optimum defrost gas solenoid valve setting question

[racknovice]

Dear fellows:
Just recently I noticed that the defrosting action of the hot gas in this particular rack I am assign to has became not very efficient. Whenever one of the circuits is on defrost, the temperature of the hot gas going through the pipes is quite tolerable to my bare hand. I know that the function of the large throttling valve located in the discharge line downstream from the compressors is to partially block off the gas going to the condenser in order to have it rerouted toward the desfrosting circuit. I also know that as this valve becomes closed, discharge gas pressure and temperature rise. What should be the optimum adjustment of this throttling valve in order to have a good defrost gas temperature?

[1torr]

From memory about 15 to 20psi difference.Otherwise the rest of the system, cases etc will be starved of liquid.

[Pooh]

I think you may find that it is not the valve in the discharge line that is at fault it more than likely the differential valve in the liquid line that loweres the pressure in that line to induce flow through the evaporator on defrost. What is the defrost temperature like when there is nothing on defrost?

Ian

[racknovice]

Thank you for your interest Ian.

In this particular rack system, as the liquid exits the condenser, it can / cannot be fed into the the receiver ( Tyler Enviroguard system). Other than this, liquid then goes through the filter drier directly into the liquid manifold and into each circuit by means of a solenoid valve. I cannot remember any other valve in the liquid line. Also, during a hot gas defrost testing cycle, I checked the suction line temperature up in the evaporators and found it not hot but rather warm.