Hot water baseboard system

[Mach7]

Hello;

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

[bkrahmer]

So what is the question? It sounds like you are questioning the pressure drop. Where is the pump located in relation to the pressure gauge? If the gauge was on the intake side of the pump, it is quite possible to get a difference in pressure, right? This is what I would expect with a radiant system anyway, having the resistance of several hundred feet of tubing. Not sure with a baseboard system.

brian