Radiators Not Heating

One or two cold radiators with the rest of the house warm points to something local in that loop, so call and mention exactly which rooms have gone cold.

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When this becomes an emergency

One radiator has stayed cold through several full burns.
The rooms nearest the boiler are fine while the far end of the house is not.
There's a bang in the piping every time the system comes up to temperature.
A radiator that used to heat has been cold since the house sat empty.

What a pro does

The pattern of which radiators are cold does most of the diagnostic work. Everything cold at one end of a run usually means flow is not getting that far, whether from trapped air, a lazy circulator, or a zone valve that has failed closed. A single cold unit in the middle of a warm run is more likely to be that radiator's own valve or vent. On steam the vent is nearly always the answer, and a vent that has crusted over from years of use keeps air in and steam out. Houses that get closed up for part of the year add a wrinkle: sitting idle lets valves seize and vents corrode, so the first heating season after a quiet stretch turns up problems that were fine when the place was shut down.

Frequently asked questions

Why would a radiator quit after a house sat unused?

Valves that don't move for months tend to seize, and vents corrode while the system sits cold, so faults show up on the first real call for heat rather than during the idle time.

Does it matter which end of the house is cold?

A great deal. Cold at the far end of a loop suggests flow is stopping short, while a cold radiator surrounded by warm ones points at that unit's own valve or vent.

What causes the bang when the system heats up?

On steam it's water sitting in a pipe getting driven along by incoming steam. On hot water it's more often pipe expanding against a hanger or a hole cut too tight in a joist.

Are old cast iron radiators worth keeping?

Generally yes. They hold and give off heat steadily, and most of what goes wrong with them is a vent, a valve, or trapped air rather than the radiator itself.

Radiators Not Heating?

Get connected with a local pro now.

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