Cold Steam Heating Radiators, Baseboards & Convectors - Diagnose & Cure

How to Troubleshoot & Fix Cold Steam Radiators in 5 Steps - a complete diagnosis & repair guide & checklist for cold steam radiators
- 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 that can lead to inadequate heat - radiators not hot enough or distant radiators not heating up - diagnostic checks
- Troubleshooting Steam Radiators that are too HOT
COLD HOT WATER BASEBOARD or RADIATOR - separate article
STEAM RADIATOR PIPING CONNECTIONS - separate article
Questions & answers about how to troubleshoot cold steam radiators, baseboards, or convector heaters
References

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How to diagnose & fix a too-cold steam radiator? No steam system heat in some or all building areas? What to check first. Troubleshooting cold steam radiators: this article describes the diagnosis & repair of cold steam heating convectors or steam radiators. We also describe how to fix a steam radiator that is too hot. And we list less common causes of cold steam radiators in buildings and we describe how to fix these conditions.

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 that 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 steam 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 is 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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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' provides:
- Commercial Building Inspection Courses - protocol ASTM Standard E 2018-08 for Property Condition Assessments
- Home Inspection Education Courses including home study & live classes at eleven colleges & universities.
- Home Inspection Education Home Study Courses - ASHI@Home Training 10-course program.
  Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on these courses: Enter INSPECTAHITP in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
  Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones.
  Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter inspectaehrb in the order payment page "Promo/Redemption" space.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors.
  Special Offer: For a 5% discount on any number of copies of the Illustrated Home purchased as a single order Enter INSPECTAILL in the order payment page "Promo/Redemption" space.
- The Horizon Software System manages business operations,scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
[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, 25th Ed., 2012, 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. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.

Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.

Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a 5% discount on any number of copies of the Technical Reference Guide purchased as a single order. Just enter INSPECTATRG in the order payment page "Promo/Redemption" space.
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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