bit of frost is developing. We just don't want the entire coil to be clogged with a sheet of ice.

So from a diagnostic standpoint when you show up this is a lot of people ask like well, how do you troubleshoot you know Defrost on on heat pumps We're going to show you some things that you can do, but from a practical standpoint, if you walk up to a heat pump and it's cold outside side and you see just a little bit of frost on it and it's been running, that's a pretty good indication that it has been defrosting. otherwise it would be ice bound. If you walk up and you see a sheet of ice or you see you know ice coming out the side of it or it kind of like frost coming off the side, then that's an indication that the defrost has not been working it. There's really only a couple things to check, which is what we're going to cover here.

and I did get a lot of those calls on the last cold spells. Some people seeing, uh, these heat problems for the first time and it's like as soon as it goes on, ice starts forming like there's ice on the side. That sounds like a problem. Well, it's not a problem.

It was 30 degrees outside. Yeah, ice was supposed to start forming. Frost Frost Yeah, Frost it's supposed to form so you just see that on the coils and right after the metering device. and yeah, yeah, cool.

All right. So uh, what we're going to do now is we're going to go ahead and run it in heat mode. Um, and we're going to kind of show a basic defrost how to actually test a defrost. Now Obviously, right now we're inside of a warehouse we're also in Florida so it doesn't get as cold here and so we're going to have to actually trick the thing into thinking that it's time for it to go and defrost.

But along the way we're going to talk about kind of some of the different things that occur when it goes into defrost. So let's do it. Okay, so ah, Heat let's get that house to 90 degrees. We're running in heat mode, which means that we're actually going to be blowing cold air at the top of this rather than hot air because this is the evaporator coil, not the condenser.

and so if this coil were to get ice bound and run for long enough, then it should go into your defrost. Let's talk a little bit about how that works on this type of unit. This type of unit uses a thermostat not a thermistor and that's a big difference. So a lot of equipment like Trane for example, for years has used two thermistors that measure coil temperature and air temperature in order to kind of figure out a demand.

Defrost. A lot of equipment like this pane unit here uses a thermostat which is just looking at the temperature of we can call it the liquid line but in this case it's actually the temperature of the coil because it's on the feeder tubes that are coming out of your metering device. In this case our metering device is right here behind this chat lift connection. Uh and so we actually get flashing coming past the service valve.

And so if we were to measure the pressure here, we would actually be measuring a low pressure. We would actually be measuring something not not quite evaporator pressure because it still has to go through the distributor and it actually has some more pressure drop in the distributor inside. Yeah, but we're going to be measuring low pressure here. And so this is where the majority of our pressure drop occurs.

right here. And so our thermostat is measuring on the evaporator coil in this case, not the liquid line. And when it switches into cooling mode when it goes into a defrost, now, it's measuring on the liquid line. Right? Because it's running in heat mode, we are not energizing the reversing valve.

This is kind of the normal configuration, so that means we're going to have zero volts between o or orange and common on the defrost board. If we wanted to drive it into cooling mode, we would energize the orange or O terminal and that would energize the reversing valve putting it into cooling mode, which in fact is what the defrost board does when it initiates a defrost. Um, but in heat mode Oracle mode, you are good. It's still getting your Y call.

You still need the contactor to pull in? Yes, Absolutely Absolutely. The contactor needs to pull in needs to be pulled in whether it's heating or Cooling Between Y and common, we have 27 volts. That's what pulls in the contactor. So right now it's operating without any kind of need for a defrost.

right temperature. outside is warm enough, the coils aren't building up any. Frost This thing is gonna keep the house fine. We have no need for defrost.

Yeah, so now what we're going to do is show what happens when we go into a Defrost and this has two benefits. One is is to kind of show you on a video what actually causes it to go into a defrost, but also this is valid as a test to do on the equipment to see whether the defrost is actually in fact functioning on the equipment. So we're going to go through this test because there's always a couple different parts. We have the circuit board that can have an issue, We have whatever sensors or thermostats can potentially have an issue.

We're going to talk about how to test both of those types and we have potentially the connectors of the harnesses which are you know, going to be pretty rare that that would be an issue, but it can be in some cases. so we need to be able to know. is this thing under ideal circumstances going into a defrost and then we can diagnose and troubleshoot which is the issue so it's not. Why is it not in Defrost now? and how does it know when to go into the process? That's a really good point.

So in this particular unit, it's a 32 Degree initiated defrost based on a thermostat and a thermostat is just open or close. So it's a bi-metallic snap action disc. You have two different metals that are kind of layered on top of each other and when it gets to a certain temperature, it snaps and in this case it snaps closed. So under normal operating conditions, when the coil is not below 32 degrees, that's going to be open.

