A defrost controller thoughts.....

It is a well known fact that all freezers controllers switch from colling to defrost at once.

In case of hot gas defrost (HGD), this accrue when the evaporator is usually full of refrigerant.
The liquid refrigerant is being pushed by the hot gas to the compressor head via a liquid separator that can not cope and the unfortunate result is damage to the suction valves and the pistons.

To overcome this problem, I have connected an in line timer between the controller and the defrost solenoid, setting it for 4 min.
This is enough time for the compressor to preform a pump down and get a smooth useful and quick defrost.

Before any silly question, of course there is a KVC ahead of the liquid separator.

Chemi:)

Minus the 4 mins your using for pump down, is it still a sufficient defrost?

Yes.

The total defrost time is 30 min, every 3 hours at -20°C room temp.

There are two evaporarors in the freezer.

When I return from beatiful southern Italy at the end of may, I will post a few pictures {of the freezer....:D}

Chemi:)

the controllers we normally use in supermarkets integrate an adjustable pump down time to allow for this phenomena

I was talking abot Dixell XR06CX which is commonly used or eliwell 974.

Supermarket controlls are much more inteligent and vesatail.

Chemi :)

ah I see, yes the little ones can be pretty basic thats for sure