Federal open face cooler freezing

[mwright]

Freezing starts at TXV and continues to the evap coil. 404ALow side is 43.2. High side is 323. SH is 20SC is -45. 5.12 amps on run wire from compressor. Do you think I have a restriction in the TXV or am I low on 404?I have evacuated this thing twice and put in 64oz as specs say. It ran fine for about 3 weeks then started freezing up. Any help is greatly appropriated. Thanks

[marter]

id say pull the gas out, replace txv, while its out blow both sides out with nitrogen. make sure your pulling a DEEP vacuum

[ECtofix]

I agree with the TXV. The high discharge pressure is an issue too though. You didn't mention concern over that, but check that condenser and clean it good. POE oil doesn't fare well to a high side running hot.

[icemeister]

Post the model number of the case and we'll have a much better chance of helping you.

Where were you measuring the superheat? At the evaporator outlet or at the compressor? A 20ºF SH might be OK at the compressor but way too high at the evap outlet.

Did you say 45ºF subcooling? That's too high, but may be explainable if your evaporator SH is high as well...and there's no receiver.

The Federal cases I've seen are control temperature by a low pressure control, typically set at around 42#CO/85#CI for R404A and defrost is controlled by a mechanical timeclock. I'd start by verifying these items' operation along with proper SH before condemning the TXV.

Do you have the manual? Here's Federal's manuals page:

http://www.federalind.com/index.php?...ls-parts-lists

[mwright]

Yes I do have the manual thank you

Model is SC478

SC Temp is Negative 45 not positive 45
Measuring SH next to compressor so yes 20 is not bad. Measuring SC just before the condenser coil.
I am concerned about the high pressure on the high side sorry I don't mention it.
Also pressure setting are set to the manual which are 42 & 82. I was thinking maybe the pressure switch was bad because it will come on then the low side pressure will drop fast but not low enough to shut it off according to set pressure but it will shut down.
Thanks for all the help!!

[crackertech]

Yes I do have the manual thank you

Model is SC478

SC Temp is Negative 45 not positive 45
Measuring SH next to compressor so yes 20 is not bad. Measuring SC just before the condenser coil.
I am concerned about the high pressure on the high side sorry I don't mention it.

You need to take sh at the evap coil as well.

[mwright]

You need to take sh at the evap coil as well.

So take it next to the TXV? The TXV is a bout 10" from the evap coil.

[2sac]

Any air diffusers located above the unit? Honeycombs clean?

[icemeister]

For evaporator superheat you need to measure the temperature at the outlet end of the coil where the TXV bulb is attached.

For subcooling, you need to measure the temperature at the outlet of the condenser coil.

There is no such thing as negative subcooling. It sounds like you were measuring the discharge line temperature, not the liquid line.

[crackertech]

So take it next to the TXV? The TXV is a bout 10" from the evap coil.

Yep 6 to 8 '' from the evap coil.

[jpsmith1cm]

Yes I do have the manual thank you

Model is SC478

SC Temp is Negative 45 not positive 45
Measuring SH next to compressor so yes 20 is not bad. Measuring SC just before the condenser coil.
I am concerned about the high pressure on the high side sorry I don't mention it.

Is that a typo or did you mean to say that you are measuring the temperature at the inlet to the condenser. At that point in the system, you will have superheated gas as you are supposed to, explaining your 'negative subcooling' reading.

[jpsmith1cm]

Yep 6 to 8 '' from the evap coil.

How ya been, Cracker?

[mwright]

Is that a typo or did you mean to say that you are measuring the temperature at the inlet to the condenser. At that point in the system, you will have superheated gas as you are supposed to, explaining your 'negative subcooling' reading.

Yes between the compressor and the condenser coil but closer to the coil. Am I supposed to Benin the other side of the coil, the output side?

Incase you haven't figured it out I'm new to this and I appreciate all the help. Where I work doesn't have anyone with the time to train me so I'm digging in and learning as I go. :-)