So if we were to test it right now, it should show open on that thermostat. All right, So we can see that it is Ol Meaning it is currently open, which is what we would expect because we can see this coil doesn't have any frost on it. This coil is definitely not below 32 degrees right now because the conditions in this space right and the board knows it's open because what it does is it sends voltage out on one side. 27 volts out.

so I don't know if you can see that on the meter. 27 volts out in it and if it doesn't get it back in, going out through the wiring and back in then it notice that the switch is open. Once the switch closes, then 24 volt makes it back into the board. So there's two different ways to test this and the one way that would be the most typical way in the case of a thermostat would be to just jump around the pins on the board and then speed up the operation in order to initiate a defrost.

The problem with that is that you're not actually testing the thermostat Now in the case of a thermostat, specifically, that sort of snap action thermostat. they really don't fail that often. They they don't tend to drift much. It very rarely is the thermostat now.

It could very easily be the wires though. and that happens a lot of times when maybe somebody's been in there and maybe the wire is laid across the discharge line and damaged the wire or something like that. So that can definitely happen because it's requiring that to close. So it's requiring.

So at the board, it's looking for those pins to be closed or connected in order for defrost to initiate. But like we've talked about before, that defrost doesn't initiate all at once. It's actually based on a timer. Yeah, so talk through that a little bit.

Okay, so there's a timer in here that you have the options to set controls on the board and the timer is basically that once the sensor has gone below 32 degrees and closes and we start developing frost on this the this preset timer here which we have 30 minutes, 60, Minutes, or 90 minutes. the compressor has to keep running for that amount of time and not satisfy inside the house not actually be able to keep up. Yeah, so once it's gone through that amount of time, then defrost is initiated. So uh, that that is on there Because we don't want our system coming in and out of Defrost a lot and not actually trying to heat the house.

we know on a cold day, ice buildup is normal. that sensor will almost immediately close. On a really cold day, there's going to be frost on that line and so it needs to at least attempt to satisfy the thermostat running in those conditions before it initiates. Defrost.

Yeah, again, it's gonna. It's based on runtime, so it's got to run that 90 minutes. And in this case of this particular unit, that thermostat has to be closed and the thermostat closes at around 32 degrees. On this particular model, I've actually seen some that are as low as like 28 degrees in the past.

This this one the if you look at the manual, it says 32 degrees and so it's got a close. and then when it goes into Defrost, it actually takes that thermostat getting all the way up to 65 degrees before it opens again and brings it back out of Defrost. Or uh, 10 minutes, whichever 10 minute timer in this case, which is just built right into the board. Whatever comes first, so it's not going to run longer than 10 minutes in Defrost.

Um, before it tries to come out of of Defrost even if that thermostat hasn't opened yet. Yeah, and that's very brand specific. We talk about the white Rogers universal control You can actually program that in and that's one of the really nice things. You can just select it's a typical carrier or it's typical train or typical Linux or whatever.

Or you can go in and actually set that up specifically for what you want in your Market which is kind of a nice thing. Yeah, so the speed up is there for a couple different things. You can actually bypass the short cycle delay that is five minutes or you can initiate your defrost when you you need to test the board. so you make a connection between these two points and uh, that will initiate a defrost on the system which bypasses this timer that we've been talking about.

That way, you don't have to wait your full 90 minutes in order to test the functionality of the board and make sure it goes through its whole defrost cycle. and again, it will only initiate that if you either jump her out to Defrost thermostat or if the defrost thermostat's below 32 degrees. All right. So from a sequence of operation standpoint, when you when the system goes into Defrost I just want to cover that quickly.

Most techs know this, but it's it's a good thing to cover. First thing that happens once it's gone through its appropriate amount of time. In this case, once the thermostat's close or the thermistors are saying hey, it's time for a defrost, what happens in the system? Okay, so the board then energizes our O terminal that the thermostat has dropped 24 volts from it, energizes it and that switches the reversing valve allowing the hot discharge gas to then Circle through this coil that has Frost buildup on it and in order to maximize that heat, it also shuts off the fan function through this relay. So that's the purpose of this relay.

This relay opens, the fan, shuts off. Now the heat that is circulating through that coil stays there. We don't have any cold air being pulled across that right? it's concentrated that ice starts melting so we have our fan shutting off. We have our reversing valve switching which usually is a pretty loud makes a lot of noise you will sometimes see Steam come pouring off of here and it goes through its defrost cycle trying to get the thermostat switch to open.

Which that'll happen around 65 degrees because in this case, the thermostat when it's in cooling mode now is actually on the liquid line. Yep, so it's no longer on the evaporative coil. In heating mode, it was mounted on the evaporative coil, so that's where 32 32 degrees would be expected in most sort of heating applications. But when it's in cooling mode now, it's the liquid line so that should heat up pretty quick.

