Kysor/Warren low temp. rack

[iceburg]

I am doing a start-up on a Kysor/Warren low temp. rack model #TD400-030-PL-3-NH2E-B Hot Gas defrost R507.

I have my vacuum pump hooked up to a spare circuit suction 1-5/8 and liquid 7/8 inch. I am tapped on with a micron gauge at several points-- suction header, liquid header, discharge header, and the farest case.

All the nitrogen has been purged from the system with zero pressure. I started the vacuum pump and she started smoking and shaking like hell! I valved off all the circuits including the condenser and she calmed down but I was reading a different micron reading at each point? I figured the vacuum pump just had to much of a load on it. I opened one circuit (fathest) and she started shakinf again?

I was told that I need to jumper across the headers with a hose in order to bypass all the check valves in the system? This one has me stumped anybody ever experiened this? Any suggestions would be greatly appreciated!!

Regards,

Iceburg

[Brian_UK]

Sounds like your pump is seeing some positive pressures.

In which case then, yes, you need to ensure that all check valves are bypassed and that the whole system is depressurised and linked to form one continuous circuit.

[iceburg]

There was no positive pressure in the system, gauges were showing 30in. But need to pull a 200 micron vac throughout the system. I finally got it but it is an extremely slow pull down. Check valves through out the system were giving me a real problem. I had to jumper around them which slowed things down a bit too. If you ever get on one of these racks and need a low vac on it expect to spend a couple of days and bring the asprin.