capacity issue

[2cool4u]

hi everyone,got called to a site running a low temperature Thermogensis cabinet,set point at -42'C.
anyway,the intial fault reported was oil failure,so upon arrival reset fault and monitor the compressor(a dorin 2s 2500)operation.as in the past the oil sight glass slowly refilled to half way and the darn thing kept on running.tested oil pressre,very good,checked oil sep,again ok.
so i'm sitting there as usual scratching my head thinking this is a one off when the system cycles off at temperature,the control is a solonoid pumpdown type.after a few minutes or so the compressor cycles back on the lp diff,but only until it pumps down again,and again and again.
because of this short cycling i suspect this is the cause of my oil migrating out of the comp. and not returning.
further inspecting i find a sorit or PI type vavle fitted to the suction.this has been used to set up the evaporating pressure on the cabinet.
this also has a pilot valve fitted with an hp signal.
my question is(finally they say!),should this valve be able to provide capacity control to prevent the compressor pumping down and short cycling.
it's been so long since i've seen a valve like this,i don't want to venture into the unknown and make the fault worse.
the only visable info on the pilot is that it's a danfoss cvc type valve,and a vavle stem on the main body which is used to set evap.pressure.
any helpful input would be greatly appreciated.

cheers

[LRAC]

Hi 2cool4u

The constant pump down operation will not help the situation and it may be the EPR valve gradually opening and allowing the pressure to rise and cause the comp to pumpdown again and again.

I cant think why a suction valve would be required at those temperatures when it would have been better fitting a CPR.

May be worth checking on that low temp if the oil sep has its own heater and the crankcase heater is ok.

[Brian_UK]

Why not convert the constant pump down to a one-shot pump down?

Lock out the pump down circuit until the next run period.

[The MG Pony]

I need a evaporator coil for Carrier 40 Ton Condensing Unit Split System and tell u which is ur suggestion for Coil Construction Capabilities Tube sizes; Tube and Fin Materials; Headers and Protective Coatings for a Potato storage.

^ You win A$$ hole of the day award you know that? Spamming multiple forums is bad enough jacking some ones thread to spam one more time is just pathetic!

[2cool4u]

thanks LRAC,just had a look at a danfoss website and indeed it looks like a PM1 CPR valve.i'll check the heater operation on sep and crankcase as well....
roll on monday