Confused - Zone Heats Up But No Pressure Reading On External Pressure Gauge & No Flow - HVAC - DIY Chatroom Home Improvement Forum

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Old 11-04-2013, 05:36 PM   #1
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Confused - Zone Heats up but no pressure reading on external pressure gauge & no flow

I have a two zone hydronic heating system. I changed out the pump and and purged the lines. On the 1st zone I purged the zone and pressurized they line to 15 psi. On the 2nd zone (upstairs), I opened the drain valve and no water came out. I added water until about 20psi and stopped. I turned on the heat anyway and had the 2nd zone call for heat. All the radiators were heating but when I opened the drain valve water was emptying. After a few days the psi on the boiler dropped to zero again. I can't find any leaks.

Why is there heat in the pipes but I can't detect any pressure using an external gauge or purge the line?[IMG][/IMG]


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Old 11-08-2013, 09:43 PM   #2
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can you isolate each zone? does each zone have have a separate draw off? If so close each zone and open valve and draw off for the same zone. attach a hose or get a couple of buckets get a flow the water through the zone until all of the air is pushed out and you get a good stream. You can let the pressure get as high as 25-30 lbs when purging. shut of the valves and do the same to the other zone. If it is a big house or has a lot of radiation it make take a while and 15lbs may not be enough initially to over come the existing air in the line.When yo get a good flow turn of water and let pressure drop to around 12-15 pounds reopen all the valves and turn the heat on.


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Old 11-09-2013, 08:52 PM   #3
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If you have automatic air elimination (in some form) on the system the pressure may be dropping over time due to trapped air being released. If the system has an automatic make up water system on it the air leaving should be replaced by water and the pressure drop shouldn't be happening.
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