R12/R134A refrigerant relief line 1

[dmaffei]

We have a chiller room that had three 800 ton R12 chillers in it. All three were piped into one 6" relief line to the outside. One chiller was replaced with an R123 chiller and had its own relief line put in. We are now changing out the second chiller and want to know if the two refrigerants, R12 and R134A, can be in the same relief line.

 

[bruiseandy]

Ashrae standard 15 covers this...as long as the dishcarge header is equal or greater than the sum of the two chillers you fall within the standard. What are the relief valves set to? The 123 would most likely have rupture discs so yes piping its own relief line is recommended.

 

[lilliput1]

It would be better if each chiller has its own vent. If not, there is a possibility that a relief vent blowing off in one chiller can cause the relief valve of the other chillers to also blow. You can combine multiple vents of one chiller.

 

[RossABQ]

I don't see how one PRV blowing would cause an adjacent one to blow; if anything, the issue is that the backpressure in the manifold would be marginally higher, and it would affect other PRV's oin the manifold. It's not easy to think of a situation where multiple chillers would be blowing at once (a fire? all bets are off anyway).

 

[lilliput1]

I heard it happened at a casino in Atlantic City. The chiller used rupture disk relief and when it blew the backpressure was enough to cause the others to blow. All chillers went down & refrigerant lost.

 

[cme]

i would vent each chiller independently ...... agreeing with lilliput

 

[RossABQ]

No question that independent vents are a sure thing, but I'd be curious what mechanism would cause another rupture disk to blow with high downstream pressure? This would be a similar pressure/loading situation to the disk blowing at a lower internal pressure. Temperature effects?