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Commercial technician Eric Mele diagnoses improper dehumidification on a Seasons 4 system with reheat. He goes through the diagnostic process on the Seasons 4 RTU in the field.
Eric starts by tracing the wiring so that he can understand exactly how the system is wired. He checks his control board to see where all the wires are hooked up and how they’re configured. While checking the system, he notices that a three-way valve is closed, so he opens it. He feels water moving through the hot water coil, but he needs to be sure that the flow rate is correct.
When Eric finds the analog output for the modulating damper, he measures it with his voltmeter and reads 6.1 amps DC, which falls within the 1-10-volt throttling range.
The choice to open the valve affected the dew point, and the hot water coil became warmer. Eric wonders if the system didn’t have enough water flow to retain the heat in the water until he opened the valve. He also notices that the “Compressor 1” switch has been set to “Module Reset,” which seems odd. We can verify if that is correct or incorrect by checking the manual. Compressor 1 also plays a role in dehumidification. Only two steps of cooling are on at the moment, too.
The dew point comes back up, and the supply temperature is a bit high. However, the AHU status is in “Reclaim Cool Dehumidify.” When Eric attempts to change the Compressor 1 switch, it flips back to “Module Reset.”
Eric checks out the discharge and notices that the hot water reclaim is using up all of his discharge gas. So, none of the discharge gas is going to the air handler!
When Eric returns to the control boards, he notices that the dew point is nearly back down to normal, and the DC voltage on the valve continues to drop but is still in range. So, the valve is trying to open a little more. After reviewing the dew points over the past few days, Eric becomes more confident that the system is not getting enough hot water from the rack.
The discharge gas going into the heat exchanger is extremely hot, but the pipe leading out of the heat exchanger is cool enough to touch for a long period of time without Eric burning his hand or feeling uncomfortable.
When Eric returns to the control boards again, his voltmeter reads 2 VDC at the analog output, meaning that the valve is entirely open. All compressors are running, and we have a 5-degree temperature rise, which is optimal. So, it appears as though the issue was the closed three-way valve all along.
The three-way valve is a bypass valve. In this video, it is near the return side, so it is a mixing valve. (A valve on the supply side is called a diverting valve.) When that bypass valve was closed before Eric came, the system got very little water flow from the return pipe, as the water wasn’t mixing with the supply water. So, the valve did not properly respond to a call for dehumidification because the coil never got warm enough.
Since this application only has one coil, it must have a three-way valve. You can use some two-way valves on systems with multiple coils.
When Eric goes back to check the discharge after fixing the problem, the pipe leading out of the heat exchanger is finally very warm to the touch. The shaft seal is leaking, but that is easy enough to repair without an extensive diagnostic process.
When the coil is inactive, Eric’s voltmeter reads 10 VDC, which indicates that the valve is closed. However, dehumidification is active. It turns out that the dehumidification signal to the valve is flipped. Eric overrides the dehumidification to “inactive.”
Eric comes back and discovers that once the space dew point is satisfied, the controls display the outdoor air dew point. That indicates that the system has a flexible combiner that shows a new relevant measurement when one is satisfied. (In our case, the space dew point was satisfied, so the controls show the outdoor air dew point afterward.) The drive was also not initially programmed for the correct application.
Overall, Eric fixed the three-way valve (water flow to the hydronic loop), corrected the analog output setting to the valve, and communicated with Seasons 4 to configure the drive properly and confirm that the system was working properly.
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Hey thanks for watching in this video commercial technician, eric melle is diagnosing why a seasons 4 unit isn't dehumidifying properly with reheat. Many of you may have not seen large rooftop units like this, that utilize reheat. So this is a good introduction to this concept and also he's going through a real life diagnosis that he's troubleshooting as he goes so, hopefully you find it helpful big thanks to eric for being willing to shoot this video for us right now. I'm looking at this uh season, spore unit, four seasons, whatever it's called.

