check valve

[mori69]

Hi everybody
Please have a look at the picture,

evaporator is 12 meters above the compressor and condenser .
- Possibility Return of the liquid to cylinder head at the off time?
- can check valve use at the Point 2 ?
Cheers

[RANGER1]

mori69,
Do you have aproblem ? or are you trying to prevent possible problem?

The only thing with check valves is possibility of hydraulicing pipework.
Check valve would be after solenoid valve if it has one.

If liquid reciever is big enough I would'nt worry.

[mbc]

check valve goes between compressor and condenser and after receiver normally we have stop valve- filter-
solenoid valve - sight glass - stop valve -TEX valve -Evaporator -suction accumulator to prevent liquid returning back to compressor or you use pump down system to prevent liquid back
in your drawing check valve those not sense you have not have that much refrigeration in evaporator it can return through liquid pipe to receiver and then condenser except you say it is wet system and in wet system this drawing
is not right and it is totally different

[chemi-cool]

Check valve is not the solution.
You need to add SV before the TXV and open it only when that high evaporator needs to cool.
A pump down will empty the suction line and evaporator and the compressor is safe.

[RANGER1]

mori69,
Check valve should be installed in discharge line after compressor ( & oil seperator if it has one) , before condensor inlet.
This will prevent liquid condensing on compressor head/valve plate

[Tayters]

I think you should consider having the compressor discharge pipe looping down to the floor then up to the condensor. This way, any liquid or oil from the condenser inlet will dribble back but wont be able to get into the compressor. Recall seeing the piping arrangement in Mr Dossats book. Pipes should slope in the direction of flow so nothing can run back in the off cycle.
The inlet to the condenser could also be trapped/riser, i.e comp discharge higher than condensor inlet, then going down 90 degrees to meet condensor inlet.

At the compressor discharge I think more to worry about is oil making it's way back to during to off cycle as opposed to liquid refrigerant.

Cheers,
Andy.

[mori69]

Suppose this cycle Complete &
solenoid valve is high(evaporator) and is close
so Compressor is off
Now, can run back liquid that solenoid valve backdoor ? (liquid down)

[Sandro Baptista]

Suppose this cycle Complete &
solenoid valve is high(evaporator) and is close
so Compressor is off
Now, can run back liquid that solenoid valve backdoor ? (liquid down)

Mori69,

If it does what is the problem of that?

[Sandro Baptista]

mori69,
Check valve should be installed in discharge line after compressor ( & oil seperator if it has one) , before condensor inlet.
This will prevent liquid condensing on compressor head/valve plate

If the the condenser is colder than the place where is the compressor and oil separator check valve it is not need...I hate pressure loss specially certain cheap check valves with low KVs.

Of course vapor ***** diffusion will travel to the oil separator and mixes with oil. However that quantity of *****-oil is low and there is crankcase heater, EVR at oil return...

[research]

http://www.refrigeration-engineer.com/forums/images/re2011/misc/quote_icon.png Originally Posted by mori69 http://www.refrigeration-engineer.com/forums/images/re2011/buttons/viewpost-right.png (http://www.refrigeration-engineer.com/forums/showthread.php?p=226033#post226033)
Suppose this cycle Complete &
solenoid valve is high(evaporator) and is close
so Compressor is off
Now, can run back liquid that solenoid valve backdoor ? (liquid down)

If your receiver is too small, this may happen. The best fix is to ensure the receiver is large enough to handle the entire refrigerant charge with appropriate safety factors.
However, depending on the velocity in your liquid line, it may take several seconds for the liquid to reach the TXV. This sometimes requires the use of a low pressure control bypass timer to get the system started. (IE if liquid travels 5 feet per second (MAXIMUM recommended velocity) Then the liquid takes 10 seconds to go 50 feet. Most liquid lines are sized larger than this and then it will take longer for the liquid to get up the riser. )

BE VERY CAREFUL of putting a check valve in the liquid line. IF the solenoid is closed and the liquid line is full of liquid, and you prevent back-flow by a check valve, then you have trapped liquid between two stop valves. The Refrigeration Code prohibits this, without a means of preventing overpressure.
Carrier uses a double valve arrangement to prevent this inevitable circumstance. Search "38AP-5SI.PDF" for a picture and installation instructions.
The same can be made using standard liquid line check valve, and a Sporlan ORD4-30 ( good for 60 feet vertical) piped in the reverse direction.

good luck

[chillyhamster]

Simples, fit a suction accumalator with a liquid loop installed and DO NOT insulate. this should prevent any liquid, either flood back or carry over to enter the compressor, also a CPR may be of benefit, if defrost is assisted.