Steam radiator (C) Daniel Friedman Guide to Heating Radiators, Baseboards & Convectors
Diagnose & Repair Cold Radiators or Baseboards

  • RADIATORS - CONTENTS: How to identify, inspect, diagnose, and repair problems with hot water or steam radiators, baseboards, or heating convectors - if your radiator or baseboard is cold and the heating system is "on" - here we diagnose the problem. Where leaks occur on hot water and steam radiators, convectors, and baseboards. We discuss: cold radiator problems, how baseboard heat works, how convector heaters work, how to assess unusually sized or shaped baseboards, heating convectors, or radiators.
  • POST a QUESTION or READ FAQs about troubleshooting heating system radiators, baseboards, convectors - hot water heating systems and steam heating systems
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Cold radiator diagnosis & repair home page:

This article series describes the types of all types of heating radiators: hot water, steam, cast iron, heat convectors, baseboard heat, electric heating convectors, and we explain the diagnosis and repair of no-heat or leaks or other problems with heating radiators.

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How to Identify and Diagnose Problems With Hot Water or Steam Radiators, Baseboards, or Convector Units

Steam convector heater (C) Daniel FriedmanIn addition to cast iron radiators using hot water or steam as a heat source, we describe two other very common hot water heat distribution methods below. Our photo above (at page top) shows a typical "one pipe system" steam cast-iron heating radiator. A single pipe delivers steam to the radiator and condensate from the cooling steam returns to the heating boiler via that same pipe.

[Click to enlarge any image]

This article series answers most questions about all types of heating systems and gives important inspection, safety, and repair advice.

Below we describe the identification and function of different types of heating output devices in hot water or steam heated buildings. First, here is a quick no-heat diagnostic guide for radiators & baseboards. Detailed diagnostics are in the articles we cite.

Article Contents

Radiators or baseboards do not get hot? - Quick Troubleshooting

Is the heat on? Make sure that your room thermostat is set to a temperature higher than the temperature in the room - so that it is calling for heat.

Is the heater working? Make sure that your heating boiler is working, that is that the heating boiler turns on and off normally. A hot water heating boiler may not turn on immediately when you turn up the room thermostat: if the water temperature in the boiler is already above the aquastat's cut-in temperature the circulators will send hot water to the radiator and the boiler will turn on later when its temperature is dropped by returning water from the cooler radiators in the building.

Don't forget to check for having run out of heating fuel. If your heating system is not working properly, see NO HEAT - BOILER.

Are the radiators turned on? Make sure that the control valve at the heating radiator is "open" or "on".

Are your radiators heated by hot water or steam?

The heating system troubleshooting articles listed just below address nearly all problems with hot water or steam radiators.

If you don't know what kind of heat your building uses, we explain how to figure out the answer

How Does Heating Baseboard Work?

Hot water heating baseboard is warmed by hot water circulating through either finned copper tubing or through cast iron baseboard sections. Carson Dunlop's sketch (below left) and our photo of a heating baseboard (below-right) show a typical modern hot water heating baseboard system installation.

Heating baseboard (C) Carson Dunlop Associates Heating baseboard (C) Daniel Friedman

Heating baseboard warms the room by a combination of radiation (the hot baseboard radiates heat onto surfaces in the room) and convection (cool air enters at the baseboard bottom, is warmed, and exits at the baseboard top - see Carson Dunlop's baseboard sketch above left). Electric heating baseboard also warms by radiation and convection but the baseboard itself is heated by an electric element rather than hot water.

What is a Heating Convector or Wall Convector? & How Do Heating Convectors Work?

Heat convectors (C) Carson Dunlop Associates Heating convector unit (C) Daniel Friedman


Heating convector wall recessed (C) Daniel Friedman

Sketch of a wall convector (above left) courtesy of Carson Dunlop and our photo (above right) show a traditional wall-mounted heating convector unit.

Our photo was taken in a 1920's home in New York. A heating convector unit operates much like a radiator (page top photo) but instead of thick cast iron used to radiate heat, the convector is made of copper tubing covered with metal fins, or of cast iron with cast-in fins.

Our photo (left) shows a leaky heating convector that was recessed into the wall. While recessed heating convectors were popular for aesthetic reasons (no radiator projects into the room), often a high percentage of the heat is flowing through the exterior wall to outside.

We discuss this problem in more detail

Steam convector heater (C) Daniel Friedman

The heat source in a wall-convector may be forced hot water, gravity hot water, steam, or the unit may be heated by electricity.

Electric-heated wall convectors and some other convector units may incorporate a blower fan to increase the heat output from the device. Our photographs of a wall-mounted heating convector (above) show a wall unit that is heated by steam.

Conventional wall-mounted heating convectors (units that do not include a fan or blower) rely on natural movement of warm-air upwards to draw cooler air in from the floor level. You'll notice that there is a very generous air intake space along the bottom of the convector - it is designed to move plenty of air across its heating coil.

As the convector gets hot, cool air is drawn up from floor level, is heated by the fins on the convector, and warm air is supplied out of the convector's front grille.

Details about wall convectors used for heating or cooling and about convector blower fans are found


Fan-Driven Heating Convector Units

Electrically-heated, steam heated, or hot water heated fan convector heating units similar to what you see in our photo here but boosted by a fan that blows room air across the heater are discussed


Wall Heating Convector Heater Maintenance

Heating convector unit (C) Daniel Friedman

Once every year or so, we like to take the covers off of heating convectors to inspect the unit for leaks.

While we're at it, we make certain that the heat exchanging fins on the heating convector are not dust-clogged (photo at left). If your building is occupied by pets who shed much hair this step can be very important.

Getting good air flow through the heat exchanging fins of all finned heat exchanging devices such as heating convectors or finned copper tubing heating baseboards can make a significant difference in liberating the heat output from the device.

Just gently vacuum off the convector using a brush attachment and your vacuum cleaner - take care not to bend the fins. A heating service contractor can provide more aggressive cleaning using special products, but on residential heating equipment that has not been exposed to some unusual problem we usually don't find it necessary.

Also see FAN CONVECTOR HEATERS - HYDRONIC COILS for additional details.

What are These Unfamiliar, Weird-Shaped or Oddly-Located Heating Radiators?

Ceiling mounted heating radiator (C) Carson Dunlop Associates

If you are wondering why a cast iron radiator is found mounted high on a building wall or even on a ceiling, the explanation may be found in the sketch (above left) from Carson Dunlop Associates.

Plate warming home heating radiator (C) Daniel Friedman

For buildings in which hot water circulated through the heating distribution system by gravity - that is, without using the forced hot water provided by a circulator pump - the only way we could get hot water to rise into a heating radiator was to be certain that the radiator was physically located higher than the top of the heating boiler.

If you find a shelf-like cast iron radiator like the one shown in our photo (above right) where it is being admired by a red-jacketed realtor the radiator will probably located in the kitchen or pantry of an older home where it performed double duty as a plate warmer. The cast iron radiator in our photo, with its three flat shelves, was serving dual-duty as a both a heat source and as a plate warmer for plates coming out of a chilly pantry or dish closet.


Continue reading at ANTIFREEZE for BOILERS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see RADIATOR REPAIR FAQs for help diagnosing & repairing all types of radiators & baseboards.

Or see these

Heating Radiator Articles

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