Cold radiators mystery

George Walsh

With a new Lennox steam boiler, I get good heat from all but two radiators, both on the second of two stories. I have cleaned or replaced the vents on all radiators and included a number of adjustable ones. All are full open at this point and I have a nice quiet system. I skimmed and drained the boiler clean after some initial frothing and banging. But the only way to get heat to one of the cold radiators is to close the valve on a larger one downstairs. That still doesn't help the second cold radiator, which is out a much longer run. Assume for now that pitch is not a problem. Would bumping up the pressuretrol by a half a pound conceivably help?

Mad Dog

NO! it always pays to crank it down

you either need better or new main vents. Just make sure the boiler isn't too small. Mad dog

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Unknown

A couple things come to mind

The first is that the boiler firing rate is too small.

The other is that insulation is missing from the piping, which makes it two sizes too small for the load plus the bare piping. No matter how big the boiler is, the piping won't carry it.

Noel

Dale

thermostat

One of the reasons may be the thermostat placement, if it sees set point it will shut off the boiler before the upstairs rads get hot. I too would add main venting and check boiler input. Once you have quick main venting you could slow down the vent at the rad closest to the stat and full open the ones upstairs.
To see if the upstairs supply is ok make sure the rad inlet valves work and then compeletly take out the vent on the offending rad and call for heat. If the air gets out fast and the rad heats quickly the supply piping from the main is probably OK.