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I am kind of stumped on this unit I am working on, so here goes. On some side work I am doing, a customer wanted me to check their system on their mobile home.
They said the last person to look at it, which was 2 years ago, said the compressor was bad in it. I said sure I'll take a look at it. You never know right?
Quick system rundown - old school green box Rheem 4 ton condensing unit, Intertherm AHU with 15kw, and a Nordyne 4-ton evap coil
So I had to hook the power back up to the condenser (they are running window units), bumped the contactor had a good compressor start. It was pulling around 11 amps but my gauges were reading 50 psi with no changes.
At first I was like "ah, bad valves" but then I thought, but it is pulling a decent amount of amps. Well I decided to check the servicing valves and they were completely closed. Opened them up and the pressure went up to almost 100 psi. Hit the contactor and liquid pressure started rising and suction started dropping to damn near vacuum.
I put almost 6 pounds of 407c in the system, got the pressure somewhat dialed in to 295 psi liquid (yes I know thats high) and about 57 suction with 6 degrees superheat (that puts the EVAP temperature at about 35 at that pressure). I recommended to them to clean both the indoor and outdoor coils because of the liquid pressure and the indoor coil being almost as bad. Oh, and my temperature split on the indoor unit was about 17-18 degrees. So it was cooling good and thought that's all was wrong with it, I said I would return with the necessary stuff to clean everything. Again, I am doing this on the side now in my little truck so I don't have everything on me all the time.
So I come back a couple of days later to clean the condenser and EVAP. Get them cleaned and the liquid pressure drops to 225 (MUCH better) and suction is still the same. Between 55-60 but now my suction line temperature is 29 degrees F!!!
I was thinking, "well what is going on here? Must be airflow" so I go inside and pop the air filter out (which is perfectly clean by the way) and I see the capillary tubes in ice but the rest of the EVAP is NOT iced up. (It just happens very slowly) I test my temperature split again and its sitting still around 17 degrees.
Something doesn't seem right so I check the blower wheel, blower motor capacitor, and which speed tap it's on. Blower wheel is really dirty, the capacitor is weak, but the blower speed is set to high.
So I come back and clean the blower wheel, one of the worst I have seen, and swap out for a new capacitor and I fixed a minor thermostat wiring issue. Pressures look the same, my temperature split looks the same (the customer did say though that he is feeling more air come out of the vents from the blower wheel cleaning) but the capillary tubes start to freeze within just a couple of minutes from startup.
So THEN I recommend to changed out the orifice ( I went from an .080 to an .081) and to change out the copper piece that screws on the distributor just incase the screen is dirty because there just might be a restriction in those two.
I did those two things today and I told them I wouldn't charge them for this if it didn't work.
Well.....it didn't work. The suction pressure stays at 52 psi with a suction line temperature of like 29 degrees. I even tried pulling refrigerant out of it and got the suction line temp to 42 degrees but my suction pressure was down to 45 psi. Even with those weird readings, it was still doing a 17 degree temperature split.
Some more back story with this unit, the indoor unit/coil was swapped out with a USED one and then after that (the "tech" they had working on it) said the compressor was bad (I know, someone screwing someone else over. Not the customer's fault because they don't know any better.) I told them that the equipment was used for a reason so there ain't now telling what is going on. The AHU does have a 4 ton blower in it, the evap coil is 4 tons and the condensing unit is 4 tons, I verified this for absolute certain today.
The only strange thing I notice about the freezing is that it starts at the very beginning of the capillary tubes, not the distributor itself and I have always seen that if there is a restriction at the fixed orifice the distributor AND capillary tubes freeze.
This system does not have a filter drier on it but I did pull a pretty good vacuum on it today so I don't THINK moisture is to blame.
So does this mean that there is the slightest of restrictions in the distributor itself? After everything I have tried on this thing I honestly don't know what else it could be. I am actually worried that I'm going to put a new EVAP in this unit and its going to do the same thing. I do not want these people the spend that kind of money to have the same damn issue and to be honest, I don't want to have to pay for it myself. I have never really come across a refrigeration issue as curious as this.
Again, I don't work for anyone anymore and I am doing this on my own. If I had the equipment I would take airflow measurements at the return and at each supply register. I do not have a manometer either, but 99 times out of a 100 though the temperature split would be abnormally high, not at 17 degrees. I also don't see any apparent way for the air to bypass the coil, it is in a mobile home. It feels like I am missing something.
I just thought of this but the only thing I didn't do (I didn't think of it because there was no filter drier) I guess I could try taking a liquid line temperature measurement at the condenser and then one before the orifice. That would tell me if there was a kink in the line somewhere but usually you would see high liquid line pressure though. sigh
If anyone has any ideas or questions please let me know, it would be greatly appreciated.
