Low side, high side and suprheat too high

[TERRENAS]

Hi!
Two days ago, i have detected a gas leak on a r12 domestic refrigerator, the leak was on the pipe that goes around the door rubber of the freezer.
So... cut out that pipe and add a new one around the condenser with same diameter and more or less same length... so far so good, i guess...
Then... vacuum and charge it... whith R437a... I ended with low side to high (0,8 bar/ -19ºc ); high side too high (60ºc mesured with a thermometer on the middle of condenser) and the superheat was very high too.

What to do to get the correct pressures?
Add more pipe to the condenser ?

[install monkey]

did you change the drier? vac with a torr gauge? deburr the ends of the pipe?

[TERRENAS]

yes to all, i used a SMAN3... vacuum until 250u....If there was any obstruction, the high side will be high but the low will be low, right?

[nike123]

What is temperature inside?

Probably overcharged! Don't look at superheat until temperature inside is near designed.

[TERRENAS]

in the inside there is -15ºc, compressor never stops, the evaporator frozed just until half ...tomorrow I will go make vacuum and charge it again with less refrigerant, adding later more if necessary .....lets see what happens...

[install monkey]

check tev is set correctly
also check the gauze isnt clogged

[nike123]

I don't think it is txv system. Therefore overcharge raising high and low pressure.

[install monkey]

oops just reread the original post, domestic refrigerator originally on r12 recharged with isceon 49- suitable for r12 replacement - medium temp applications- wheres the -15c coming from?? - stat welded??

[nike123]

I would say wrong terminology. Domestic fridge-freezer and -15°C is in freezer compartment.

[monkey spanners]

Cap tube systems are finicky when you change to a blend, they will only work right if the pt relationship is the same as the old refrigerant, the viscosity of the liquid, the ratio liquid to vapour, and mass flow rates etc are similar.

[PaulZ]

Hi Terrenas
Did you charge as a liquid?
Paul

[TERRENAS]

ok... today i did a new vacuum and a new charge, ended with same weight of refrigerant that is indicate for r12 on the nameplate, now runs perfect!!!
Not understand what went wrong the first time...

[nike123]

Overcharge
Fractionation (charge from gas side)
Noncondensables


Pick one, or maybe 2 or all! http://www.refrigeration-engineer.com/forums/images/smilies/wink.png

[TERRENAS]

Something went wrong, that's for sure...
In my understanding, if it was overcharged, the superheat should be low... right?
It was charged in liquid...
Maybe noncondensables cause that problem...

[mikeref]

An over charge on a warm cabinet using a cap tube will give a high suction pressure along with high superheat and high discharge pressure and temperature. Heat in the evaporator is being removed slowly so it takes some time for a critical charge system to pull down the temperature and your superheat to stabilize.

Hmmm...looking back over the comments, Nike123 has already summed this up on post #4.