Guide to Baseboard Heat: Inspection, Repair, Maintenance
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How to identify, inspect, diagnose, and repair problems with hot water or electric heat baseboards
How to inspect, diagnose, and repair problems with baseboard heat
Inadequate linear feet of hot water baseboard: factors that determine how much baseboard is required
If your hot water baseboard is cold and the heating system is "on" - here we diagnose the problem
Where leaks occur on hot water baseboards; Guide to unusual heating baseboards in buildings
How to raise up heating baseboard that lacks adequate clearance from the finish floor surface
Questions & answers about baseboard heat and heating baseboard installations

This article describes the types of baseboard heat used in buildings and we explain the diagnosis and repair of heating baseboard troubles including no-heat or leaks or other problems. This article focuses on the installation, diagnosis & repair of hot water heating baseboards. Heating radiators and convectors are described separately at RADIATORS. Electric heating baseboards are detailed at ELECTRIC HEAT. This website answers most questions about all types of heating systems and gives important inspection, safety, and repair advice.

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Baseboard Heat: How to Identify and Diagnose Problems With Hot Water or Electric Heating Baseboards

If you don't know what kind of heat your building uses, we explain how to figure out the answer at HEATING SYSTEM TYPES. If your heating system is not working properly, see NO HEAT - BOILER or NO HEAT - FURNACE.

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 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 below left). Electric heating baseboard also warms by radiation and convection but the baseboard itself is heated by an electric element rather than hot water. Details about electric baseboard heat are at ELECTRIC HEAT.

If your heating baseboards are not in fact getting warm when your thermostat is calling for heat and the boiler is indeed running, see AIRBOUND HEAT SYSTEM REPAIRS. You may also need to see Air Bleeder Valves.

How Does Cast Iron Heating Baseboard Work?

Carson Dunlop's sketch of cast iron heating baseboard (below) shows the heating water and air flow pathways of these heating units.

You can see by the larger water volume as well as the increased mass of the cast iron, that cast iron heating baseboards have more thermal mass than conventional finned-tube baseboard.

The increased thermal mass means more even heat distribution as the baseboards will continue to radiate heat for some time even when hot water stops circulating through the system.

Sketch of a cast iron heating baseboard courtesy of Carson Dunlop.

How Many Feet of Baseboard Heaters do We Need to Heat a Room?

The answer is ... it depends. Electric heating baseboard is figured at five to eight watts per square foot of the room. And for hot water heat, running a heat loss model such as the excellent program provided by Slant Fin™ can give a good estimate of the number of linear feet of heating baseboard will be needed for a given room or building area. But the following variables make an enormous difference in the answer:

The number and square feet of windows in the room and the window's R-value
The room's insulation levels or R-values for its walls, floor, ceiling
The room ceiling height
The level of air leakage into or out of the room
The heat output per linear foot of the model of heating baseboard chosen
The flow-rate and temperature of hot water passing through the heating baseboard.
Electric baseboard heat linear feet requirements are discussed at Feet of Baseboard Heat Needed?

Heating Baseboard Defects

Air-bound heating baseboards can prevent sections or entire loops of heating baseboards from getting hot. Details are at AIRBOUND HEAT SYSTEM REPAIRS

Missing baseboard end cover (C) D Friedman

Missing baseboard covers: the covers are required to assure proper heating of room air by convection
Missing baseboard end caps: same as above (photo above right)

Dirt dust clogged heating baseboard (C) D Friedman

Damaged or dust-clogged heating baseboard fins - reduces air-flow and thus heating output. It's easy to fix this problem by careful vacuuming of the heating baseboard fins using a crevice tool on your home vacuum cleaner.

Watch out: be gentle or use a special brush attachment when vacuuming heating baseboard tubing and fins, or remove the baseboard covers if necessary. If you are heavy-handed with the vacuum cleaner you may bend and damage the fins covering the baseboard tubing, resulting in reduced heat output.
Inadequate clearance between the baseboard bottom and the floor surface - blocks entry of cool air into the baseboard
Leaky hot water baseboard connections, air bleeders, elbows - see LEAKS at BASEBOARD, CONVECTOR, RADIATOR for details.

Heating baseboard installation (C) D Friedman

Inadequate total linear feet of heating baseboard for the room size - inadequate heat output may leave the room too chilly on cold windy days.

Solutions to inadequate hot water heating baseboard installations include increasing the hot water flow rate through the baseboard by changing the circulator pump to a higher output unit, increasing the water temperature flowing through the baseboard, increasing the diameter of piping between the heating boiler and the baseboard input and output ends, or changing the baseboard itself to a higher BTU output (per linear foot) model.

Our photo (left) shows heating baseboard being installed in a Poughkeepsie, NY home. The linear feet in this room was held to a minimum for room design reasons, leading the builders (DF & Galow Homes) to select a higher-output baseboard design.

Watch out: Unfortunately the installing Poughkeepsie plumber took some shortcuts and "saved money" by reducing the hot water piping feed and return piping from our design point of 3/4" diameter to his own preference for (easier and faster to install) 1/2" diameter piping. We may need to install a higher capacity output circulator pump at this home or perhaps we'll need to install larger diameter supply and return piping. This installation remains under evaluation.
Unsafe electric heating baseboard installation details & clearances such as from curtains and electrical outlets or wires - see Electric Baseboard Heat Safety

How to Fix a Baseboard that Does Not Get Hot - Quick Advice

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.