This is the hot water coil we're really not dehumidifying anywhere close to what we should be. We've got really no flow happening here. It seems like so we got to see what's going on with this motor. I don't know that this should be closed or not.

I don't think this should be closed. This is a three-way valve, so i just wanted to get an idea of the wiring, because i'm trying to trace it looks like it's hwac and 21c 121c and this red and white stripes that go back to the control section over there. That should be our bypass. Obviously, when i open that valve, you can feel the supply flow increase significantly, just by putting your hand on the pipe.

I know that's just bypassing through the valve, but as these pipes come over, we need to have the correct flow rate pick this valve. It looks like this valve is trying to find a new position now, so it might have been as simple as that, but i'm going to go through it more we'll come back to that in a moment. So those wires should come back to one of these boards, but it's not super clear where they're landed. That fan looks like these are cool dehumidifiers, so these are most likely all compressors you got damper.

I don't see that same label anywhere, so it might be landed somewhere else on this unit. I'm gon na have to do some searching because i don't see it cool relay high pressure, shut down, fan, airflow cool up, speed, cool damper. Let me track down exactly where this thing is because it should be getting a 1 to 10 volt dc signal, because it's a modulating damper, so i believe it should be landed on one of these boards. I'm just probably gon na have to do some trial and error here to see exactly where it's landed.

Now on the schematic, cpc, emerson, ad2-2 or a02-2 analog output 2-2, i'm guessing that would be input, input, input, input, input, input, lots of inputs yeah. I don't see that in a log-out analog output - maybe it's one of these! Let's see there, we go trying to do all this one-handed, sorry for the shaky foam and i'm trying to shake my meter leads loose. So we're going to get our meter out volts dc 6.1 volts dc, so we should be somewhere in the middle of the throttling range for that valve. Since i established more flow, i'm going to give it some time and see what happens to that coil temp.

In my store dew point which, if i go to my home screen and i go to air handlers - okay, well, we were at 72 before dew point with a set point of 51, and now we're really close to set point interesting. Also one thing i noticed on this and i got ta look into - is the digital compressor. One switch is switched to module reset and i'm not sure that's where it's supposed to be. I'm gon na have to pull out this book and uh figure that out.

Let's go: take a look at our hot water coil and see what's going on all right back inside, i hope you can hear me. An outlet is noticeably warm now, whereas before it was not and the supply is way warmer, i think the valve was trying and it looks like the valve is further this way than it was before. I don't know if that's either here nor there, but i don't think i had enough water flow to retain the heat in the water coming over to this unit. Put that back on, of course, but i know that compressor one helps dehumidification.

That's why it's a digital compressor, or at least that's what i've been led to believe from the manual this unit. So that is also in not the correct position which module reset doesn't seem like. That's where it should be, because everything else should be up. So it would be highly unlikely to me that that should be stuck in module reset, so we are going to get out the old book.

It's a nice thick one and locate that and looking at this again my dew point is back at 73, but i did have the door open to the unit. So, let's see, if that drops back down, we were close to set point before see. If our valve has changed position, it's moved a little bit, we'll see what that should be doing. It's not all the way at the higher low end of the range, so it doesn't seem to be wanting to really kick full dehumidification on.

I don't really know how many compressors i have on right now. It looks like stage one. That's fan, compressor, compressor, compressor, we're not in step three. If this is to be believed, supply temp is 66 return.

Air attempt at 67., okay, so we're doing some pretty decent reheat. If you look at the sensors right now we're pretty much neutral air and it says it's in heat mode, so that could be affecting our dew point anyway. Let me dig more into this uh manual. So we're dropping voltage to our actuator in there.

You could probably see it in the previous one, but i was fixated on where it's at heat, but it says ahu status, reclaim cool, dehumidify right. Our supply temp is pretty warm right now. I don't know if we're going to kick on that third step of cooling, so i've played with this switch. It springs back to module reset.

Maybe that's how it's supposed to be. I didn't find it in the book just yet it's a very informative book, but i have not been able to locate it. Yet it's not a good table of contents, so i will find it but i'll. Let it do its thing.

