Problems with a Hitachi 4001SCH Compressor

HI I wonder if anyone could help. I have a Hitachi 4001SCH Screw compressor on a 1993 Hitachi Chiller, running on R22. On start up the compressor pulls 16 amps and slowly ramps up to 75 amps full load over a period of 30 minutes or so. This is a old chiller and works on a primitive loading and unloading system. However test have proved that there is no power to the unloading solenoids, there doesn’t feel that the solenoids are letting by, and the suction pressure is 5 bar, discharge 15 bar at low amps but then at full load amps of 75 amps drops to 12 bar with a SP of 4 bar. on low amps there is limited cooling, however once full load has been reach full cooling. But I can’t see where the compressor is losing. Other things I have tried and tested, Compressor windings, Contactors, and electrical circuits. Liquid by pass appears to be intact and not letting by. The compressor is a rebuild, and was replaced by a and other in 2008. Any suggestions would be appreciated.

Hello steve.

Just a few observations.

I'm not too sure I understand your problem.

You say the comp runs and when it is fully loaded it
runs with about 12b head and 4b back pressures?
You say it takes about 30 mins to fully load but the loading mag valve is not energised?

First thing is, if the system is running fine when fully
loaded what is your concern?

Secondly, How is it loading if the mag valves are not opperating?

I know there are more questions but I think the
logical aproach would be start with the control (loading / unloading) and take it from there.

taz.

.

Hi steve i don,t quite understand the question but when the solnoid valve coils are denergised the compressor is fully loaded,if you need any extra info on how the valves work to load and unload the slide valve ,let me know and i will explain in depth.

Quote:

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Originally Posted by Clive Robert

Hello steve,

Maybe your problem can be solved if you call this no 832-369-8277. They are experts in repairing the Air Conditionings.

Thanks

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Seems like they are experts at being on the wrong continents too!