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.

If your system uses hot water heat and a hot water radiator is not getting hot,see COLD HOT WATER BASEBOARD / RADIATOR and see Air Bleeder Valves

Complete details about diagnosing and fixing cold radiators are found at COLD HOT WATER BASEBOARD / RADIATOR. and at COLD STEAM HEAT RADIATORS

Frequently Asked Questions (FAQs) about how to diagnose and repair problems with hot water baseboard heat systems

Question: mix up between hot water baseboard heat trouble, domestic hot water supply for washing bathing, and pump troubles that lose water pressure

I have a Hot Water Baseboard heating system in my mobile home. The other night a hot water faucet was left on slightly. It trickled out all night. This caused the system to run for over 8 hours straight. When we woke up we had no hot water. Come to find out the Water Heater circuit breaker tripped.

When I reset the breaker I started up the system and everything seemed to work perfectly...the heater fired up, the pipes got hot, the exhaust fan kicked on. But, no hot water was going to the faucets.

It does not appear that the circulatory pump was running. I replaced the pump two years ago when I moved in and it was working flawlessly. Is the pump bad or is some electrical problem happened that caused the circuit breaker to trip? - Conrad

Reply: a bit of clarification before diagnosis

We need to clarify the question as it looks as if you cite hot water baseboard heat and an electric water heater. Usually those are independent systems ... Or are you using a water heater both to make domestic hot water and also to run through your space heating baseboard ?

Question: the baseboard heat runs lack adequate clearance from the floor, blocking cool air inlet - how do we fix this?

I have inadequate clearance between the baseboard bottom and the floor surface - which blocks entry of cool air into the baseboard. What can I do to improve air flow without removing and raising the entire baseboard heater? - Dave

Reply: lack of air inlet at baseboard bottom cuts heat output and raises heating cost. Here's the cure:

Dave,

I agree that if you block air inlet at the bottom of baseboards you are significantly cutting off the heat output of the system and thus increasing heating system operating cost.

Increasing floor clearance without having to remove and reinstall heating baseboard covers

If the blockage is due to wall-to-wall carpeting, you can try pulling back the carpet (with care to avoid tearing it) and cutting the carpet padding away for about 3-4 inches from and parallel to the wall where the heating baseboards are installed. Or remove the carpeting entirely up to an inch in front of the lower baseboard edge.

If there is no carpeting, and if air entry to the baseboard is blocked by wood flooring, I have to guess that someone added a layer of wood flooring atop the original - as it would be otherwise almost impossible to install the baseboard too low.

It might be possible to remove and replace the baseboard front cover with one whose total width gives adequate clearance from the floor- be sure that the bottom edge of the baseboard front cover protects the baseboard tubing fins from view and damage.

Too-low heating baseboard "fixes" to avoid

I would NOT "fix" this problem by leaving the baseboard covers off entirely. That mistake is ulgy, exposes the baseboard heat to damage, loses the convection effect of air movement up through the bottom and out at the top of the baseboard as designed, and risks occupants having cut bare toes that stub against the baseboard fins.

Similarly drilling holes in the baseboard cover loses the convection effects and prevents proper baseboard operation.

How to improve heat output & cut heating costs by raising heating baseboards that are too low

If the whole baseboard installation was made too close to the floor (check this by seeing if the bottom edge of the fins on the baseboard tubing is less than 3 inches from the floor surface (less than 3" is too close), then you have little choice but to relocate the baseboard installation higher on the wall.

The fix is an ugly one: one would have to

shut down, cool off and drain the heating system
cut the baseboard heating pipes at the inlet and outlet ends of the baseboard runs
remove the remaining baseboard covers
with CARE to avoid bending pipes, damaging fins, or causing a leak, pull the screws that fasten the baseboard to the building walls and then
raise the baseboard high enough to give the OEM clearance distance from bottom of the baseboard front cover to the floor surface - typically that's 2" between the floor surface and the bottom of the front baseboard cover. (That's the distance you'll get if the baseboard was installed so that its back or wall-mount surface was installed just about touching the floor surface. I install the baseboard with about 1/8" clearance off of the floor surface itself just to reduce the chances of noises during heating component expansion and contraction.)
restore the baseboard backer support screws
re-plumb the copper connections in the baseboard tubing (you will need to need to gently lift the runs of baseboard up off of the baseboard back-mounts in order to prep and assemble the copper unions or couplings)
restore the heating system water in the line and bleed out excess air
turn heat back on and when the system is up to full temperature and pressure, check for leaks in the newly soldered joint

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Questions & answers about baseboard heat and heating baseboard installations

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BASEBOARD, CONVECTOR, RADIATOR TYPES

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Eric Galow, Galow Homes, Lagrangeville, NY. Mr. Galow can be reached by email: ericgalow@gmail.com or by telephone: 914-474-6613. Mr. Galow specializes in residential construction including both new homes and repairs, renovations, and additions.
Steam Boiler Inspection, Diagnosis, Repair books at the InspectAPedia bookstore - Amazon.com
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update, (see next item in this list). ITT Fluid Technology, 1133 Westchester Avenue
White Plains, NY 10604, tel +1 914 304 1700 fax +1 914 696 2950 www.ittfluidbusiness.com
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
The Heat Efficiency of Steam Boilers, Bryan Donkin
Steam Boiler Operation, Principles & Practice, James J. Jackson

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. InspectAPedia.com ^® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.

