Retrofit

Greetings From Sri Lanka to all RE members out there.

I am preparing students for ref & ac advanced diploma exam. Past question papers refer to fade out vessel, hunting, etc, ( in retrofit ). I cannot find any info even in latest books.

Someone pl help with required info OR point me to possible sources of info.

Hi environtech,

The words you mentioned are used in refrigeration but I am not sure about the retrofit.

I explain them anyway.

Fade out vessel : This is a vessel just as the receiver to give extra volume for refrigerant expansion. This is used in Cascade systems where the lower stage refrigerant has high pressures at higher temperatures like R23. When the system is off then the components reach ambient temperature. All the R23 liquid vaporizes so to overcome high pressures there must be an extra volume for the expanding refrigerant. The fade out vessel is that extra volume.

Hunting : This is a phenomena in Thermostatic Expansion Valves. What actually causes this is really unknown as there are two different theories. But it happens alright.
In simple word hunting means that the valve is "confused" and it starts to close and open and never equalizes. When this happens the suction pressure starts to fluctuate (goes down and up).
There are ways to minimize the occurrence of hunting but when it happens it might be difficult to correct it.

These basic words are mentioned in every good refrigeration book. Check ASHRAE.

Hope this helps.
Cheers

Please find the attached file which is the ASHRAE explanation for Hunting.

Cheers