Hot gas defrost in commercial refrigeration

[tralex]

Hello, experts
I'm looking for information about hot gas defrost system.
I know some theory, but never seen real system.
It would be great to see working system photo.
Has anyone tried an hot gas defrost system for low temperature islands, how did it work out?
What world's manufacturers use it?
What advantages and disadvantages hot gas defrost system in comparison electrical defrost system?
Thanks for any advance or link.

[tranquanghvac]

the advantages: short time deforst ( my system is 1 minute), no danger of electric leakage, energy saving.
the disadvantages: can make compressor head temperature high, need hot gas solenoid valve+pipe+timer+control devices depend on required design.

[Brian_UK]

Here's a Parker book on HG defrost for ammonia which should be useful to you...
http://www.parker.com/RS/90-11a.pdf

[Pooh]

Tralex
I agree with the advantages listed however if the evaporator coil is not designed for hot gas do not use it as there is secere thermal shock on the coil which in a short time will lead to leaks. The better alternative is saturated gas of the top of the receiver, you still get quick defrost but without the thermal shock. I am presuming you are running multiple evaporators from one compressor or pack otherwise things get very complicated. If yo PM me with an email address I will send you some drawings to have a look at or take a look at the Sporlan site they have some good drawings.

Ian