High head pressure fluctuating on a new 410a install

 
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Old 06-02-2012, 02:03 PM   #1
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High head pressure fluctuating on a new 410a install


I installed a new 410a complete system with new Orfice coil and new lineset. 70 degrees on install date and initial start up. Suction pressure was 110 and high side of 280. It ran for about 15 minutes. I added a little freon and the high side shot up to 425. I immediately thought I had a noncondensable stuck either at the filter drier or the metering device. Pumped the system down and checked, replaced drier and orfice. System does the same thing. The evaporator coil was a new Nordyne aluminum coil. I can't seem to figure out the problem. Any suggestions?<br>

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Old 06-22-2012, 02:55 AM   #2
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Re: High head pressure fluctuating on a new 410a install


Finding actual superheat or subcooling is easy . Simply hook it up to the system, let the system stabilize, and get your actual superheat or subcooling reading in real time. No charts, no calculations. Itís all done for you in the instrument.
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Old 06-25-2012, 12:46 PM   #3
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Re: High head pressure fluctuating on a new 410a install


if you thought it was noncondensibles why pump it down? you didn't say what happened to the suction pressure, and when you added some juice was it liquid?
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Old 06-25-2012, 07:09 PM   #4
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Re: High head pressure fluctuating on a new 410a install


It's overcharged.

How much is a "little" that you added?

410 systems are precise, a couple of ounces can make the difference between...

110 / 280

and

130 / 320

a couple more ounces makes

140 / 475

Last edited by VersaTek; 06-25-2012 at 07:12 PM.
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Old 06-26-2012, 05:44 AM   #5
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Re: High head pressure fluctuating on a new 410a install


On 70 degree days. I see a lot of R410A systems running at or around 110/280. So why did you add gas. Was the SC low, or the SH high?
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Old 06-26-2012, 05:47 AM   #6
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Re: High head pressure fluctuating on a new 410a install


Quote:
Originally Posted by beenthere View Post
On 70 degree days. I see a lot of R410A systems running at or around 110/280. So why did you add gas. Was the SC low, or the SH high?
I'm curious what the load on the evap was.

110 is just a tad low, but you are right, I see many running at that pressure (which I think is right around 32 degrees) if there is no load on the evap.

Fairly certain the unit is overcharged now.
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Old 06-26-2012, 05:52 AM   #7
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Re: High head pressure fluctuating on a new 410a install


Quote:
Originally Posted by VersaTek View Post
I'm curious what the load on the evap was.

110 is just a tad low, but you are right, I see many running at that pressure (which I think is right around 32 degrees) if there is no load on the evap.

Fairly certain the unit is overcharged now.
R410a at 110 PSIG is 36 degrees saturation. Roughly equal to 63 PSIG with R22.

Good chance its over charged. Specially if that condense has a micro channel coil.
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Old 06-26-2012, 06:53 AM   #8
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Re: High head pressure fluctuating on a new 410a install


Quote:
Originally Posted by beenthere View Post
R410a at 110 PSIG is 36 degrees saturation. Roughly equal to 63 PSIG with R22.

Good chance its over charged. Specially if that condense has a micro channel coil.
True.

I would have walked with it at 110 (without asking any questions) if it had a TXV.

Time for deminimus.
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Old 06-26-2012, 10:39 PM   #9
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Re: High head pressure fluctuating on a new 410a install


Set your superheat or sub-cooling and get it set it right. Then see what happens.
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