Cold Steam Heating Radiators, Baseboards & Convectors - Diagnose & Cure
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A complete diagnostic guide & checklist for cold steam radiators
Cold steam radiator? No steam system heat in some or all building areas? What to check first
How to identify, inspect, diagnose, and repair problems with steam radiators or heating convectors
How to inspect, diagnose, and repair problems with steam radiators
If your steam-heating system 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
Guide to unusual steam radiators and steam heating convectors in buildings
Questions & answers about how to troubleshoot cold steam radiators, baseboards, or convector heaters

Troubleshooting cold steam radiators: this article describes the diagnosis & repair of cold steam heating convectors or steam radiators. We provide articles that help in diagnosing and repairing no-heat problems with each types of hot water or steam or fan convector heat delivery systems.

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© Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

How to Troubleshoot & Fix Cold Steam Radiators in 5 Steps

Our page top heating system illustration is provided compliments of Carson Dunlop Associates.

If your heating system uses hot water (not steam) radiators, convectors, or baseboards, in other words, not steam heat, see COLD HOT WATER BASEBOARD / RADIATOR for help in diagnosing and fixing radiators that won't get hot. This website answers most questions about all types of heating systems and gives important inspection, safety, and repair advice. 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.

Cold Steam Radiator Diagnosis Step 1: Check the thermostat & the steam boiler

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 steam boiler will usually turn on right away in response to the thermostat being turned up or on a call for heat.

Step 2: Check the radiator control valve

Make sure that the control valve at the heating radiator is "open" or "on" as we describe just below.

First check the radiator valve itself. At COLD HOT WATER BASEBOARD / RADIATOR we illustrated different types of heating radiator control valves and explained their operation. Details are at RADIATOR VALVES & HEAT CONTROLS.

It's standard to ask first "is the radiator valve turned on or "open" (fully counter-clockwise)?

Experts warn that a radiator slow to heat could have a supply valve that is too small (the problem would always have been observed since date of installation) or a supply valve that is partly closed (the problem would have originated when the valve was closed and would go away when the valve is fully opened, provided the valve is undamaged and really opens internally when its handle is turned.)

But other problems can cause a steam heat radiator to stay cold when you want heat. Below we continue our diagnostic and repair advice for cold radiators or convectors in steam heating systems.

Step 3: check the steam vent on the radiator

Steam vent on a radiator (C) Daniel Friedman

If some of your steam heat radiators are not getting hot, the steam vent may not be working, may not be venting at all (radiator stays cold) or may be venting too slowly (radiator heats to proper temperature but too slowly)[2]

If a steam radiator valve is open but the radiator is still cold, the steam vent may not be working. Our photo (above right) shows a typical steam radiator vent.

When steam is first rising in the heating system, the steam heating radiator will be cool as will be the steam vent. The vent opens, allowing rising steam to enter the radiator by pushing air out through the vent.

When the steam radiator and steam vent are warm or hot, the vent closes. If a steam vent stops working, rising steam cannot enter the radiator and it will be slow to heat or may not heat at all.

See Steam Vents and also STEAM HEATING SYSTEMS for details.

Step 4: Check which radiators are not getting hot - check radiator slope

Steam radiator sloped the wrong way - steam condensate blockage

As our Carson Dunlop sketch shows (above, left), steam radiators can be sensitive to exactly how they are installed and pitched or sloped.

You'll want to learn if your steam heating system is a "one pipe" or a "two pipe" design, but in either case, if the steam supply or condensate return piping have been moved or settled so as to have lost the proper slope, correcting those conditions may be needed.

That's because condensate, produced by cooling steam in the radiator, has to be able to drain back out of the radiator.

A steam radiator that is sloped the wrong way, perhaps due to building floor settlement or a change made by an inexperienced remodeler, will become partly or even completely blocked by accumulated condensate, leading to loss of heat.

Steam heating system controls, inspection, diagnosis, and repair are discussed beginning at STEAM HEATING SYSTEMS.

Step 5: Check these other causes of cold steam radiators

Internal leaks in the steam boiler can cause cold radiators - diagnosis:

Small boiler leaks can be hidden from view: As reader Robert discovered and kindly explained in our FAQs section below, several clues can point to an internal leak in the steam boiler. A relatively small leak in the steam boiler may never show up as water on the floor around the boiler - the leaking water may just evaporate on boiler internal surfaces. A larger steam boiler leak will probably show up as water on the floor, boiler running continuously, or if the leak is fast enough, a low-water cutoff switch will shut down the boiler.

Watch out: as Robert points out below, leaks in the condensate return system increase the rate of water feeding into the steam boiler. Abnormally high water feed rates into the boiler can in turn speed up corrosion within the boiler leading to costly or even ruinous leaks in the steam boiler itself. The rate of corrosion will vary depending on not just the water feed rate but also other factors such as the water chemistry and the overall boiler on-time.
Check boiler steam pressure - lower than normal steam pressure can result in heat being delivered too slowly to all radiators, slower heat or even no delivery of heat to radiators on upper floors. If all of the lower floor radiators in a building heat up but none of the upper floor radiators do so, or if no radiators near the end of the steam risers get hot, low steam pressure could be the problem. Don't rush to "fix" this by changing the steam pressure control switch - that's treating the symptom not the illness.
Check the steam boiler water usage rate - an increase in water usage at the boiler can be due to a leak somewhere - in the condensate line, or in the case of cold radiators, in the boiler itself.

