R22 to R410 conversion

jpm136

Hi

I found this forum through a web search and I am hoping to get some help with a job...

I was called in to replace (York) condenser (15 ton single circut) The (York)air handler 20 ton single circut with 2 coils, 2 tx valves - R22.
Compressor would not come on. I never checked anything on it.

I installed new (Allied Air)10 ton R410 condensing unit.(This was biggest single circut unit available) Flushed system...I did not replace tx valves due to them being in a hard to reach and braze spot.

System is cooling - not great, but holding temp in space.

High side pressure at roof condensing unit is normal - about 325lbs 80 degrees outside.
Low side pressure is low - about 70lbs maybe alittle less
Coil temp around 46 degrees
I take gauges off and get alot of foam at suction connection.

Anyways - high side seems good and low side is low.

Any help on getting this to run better? I may be putting a new airhandler if nessacary - I would rather not.

I figure the tx valves are oversized due to them being 10 ton each for R22 and with the R410 they should be oversized. I was told to replace them with 2- 8.5 ton R410 tx valves. I hope not to have to do this.

Thanks for any help...

newtech

A 20 ton evap with a 10 ton condensing unit???
R-22 TXV's on a 410a condensing unit???
Coil temp 46??? How did you get that?? At 70psi you would be around a 15 degree coil.

Maybe you should have passed on that job if you weren't going to do it right. jmo

jpm136

A 20 ton evap with a 10 ton condensing unit???
R-22 TXV's on a 410a condensing unit???
Coil temp 46??? How did you get that?? At 70psi you would be around a 15 degree coil.

Maybe you should have passed on that job if you weren't going to do it right. jmo



Thanks for reply....

it was a 15 ton condensing unit originally and the higher eff 10 ton R410 should need about the same size coil as the 20 ton R22 - having the R22 txvs fit for the 20 ton should be a very similar opening size as a R410.

The coil is condensating and there is lite frost on distribution tubes.
Like I said I may have to put in a new (10 ton R410) air handler/coil
or
Maybe I should just put the R410 txvs in and try...

Thanks again

nicktech

the superheat swing on the tev is based upon refrigerant pressure internal to the tev. You cannot expect the 410 to work with 22 tev's. those valves must be replaced immediately. make sure there are sight glasses near the tevs in the liquid line to help determine charge. double check the super heat to make sure the old coil isnt to big. to much superheat can kill the compressor over time. not to mention the 4000 cfms required for 10 tons, where your delivering 6000.

DuMass

With the low or fluctuating suction, it sounds like those now oversized txv’s are partially flooding the evaporator.
The thing that would concern me though, is the large amount of foam you’re seeing at the suction port with an HFC refrigerant. My guess would be that it is most likely liquid refrigerant churning the oil in the bottom of the compressor. If the oil slugs the compressor enough, then that will be the end of the suction valves. If it were me, I don’t think I would leave it running like that for very long.

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jpm136

I am going to change the xvalves tomorrow - thanks all for your help.
I will post when complete.

jpm136

Workin great now....
Thanks for the responses!