I wonder why the dew point dropped so quickly and back up so high the door's been closed for quite a while. Now, at least i hope i closed it. I have to check that i'm gon na try to talk real loud because if you thought the audio sucked before it's gon na be terrible now. So this is our discharge from a rack through the oil sep out and it goes two directions up to our water.

Heater reclaim over there and through our heat exchanger here, that's going through our pumping system to that air conditioner co2 rack by the way, kind of cool that pipe there is going into these water heaters back. Is the outlet back on that uninsulated pipe all the way down? Now, that's getting all of our refrigerant flow right now, 140.. So our water out is 140 to our actual real water heater. These are just uh heat, reclaim, so heat reclaim to the water is taking all of my discharge gas, and i got none to my air handler now.

I did have it before we're gon na have to go play with this thing and see why that is. That's our valve position now, even though we aren't getting super hot water out here. If we look at analog output, 2, 10 to 2 dc, so 2 volts dc is fully active, and when i keep checking this valve, i mean our dew point is really close to where it needs to be now. But our valve keeps opening from where i started.

Where i started was like six point, something or maybe even seven and we've been dropping dc voltage, so that valve is trying to come open, although i don't feel that it's very warm water. It's definitely like around my body temperature, it's not cold, so we must have enough heat in that water that it's been able to pull down to the proper dew point, so we're gon na. Let it run and uh see here, let's log this, what the heck! Okay! That's not helpful, okay viewpoint, so in three minutes it dropped. That's pretty crazy.

Let's go back and graph it okay, so we were up at like 60 and then whatever happened was about the 18th started, having some big swings and even earlier. Okay, so we'll have to see what's going on there. I think there might be an issue with uh getting enough hot water from the rack stuff is happening, less compressors. It sounds like keep an eye on that and see make sure the rack is controlling it right.

All right, so as i'm looking at this more, this goes to the hot water and it's coming back here and it's very hot. Now that's going here, 90s around and down to this pipe to my heat exchanger for my water and it's coming out of there super cold. It's not going through this valve straight back to that um splitting valve to the condensers we're just taking that much heat out of this water or out of that refrigerant. I should say everything appears to be working correctly here on the control end, i'm just not looking at the piping as thoroughly as i should be, because we do have a good supply of hot discharge gas to the heat exchanger, but that water is just sucking all That heat out i mean because this is discharge in.

I can't hold my hand on that line. It's way too hot, but this is the discharge gas coming out and i can hold my hand there all day. That's not even a problem we'll see if it was just a flow issue because of that valve being closed, go from there. Now we got way better loop temperature and our valve's liking it because it's gone to fully open and if you look now we got a five degree, temp rise, all the compressors are running having that bypass is important.

So if you're not familiar with how one of those three-way valves works, let me go over to it. So in this configuration the supply pipe is the bottom, and the valve is right there, basically on the tee. So when the valve is on the return side, it's called mixing when it's on supply, it's called diverting because diverting would completely avoid the coil with the flow and bypass either way it's not going to really go through because you've got a stopped valve there. It really doesn't matter as long as the air is pointing the right direction, a y strainer there most likely in there and a flow regulating valve on the outlet.

So what was happening was since this loop is so long and all that water in there, with the bypass, closed you're only getting the very little bit of flow. That goes through the valve itself. So that gives the water a really good chance to cool off, especially if we're in situations where we're not calling for dehumidification. And it was also causing the valve to incorrectly respond to the call for dehumidification, because it didn't have a warm coil to work with.

In general, so it was kind of driving it more more to the closed side and staging compressors down, but now, with this bypass open, we keep our good water flow all the time now. This is the only coil on this hydronic loop and the loop pump is constant volume, so you have to have a three-way valve for it to work properly. If you have multiple coils on a loop, you can have some of them have two-way valves, but the end of each run still has to be a three-way in order to keep the loop temperature from getting too uneven from wherever it's being sent from. So as further indication of how much heat we're putting into that hydronic loop for that air conditioner over there, this is the discharge line for our condensers.

I mean i could do this all day when i got here, though you could not all right now. I can't hold my hand on this anymore. Unfortunately, the shaft seal on this bump is leaking, so that's gon na have to be replaced. This looks like a completely closed loop, we'll have to refill it there, but we're good for now.

It's a small leak and see how warm this discharge line is now. Let me grab it over here, because i don't have to bend down. Let's see oh yeah, i can't barely hold that anymore. So, let's take a walk back over dehumidification active supply 1055 returning 68., our due temp went up a bit, but i checked: none of the case.

Doors are sweating. Our space temp sets are still reporting 76.. So now our coil is completely inactive. It says dehumidification is active.

It says it's in reclaim cool dehumidify. So are we just waiting on a control reference issue to catch up, because now we're delivering way hotter water to this unit, but also the coil is inactive. So, let's see what happens, i thought i was going to be able to get out of here. Settings set up, i'm not sure exactly where it is in here.

Humidification occupied 51.5 stage delay minimum space. The minification is 65. interesting. It says it's active though.

Let's see if it starts to react and open back up so come to find out. I thought i was doing good, but apparently the dehumidification signal to the valve was flipped. So that's interesting why it was uh reacting so erratically, because i was calling for dehumidification. The store came down to set point while my water was still cold but then came completely off of it, as you can see, we're back up to 55 dew point, but i flipped the analog output to the valve, and now my supply temp went from 55 to 85., so we'll see what this machine does if it brings in that other compressor there, space temp's still good.

So hopefully this pulls down this dew point. Just when i thought i was gon na be out of here, so i'm just testing it now i have it overridden to inactive, which is giving me closed and i'm going to override it. I'm going to take it out of override and it should come back in see my supply temps already dropping. So i'm back here it's another day.

I got chased off of the roof by severe thunderstorms and wasn't able to completely finish going through this unit. Pick up where i left off when we were looking at the space dew point how it was uh a discrepancy there, apparently because of how this unit's wired. Once the space dew point is satisfied, it will go to showing outdoor air dew point in the same location. But if you go to alt i and go to inputs, you'll be able to see your actual, because here you have your alt n for your analog input.

For your outside air dew point space dew point is in here somewhere sales dew point all right, analog input, one you see they're both on analog input, one so there's a device called a flexible, combiner and it'll show whatever one is like once the store. Dew point is: met it'll go to displaying this one, so that was kind of weirding me out, but i learned that by calling the manufacturer about it. Another issue we had that i couldn't resolve was the drive was not programmed for the correct application. The issues i did resolve were the were the three-way valve issues with it, analog, output being configured wrong and the valve being closed.

The drive is now set up properly. It's set just as one constant speed on this unit. That's their application once they get their airflow set. They want to leave the drive configured there and um.

I played with compressor 3b pressure control to get it to cut in, but that wasn't necessary because we were at setpoint in the store. I was just being thrown off by the by being ignorant to the fact that this dew point will change depending on which sensor it's referencing, and it doesn't really give you any warning so other than that this unit's running normally so just to go over it again. The issues we fixed where the water flow to the hydronic loop, the analog output setting to the valve, and then i talked with seasons four and luckily they had remote access and they were able to double check. What i did and confirm that it was set up properly and they were also able to configure the drive correctly for the application, which is something i really want to learn to do in the future.

I'm going to have to read the manual for this e2 controller figure out exactly how to do that, but other than that. This unit's running good, no issues 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.

26 thoughts on “Commercial hvac diagnosis – seasons 4 reheat issue”
  1. Avataaar/Circle Created with python_avatars Andrew Clark says:

    I do preventive maintenance on 4 seasons every now and then, keep in mind I'm only 6 months into this job. The idea of trouble shooting one of these things feels intimidating to say the least. But I have to say being in this job knowing nothing, I can still tell when certain people shouldn't be doing what they're doing, if you know you know

  2. Avataaar/Circle Created with python_avatars TechFive says:

    ……one day I'll be there lol. Are you in Ottawa ?

