Hot water baseboard system question

Old 01-10-10, 04:48 AM
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Hot water baseboard system question


I have an oil fired hot water baseboard heating system in my home. 7 zones...pretty standard system for Nova Scotia.
The furnace is located in the basement.

When all zones are shut off the pressure gauge reads an exact 10psi.

when an upstairs zone comes 'online' the pressure drops to 4 psi and sometimes 8 psi...depending on the intiail temperature of the boiler.

For example....if the respective zone opened when the boiler happened to be at 'cold' say 160 degrees, then the pressure would drop down to 4 psi and slowly increase to 8 psi when the system heated up to the high temp shutoff of 200 degrees.

If the zone happened to open when the boiler was already warmed up ...around 200 degrees. then the pressure usually stabilizes at 8 psi.

the downstairs zones (same level as furnace) give an initial 10 psi when the system is warm and 8 psi when the system is cold.

I have listened to the circulation pump and will 'occationally' hear some air bubbles being passed,but otherwise it sounds normal. I have installed new airerators on the high points of the system,and they seem to work normally.

A new expansiion tank has also been installed.

I have only been in the house for 6 months, but it is 8 years old....not leaks have been detected anywhere.

Thanks for your help

- Jim
Old 01-10-10, 02:47 PM
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You need to get the "cold" pressure to 12-15 psi. There should be a pressure reducing valve in the line between the house pressure & the boiler. It may look like one of these: Pressure Reducing Valves - Bell & Gossett world leader in supplying the Heating/Ventilating/Air Conditioning (HVAC) industry.

You could also have one of these: Amtrol - FILL-TROL
(The key part is the brass piece directly above the tank)
With it the boiler fill pressure is regulated by the pressure in the tank. Get the tank pressure up to 12-15 & water should be fed into the system.

Make sure any valves in that line are open. If all valves are open, you might have a plugged or bad reducing valve.

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