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Baseboard heaters are hot water radiators laid flat along the wall: a copper pipe with aluminum fins inside a metal cover. Air rises through the fins and warms the room. They are quiet and reliable, and when one stops working, the fault is almost always something small.
One baseboard is cold
Air in the loop. The most common cause. Air collects at the high point and stops the water circulating through that section. Look for a bleed valve: on some baseboards it is under the cover at one end; on many houses it is on the pipe in the basement where that loop returns to the boiler. Open it with a bleed key or a screwdriver and a cup until water comes. Then check the boiler pressure, which should sit around 12 to 15 psi cold, and top up if bleeding has lowered it.
The damper is closed. Baseboard covers have a hinged flap along the top. Closed, it blocks the airflow, and the room stays cold with the pipe hot inside. Open it.
Dust and fins. Fins packed with dust and pet hair cannot move air. Take the cover off, vacuum the fins with a brush attachment, and straighten bent fins with a fin comb. Do this every autumn.
Furniture and curtains. A sofa against a baseboard, or curtains hanging over it, stops it working. Leave a few inches of clearance.
A whole zone is cold
Most baseboard systems are divided into zones, each with its own thermostat and either a zone valve or a circulator pump near the boiler.
- Check the thermostat. Batteries, if it has them, and that it is calling for heat.
- The zone valve. A small motorized valve near the boiler with a lever or a light. When the thermostat calls, it should open, sometimes with a click. A valve that does not open, or a zone pump that does not run, is a plumber's job, and usually a quick one.
- A large air lock in the zone, which needs purging at the boiler with the fill valve and a drain, rather than bleeding at a baseboard. Ask the plumber to show you the procedure if it recurs.
The whole house is cold
The boiler: power, thermostat, pressure, and whether it is firing at all. If the boiler is running and hot, but nothing circulates, the main circulator pump has failed. If the boiler is not firing, it is a service call.
Noises
- Ticking and clicking as the heat comes on: the copper pipe expanding through its brackets. Harmless. A little foam where the pipe touches a bracket quiets it.
- Gurgling: air in the loop. Bleed it.
- Banging: rare on baseboard; more likely water hammer in the supply pipes, or a pump problem.
Keeping it working
- Vacuum the fins each autumn
- Bleed the loops at the start of the heating season
- Keep the covers' dampers open and the fronts clear
- Have the boiler serviced yearly
When to call a plumber
- A zone valve or pump that does not respond
- Pressure that will not hold, which means a leak in the loop
- A boiler that will not fire
- Purging a badly airlocked zone
Find a licensed plumber near your town.