Nov 14

Cold radiators, where is the heat?

It’s that time of year. The skies are growing dark, the store isles are crowding with Christmas displays and your boiler needs to be serviced. The annual “Startup” of a boiler can most of the time be as easy as turning the thermostat from cool to heat and listening for the roar of the burners. Sometimes, it’s not that easy. Sometimes you may hear the roar, but you don’t feel the heat. That’s what we will focus on right now, “My boiler is running but where is the heat???”

The usual suspect is air. Air is a total show stopper for the hydronic heating system and can cause major grief. Imagine this, water is the mode of transportation for the heat. Heat is doing nothing more than using the water to get itself to where its most useful, cold spots. Once the heat finds a cold spot it unloads on that spot until it is hot and then it moves on. Here is where air causes the problem; where there is air there can be no water. So we have this basic principle: Air means no water, No water means no heat.

Air can mostly be taken care of by bleeding your radiators from the key vents installed on the return side of the radiator, the same process would be applied to convectors. Copper fin baseboard or radiant loops are different in the way that they will most of the time be bled from the mechanical room or wherever the boiler is located. If you require assistance in bleeding your system, please feel free to call for service.

If you are confident that you have removed all the air but there is still no heat to that radiator or baseboard loop, then you have a flow issue. Flow issues are generally caused by circulator pump sizing, expansion tank location or piping arrangements. Keep this in mind; if you bleed and there is no air, then there is no air problem. To learn more about flow issues in depth check out my favorite author, Dan Holohan.


Crown Boilers. Located and assembled in Philadelphia Pennsylvania.

15+ year old boiler with an indirect tank.

Typical radiator. This is one is being used for steam heat.

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