help needed ,

[wilks]

Hello guys ,

i have just fitted a new comp on a domestic fridge on r134a, 130g put in , what would you think is a reasonable ruuning pressure?

when i added the gas and turned compressor on , it pulled my gauge down into a vac as if i had front seated the service valve ?? its on a capillary device which coming from air con back ground i have not really worked on ,

i changed the gas dryer , could there be a blockage on the capillary when i re-inserted it ?

after re-fitting the dryer , i was getting 0.6bar low side pressure and about 12bar high side ??

any help is much appriciated

thanks alan

[DVaider]

Check out the phase connection accuracy in your compressor.

[Andy W]

Is the compressor bigger than the old one, if it is that could be the problem, if it is an exact size for size match the chances are that you have blocked the capillary with solder.

[wilks]

thanks for your help guys ,

[taz24]

thanks for your help guys ,

How are you measuring the pressures because domestics have no access to the discharge.
.5 of a bar is not untoward for the suction of a domestic fridge.
The cappilary line could be blocked or partialy blocked, but if it is running what are the temps in the fridge?

taz.

[wilks]

How are you measuring the pressures because domestics have no access to the discharge.
.5 of a bar is not untoward for the suction of a domestic fridge.
The cappilary line could be blocked or partialy blocked, but if it is running what are the temps in the fridge?

taz.

hi taz

its a drug fridge at a hospital , it has a access port on the gas dryer ,

it actually gets down to 3oC so its working , it a medium size fridge , do you think that 150g is enough??

[taz24]

hi taz

its a drug fridge at a hospital , it has a access port on the gas dryer ,

it actually gets down to 3oC so its working , it a medium size fridge , do you think that 150g is enough??

So its approx the size of a domestic fridge.
150g seems a reasonable figure but the temps and the pressures will prove it to be ok.
If its down to temp then let it run and see what happens.
Cheers taz.

[wilks]

So its approx the size of a domestic fridge.
150g seems a reasonable figure but the temps and the pressures will prove it to be ok.
If its down to temp then let it run and see what happens.
Cheers taz.

thanks taz

[coldcraft]

Hi,
The Normal runnig back pressure foa a domestic unit is
5 - 8 PSI

[paul_h]

Fridges these days are dodgey things at best. They are designed to run at low presure, high TD because humidity isn't considered anymore. This setup means minimal evap size and refrig charge.
First of all, did this cabinet have a critical charge labelled on it?
If not, it's best to find that out from the manufacturer directly. Otherwise the best bet when charging is to disconnect the evap fan and charge until the suction line frosts back to the heat exchanger (if fitted) or compressor.
If there's a blockage in the capillary it usualy runs in a vacuum on SP, plus you'll never get liquid frosting to the HX/compressor with the fan off (which is why it's a handy way to charge capillary systems.)

[AYIBIBIO]

Hello guys ,

i have just fitted a new comp on a domestic fridge on r134a, 130g put in , what would you think is a reasonable ruuning pressure?

when i added the gas and turned compressor on , it pulled my gauge down into a vac as if i had front seated the service valve ?? its on a capillary device which coming from air con back ground i have not really worked on ,

i changed the gas dryer , could there be a blockage on the capillary when i re-inserted it ?

after re-fitting the dryer , i was getting 0.6bar low side pressure and about 12bar high side ??

any help is much appriciated

thanks alan

NOW YOU DON,T HAVE TO WORRY ABOUT THIS, BECAUSE MOST OF DOMESTIC FRIDGES WITH R 12 AND R 134A WORKS ALMOST IN VAC. R 134A AT -30 IS ALMOST VAC. YOU NEED MORE EXPIRIENCE TO WORK ON DOMESTIC FRIDGES. THEY LOOK SIMPLE BUT THEY ARE NOT. SEE YOU

[coldcraft]

Domestic refrigeration back pressures are normally left running at 5 Psi.
From what you are saying it would seem that there may be a blockage at the evaporator plate end (this is not unusual with domestics). I would suggest that you refit a new drier whilst purging the system with a small amount of N2,if after you have fully vacc'd the system and charged it if you are still getting a negitive pressure then it may be time to replace the cabinet.

[przemo2]

thanks to you all