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Replacement condenser

I installed new Goodman condenser matched to an existing year old mortex coil. Removed old unit cleaned line set with dry nitrogen. Installed new unit with new LL dryer. After all connections were made did triple evac as always to make sure lines were free of all contaminants. Old Compressor was shorted to ground but no acid in refrigerant. On startup (r22) head pressure climbed to 400+ very quickly and suddenly dropped and unit performed perfectly. All this happened within 2-3 minutes. Ran unit an hour starting and stopping it with t-stat. Switched over to cooling mode numbers right on with chart. Anybody seen this or have a clue what caused high head pressure?
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Comments

  • Eugene SilbersteinEugene Silberstein Posts: 349Member ✭✭
    More information please.

    What was the ambient temperature when you put the system into operation?

    What type of metering device is on the system?
    Eugene
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  • Flounder1310Flounder1310 Posts: 14Member
    More info

    The ambient was 62f and system has a metering device. After the head pressure went high and suddenly dropped the unit has and is running well within the manufacturer specs. The pressures held steady ( use digital gauges) not fluctuating more than .2-.5psi on suction and liquid lines. The condenser was matched to the coil by supplier. I also called the coil co. To make sure of the match. After talking with their tech I was assured that it is a good match. It was in heat mode and before I left the job I also ran the unit in ac mode. Pressures, Sh& Sc, were where according to chart they were susposed to be. The incident was a momentary incident, lasted only a couple of minutes. I was wondering maybe stuck RV.
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  • Flounder1310Flounder1310 Posts: 14Member
    Apolygy

    Piston metering device
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  • TechmanTechman Posts: 2,023Member ✭✭✭
    edited February 2014
    What is it?

    How long is the line set? RV stuck? If you were at the outdoor unit and that stuck RV suddenly became unstuck ,I think there would have been a noise, of some sort.

     I think that ,Nitrogen does not clean out the lines, and an evacuation doesn't remove contaminants. That junk is still in there. And on a 15-20 min to 2-3 hrs of a slow burn of the comp motor there may not be enough time for the refrigerant to pick up the acid that's  in the oil in the comp crankcase and in the  discharge line and in most of the tubing of the outdoor unit and finally the breaker trips.
    Post edited by Techman on
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  • John MillsJohn Mills Posts: 529Member ✭✭
    Mismatch

    After that first spike, how are pressures in heating mode? Mismatching is more likely to cause problems with HPs in heat mode since they need less charge to begin with AND the older indoor coil is physically smaller than the ones designed for today's units. So not unusual to run high heads in these situations though it would be all the time, not just on startup.



    Is there a built in drier and a liquid line drier? If so watch that little toy Goodman usually puts IN their units. Doesn't take much to plug up.
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  • Flounder1310Flounder1310 Posts: 14Member
    Pressures after startup

    The head pressure spiked and the pressure dropped in less than 2 minutes, probably closer to 1. After it dropped the pressures were spot on per mfg. charging chart supplied. Ran unit for an hour. Switched unit over into cooling and ran about 20 minutes and pressures were again spot on per charging chart. Left the unit running in heat cycle. As always gave my customer a call Tuesday evening ( unit at this point running for 24 hours in 35 and less temps) and he was very happy with warmth of house. Said that aux. heat had not run any. It was something I had not seen before and am young to the business even though I am retired after 40 years of industrial mechanic work. Yes I did install a LL FD. Plan on going back after our weather breaks to check unit operation, line dryer, and performance. Am still trying to figure out what happened even though unit is running great. Thanks to all of the support on my first post and am glad to know I have found some genuinely good support from good folks:)!
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  • TechmanTechman Posts: 2,023Member ✭✭✭
    Hi press

    How long is the lineset?
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  • Flounder1310Flounder1310 Posts: 14Member
    Lineset

    It is only 19-20 feet.
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  • TechmanTechman Posts: 2,023Member ✭✭✭
    Hi press.

    The HP was started in the heat mode so the indoor coil was acting as a condenser. Slight delay of the indoor fan? cover not on properly?
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  • Flounder1310Flounder1310 Posts: 14Member
    Cover

    Thanks first of all for your help! I am pretty sure you hit the nail on the head! I know the cover was off when I started unit. After I had pulled vacuum, added refrigerant system pulled in I let pressure equalize! Factory charge called for 188oz. Or 11.75 lbs. I turned on the breaker, went inside to set unit in heat mode, nothing happened. I checked voltage to tstat had nothing. Then I went to air handler checked for control fuse sure enough it was blown. I turned power off replaced fuse turned power on unit came on, went out to make sure condenser was running and saw the high pressure and started to cut power outside but pressure dropped before I could cut power. I let unit run went back inside replaced the covers and went back to finish adjusting my charge. So I feel confident that you have solved my mystery And helped me gain some valuable experience. So again I say thank you Techman! I appreciate you my man!!
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  • hheaddonhheaddon Posts: 9Member
    hi press

    I seen that happen when units were started up with all the charge in the odu as in crankcase htr not on, or comp and accumulator full of the factory charge .unit comes on, pumps a little or  a lot of liquid and some carryover oil from the sump of the comp, usually with some not so good noises from the comp, until things get moving. or yay the indoor door panel was off.
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