Coolzone Fridge/Freezer Problem

[Rotax100uk]

Could anyone advise me as to a running pressure of a R134a Coolzone fridge/freezer please?

Gauges read 20psi standing and 0psi running on suction?

Does this sound about right?

thanks

[drew71]

Hiya Rotax

Sounds about right mate, most domestic R134a gear seems to run between 0 and -5 kPa , Unfortunatly this stuff has very limited points of system access (if any). If you want more of an idea of what the sytem is doing you could possibly use an I.R thermometer and a pressure temp chart to work out superheat/subcooling via a two temp method, though thats probably overkill.
Is this for a job or as part of your studies ?

Cheers
Drew

[Rotax100uk]

Is this for a job or as part of your studies ?

Both really, i do work with fridges (R134a) and freezers (R404a) and i havent really had anything to do with fridge/freezers.


Sounds about right mate, most domestic R134a gear seems to run between 0 and -5 kPa

Yeah it was around this pressure on the gauges and assumed that the charge was low.


Unfortunatly this stuff has very limited points of system access (if any)

With this fridge/freezer i used a line tap valve.

My only reason for fitting a line tap valve was because the freezer at the top had a report of not freezing but the fridge was working fine, so i fitted the line tap valve to just check the suction pressure as there was very little heat on the discharge pipe and on the condenser. which lead me to believe the charge was too low, charged up the fridge/freezer to around 2psi suction and the suction pipe started freezing over so this indicated to me that there was a overcharge of refrigerant and i checked inside the fridge the next day and the fridge had became a freezer and everything inside was frozen, thermostat was set at 5 (1 low - 5 max) so after turning the thermostat down to 1 the fridge and freezer apeared to be working fine.

I think i will recover the refrigerant and recharge to the correct amount from the data plate inside the fridge using scales.

Thanks for your reply this has helped alot.

[paul_h]

look at a PT chart, r134a at the temps freezer run is close to 0kpa, so it's normal for fridge/freezers.
Normally an undercharged/blocked system will run very high discharge temps.
By all means weld in a schraeder valve and recharge to given specs, but I would be looking more to poor air sealing of the freezer or inefficient compressor if discharge temp was low and the freezer wasn't cold enough but the fridge is OK temp.
Make sure to give it a really deep vacuum before charging too.

[Rotax100uk]

Thanks paul i will have another look over at the weekend, thanks very much for your reply.