Replacing Evaporator Coil - http://www.hvacmechanic.com/ Forums
Original message
| almazco
 |  "Replacing Evaporator Coil"
, posted Wed 18 Jun 10:25  
I just replaced a 3-ton condensing unit in a 30+ year old York central air and heating system. It appears there is a restriction in the evaporator. It's the original evaporator that has a single capillary tube metering device. I think that capillary tube is blocked. I am getting totally different pressures on the liquid side and suction side, when the system is not running (10psi, 125psi) and a build up of pressure on the liquid side when the system is turned on (goes up to 450psi).
What are the chances that new matching evaporator coil is going to be the same dimensions as the old one, so I don't have to futz with the duct work? The old evaporator is York model 36UF18-A, the box measures 18.25"x22"x7". I would really love to pull out the old coil and slide in the new one if that's possible. Did I make the right diagnosis? Any thoughts?
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Replies:
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| Freon
| "Re(1):Replacing Evaporator Coil" , posted Wed 18 Jun 12:57
The evaporator coils you'll mostly see are the higher SEER coils. One difference is they tend to be larger than their older counterparts. You can use any manufacturer's coil so go shopping for dimensions. A 3 ton 13 SEER coil will likely be bigger than your existing coil. You can look at 2.5 ton coils to see if the dimensions are closer. With a 2.5 ton coil be sure to add a TXV metering device.
Your diagnosis seems accurate
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| | almazco
| "Re(2):Replacing Evaporator Coil" , posted Wed 18 Jun 19:22
Thanks for your reply and comments. Much appreciated.
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| | almazco
| "Re(3):Replacing Evaporator Coil" , posted Mon 23 Jun 14:44
I can't find evaporator coil that will fit this system. The old one is flat type (7" tall). It's going to be very hard if not impossible to fit the newer evaporator coil in to my duct work. I am thinking about unclogging or replacing the capillary tube and filter-dryer in the old evaporator. The simplest thing to try first is to use heat to melt whatever is obstructing the tube. I am thinking about running the compressor for a few minutes to build up the pressure on the liquid side and use a small torch to heat up the capillary tube in the evaporator. Any thoughts? Suggestions?
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| | hvac122
| "Re(4):Replacing Evaporator Coil" , posted Mon 23 Jun 16:54
Boom!
Its a good life!
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| | almazco
| "Re(5):Replacing Evaporator Coil" , posted Mon 23 Jun 18:09
I know it is done. I was wondering what was the best way to do it? I was planning to run the compressor only to create a pressure difference on two sides and shut it off before proceeding with the torch. That would leave 120 psi on the liquid side for at least two hours or more depending on how bad the clog is. The pressure may be equal at this time after the system was idle for a week. Just enough heat to melt the wax or whatever is in there. All of the connections in that area are brazed.
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| | theduke03
| "Re(6):Replacing Evaporator Coil" , posted Mon 23 Jun 20:25:
Instead of burning the refigerant and causing more problems I would suggest pumping system down,cutting the liquid line near the coil, and then blast nitrogen thru from the low side port. If that doesn't remove the restriction then nothing will. I recommend taping a rag around the pipe to catch restriction this way you can see what comes out. Finish with a nice filter drier right where you cut it, evac. and crack!
BTW, subcooling and superheat readings will confirm if indeed it is a restriction. High superheat + High subcooling = restriction.
"My dad was the most feared furnace fighter in Northern Indiana."
[this message was edited by theduke03 on Mon 23 Jun 20:28] |
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