Author Topic: high head pressure new install  (Read 7241 times)

Offline oldguy2

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high head pressure new install
« on: June 09, 2012, 06:14:00 AM »
a former working budding who is now retired from the trade . recently installed a 2ton ac system. concord 13 seer 410a.he told me that it would cut out on high pressure and he thought it was because he may have put the liquid line dryer on backwards arrow towards condenser. we removed and replaced dryer arrow towards indoor coil.the system now ran without cutting out. still had high head pressure. when i looked at coil i noticed it was a 1.5 ton coil so wrong piston. .51 when it should have been .57 went on concord website and found that coil is wrong but supplier said just change the piston it should be ok .changed the piston to a .57 still had high head pressure 460lbs on a 75 degree day. it should have been condensing at around 90. 75 degree day plus 15 for a 13 seer equals 90 which is 236lbs . i;m guessing at the 236 i dont have my charts with me but i;m close enough on the 236.so he told suppler he needs a 2ton coil. we change it out 2ton coil .57 piston .still has high head pressure. buy changing the coil it brought the head pressure down to 360lbs still too high now it was a 65 degree day plus 15 for a 13seer equals 80 condensing which is 216 again i;m guessing on the 216 no charts here in my kitchen.so i;m stumped.i messured the liguid line temp outside 65 and insideby the coil 65 it has a new copper line set he said it was capped while installing into hole i not sure what else to look for that is causing the high head pressure. first time ive ever seen this happen. thanks if anyone can help

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Re: high head pressure new install
« Reply #1 on: June 09, 2012, 03:44:57 PM »
What's the suction pressure and suction line temp?  We should determine our superheat on a orifice system.  At 360psig the saturation temp is around 109F which means our subcooling is 44F if in fact our liquid line is 65F.

Given that the head pressure dropped when you switched to a larger coil I would suspect you might be overcharged.  I would calculate the superheat to confirm.

If the suction pressure is high, superheat low, discharge pressure high, subcooling high and compressor amps high it would indicate an overcharged condition.

What is the difference between the return and supply temps at the coil?

Offline oldguy2

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Re: high head pressure new install
« Reply #2 on: June 09, 2012, 04:23:00 PM »
i would think i would need to get the head pressure in line before taking any measurements. and my suction pressure was low saturated at 28 or close to it. my superheat was in the 70's i think it was 75.high superheat undercharged. so if i add refrig to the system my head goes up.about 15ft lineset. i have never seen this kind of head pressure on a new install. wondering if compresser is junk. like everything else these days. i should add that i have never had a problem with concord or armstrong. geezz cant wait till lennox and carrier move production line to mexico...

Offline oldguy2

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Re: high head pressure new install
« Reply #3 on: June 09, 2012, 05:53:56 PM »
everything is pointing towards a restriction.i should have gone with my gut instinc and changed the 3/8 line. but he said the lines were capped. i mean geez wrong coil. liquid line dryer in wrong.stupid of me to believe lines were capped off.

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Re: high head pressure new install
« Reply #4 on: June 09, 2012, 07:26:49 PM »
I agree, if you have a low suction pressure and high superheat you could have a liquid line restriction.  The compressor amps would be low in this case.  Maybe the liquid line filter is causing the restriction because it was reversed.  I would pump down and run some nitrogen into the suction side and see how quick it leaves the liquid side.  I would cut out the filter if the pressure seems weak and see if the nitrogen comes out more freely.

Offline oldguy2

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Re: high head pressure new install
« Reply #5 on: June 09, 2012, 07:40:40 PM »
i put a new liquid line dryer on it. its funny cuz i use to be his helper. but thats what happens when you only install and never service anything you do install. problem with the install call the service department. lol

Offline pas1216

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Re: high head pressure new install
« Reply #6 on: July 14, 2012, 07:32:51 PM »
if there is a restriction in the line would you not have a line temp difference at the blockage? that might point you in the right direction. I say reclaim the system and purge it (open the coil and remove the orifice) with nitrogen. Pressure test, vacuum and recharge. 

Offline oldguy2

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Re: high head pressure new install
« Reply #7 on: July 25, 2012, 06:42:47 AM »
this problem i ran into got solved . ended up being air in the lines non condensibles. buddy didnt use a micron gauge. he never used one in the 30yrs he installed ac lol
so when i use looking at this problem all i was doing was pumping the system back to condencer. then checking everything else out microned the system and opened the system back up with the same refrigerant. learned a good lesson on that one.