compressor suction valve broken

[comfortable air]

a customer call no cooling. I went to there. hook the gage on the pipe. when the compressor started,it make a click noise, the high pressure go up to 300. the suction pressure keep at more than 120 psig and it is warm. at the same time, the condensor fan have a big noise, then stopped. I think the condensor is overheated. but the compressor still working. I shut off the comprssor. I touched the suction line, it is as hot as the discharge line. so I diagnosed the compressor suction valve broken. it could not pump the r22. why the compressor and condensor moter have the problem at the same time? does the codensor moter not working properly damaged the compressor. is my diagnose right? I suggested to replace the compressor and condensor moter at the same time.

[joeywpittman]

When the condensing fan motor stops working, the head pressure will continue to climb until something gives. Normally the internal relief valve opens. After this happens 3 or more times the compressor starts to get really hot. Eventually the compressor motor's overloads trip out the compressor.

I would suspect that the internal relief valve is stuck open or broken.

[Edited by joeywpittman on 06-28-2005 at 10:37 PM]

[joeywpittman]

Originally posted by comfortable air
I suggested to replace the compressor and condensor moter at the same time.

Go ahead and sell them a BRAND NEW UNIT please.

[Carrene #2]

Is it possible that the internal pressure relief valve was open due to high head pressure ( due to fan motor crappin' out ).
New unit's always good though, if they'll spend the bucks and you can sleep at night.

[comfortable air]

why the suction pressure is high. I can not read it from the low side of my gage, It looks it is not change at all when the compressor began to start. and I stopped the compresor only at 300 psig. the compressor is still work when I shut it off.it is not shut off by overheating. the fan moter is shutoff for a few minutes automaticly.
after the compressor stop working , the suction line became hot. when the compressor is working, it is warm. so I think some of hot gas come back to suction line due the broken suction valve.

[Edited by comfortable air on 06-28-2005 at 11:13 PM]

[Carrene #2]

Know anything about a car engine?
Basically the same thing, only no ignition and other stuff.
The same, but different. I'd have to say it's the internal relief passing discharge gas into suction or the discharge valves shot.
Sit down and think about how a recip. comp. works and go from there.
Hint: if there is hot discharge gas passing back into suction, how could this happen? Internal relief or discharge valves? You decide. If it was suction valve would you have hot gas passin' back into suction when compressor shut off ( when discharge valve closes )?

[comfortable air]

of course. if the internal suction valve(it is at the inlet of the cylinder of the compresor) broken, the hot gas will back to suction line when the compressor stop to work. because the gas will flow from high pressure to low pressure.
hopely, the dicharge valve(inside of the comprssor) is good.
please don't misunderstood the suction valve as the suction valve of the outside the compressor

[Carrene #2]

Both suction and discharge valves work like check valves, go from there.
They close on reverse flow.

[comfortable air]

the main reason make me decide the internal suction valve broken is the suction line pressure did not drop down when the compressor start.

[Carrene #2]

If the dicharge valve is broken, what stops discharge pressure from entering cylinder on suction stroke?

[comfortable air]

if one of broken. what is happening? if the suction valve broken,
the suction line pressure will be high. if the discharge valve broken, the discharge pressure will be low

[comfortable air]

yes. maybe the discharge valve is broken. not the suction valve

[Carrene #2]

Hook up gauges, run comp., close suction valve and watch gauges. Shut system off. If suction pressure rises, bingo, discharge valve!

[comfortable air]

the rooftop usually have no suction valve and discharge valve in the pipe

[Carrene #2]

Yep, you're right.
Can't help ya there.
I guess this is one where good judgement comes into play and knowing how a system reacts to different problems.
Good luck.

[Edited by r718 on 06-29-2005 at 12:03 AM]

[comfortable air]

sorry everybody. I thought I make a mistake on my gage when I measure the presure in that machine. today I found I didn't close both of the gage manfold valve. so the r22 bypass with the gage manfold. and I got high suction pressure.anyway, hope everybody can learn from the discussion.