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Hello Mark,Mark I sent you a question the other day about…

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Hello ,  I sent Mark a...
Hello ,  I sent Mark a question the other day about a 5ton ac unit. The high side was getting cold and he told me there was probably a restriction somewhere in the line, he was correct, I followed the line until it got hot and found the filter/drier was clogged. I removed it to and tried the unit to see if it would work. It did take a charge 65psi on the suction side. The compressor was kicking out before, now its not. The compressor runs and you can hear the freon flowing but the suciton side now is not getting cold. What would cause this?
Submitted: 8 years ago.Category: HVAC
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Answered in 29 minutes by:
6/17/2010
HVAC Technician: BillyHvac, Journeyman HVAC Tech replied 8 years ago
BillyHvac
BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 23,151
Experience: Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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Billy :

what are your high and low pressures now? I assume this is R22?

Customer:

Yes it is r22, i am not sure now, i am not at the unit, the low side was 67

Customer:

great feedback btw

Customer:

If it was undercharged wouldn't it start to get cold though?

Billy :

sorry computer issues.....that is why I need the high side reading.....a unit can be low and actually start to freeze...and it can be low with a warm suction pipe....The head pressure and super heat would give me better direction

Billy :

If head is 300 or 200 would tell more of the story

Customer:

yeah i have seen them freeze when low. i am not a hvac tech but know a little about it, both suction and high side feel the same temp. i can hear the freon flowing but neither line is changing temp.

Customer:

could it be possible for a restriction in the line still?

Customer:

before the high side was getting cold and kicking out the compressor now the compress is running normal but no temp. change

Billy :

Thanks....the reason I ask is if the valves are compromised it will run...but there is no compression...or little compression....this leads to somewhat equal pressures and a warm suction

Billy :

I would reclaim...and then run a reverse nitrogen blast through to clear the system...then vac and recharge. Air in the system with refigerant also gives warm line

Customer:

can you explain abou the valves being compromised?

Customer:

you mean blast through the high side?

Customer:

ok i got you, i understand. if the readings are say 300 then what?

Customer:

there is no isolation valve on the high side

Billy :

Then we are looking at obstruction still or bad metering device

Customer:

the reading should be?

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HVAC Technician: BillyHvac, Journeyman HVAC Tech replied 8 years ago
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HVAC Technician: BillyHvac, Journeyman HVAC Tech replied 8 years ago

No king valve or anything at condenser for high side?

9:18 AM

If the valves were compromised by high head....then we could be leaking refrigerant back around the valves...this would cause low head

9:19 AM

I apologize but I must take care of some issues and will be offline for 30 min...I will respond asap.

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Customer reply replied 8 years ago
This unit was damaged by thieves, and the tech removed the valve in order to repair it and couldn't get the isolation vavle so he just installed a tee with a schrader valve
Customer reply replied 8 years ago
This unit was damaged by thieves, and the tech removed the valve in order to repair it and couldn't get the isolation vavle so he just installed a tee with a schrader valve
HVAC Technician: BillyHvac, Journeyman HVAC Tech replied 8 years ago

I understand....well here is where you must decide on how much to put into the unit...In my opinion, the system needs to purged out with nitrogen and vacuumed and recharged...it would be best if a valve were there....but....if you evacuate...remove liquid line from condenser, then you can purge through the evaporator and blow right out the liquid line.

 

I know you do not want extra work...but you are in a situation requiring replacement or adequate repair. To achieve adequate repair means starting with a system that is known to be clear. This sets the stage for all other testing and or work.

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Customer reply replied 8 years ago
I will take the extra work if I can get this unit running. Do you thinkg a kink in the line would cause this? BOth lines are going in the roof and can't be seen for about a foot. Is it possible that one of the lines is kinked causing this problem?
HVAC Technician: BillyHvac, Journeyman HVAC Tech replied 8 years ago

That is a great question...if I see high head pressure..that leads me towards blockage..or overcharge. If I see med to low head it sends me a different direction

 

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Customer reply replied 8 years ago

ok if its low then where are we?

 

HVAC Technician: BillyHvac, Journeyman HVAC Tech replied 8 years ago

Then we are at a point of seeing if the metering device (txv, cap tube, orifice etc) is damaged, stuck etc. or if the valves have been damaged by pushing against the high head pressure

 

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Customer reply replied 8 years ago
ok thanks for your help I am going to go try out this and see what happens. Thanks again.
HVAC Technician: BillyHvac, Journeyman HVAC Tech replied 8 years ago
You are very welcome. I will leave this open for you to respond to in case you have any issues. I wish you luck!
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