Flow con valve....

[Rob.S]

can someone tell me the exact purpose a flow control valve is used for..... is it something to do with hot gas defrost??? when the gas goes up the suction stub to the case does it reduce the liquid line to allow the hot gas to circulate round???? cant work it out please someone she some light...

[botrous]

try this web , maybe it's usefull
http://www.danfoss.com/BusinessAreas/RefrigerationAndAirConditioning/Products/Categories.htm

maybe that's what you are searching for

[Mark]

http://www.refrigeration-engineer.com/forums/showthread.php?t=1580

Take a look Rob:)

[Mark]

The discharge flo-con A8 Discharge serves two purposes for one the valve is either wide open or( bypassed) ie solenoid energised to allow mimimum pressure drop when no cases or coldrooms are defrosting ,the second being when defrost starts the solenoid de-energises converting valve to a differential pressure regulator.
For example if set at 25psi the valve will maintain a 25psi differential pressure upstream of the valve regardless of fluctuations in pressure downstream,this ensures that the hot-gas pressure will be high enough to overcome pressure drops through the supply line,the losses through the valves etc.
The A9 flo-con various models and application acts as a negative differential valve so that defrost can be performed successfully by allowing the condensed gas to re-enter the liquid line.
Another application for flo-con (A9 or A8-0E) is to act as a bypass line to the reciever allowing hot-gas from the discharge to maintain a minimum pressure in the reciever

Hope this helps:) kind regards. Mark

[Gary]

Whether the gas used for defrost is hot gas (from the discharge line) or cool gas (from the top of the receiver), it will condense into a liquid in the evaporator.

It must then be moved backwards through the liquid line into the liquid header. This requires a pressure difference between the hot/cool gas and the liquid header. In other words, the defrost gas pressure must be increased or the liquid header pressure decreased.

In a cool gas defrost system, the pressure is reduced in the line between the receiver and the liquid header (liquid suppression).

In a hot gas defrost system, the pressure is reduced in the discharge line before the condenser. Since the condensing pressure is held relatively constant, this results in an elevation of the discharge line pressure.

I have also seen liquid suppression used in hot gas systems, rather than discharge elevation.

Although 25psi differential is a reasonable average, it does not take liquid lift into account. If the liquid header is up on the roof, there must be added differential pressure to lift the liquid up to the roof.

This brings us to the "20, 30, 40 rule":

20 psi differential for ground level, 30 psi for mezzanine, 40 psi for rooftop.

[stan1488]

any actual system diagrams guys? cheers

[Rob.S]

thanks mark thats a great help......i see you work for coldservice too??? what area are you looking after?
rob.s :)