Steam boiler operating problems can lead to inadequate heat - radiators not hot enough or distant radiators not heating up - diagnostic checks.

Steam boiler problems: An oil or gas fired steam boiler may fail to deliver enough heat for a number of reasons pointed out by ITT [2], including:
- Inadequate draft
- Poor fuel quality
- Improper attention or firing (lack of maintenance, burner not firing properly)
- Boiler is undersized - if this is the case the heat inadequacy would always have been present but may not be noticed until very cold windy weather
- Improper steam piping - as above, if this is the case the heat inadequacy would always have been present or present ever since steam piping has been changed or modified.
- Improper arrangement of boiler sections
- Lack of boiler cleaning/maintenance, leaving soot in the boiler. Soot acts as an insulator, slowing heat transfer from the fire into the boiler water
- Improper firing rate of oil (nozzle size, fuel unit pressure) or gas
- See STEAM HEATING SYSTEMS for details
One pipe steam system radiators fail to heat - check these
- Radiator vent problems: The radiator vent is improperly sized or not working. See RADIATOR STEAM VENTS and also RADIATOR STEAM VENTS, AUTOMATIC.
- Steam pipe problems: The steam pipe feeding the radiator is under-sized or is not properly sloped (steam supply pipes in a one pipe system also return the condensate and must slope away from the radiator and down towards the boiler - always) - (the problem will have always been present but may not be noticed until very cold weather)
- Air vent problems: The drainage tongue on the air vent has become damaged or lost or corroded away
Two pipe steam system radiators fail to heat - check these
- Radiator pitch problems: doesn't slope towards the steam trap - the radiator should slope away from the steam supply valve and towards the steam trap
- The radiator steam trap is clogged, damaged, or stuck closed
- The steam pipe feeding the radiator is undersized or the condensate return not pitched properly, leading to blockage
Steam convectors or "unit heaters" are not putting out enough heat

Heating convector unit (C) Daniel Friedman

Dirty heater coils - check for dust or debris blocking the fins on the heater coil - see our photo at left
Dead unit heater fan - if the unit heater such as a ceiling-mounted garage heater is driven by a blower fan (not just a convector (driven by gravity), check that the fan operates normally
Blocked steam piping feeding the unit or within the heating coil - due to air or water blockage in the piping
Also check these more technical problems with unit heater heat output:
Design mistakes: the unit is too small for the heated space (the problem will not be new), or the unit has been improperly located - too far from exterior walls can leave cold areas between the heater and the exterior wall;
Improper installation: the steam pipe supplying the unit may be inadequately insulated, improperly sloped, or routed through a cold area where it loses too much heat
Abnormal or too-low steam pressure in the system (there may be hidden leaks in the system)
Maintenance problems: oil and debris in the steam, coating the heat transfer surfaces of the interior surfaces of the heating coil itself

Steam system design or building heat loss rate problems
If the steam radiators get hot but the building does not get warm enough, check these
- The number of radiators is inadequate, or some radiators are turned off or not heating for other reasons - the remaining radiators can't keep up with the building heat loss rate. You'll notice this more in colder windier weather
- The building is losing heat too rapidly for the heating system to keep up. If this is a new problem look for a new draft - a window left open, an attic door or pull down stair left open, etc.
- The steam pressure is set too low - steam doesn't rise to upper floors or rises too slowly. Check with your service technician as other problems such as a boiler leak or condensate return leak can result in low steam pressure.
- Building design, such as many open stairwells, high ceilings, can make it hard to heat - this problem will have always been present.
- See HEAT LOSS in buildings

Troubleshooting Steam Radiators that are too HOT

If you steam radiator is too hot in a two-pipe steam system, according to the U.S. DOE, check the steam traps:

In two-pipe systems, older steam traps often stick in either the open or closed position, throwing off the balance in the system. If you seem to have problems with some radiators providing too much heat and others providing too little, this might be the cause. The best approach is often to simply replace all the steam traps in the system.

Frequently-Asked Questions about troubleshooting steam heat radiators & convectors

Question: trouble finding the cause of cold steam radiators in two buildings - traced to internal leak in steam boiler

I have done all the above. Pitched the radiator, changed the air valve, even putting a larger orifice air valve and removing the radiator to check the open and closed position of the supply valve. I still get cold radiators. The larger steam supply valves are properly pitched in the basement and the boiler runs a sufficient amount of time to build up pressure. Is there anything else?? - Robert

More information:

This problem exists in both a private house and in a six family dwelling. Both have a one pipe system. In the private house, only the second fl rear (about 3 radiators) are cold. The radiators directly below are hot. In the 6 family, both apartments on the 2nd fl are cold or get hot on one side only. - Robert

Reader Diagnosis: cold radiators traced to boiler leaks caused by condensate return line leaks

If anyone has this problem check for leaks, cracks or holes in the sections of the steaam boiler. Also check return lines for leaks. It seems if fresh water is constantly being fed to the boiler, a corrosive reaction takes place in the sections of the boiler.

