No fail... no cold???

[AlexLPD]

Well, as always bring you up, some weird stuff guys... Any tougths please leave in the comments...

The unit in this case is a small meat chiller. The condensing unit originally was of 1/2Hp at 115v, running on R22 and stuff... However the old compressor burnout and other tech, change it for a 3/4Hp compressor.
The past season, we were call because the machine don't work properly... Any way same old... Clean the evaporator, clean the condenser, small leak earl it... Proper charge it... We left working properly....

The Saturday the client call us, the machine wasn't working properly, we showed up... Chek the pressures and Amp on the compressor and funny things start;
LP 30psi, HP 250 psi, 14Amps (10 is the working amp for 1HP to 115v)

as you may guess the compressor was running very hot, so we recall rate the pressures by remove some refrigerant... And try to keep the compressor near 10amp...

At about 30psi and 170psi we achieve this, the TXV was all frosty and nice... Was late and we called a day....

So today I received a call the unit still isn't working properly... So we showed up... Reclaim refrigerant... Fresh charge of R22... And we wait... This time a little more time but the low pressure never move from 30psi ... So I think we got a defective TXV... We changed from an Alco to a Danfoss I haven't have an 00 orifice, so we try an 01...

The low pressure went to 20psi.... We move to the 02 orifice... 25psi... So we changed to another TXV...same... Incredible I have to put an 05 orifice (way to much for this capacity) to get a decent pressure of 50psi @ 170psi an nice 10Amp...

Surprise !!!! .. The evaporation temperature is about 14C even with the frosty TXV ... The evap and the condenser are clean... Also I changed the liquid line filter the TXV respond and eventually goes from 60psi in the star to 50psi and then stop... The suction line don even sweat, isn't even a little chill... No ice on the evaporator...

So we're all the cold went?
it the TXV wasn't working will be no frosty right?... Or even if there wasn't working I will have a flooded suction line and a much lower high pressure... But no...

Any thoughts???

-Alex

[marc5180]

Firstly, why was the compressor changed for one that has 50% more duty? For a refrigeration system to work properly the parts are carefully selected and have to balance. Without seeing the specs of both compressors I suspect this is where your problem lies.

You also say that you changed the expansion valve for a different make? Is it the same type of valve? Is it internally or externally equalised?
Has this system ever worked? And if so then why change the orrifice from a number 00 to a 05? Surely if it's worked in the past then there would be no need to change the orrifice size

Did you even measure Subcooling and superheat at any point? This is much more accurate than measuring amps and pressures.

A full set of figures would be required

Air on to the Evap
Air off the Evap
Saturated suction temperature
Superheat
Air on to the condenser
Air off the condenser
Saturated condensing temperature
Subcooling

[AlexLPD]

Firstly, why was the compressor changed for one that has 50% more duty?

Well it seems the people who changed don't think too much.

You also say that you changed the expansion valve for a different make? Is it the same type of valve? Is it internally or externally equalised?

yes I change the TXV after I saw no pressure adjustment was made... Even holding the bulb with a hand Don't open the valve.

It is a internal equalized valve, yes I chek the Danfoss table the orifice must be in the therm of 00 to 01 ... However as I mentioned before I had a very low pressure, so I change it until I saw a near adequated pressure to work.

Has this system ever worked? And if so then why change the orrifice from a number 00 to a 05? Surely if it's worked in the past then there would be no need to change the orrifice size.

Yes, we let the system working on a nive -6 evap temperature, about 6months ago... Somebody mess with it, as usual. I change the valve as mention, because it won't move even with high temperature on the bulb, an to my understanding it a fault TXV, of course, maybe I'm wrong.


Did you even measure Subcooling and superheat at any point? This is much more accurate than measuring amps and pressures.p

Pherhaps this is the only data I can't have you right know... I don't have a proper clamp or the kit thath comes in to the liquid and suction line to determine the temperature of the gas... What tool do you use.? ... I saw an UEI clamp meter Thath comes with capability of reading a k type probe, and a k type probe in clamp form.
This will be sufficient.?


A full set of figures would be required

Air on to the Evap
Air off the Evap
Saturated suction temperature
Superheat
Air on to the condenser
Air off the condenser
Saturated condensing temperature
Subcooling


Thanks for the reply!