simple hot gas defrost circuitry

[mikeref]

Also, at -2C...there is no need to run a pump down. Just have the liquid solenoid de-energize when defrost cycle initiates.

[Rob White]

Also, at -2C...there is no need to run a pump down. Just have the liquid solenoid de-energize when defrost cycle initiates.

I don't want to sound pedantic, "me pedantic" I know, I know..................

But not wanting to be pedantic is that not a pump down anyway?

Controlling the liquid so it is pumped into the receiver whilst on
defrost or at temp is called a pump-down cycle in the UK?????

Edit I have just re-read your post and I get it, "by Jove he's got it", I think?
You mean turn of the comp on the controller and de-energise the mag valve
at the same time????

If that is what you mean, I understand what you mean, if not sod off I'm confussed



Rob

.

[mikeref]

I don't want to sound pedantic, "me pedantic" I know, I know..................

But not wanting to be pedantic is that not a pump down anyway?

Controlling the liquid so it is pumped into the receiver whilst on
defrost or at temp is called a pump-down cycle in the UK?????

Edit I have just re-read your post and I get it, "by Jove he's got it", I think?
You mean turn of the comp on the controller and de-energise the mag valve
at the same time????

If that is what you mean, I understand what you mean, if not sod off I'm confussed



Rob

.

Haha Yes Rob. May i re-submit. No need to pump the system down for a defrost cycle.

When power to the Compressor is cut via thermostat or Defrost cycle, power to the Liquid line solenoid is shut down. ( Comp And LLSV on the same control circuit.)

[chemi-cool]

Haha Yes Rob. May i re-submit. No need to pump the system down for a defrost cycle.

When power to the Compressor is cut via thermostat or Defrost cycle, power to the Liquid line solenoid is shut down. ( Comp And LLSV on the same control circuit.)

I'm with you on that one mike. Just one little thing, LLSV should as close as possible to the TXV.

[Tycho]

I'm with you on that one mike. Just one little thing, LLSV should as close as possible to the TXV.

Better to have the defrost controller close the solenoid and pump let the compressor run till it stops on low pressure. This way you remove the refrigerant from the evaporator and make an ambient defrost faster.

That is basically what a pump down is, closing the liquid supply and let the compressor stop on the low pressure switch, but start again as soon as the LP switch rises when the solenoid opens after a defrost.


on the other hand, you have Pump out, which means that once the compressor stops on the LP switch, you have to manually start the compressor again.

[mikeref]

Better to have the defrost controller close the solenoid and pump let the compressor run till it stops on low pressure. This way you remove the refrigerant from the evaporator and make an ambient defrost faster.

That is basically what a pump down is, closing the liquid supply and let the compressor stop on the low pressure switch, but start again as soon as the LP switch rises when the solenoid opens after a defrost.


on the other hand, you have Pump out, which means that once the compressor stops on the LP switch, you have to manually start the compressor again.

The "standard" Pump down cycle on many commercial cool room kits are using the method i mentioned above. Two reasons. 1. It's a waste of energy to constantly pump down on every cycle.

( Credit to Chemi for mentioning the position of LLSV.)

2. Mechanical contacts on a LP switch tend to fail after X number of cycles.