They said the last person to look at it, which was 2 years ago, said the compressor was bad in it. I said sure I'll take a look at it. You never know right?
Quick system rundown - old school green box Rheem 4 ton condensing unit, Intertherm AHU with 15kw, and a Nordyne 4-ton evap coil
So I had to hook the power back up to the condenser (they are running window units), bumped the contactor had a good compressor start. It was pulling around 11 amps but my gauges were reading 50 psi with no changes.
At first I was like "ah, bad valves" but then I thought, but it is pulling a decent amount of amps. Well I decided to check the servicing valves and they were completely closed. Opened them up and the pressure went up to almost 100 psi. Hit the contactor and liquid pressure started rising and suction started dropping to damn near vacuum.
I put almost 6 pounds of 407c in the system, got the pressure somewhat dialed in to 295 psi liquid (yes I know thats high) and about 57 suction with 6 degrees superheat (that puts the EVAP temperature at about 35 at that pressure). I recommended to them to clean both the indoor and outdoor coils because of the liquid pressure and the indoor coil being almost as bad. Oh, and my temperature split on the indoor unit was about 17-18 degrees. So it was cooling good and thought that's all was wrong with it, I said I would return with the necessary stuff to clean everything. Again, I am doing this on the side now in my little truck so I don't have everything on me all the time.
So I come back a couple of days later to clean the condenser and EVAP. Get them cleaned and the liquid pressure drops to 225 (MUCH better) and suction is still the same. Between 55-60 but now my suction line temperature is 29 degrees F!!!
I was thinking, "well what is going on here? Must be airflow" so I go inside and pop the air filter out (which is perfectly clean by the way) and I see the capillary tubes in ice but the rest of the EVAP is NOT iced up. (It just happens very slowly) I test my temperature split again and its sitting still around 17 degrees.
Something doesn't seem right so I check the blower wheel, blower motor capacitor, and which speed tap it's on. Blower wheel is really dirty, the capacitor is weak, but the blower speed is set to high.
So I come back and clean the blower wheel, one of the worst I have seen, and swap out for a new capacitor and I fixed a minor thermostat wiring issue. Pressures look the same, my temperature split looks the same (the customer did say though that he is feeling more air come out of the vents from the blower wheel cleaning) but the capillary tubes start to freeze within just a couple of minutes from startup.
So THEN I recommend to changed out the orifice ( I went from an .080 to an .081) and to change out the copper piece that screws on the distributor just incase the screen is dirty because there just might be a restriction in those two.
I did those two things today and I told them I wouldn't charge them for this if it didn't work.
Well.....it didn't work. The suction pressure stays at 52 psi with a suction line temperature of like 29 degrees. I even tried pulling refrigerant out of it and got the suction line temp to 42 degrees but my suction pressure was down to 45 psi. Even with those weird readings, it was still doing a 17 degree temperature split.
Some more back story with this unit, the indoor unit/coil was swapped out with a USED one and then after that (the "tech" they had working on it) said the compressor was bad (I know, someone screwing someone else over. Not the customer's fault because they don't know any better.) I told them that the equipment was used for a reason so there ain't now telling what is going on. The AHU does have a 4 ton blower in it, the evap coil is 4 tons and the condensing unit is 4 tons, I verified this for absolute certain today.
The only strange thing I notice about the freezing is that it starts at the very beginning of the capillary tubes, not the distributor itself and I have always seen that if there is a restriction at the fixed orifice the distributor AND capillary tubes freeze.
This system does not have a filter drier on it but I did pull a pretty good vacuum on it today so I don't THINK moisture is to blame.
So does this mean that there is the slightest of restrictions in the distributor itself? After everything I have tried on this thing I honestly don't know what else it could be. I am actually worried that I'm going to put a new EVAP in this unit and its going to do the same thing. I do not want these people the spend that kind of money to have the same damn issue and to be honest, I don't want to have to pay for it myself. I have never really come across a refrigeration issue as curious as this.
Again, I don't work for anyone anymore and I am doing this on my own. If I had the equipment I would take airflow measurements at the return and at each supply register. I do not have a manometer either, but 99 times out of a 100 though the temperature split would be abnormally high, not at 17 degrees. I also don't see any apparent way for the air to bypass the coil, it is in a mobile home. It feels like I am missing something.
I just thought of this but the only thing I didn't do (I didn't think of it because there was no filter drier) I guess I could try taking a liquid line temperature measurement at the condenser and then one before the orifice. That would tell me if there was a kink in the line somewhere but usually you would see high liquid line pressure though. sigh
If anyone has any ideas or questions please let me know, it would be greatly appreciated.
