Mismatched system?

[DaveinOzark]

Ok guys- I have an issue with a walk in cooler.
Evaporator: LET0941V- looks like it is rated at 8550 btu/hr @ -20 evap, 10º TD
Compressor: RS70C1- PFV… looks like it is rated at 6800 btu/hr @ +20 evap if running R-502 (or some variant thereof). Oil is listed as mineral on data plate.
Box is 13.5' x 5.5' x 7' tall
This unit has an R-22 expansion valve (and presumably running R-22)and a terrible pull down time. My suction pressure was high and was not coming down- can't recall exactly how high.
The customer just moved into a building that had been vacant for a bit and this equipment was existing. I started it up for him- told him there was going to be a problem here but, with no traffic, the temp dropped overnight. I told him I'd see him when he got some traffic in and out because there was no way it was going to hang in there.

So I am heading there tomorrow. I am not sure what this evaporator will do at a 20ºF but I am sure it is a hell of a lot more than the compressor will.

Is there any hope here? Where would you start?

[UmmScott]

What were you're actual running pressures?

At FIRST glance it appears that the evap is rather big in capacity wise for that condensing unit. It's a 2 fan?
So basically your going to have a low TD like maybe 10 or even lower depending on how big that evap is.
You never know
...maybe it was sized for high humidity which would = larger evap coil.

[DaveinOzark]

I do not recall the running pressures but I am going back this morning. The evaporator has defrost heaters and seems to be intended for low temp operation according to the ratings I can find.
This is one of those calls you walk into and look around to see if anyone saw you there because just maybe you can sneak back out
It is storming like crazy here but I will be fighting with this this morning- Ill have more info in a bit. Any info on running running R-22 on a compressor that is rated for running med temp with R-502?

[icemeister]

I don't have the original data sheet for this one, but the current one indicates that the LET094 would have a nominal capacity of 9400 Btuh at a 10 Deg F TD with a -20 Deg F evap temp. There's a correction factor of 1.15 for operation at +20 Deg F evap temp, so the capacity would then be 10,810 Btuh. See p.6 for the correction factor chart:

http://www.heatcraftrpd.com/PDF/Bohn...-WALKIN-LP.pdf

The RS70C1 compressor is probably in an F3AM-A105 condensing unit, which at a 25 Deg F SST with R22 and a 90 Deg F ambient would have a capacity of 9620 Btuh. It looks like the LET evaporator would then balance with this unit at around 26 Deg F SST, or approximately a 9 Deg F TD. It's a little bigger than average, but not what I would call significantly so.

Get your suction & discharge pressures and the actual supply voltage and check the compressor performance using the Copeland mobile app or their performance calculator program.