As soon as that ice is gone, it should heat up pretty quick. As soon as if there's not a block of ice there. that Frost should melt off pretty quickly and that switch come up above 65 degrees and then the Defrost cycle will end and we'll switch back into heat mode. So another crucial thing that happens.

not just the fan shutting off and the reversing valve switching, but also the board energizes So it takes red and energizes our auxiliary backup heat wire here. and so if this is connected all the way back into your indoor system usually a heat kit, electric heat strips inside. they're now being energized because the customer's experiences they're running. Heat This thing goes into Defrost.

It switches into cool mode. now. we have cold air coming off of that coil and cold air blowing through the house. So the board during that process will energize electric heat to kind of take off some of that chill that's happening.

And so you have technically Heating and Cooling happening at the same time inside. So that's another function that happens. The the auxiliary gets energized, you will see some piece of equipment that will also have a quiet Mode function on the Defrost board. We actually just talked about this in a recent meeting about right here.

Yeah, and all that does is when you put it in quiet mode is it shuts the compressor off, then shifts, then turns back on. So that way it doesn't make quite as loud of a shift? Yeah. So one question that comes up a lot is why would we select one of the different times here? Why would we select 30 versus 60 versus 90.? And that just comes down to your market. So if you select 90 and the thing's still icing up because it has, um, excessive humidity.

Yeah, and it has that 10 minute limit too. So if it's only getting a 10 minute defrost and it's still having an issue. Wetter climates, Colder climates. So especially Coastal climates, you may find that you need to drive it down to those lower numbers when it's colder and wetter, and that lets not as much ice build up before it initiates that 10 minute beat.

Frost Yeah, Whereas in the climate we're in, it's typically not cold enough that we put it on 90 minutes because it's typically not a lot of ice is going to build up fast in the climate we're in. Yeah, this is why it's important to have Red actually coming into our board. It does power the logic of the board, but also this is how the board directs voltage where it needs to. So with red here, red does come out of our thermostat wire and if it's closed, it makes it back to the board.

And then red gets redirected on white and red gets redirected on orange in the defrost mode. So we do actually need our red and our common here for this board to power the logic and also to use red to redirect it. There are some systems that if you just don't, if you don't have red here, for some reason it's broken, it will still call Y It'll still bring in your contactor and the system will still run. but you won't have your your defrost operation.

So don't condemn a board without actually testing red to Common here, making sure you have your bolted. Okay, so we're operating in heat mode and we're going to go ahead and test our defrost cycle. and the way we're going to test this is by unhooking the fan and that will allow the coils to start freezing over to start frosting and our thermostat will then close. And that helps us not only test the function of the bore, but also the thermostat.

So let's go ahead and get started. I'll unhook my fan. We're running in heat mode right now, so I'm going to unhook my fan. So right now our switch is open.

Let me go ahead and demonstrate that switch is open so it's not the main, it's there's no demand now for defrost and as the system runs, what will happen is that the switch will close once the coil gets below 32 degrees. Okay, we're around 32 degrees now. Let's see. let's see how accurate this switch is.

Okay, so I do have a temperature clamp down there on the line where this sensor is and it's uh, that way I can actually kind of see what's happening. Thermostat switch on there. It's a piece of metal and that entire metal has to get to the same temperature as our coil. So right now our coil is at 25 degrees and the rest of that bi-metal right now is, um, slowly coming down to that temperature.

There you have it. our thermostat has closed, so now we have a closed path across here. Let me plug that back into the board and so this is where the timer begins on the board. So once that has closed, we're getting frost on our system and you can actually see that in there if you want a good shot of that.

So on this board a 30. I Have the timer set on 30 and then the speed up will reduce it down to like seven seconds. So I'm gonna go ahead and hold this on until I Hear the defrost engage. Okay, so our defrost is engaged.

I Can go ahead and plug our fan back in and you'll notice the fan is not running. So our relay has opened up not allowing the fan to run and then right now, the reversing valve has now become energized between O and C. Let's take a look at that. We now have 26 volts so we are running in cool mode and that hot discharge is circulating across that and as that thermostat switch gets hotter and hotter, eventually the switch is going to open and bring us out of defrost and or it'll run for 10 minutes.

And if that switch hasn't opened, it'll go ahead and come out of Defrost. 10 minutes is the maximum time for this board to run and defrost. Okay, so our coil temperature is still pretty low. once this has reached around and there we go.

we're starting to get warm. Now once it reaches above 65, that switch will then open again. The board comes out of defrost back into heat mode. Our fan is now running.

We don't have 24 volts on on. Orange Okay, so I just wanted to show one other thing it does is it red is now being directed onto our white, our auxiliary. So let me go ahead and show that between white and common, we now have 26 volts. So red is being redirected onto our auxiliary backup heat and that's going inside and powering our auxiliary heat.

