Subject: testing oil miscibility/oil return

From: [email-masked] (George Goble)
Date: 21 Oct 1995 11:52:52 GMT

For all you experts out there on oil return in R-12 low temp systems.

I built a refrigeration test stand out of a 2-ton med temp R-12
semi-hermetic Copeland compressor.  The goal is to try to force
oil logging (poor oil return) to occur.

Evaporator is a 50 foot coil of 5/8" refrigeration copper, in free air,
no fan or fins.  The coil diameter is around 14 inches and spread out to
be about 2 1/2 feet deep.  The centerline of the coil is parallel
to the ground, providing each loop (11 of them) a chance to "trap"
oil.  Sight glasses all over the place.  Evaporator heat can be provided
>from  direct electric heating of the coil, upto 310 Amps, approx 5V.
The liquid line has a 1 foot rubber hose (automotive barrier hose) 
segment to block current flow thru the condenser and compressor.

The (hand operated) metering device is a multiturn needle valve, 
approx 4 tons capacity wide open.

The suction line, is a 6 foot piece of 7/8" vertical (straight up)
copper, followed, by a 6 foot horiz run (also 7/8").  The horizontal
run has a "low spot", about 1 inch lower than the ends, for oil to
collect in (and a sight glass).  There is also a manual EPR
(ball valve, with 3/4" opening), with low side gauges on either side
of the valve.

Operating temps on the evap, with R-12-like refrigerants will be -30 to -40F,
so the 2 ton med temp compressor will be delivering less than 1/2
ton effective.  This should further magnify the effect of the
large diameter suction line on poor oil return.

Can anyone think of anything more torturous for oil logging?
100ft suction line?

thanks in advance
--ghg

---

From: [email-masked] (James Storm)
Date: Mon, 23 Oct 1995 02:22:58 GMT

In article <[email-masked]>, [email-masked] 
says...
>oil logging (poor oil return) to occur.
(snip)

I admire your test stand but I don't think you should use R-12 as your 
test refrigerant. Pick some of the newer refrigs. and see if what the 
manufactures are telling us about oil return and old oils are true. You 
might open a few eyes...;)
                       Stormy ([email-masked])