Printable View
Just wondering, if system is over capacity and to reduce the same, if we close the rota-lockvalve (King valve) on the suction side.
This will reduce the pressure in the compressor, reducing the compression ration but will increase the evaporator pressure.
Any drawback, like compressor motor cooling, oil returns, etc.
Hi jwasir
to maintain evap pressure use a EPR and for compressor use a CPR
this link will help https://docs.google.com/viewer?a=v&p...lNmUw&hl=en_GB
more docs here http://www.refrigeration-engineer.co...Tips&highlight=
and here http://www.refrigeration-engineer.co...tins&highlight=
R's chillerman
Sure!! Just a thought, how is choking different than using EPR & CPR??
with an epr/cpr you control a pressure which remains constant, by closing off the suction port you restrict the flow, which is then variable depending on the fluctuating suction pressureQuote:
Originally Posted by jwasir
R's chillerman
One drawback not mentioned here.Quote:
Originally Posted by jwasir
If you partially close the suction valve you INCREASE the compression ratio. This can put the compressor out of it recommended parameters. Discharge temperatures will increase. This can case shortened discharge valve life at the very least.
Sir,Quote:
Originally Posted by NH3LVR
I practically checked this, CR almost stays constant. Is CPR not doing the same thing as what we do by closing the port!
with an epr/cpr you control a pressure which remains constant, by closing off the suction port you restrict the flow, which is then variable depending on the fluctuating suction pressureQuote:
Originally Posted by jwasir
Just to make sure that we are talking the about the same thing here I will give an example. Sorry about the Imperial units, it is all we know in the USA.Quote:
Originally Posted by jwasir
Compression ratio is calculated by dividing the discharge pressure absolute by the suction pressure absolute.
Example: suction pressure 10lbs gauge-discharge 150lbs gauge. Add 14.7 pounds to each for 24.7lbs and 164.7. Divide and you get a compression ratio of 6.67.
Remember I am an industrial refrigeration person with limited commercial experience. I have seen ammonia compressors ruined by running too high a compression ratio. Unless your discharge pressure falls when you restrict the suction your compression ratio goes up. If the discharge temperature goes too high you will have problems.
A CPR is useful to eliminate motor overload on start-up and after defrost. A EPR is useful to maintain a more appropriate suction pressure in a room for example. However they cause a lack of efficiency because the gas is being compressed at a less dense state. Remember that the total refrigerant effect is dependent on the amount of refrigerant being circulated through the system. Lower suction pressure=less refrigerant being circulated=lower capacity. Higher discharge=a less efficient compressor=reduced capacity.