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Need help with a 15tom R22 system

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Old 07-12-2016, 01:26 PM   #1
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Need help with a 15tom R22 system

Hi..this system is called a pca (precondition educated air) it for cooling a passenger boarding bridge at an's a 30ton unit which is made from 2 separate 15ton units.. the primary side is working perfectly R22 press is 58.9/213.8 at around 70deg ambient..the secondary side had a bad leak at the txv..we replaced the txv and ensured it didn't leak anymore..the system comes with a predetermined 20lbs of after vacuum we put 20lbs in...right away the evaporated coil started to freeze and readings were 41.2/225 evaporated temp-18.3 cond temp-109.6...I figured it was still low on refrigerant and added a few lbs but nothing changed with my pressures and temp..note that coming off the discharge side there is a hot gas bypass valve going to the evaporated coil..any ideas what I should look at next
. Any help would be appreciated..thank you

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Old 08-11-2016, 06:48 AM   #2
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Re: Need help with a 15tom R22 system

check your air filter. If it’s dirty, replace it with a new filter and turn your air conditioner back on after your coil has thawed out.
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Old 09-26-2016, 07:57 AM   #3
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Re: Need help with a 15tom R22 system

Idk if this will help but, Anytime I change anything on any system I check 95% or the time Change the filter dryer also. looks alil like theres a small restriction in the system. Make sure solenoid is opening all the way. Or if you know how too isolate low sides n check
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Old 10-20-2016, 12:13 PM   #4
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Re: Need help with a 15tom R22 system

Is the other side hot gassing? If so pull the solenoid, put a screwdriver in it obviously, and see where the pressures settle. Probably the same, it's probably not gassing much, but that should give you a good model.

The discharge air temp should be a big indicator of what's going on. If it's extremely cold then it would lean toward low air flow, if fairly warm starved coil.

If superheat is normal then the txv is doing its job but if it's high that doesn't necessarily mean that it isn't. If it's being denied a column of liquid because of a plugged drier, it may be maxed out. Need to determine if it's getting a solid column.

What's controlling that hot gas? Staging? Usually a system with hot gas won't allow suction to get so low.

225 seems like a pretty high head for a system with no load. This one looks like the supply fans not even on, there's definitely no load. Fan cycler keeping it that high? If not it must be PACKED with 22.

Are you SURE the supply fan is dragging air across that coil?

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Last edited by pintofstout; 10-20-2016 at 12:20 PM.
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