| "Pumping away" is good advice and the preferred solution. However, there may be another, simpler fix.
Although "pumping away" is accepted as good practice, it was not always so. For example, the Bell & Gossett Engineering Manual from the early '50s recommends the arrangement that you seem to have, and many systems were installed that way, and work satisfactorily - particularly for 2-story houses with the hot-water boiler in the basement. The modern book by Siegenthaler, while recommending pumping away, does recognize that your system's approach was followed for years with satisfactory results.
Has your system ever worked satisfactorily? Was the pump recently replaced with one that has greater capacity (possibly resulting in higher pressure drop around the circuit)?
Three zones for a 2200 sqft house will cause quite a bit of pressure drop when just one zone is calling for heat. Have you always had three zones?
What is the pressure of the system when it is cold and when it is hot? Try jacking it up to about 18-20 psi (cold), and see if that helps.
Bleed the radiators again with the pump off.
You should have an air removal device installed in your system, no matter what piping arrangement you use.
I'm hoping that maybe you can get by at least until spring.
Doug  |