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Thread: Suction riser
06-13-2004, 09:47 AM #27
Thankyou. So it's not like it's any more special a pump or anything. They just keep the same size pipe, they lose capacity, but keep oil velocity up. I got ya.
06-13-2004, 10:52 AM #28
While there may not be any dark secrets behind Trane's re-inventing refrigerant piping practices, it's still a little scary to me if you consider a 100-120 ton split system with four scrolls in parallel on a direct expansion VAV system running minimum load in cold weather......and no oil traps.
Here's a link to their engineering newsletter article that discusses the "new" piping rules:
You can get away with a lot of piping shortcuts if you're willing to size suction lines at 6#/100ft pressure drop.
Trane's standard pressure drop is half that at 3#/100. Supermarket piping practice is nearly half that again at 1.5 -2#/100 ft typically.
...and if you note the section on suction line piping pitch, they want the suction lines pitched opposite the direction of flow, or back toward the evaporator so the oil won't drain to the compressor during an off cycle. That's just another thing that's contrary to what I've ever seen.