View Full Version : High head 2.5 Gibson
04-28-2008, 03:28 PM
This has me stumped, I have never had a problem like this before where I must be overlooking something simple. Here is a timeline:
1. Dispatched to call, compressor has open windings (no startup load)
2. Evac unit
3. Replace with 2.5 ton Gibson HEAT PUMP.
4. Not a catastrophic compressor failure so there is no worry about contamination.
5. Flow nitrogen through while brazing (removed old bidirectional filter since new unit had one)
6. Pull vacuum.
7. Charge using superheat temp
8. Clean coils and check for airflow restriction.
9. Suction 65 (Ambient 75)
10. 16 degree difference between supply and return.
Here is the problem: HIGH HEAD PRESSURE 350#
I dont hear any non combustibles or oil. This has me really stumped.
Suggestions from someone who has no practical experience (take it with a grain of salt)...
I'm assuming that this system doesn't have a TXV since you charged by superheat.
Make sure that the piston is the correct size and not restricted by anything. Also check the liquid line for restrictions.
04-28-2008, 04:33 PM
What brand was teh old unit. And how old is the indoor coil.
04-29-2008, 06:57 AM
The indoor unit is a Trane (American Standard) and looks to be less than 10 yrs old. The original condensor was a Grandaire (made in Jacksonville)
04-29-2008, 07:15 AM
Ok, a 10 SEER indoor unit with a 13 SEER condenser. And the cause of the 10 SEER Gradaire failure is still there.
Not allowed to get too technical in the residencial forum.
If you had checked SC also, you would have seen you have a refrigerant flow problem. This is most likely what took out the other condenser. A restriction in the liquid side. You will have to locate it. Best to change out the ID unit to a match for the New OD unit though. Your going to lose a lot of capacity with that mismatch. Check out this PDF.
04-29-2008, 09:12 AM
My thoughts exactly but here is the kicker. The Grandaire was a 13 seer which worked for about a year. It was replaced with a 13 seer also. The ID unit is a 10 seer, I did not want to do a mis-match as I try not to do business like that but the homeowner rents the property out and doesnt care too much about efficency since the tenants are paying rent.
04-29-2008, 09:49 AM
should of replaced the warranty compressor and used the leftover on a new coil. is the old coil a piston, valve or cap tubes??
04-29-2008, 10:00 AM
04-29-2008, 10:56 AM
04-29-2008, 11:10 AM
You are losing up to 40% capacity and efficiency with this match up. You are going to be adjusting charge from season to season and are going to have nothing but problems with it. Let alone , the original problem was not solved. Do yourself a favor and match the equipment properly and start from scratch.
04-29-2008, 11:24 AM
I agree 110%, like I said I didnt want to do this from the begining without matching the set. The landlord does not care about effieiency since they are not the ones paying the electric bill so it was hard to convince them especially since I was pulling out a 13seer and going back with a 13seer.
04-29-2008, 11:36 AM
yea but you pulled out a 13 that was only a year old......
landlord wants the cheap way out but your the guy stuck with trying to make it work.
04-29-2008, 01:16 PM
Your right, lesson learned!!! The hard way!!! Thanks for the insight.
04-29-2008, 03:25 PM
Sometimes it is better to walk away from a job. Causes more problems in the long run.
04-29-2008, 07:44 PM
You seeing what killed the other 13 SEER condenser.
Doubtfull the evaps piston is the right size. If your charging for this swap out. Tell the landlord, that when this condenser goes out, he can pay for a new compressor, or condenser thatwill die in a year again. Or, he can pay for a new matching coil now, and have a warranty.
04-30-2008, 07:59 AM
I went to the job yesterday out of curiosity, pressures were 70low 220high (seems perfect) I wanted to check the piston so the sticker on the evap said 68 and the condensor called for 68 but curiosity got to me so I evaced it yesterday and checked the piston, guess what it was a 69. I recharged and I am still getting the incorrect pressures. I really couldnt see that much of a difference with a 68-69 piston could you?
04-30-2008, 08:08 AM
Your 70/220 is a bit more inline then the 300 you had when you started it up. The 69 piston would normally give you a slightly lower head, with a slightly higher vapor.
The OD unit calls for a #68 piston using model number xxxxx coil. Which has xx sq ft of surface area. You don't have that surface area, so the vapor pressure is slightly low, compared to head pressure.
The problem is still there, and will shows its face again.
Powered by vBulletin® Version 4.2.0 Copyright © 2013 vBulletin Solutions, Inc. All rights reserved.