Carbon Monoxide Gas Toxicity, exposure limits, poisoning symptoms, and inspecting buildings for CO hazards
DUST CONTAMINATION FROM HVAC? An Investigation of Indoor Dust Debris Blamed on a Heating/Cooling System Reveals Carpet Dust
Fuel Oil & Oil Heating Magazine, 3621 Hill Rd., Parsippany, NJ 07054, 973-331-9545
Goodman Furnace High Temperature Plastic Vent HTPV safety recall US CPSC notice
Home Heating System Should Be Checked [for proper venting and for CO Carbon Monoxide Hazards - DJF]
Inspection Procedures for Oil-Fired Heating Systems Detailed step by step approaches for inspecting complex systems]
Lennox Pulse Furnace Safety Inspection/Warranty Program: Carbon Monoxide Warning
Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
Oil Tanks Above Ground, UL Standards, guidance for home owners, buyers, and inspectors
Plastic Heating Vent Pipe & Other Heating Safety Recall Notices
Weil McLain Model GV Gas Boiler/gas valve CPSC recall/repair
Domestic and Commercial Oil Burners, Charles H. Burkhardt, McGraw Hill Book Company, New York 3rd Ed 1969.
National Fuel Gas Code (Z223.1) $16.00 and National Fuel Gas Code Handbook (Z223.2) $47.00 American Gas Association (A.G.A.), 1515 Wilson Boulevard, Arlington, VA 22209 also available from National Fire Protection Association, Batterymarch Park, Quincy, MA 02269. Fundamentals of Gas Appliance Venting and Ventilation, 1985, American Gas Association Laboratories, Engineering Services Department. American Gas Association, 1515 Wilson Boulevard, Arlington, VA 22209. Catalog #XHO585. Reprinted 1989.
The Steam Book, 1984, Training and Education Department, Fluid Handling Division, ITT [probably out of print, possibly available from several home inspection supply companies] Fuel Oil and Oil Heat Magazine, October 1990, offers an update,
Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
Principles of Steam Heating, Dan Holohan, technical editor of Fuel Oil and Oil Heat magazine, 389 Passaic Ave., Fairfield, NJ 07004 ($12.+1.25 postage/handling).
"Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Residential Hydronic (circulating hot water) Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
"Warm Air Heating Systems". Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
Heating, Ventilating, and Air Conditioning Volume I, Heating Fundamentals,
Boilers, Boiler Conversions, James E. Brumbaugh, ISBN 0-672-23389-4 (v. 1) Volume II, Oil, Gas, and Coal Burners, Controls, Ducts, Piping, Valves, James E. Brumbaugh, ISBN 0-672-23390-7 (v. 2) Volume III, Radiant Heating, Water Heaters, Ventilation, Air Conditioning, Heat Pumps, Air Cleaners, James E. Brumbaugh, ISBN 0-672-23383-5 (v. 3) or ISBN 0-672-23380-0 (set) Special Sales Director, Macmillan Publishing Co., 866 Third Ave., New York, NY 10022. Macmillan Publishing Co., NY
Installation Guide for Residential Hydronic Heating Systems
Installation Guide #200, The Hydronics Institute, 35 Russo Place, Berkeley Heights, NJ 07922
The ABC's of Retention Head Oil Burners, National Association of Oil Heat Service Managers, TM 115, National Old Timers' Association of the Energy Industry, PO Box 168, Mineola, NY 11501. (Excellent tips on spotting problems on oil-fired heating equipment. Booklet.)
Links to our list of additional information on heating system inspection, repair, maintenance
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Baseboard Heat: How to Identify and Diagnose Problems With Hot Water or Electric Heating Baseboards

How Does Heating Baseboard Work?

How Does Cast Iron Heating Baseboard Work?

How Many Feet of Baseboard Heaters do We Need to Heat a Room?

Heating Baseboard Defects

How to Fix a Baseboard that Does Not Get Hot - Quick Advice

Frequently Asked Questions (FAQs) about how to diagnose and repair problems with hot water baseboard heat systems

Question: mix up between hot water baseboard heat trouble, domestic hot water supply for washing bathing, and pump troubles that lose water pressure

Reply: a bit of clarification before diagnosis

Question: the baseboard heat runs lack adequate clearance from the floor, blocking cool air inlet - how do we fix this?

Reply: lack of air inlet at baseboard bottom cuts heat output and raises heating cost. Here's the cure:

Increasing floor clearance without having to remove and reinstall heating baseboard covers

Too-low heating baseboard "fixes" to avoid

How to improve heat output & cut heating costs by raising heating baseboards that are too low

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair