Evaporator Restriction

[addison]

I got a call to look into a Lennox 5 ton package unit that was'nt cooling as well as it was the week before.What I found right off the bat was that the TXV valve was a block of Ice from the discharge side of the valve, it then split into 3 lines which fed the evaporator coil. The lines were froze as well as the 3 areas of the coil where they were attached. Just like 3 strips at the top, middle,and the bottom. I check pressures and temps,
low side 25PSI
high side 220PSI
evap, disharge temp, 79
suction line temp at the comp, 86
comp,discharge temp. 295
condenser discharge temp, 95
temp,about 4 inches from TXV 98
Subcooling 13
superheat 80
Outside conditions sunny,windy 5-15 from the south, and roof temp taken about 2 feet off the deck. 103 degrees. Location Ft, Worth Texas
All these readings indicate that there is a blockage in the evaporator coil. Does this make since, and is there A way to make a repair. Thanks

[absrbrtek]

Replace the TXV or power element. The coils not blocked.

[conaire-one]

Low Evaporator Air Flow.

Low Head Pressure
Low suction Pressure
Low Superheat
High Subcooling
Low Compressor Amps
Low Discharge Temperature

Check Evaporator Fan blower

[Edited by conaire-one on 05-20-2005 at 09:10 PM]

[airworx]

subcooling tells us charge is good superheat is high so that means restriction and that means replace txv.

[addison]

The evaporator fan is running just fine.

[twcpipes]

low side 25PSI
high side 220PSI
evap, disharge temp, 79
suction line temp at the comp, 86
comp,discharge temp. 295
condenser discharge temp, 95
temp,about 4 inches from TXV 98
Subcooling 13
superheat 80

Whatever you do you better hurry before the compressor burns out. Maximum suction temp is 75 degrees.
Would like to know how you gained 3 degrees of temp on the liquid line and what was the outdoor ambient?

[moe-air]

how about low charge?

[addison]

Deck temp, 103.
read first post on subject

[service guy]

Whats your readings with the Evap coil defrosted?

[shogun8]

Power element lost refrigerant charge or inlet screen pluged

[airworx]

normal to high subcooling with high superheat = restriction.
txv icing = replace powerhead or txv. simple as that.

[tgray]

So did you end up replacing the TXV or what?

[addison]

I replaced the TXV

[tgray]

Thanks man! You have described the problem I am having with my 8yr. old Lennox HP26-42 including the ice formation and the pressures. At first I thought it was low freon but thought it shouldn't be low and the heating cycle had worked fine. At least I thought that it had. Added a little freon and it didn't change anything. Guys on Residential board thought there was a blockage but they wouldn't say what or where. I am an engineer who tries to understand how things work and understand what is wrong when something doesn't work. Unfortunately I am not equipped to fix this one but i have some peace of mind knowing that this must be the problem. By the way I tried to unstick it with some heat (hairdrier) but that didn't work. Now we must burn for a week or so untill I can get some one out to fix it. Thanks again for your reply

[addison]

glad to be of some help.