in-efficient compressor ?

[HelpCoolIt]

Hi I am an Australian fridgie with a background in domestic airconditioning, I have taken the leap into refrigeration with a new job and am riding the steap learning curve.

I Have replace the condenser in an under counter fridge due to a faulty compressor the old condenser at one stage ran a freezer as well which has long been disconnected so therefore we installed a smaller replacement condenser.

Apon recomissioning I had a high suction pressure, a low discharge pressure, extremely high superheat and very little refrigeration happening there was also very little heat comming of the condenser and a cool liquid line.
I tried to adjust the Tx valve which improve the superheat but not the high suction etc.
My new boss suggested replacing the Tx valve and reducing the orifice size I replaced both reducing the orifice from an 00 to an X0. This improved the operating conditions a little but the suction was still high the discharge still low etc.
I must say this system had me baffled. I spent way to
long on this system its still not running and the boss will probably loose money on it.
On the 45 minute drive home I was running over all I had done in my head and while I didn't think any thing of it at the time (My mind was on the Tx valve, it was late and Im not use the such small systems) I remembered that while trying to pump the system down to replace the Tx valve it took along time and wouldn't pump below 300 Kpa.
I now believe I was probably sent a condenser with a dud compressor, pumping but not efficiently.

what do you think ? any other suggestions ?

Thanks
Dean

[old gas bottle]

maybe, decant all the gas and run it with the gauges on to see if it pulls a vac,switch it off and see if it holds it,assuming the gas is the same as on the valve or compatable,if the unit is not the same as the manufacturer fitted you will have to guess the charge ,meaning do it by way of a sight glass and not the weight, charge it slowley if the comp seems o/k,it also sounds like it could have been overcharged ,change the drier of course, put the TEV back to where it started,if that dont do it we will think of the next step.

[Peter_1]

This is something which allways comes back: what were your pressure and temperature readings?
LP, HP, SC, SH, discharge temperature and please in both units if possible.
Used gass?

Without these numbers, we and certainly you never can't proper diagnose a refrigeration system.

[binoy]

your compressor pumping is not efficent and flush gas creating there,s

[setrad7791]

Low head pressure and high suction pressure aye!!! you will most probably find that your condensing unit is not correctly matched to the evap... if they are correctly matched than the most probable cause is a faulty tx valve! causing to much liquid to flood through the evap and back to the compressor. this would also be the reason you cant pump the comp down as the sump of the comp is full of liquid! my suggetsion would be to fit a new tx valve matched to the evap at the right suction temp and check compatabiltiy of the condensing unit! if your unsure as to the capacity of the evap, measure the dimension's (length width height/ size of tubing/ number of u-bends/finspacing i.e number of fins per inch!) then give the specs to your local supplier (kirby/actrol/heatcraft)

[DeB]

You really need to supply low and high side pressures as well as the temperature at the bulb to make the correct diagnosis. Many modern hermetics especially high temp models will not pull a vacuum. Also this can cause spot burns on the winding or track current across the back of the fusite terminals inside the compressor. As long as the compressor will pull a low pressure against a good head and does not leak back onto the low side of the compressor with the suction valve closed, it is REASONABLY safe to assume the compressor is pumping. It is possible either the wrong refrigerant or a mixture is in the system.Check the refrigerant on the bottom of the TX valve.

[wkd]

I'm with Peter1 on this one.If you are not all that experienced on this type of kit go back to basics and always record pressures and Tempsthis will give you a clearer picture of what is going on and may quicken your fault finding process.Also when you share it on the forum you can give the forum some definite numbers to work with and consequently help you out.Hope you solve the problem soon so as not to upset the boss too much good luck!