In this case there were leaks undetected in the return lines which caused water to be added constantly.

The fresh water ate at the sections in the chamber causing two small holes. This in turn did not allow enough pressure to build up for steam to reach the radiators. After replacing boiler all radiators were very hot and also at a much faster rate. - Robert

Reply/comment:

Robert, Thanks for your comments, and I apologize that we didn't catch them sooner. Sometimes the volume of comments leaves us behind.

Your cold steam radiator diagnosis success will add a helpful item to check and I'll add it into the diagnostic text above.

Indeed if your steam boiler is using more water than usual, I usually suspect a leak somewhere - often a small leak in a condensate line can go unnoticed; On occasion we also find excessive water consumption because radiator steam vent valves are not closing when they should (when the radiator is hot).

But I had forgotten that an internal leak in the boiler and that is going unnoticed and iss large enough to prevent building up adequate steam pressure to heat the radiators can result in low boiler pressure, increased water use, and failure to deliver heat to upper floors.

And your reminder that abnormal water consumption increases corrosion in the boiler is very important since, as you explain, the result can be leaks in the boiler itself.

Unfortunately the good news of a correct diagnosis can lead to the bad news of a costly repair - the need for a replacement of the steam boiler.

We're always smarter in hindsight - and now I also see that your observation that lower radiators got hot but upper level radiators all did not, could have pointed to a steam pressure problem. Too often an amateur "fixes" the problem by trying to set up the steam pressure at the control switch - not the right approach.

Thank you again. We welcome and appreciate reader questions - it helps us find where to add or clarify our information. If in the future you do not receive a prompt reply to an urgent question left on a particular web page/article, just shoot me a personal email using the CONTACT information found at page top or bottom and I'll be sure to get to it. - Daniel

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RADIATORS
  BANGING HEATING PIPES RADIATORS
  BASEBOARD, CONVECTOR, RADIATOR TYPES
  COLD HOT WATER BASEBOARD / RADIATOR
  COLD STEAM HEAT RADIATORS
  LEAKS at BASEBOARD, CONVECTOR, RADIATOR
  RADIATOR or CONVECTOR COVERS
  RADIATOR or CONVECTOR INSULATION
  RADIATOR STEAM VENTS
  RADIATOR STEAM VENTS, AUTOMATIC
    Install Steam Vents to Control Heat
  RADIATOR VALVES & HEAT CONTROLS
    Radiator Control Valves & Vents
    Manual Radiator Valves
    Hot Water vs Steam Radiator Valves
    Adjust Level of Heat
    Automatic Radiator Valves
  STEAM TRAPS
  UNEVEN HEAT DIAGNOSIS

[1] 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.
[2] 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,
[3] Principles of Steam Heating, $13.25 includes postage. Fuel oil & Oil Heat Magazine, 389 Passaic Ave., Fairfield, NJ 07004.
[4] The Lost Art of Steam Heating, Dan Holohan, 516-579-3046 FAX
[5] 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).
[6] "Residential Steam Heating Systems", Instructional Technologies Institute, Inc., 145 "D" Grassy Plain St., Bethel, CT 06801 800/227-1663 [home inspection training material] 1987
[7] "Steam Boiler Operations" (Program 4, booklet & video), Weil-McLain H.E.A.T. (Hydronics Education and Training), Blain St., Michigan City Indiana 46360 Tel: 219-879-6561

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.

Fuel Oil & Oil Heating Magazine, 3621 Hill Rd., Parsippany, NJ 07054, 973-331-9545
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.
"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.)
...

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How to Troubleshoot & Fix Cold Steam Radiators in 5 Steps

Cold Steam Radiator Diagnosis Step 1: Check the thermostat & the steam boiler

Step 2: Check the radiator control valve

Step 3: check the steam vent on the radiator

Step 4: Check which radiators are not getting hot - check radiator slope

Step 5: Check these other causes of cold steam radiators

Internal leaks in the steam boiler can cause cold radiators - diagnosis:

Steam boiler operating problems can lead to inadequate heat - radiators not hot enough or distant radiators not heating up - diagnostic checks.

Troubleshooting Steam Radiators that are too HOT

Frequently-Asked Questions about troubleshooting steam heat radiators & convectors

Question: trouble finding the cause of cold steam radiators in two buildings - traced to internal leak in steam boiler

Reader Diagnosis: cold radiators traced to boiler leaks caused by condensate return line leaks

Reply/comment:

Questions & Answers regarding this article

Ask a Question or Search InspectAPedia

Technical Reviewers & References

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