Help w/ Heavy equipment a/c Manufactuer for Manuals

[Richvacr]

Just started working at a mine site - regualr guy quit. Have a number of a/c units cooling oprator cabs and electric control rooms. I can not find any info on these units by googling. The info I have now is they are Sigma or Zigma manufactured by Air Transport International, 7-9 tons, some have R-12 convert to R134a and newer ones are R134a.
Any info would be helpful.

The latest problem is 2 units short cycling: condensor fan off first then compressor - head pressure 220 psi should too low for hps. Curious about the wiring why would the condensor fan operate separate from the compressor (unit has head master - is basically outdoors)

We were there for another unit and noticed this then chased off because the mining equipment was going back into service.

Richard

[abbsnowman]

I'm pretty good with this stuff. If you need help, I would be willing to help you.
The reason the fan cycles is to keep the pressures up. The system operates better at the higher pressure and this also prevents liquid from entering the compressor at lower temps.
Common problems on machines are air and moisture in system due to high rpm of engine which creates low pressures.
Check to see if the thermstat is causing the cycling. is suction line cold? Maybe the hot water valve is faulty?
If you give me more info we can proceed.
Abbs