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steam vacuum no heat

<span style="color:#000080">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.</span>

<span style="color:#000080"> </span>

<span style="color:#000080">Some facts:</span>

<span style="color:#000080">*The engineer has ran this system in a vacuum 25 years and before he even started there it ran lie this. </span>

<span style="color:#000080">*The boiler stays in a vacuum during the entire heating cycle.</span>

<span style="color:#000080">*Steam down feed system.</span>

<span style="color:#000080">*He runs the system with one boiler unless it is below 15 degrees outdoors.</span>

<span style="color:#000080">*The boiler has an input of 8,600,000btu’s</span>

<span style="color:#000080">*We have run two boilers each at 8,600,000 total of 17,200,000btu – outdoor temp. 49 degrees</span>

<span style="color:#000080">*Incoming gas pressure is more then required.</span>

<span style="color:#000080">*After running both boilers for 60 minutes we still have condensate return lines below 69 degrees in this one section.</span>

<span style="color:#000080">*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.</span>

<span style="color:#000080">*We have changed all ends of main traps, float & Thermostatic.</span>

<span style="color:#000080">*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. </span>

<span style="color:#000080">*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.  </span>

<span style="color:#000080">*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.</span>

<span style="color:#000080">*Checked all valves and they are wide open. </span>

<span style="color:#000080"> </span>

<span style="color:#000080">My questions are:</span>

<span style="color:#000080">*Why are my condensate lines so cool for a section of the building?</span>

<span style="color:#000080">*Is it uncommon to have a steam system run in a vacuum during the entire heating cycle?</span>

<span style="color:#000080">*Why can I run two boilers and still have what appears to be no steam movement?</span>

<span style="color:#000080">*What tests can I further run to determine the cause?</span>

<span style="color:#000080">*Am I overlooking some simple solutions?</span>

<span style="color:#000080"> </span>

<span style="color:#000080">I thank you for your time,</span>

<span style="color:#000080"> </span>

<span style="color:#000080">Bob Crokenower</span>
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