All right. So here is where the Universal Heat Pump control comes in. because there are a lot of different residential controls. We talked about all these specific things for this particular unit that uses a thermostat, which is pretty common, but there are a lot of systems that use sensors, thermistors rather than thermostats, and a really big part of thermistors to kind of differentiate from.

What we talked about here is that you don't jumper out thermistors. Thermistors are always giving you a specific resistance for a specific temperature and that's really the best way to test those because that comes up a lot. It's like, well, how do I tell if a thermistor's is an issue or maybe the wires are an issue. But this is what's handy with thermistors.

And the fact that they come with this kit? that you actually get two new thermistors and you can see one of them here is designed to attach the coil and another one is an air sensor. Basically, when you're when you're testing a system like this, whether it's this particular one or any other one, you have to look at the sheet that tells you what the resistances are going to be for a specific temperature and then ohm them out. Now some people will say yeah, but like what if I don't know the exact temperature, you know you can always take a cup of ice water and kind of mix it up. Now again, if it's not distilled water, it won't be perfect.

You can put the thermistor inside that water and then you can test the resistance to see if it matches up with 32 degrees. Or you can just do like we're going to do here and just have it out in the same air that you have a reasonably reliable thermometer and just make sure that it's that it's close. So that's what we're going to do right now. So these are standard 10K thermistors And so even though the instructions in this particular kit don't come with them, you can find 10K thermistor charts really easily.

Yeah, really common. We're actually going to show one here in the video and so what you do is you just measure. Easiest way to do it is just measure the current ambient temperature, make sure that they're acclimated to ambient temperature they're not in the sun, they're not in your hand, that kind of thing, and then just make sure that they're measuring close in resistance. So we're going to go ahead and do that real quick.

here. There we go. measuring Ohms across. there.

you've got 99.7 so that's no. 9 700 Ohms at 77 degrees. And if we look at the chart, so 77 degrees is 9.9 which is exactly what we have there. So these thermistors.

Not only do we know that the thermistors are good, but we know the wires are good too. Yeah, so that's the that's a really good kind of typical way to test these and you just want it close like you could have a difference between you know one, uh, one or two degrees wouldn't be a big deal, especially especially again, like you just have to make sure that you're getting really good connection with your meter on the metal of the plug. Yeah, and in Ohm scale. And also keep in mind that when we're measuring a K Ohm scale, you have to add a thousand to it.

It's K Ohm is thousands of Ohms. So a really nice thing about this particular circuit board. Not only does it replace almost all the single stage heat pump controls out there currently in the HVAC Market, but it also kind of provides you with a really good training opportunity for your technicians. So if you understand this particular board you really understand it, then you're going to understand all the wide range of boards that it replaces, which is really kind of handy.

So when you go through the guide, you have the ability to configure this in so many different ways. So page four talks about how you do the configuration which we're going to show in a separate video. But on page five you have these: OEM and table one you have these: OEM quick setups. In this case, you could set it up as a carrier which is time and temperature.

Defrost which is what we call this type of defrost. Where you use the that thermostat. it automatically has programmed in the defrost cycle time. the standard 90 minutes short cycle time.

They're reversing about 10 minutes run time max amount of 10 minutes run time reversing valve power is zero. You can have a reversing valve shift delay if you want to put that in for quiet mode. So let's say you had a unit that didn't have quiet mode in it. You could actually put in this board to provide that benefit for clients who are really upset by the noise.

And then it even has the Defrost enable coil temperature this one's showing 30 degrees. You could set that a little higher if you wanted and then defrost terminate coil temperature of 65 degrees which is what we saw. So just by setting that one quick setup option of one, it automatically configures everything. But if you look at something like Lennox train ream that use Demand Defrost the two sensors set up.

You already have those two sensors built right into this kit so you can easily install those and in many cases going to demand Defrost from that time and temperature. Defrost actually has advantages because it's a little more efficient way of doing defrost. Yeah, so if you don't want to directly match the manufacturer and you want to kind of customize a specific system, it's Defrost you put this in and you can. You can take something like this and turn it into a Demand Defrost which is more efficient and you know more control over what actually happens there.

I Was just going to say another really great thing about it is that they have built-in anti-short cycle delay but they also have a brown out protection so you can enable a brownout protection if you have low voltage drop Dropout That happens in the board so it's just a more reliable Um protection for your compressor and equipment and at the same time like if you switch it out with a board like this, you now have a digital display. Yeah, so that digital display will actually give you error codes. It'll tell you what mode we're currently running in so it can be a helpful actually tool for Diagnostic And to see what's been happening at a house where you have intermittent issues they have a fault. Recall the last four faults you can pull up.

Yep This is the 47d01u843 heat pump single stage Universal Defrost control from Emerson White Rogers You can find it at a local distributor near you. 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.

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