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Problems with a big vacuum system in Chicago
(I'm posting this for a contractor who was having a difficult time posting. - D.H.)
We have a 26 story condo building on Lake Shore Drive. Extremely well maintained steam boilers and vacuum pump system. Stationary engineer on staff 24 hours a day. The engineer has been in the building for over 25 years. The problem started about three months ago. One tier of the system does not heat and the condensate returns from several tiers stay below 80 degrees for hours, never really heats up.
*The engineer has ran this system in a vacuum 25 years and before he even started there it ran lie this.
*The boiler stays in a vacuum during the entire heating cycle.
*Steam down feed system.
*He runs the system with one boiler unless it is below 15 degrees outdoors.
*The boiler has an input of 8,600,000btu’s
*We have run two boilers each at 8,600,000 total of 17,200,000btu – outdoor temp. 49 degrees
*Incoming gas pressure is more then required.
*After running both boilers for 60 minutes we still have condensate return lines below 69 degrees in this one section.
*We have end-of-main traps in the basement at 155 degrees. They tie into the main return pipe and the temperature lowers to below 85 degrees.
*We have changed all ends of main traps, float & Thermostatic.
*Installed gauges on the tier up stream of the trap with the problem and the end of main stays in a vacuum of 5in wc / the return gauge reads maybe 6in wc vacuum.
*Shut off the gate valve to isolate the steam main from the main condensate return pipe and the main stays at the same vacuum reading.
*Vacuum pump keeps the system in a vacuum of 8in wc when boilers are off. Then the boilers start up and approx. 20 minutes later the vacuum may rise to 3>5in wc during heat run.
*Checked all valves and they are wide open.
My questions are:
*Why are my condensate lines so cool for a section of the building?
*Is it uncommon to have a steam system run in a vacuum during the entire heating cycle?
*Why can I run two boilers and still have what appears to be no steam movement?
*What tests can I further run to determine the cause?
*Am I overlooking some simple solutions?
I thank you for your time,
Retired and loving it.