Double Risers!

[Youssef]

wanted to get an idea of opinions on the 'double riser'.
do you think there are some definate benefits over trapped single risers, or do your think they are ESSENTIAL?(esp. on LT) or do you think their benefits are only clear 'on paper'?
discuss...

[Dan]

Hi, Youssef.

Double risers, gravitational sloping of horizontal suction lines, and reduced risers make theoretical sense to me in order to accomplish oil return. Intermediate trapping of risers does not, but this is simply my opinion.

I am currently doing a startup of a store with no P-traps properly placed and no reduction in risers of 20 feet. Oil is returning sufficiently for the compressors to run. I would hardly recommend this, and the system is working, so in a way you could say their benefits are only clear on paper.

But I would obey what we consider good piping practices and ALWAYS customer specifications in any installation that I do. These "rules" were likely put into place through the evolution of refrigeration, which when you consider, ammonia and sulphur dioxide were in the mix, no harm in being careful.

I recommend you do a search here using the word "risers" or "traps".:)

[BigJon3475]

http://www.refrig.com/Ref%20Pip%2002.pdf
http://www.hvac.amickracing.com/Refrigerant%20Data,%20Info%20and%20Articles/Refrig%20Piping%20App%20Guide.pdf
http://www.mcquay.com/mcquaybiz/literature/lit_systems/AppGuide/AG_31-011_01082007.pdf