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Vacuum system troubleshooting - guru needed
I have a vacuum return system in a building I am having some trouble with. I was at this building 1 other time a couple weeks ago. The system is essentially a standard Mills system with down feed risers, and the return side runs to the vacuum pump instead of a typicall condensate reciever. The complaint is poor distribution of steam. There are 2 boilers and they claim one is enough by itself until its really cold to heat the building. The only way I could get steam everywhere was to fire both boilers. The vacuum pump will make 10" when I close the inlet valve, so I know its capable. The boilers never make pressure on the gauge, just linger around 0 even with both boilers running.
I guess what I want to know is what is the next logical step. This is a large building, they claim the traps were all surveyed and replaced as needed, but that was a 2 years ago. Its not practical for me to take a radiator survey to prove EDR ratings needed.
How should I proceed? Should the vacuum pull down all the way to the boiler when the boilers are off? If so, this does not happen - does that mean system leaks?