walk in freezer

[ail]

Hi there
I am working on a small walk in freezer with R404a which has not fitted with sight glass. It was short of gas when I fitted the gauges on. What pressure should the unit be to get it to -20c? And what should be if it is a walk in fridge?
Thanks.

[taz24]

Hi there
I am working on a small walk in freezer with R404a which has not fitted with sight glass. It was short of gas when I fitted the gauges on. What pressure should the unit be to get it to -20c? And what should be if it is a walk in fridge?
Thanks.


You will need to find out where the old refrigerant has gone first. Pull all the refrigerant out and then repair leak. On the thing somwhere will be a lable telling you how much refrigerant to weigh into it to correctly charge the system.
You should never just add gas, but you knew that did'nt you?
As for pressures just get your compariter out and see what the saturation pressure of r404a is at about -30degC.
You will not be able to tell how much refrigerant there is in a system by pressures alone.

Cheers taz.

[powell]

Hi there
I am working on a small walk in freezer with R404a which has not fitted with sight glass. It was short of gas when I fitted the gauges on. What pressure should the unit be to get it to -20c? And what should be if it is a walk in fridge?
Thanks.
What taz24 said plus, if its your plan, its not wise to just turn the temperature up and run as a cooler.

There are other things to consider. The most important being, will the compressor handle the higher SP. Two other items that come to mind are the controls and the TD across the evap.

Many LT404A units will also pump R134a for MH temps, but this would be a permanent change if you decided to run as a cooler.

[powell]

As for pressures just get your compariter out and see what the saturation pressure of r404a is at about -30degC.

Cheers taz.
taz24,

Help out this ole Southern guy across the pond. I assume a "compariter" is a P/T chart? I did fiqure out what a "phile" is.

[Blinky]

404a evap @ -6 for a coldroom temp of 1*C = 56psig

for a freezer room @ -28*C Evap = 17psig

[Magoo]

Possibly on a capilary tube expansion, so no sight glass and hopefully no receiver. System charge on name plate.
First, find the leak if you are sure it is short of gas, if capillary it will run lower suction pressure.
More system info required.

[Gaafar]

if the room temp. is -20 oC, then the SST saturated suction temperature have to be -26 or -27 oC, temp difference for practical and ecnomical use is 6 to 7, so see pressure @ SST

[Brian_UK]

Check out the OP date guys, and he hasn't come back either.

[Magoo]

OK Brian_UK
thanks and bugger