  3. Avataaar/Circle Created with python_avatars Scott Riddle says:

    that store looks like a publix supermarket.

  4. Avataaar/Circle Created with python_avatars brushben22 says:

    This guy is an absolute genius. I do commercial HVAC ( Specifically Trane ) and I respect these guys so much and would love to learn the concepts here. Great job and know that you are most def more advanced then the average tech

  5. Avataaar/Circle Created with python_avatars BlueBeast Gamer says:

    My question is that why the property management company didn't want or use the original installation hvac contractors/company to fix it, rather than just using any contractors to fix it for less when they have No ideas of what is going on!!!!

  6. Avataaar/Circle Created with python_avatars Emilio Lopez says:

    Good ole Erick Smelly

  7. Avataaar/Circle Created with python_avatars thomas cocker says:

    So the heat exchanger for the hot water system was using the heat from the condenser? I'm a little stunned that such a large unit would be constant volume. They could have made it variable based on space temp. Did it have demand control ventilation for CO2?

  8. Avataaar/Circle Created with python_avatars Tyson Rojas says:

    Good shit

  9. Avataaar/Circle Created with python_avatars sandeep satratey says:

    Have a good day, I have to ask some general questions which come in my mind during routine works, but I forget to ask and I think its a good platform to ask such type of questions.
    1. Why are condesing units always bigger than evaporators?
    2. Why does suction line of a compressor has larger diameter than discharge line? Service area Barrhaven??

  10. Avataaar/Circle Created with python_avatars Ruben Gonzalez says:

    easy fix.

  11. Avataaar/Circle Created with python_avatars Stuart Milne says:

    Lots of complex control situations. This technician who did the troubleshooting must be very experienced with high tech control systems.

  12. Avataaar/Circle Created with python_avatars Erik holmes says:

    my question is who did the start-up, and then shut off the AB channel of the three-way valve?

  13. Avataaar/Circle Created with python_avatars kronichaze says:

    i could see flashing in that sight glass

  14. Avataaar/Circle Created with python_avatars George Robles says:

    Seeing a panel like this brings back memories of me working at my dad's shop on the CNC machine ,for the automated wrapper or the powder coat line. Are you in Orleans ?

  15. Avataaar/Circle Created with python_avatars Ashton Lanier says:

    Man I used to work on these all the time at winn dixies Service area Kanata??

  16. Avataaar/Circle Created with python_avatars luis alejandro says:

    Very interesting!👍

  17. Avataaar/Circle Created with python_avatars Johnny SaltyAirCrabCake says:

    E2… Once Known all about it , its a Great way to control just about anything,, They still keep it simple at Emerson. I work mostly supermarkets,, we do a lot through E2

  18. Avataaar/Circle Created with python_avatars Waylon Wells says:

    👍 Service area Nepean??

  19. Avataaar/Circle Created with python_avatars Robert Miller says:

    The psychotic chart can drive you insane

  20. Avataaar/Circle Created with python_avatars andres perez says:

    Commercial , yes !!!

  21. Avataaar/Circle Created with python_avatars John Rose says:

    Thank you for the information. It is very difficult to watch constant changing and shaking is like watching a music video

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

    I like those calibrated hands🤣
    I use a cheap non contact thermometer but those hand sensors are pretty good.
    Stay safe.
    Retired (werk'n) keyboard super tech.
    Wear your safety glasses.

  23. Avataaar/Circle Created with python_avatars Toyin Orodare says:

    Thank you for the Update.
    Please do a training on Emerson Pro Act

  24. Avataaar/Circle Created with python_avatars Little Chingus & BIG Picture says:

    Thanks for posting and sharing your knowledge.

  25. Avataaar/Circle Created with python_avatars Universal Service Tech UST says:

    That’s a whole different monster, complicated as ever 😬

  26. Avataaar/Circle Created with python_avatars r j says:

    Thanks for imparting the knowledge guys. Very much appreciated 👍🏼

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