Commercial HVAC Diagnosis – Seasons 4 Reheat Issue

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 gonna have to [Music] 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 gonna 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 gotta 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 gonna 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 gonna try to talk real loud because if you thought the audio sucked before it's gonna 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 [Music] 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 gonna 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 gonna 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 [Music] 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 [Music] 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 gonna 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.

pexels photo 5877455

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 gonna 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 [Music] you

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