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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I have a goodman 14 seer condensing unit new just instslled.

Customer Question

I have a goodman 14 seer condensing unit new just instslled. There us no low side pressure. And yes both valves at the conpressor are open. Is this a condensing unit defect?
Submitted: 1 year ago.
Category: HVAC
Expert:  BillyHvac replied 1 year ago.

hello,

is suction line temp hot warm cool cold?

And what is head pressure during this?

Customer: replied 1 year ago.
No low side pressureModel Number: Gsx140601ka
What have you tried so far?: Ran unit 30 minLines are room temp hi side is about 180psi
Expert:  Kcrand36 replied 1 year ago.

Good Afternoon, I am Kevin, one of the Tech's here on JA.

is it fixed orifice or TXV?

Customer: replied 1 year ago.
Txv on the evap coil
Expert:  Kcrand36 replied 1 year ago.

line set or hard piped? and has the problem been here since day 1 startup? Are you the start up tech? or homeowner?

Customer: replied 1 year ago.
Harg pipe. Yes since day one which was yesterday about 5pm. Also no freon comes out if low side schrader valve when depressed
Expert:  Kcrand36 replied 1 year ago.

system off or on at this time?

Customer: replied 1 year ago.
No low side pressure or freon from schrader valve with system on or off
Expert:  Kcrand36 replied 1 year ago.

but you have high side pressure still?

Customer: replied 1 year ago.
I have hi side pressure and yes the valve at the unit us open
Expert:  Kcrand36 replied 1 year ago.

so this is a new system, new evap coil with txv, new condensing unit, hard piped....

Customer: replied 1 year ago.
Istalked yestetday. We installed 2, the other is operating fine
Expert:  Kcrand36 replied 1 year ago.

ok, did you pressure test with nitrogen or helium?

Customer: replied 1 year ago.
Expert:  Kcrand36 replied 1 year ago.

where did you introduce the gas? in the high or low side of the system?

Expert:  Kcrand36 replied 1 year ago.

the pressure test gas, I'm talking about......

Customer: replied 1 year ago.
At the schrader valves on the condensing unit
Expert:  Kcrand36 replied 1 year ago.

yes, but which side? high or low?

Customer: replied 1 year ago.
Can't remember. Probably the low side
Customer: replied 1 year ago.
It is a sigle pase unit and it sounds kind of like the compressor is running backwards
Expert:  Kcrand36 replied 1 year ago.

ok, so you cannot determine at this point if you had a good install or not, because if you had placed it in the high side, and it bled through to the low side you would know that you didn't braze a plug in the pipe causing a restriction.

You definitely have a restriction, if you have high side pressure and no low side pressure, you have a restriction. The problem is , where is the restriction. I once remembered and never forgot, when I was an apprentice I did a "hard pipe", forgot to remove the plug in the end of the pipe. Brazed the SOB in and later figured out I had an issue. Like you, I opened up the ports though, let loose the charge. later figured out where my plug was because heating it, broke down the rubber plug enough to create a restriction just enough to frost the line, yes, I did have to cut insulation and reseal, but I knew where my joints were. Getting back to your problem.

attach a temp probe to inlet and outlet of TXV, get your delta T, After that, start looking at the piping and what you may have forgot to do during install.

Expert:  Kcrand36 replied 1 year ago.

we all make mistakes..... just making them right and not making the customer pay for them is the difference between good and bad.

Customer: replied 1 year ago.
The supplyer has replaced the unit. The caps were removed. Before installing new unit i will check to make sure i have air flow through the coil via refrigerant lines.. what do you think? I have installed over 100 of this same system
Expert:  Kcrand36 replied 1 year ago.

I don't understand how it could be the Condensing unit. You have a TXV, you have high side pressure, you have nothing bleeding to the low side of the system. Unless you have a defective king valve, which you have already determined that the high side opened, because you have high side pressure and you have a vacuum on the suction, how could it be anything else but a restriction?

Customer: replied 1 year ago.
The blickage has to be inside the condensing unit. After i disconnected, i opened the low valve , notjing csme out. Then the high side valve and there is still plenty if freon inside the unit
Expert:  Kcrand36 replied 1 year ago.

exactly, you have high side pressure to your restriction. whether it be on the liquid line, txv or suction line, your restriction is in the system, NOT in the condensing unit!

Expert:  Kcrand36 replied 1 year ago.

remember your "BASIC REFRIGERATION CYCLE". Factor in the AC condensing unit.......... you have high side pressure at the king valve on the condensing unit. You have a vacuum on the low side king valve. If the system is off, the high side pressure should bleed through the TXV to the low side, regardless if you have bad compressor or not. This is NOT happening according to what your telling me. so you MUST have a restriction after it leaves the condensing unit and prior to it reaching the king valve of the suction line of the condensing unit.

Customer: replied 1 year ago.
If i draw a vaccum on the low dide at the condenser will thst bleed over and draw a vaccum on the hi dide?
Expert:  Kcrand36 replied 1 year ago.

It may, it may not.

Customer: replied 1 year ago.
Whay about draeing from the high side?
Expert:  Kcrand36 replied 1 year ago.

what kind of situation are you in?

Customer: replied 1 year ago.
The same one
Expert:  Kcrand36 replied 1 year ago.

I would start by recovering the refrigerant, at this point, you have probably introduced air and you don't want to give the customer a "non condensable system".

pressurize with nitrogen through the high side only.. if it bleeds to the low side, pretty rapidly, ok, if not, you have a restriction. Start thinking where you could have messed up.

Customer: replied 1 year ago.
If the king valve were stuck would i have the same simptoms?
Expert:  Kcrand36 replied 1 year ago.

think, if the king valve was closed, you would not be reading the suction of the compressor. You stated you were in a vacuum, therefore, you are getting the suction of the compressor. you are NOT getting pressure back to the compressor, wether it be on the liquid line feeding the txv, or after the outlet of the evap coil. This is all part of pressure test and start up. You should have known this the second you pressure tested BEFORE you unloaded the charge into the system.