Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
AIR CONDITIONING & HEAT PUMP SYSTEMS
BACKDRAFTING HEATING EQUIPMENT
BACKUP HEAT for HEAT PUMPS
BANGING HEATING PIPES RADIATORS
BLOWER FAN OPERATION & TESTING
BOOKSTORE - InspectAPedia
BTU USAGE MONITORS
CARBON MONOXIDE - CO
CIRCULATOR PUMPS & RELAYS
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DIRECT VENTS / SIDE WALL VENTS
DRAFT HOOD, GAS HEATER
DRAFT REGULATOR, DAMPER, BOOSTER
DUCT SYSTEM & DUCT DEFECTS
ELECTRIC MOTOR DIAGNOSTIC GUIDE
FAN, AIR HANDLER BLOWER UNIT
FLOODED HEATING EQUIPMENT REPAIR
FLUE SIZE SPECIFICATIONS
GAS BURNER FLAME & NOISE DEFECTS
GAS PIPING, VALVES, CONTROLS
GEOTHERMAL HEATING SYSTEMS
HEAT PUMPS, DIAGNOSIS, REPAIR
HEATING COST SAVINGS METHODS
HEATING OIL PIPING TROUBLES
HEATING OIL TANKS
HEATING SYSTEM NOISES
HEATING SYSTEM TYPES
GAS LP & NATURAL GAS SAFETY HAZARDS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
MOTOR OVERLOAD RESET SWITCH
NOISE, HEATING SYSTEMS
ODORS FROM HEATING SYSTEMS
OIL FILTERS on HEATING EQUIPMENT
OIL FILL PIPE LEAKS
OIL SPILL CLEANUP / PREVENTION
PLASTIC PLEXVENT ULTRAVENT RECALL
PUFFBACKS, OIL BURNER
RELIEF VALVE LEAKS
RESET SWITCH, HEATER PRIMARY CONTROL
RESET SWITCH, ELECTRIC MOTOR
RESET SWITCH, STACK RELAY
SAFETY, HEATING INSPECTION
SAFETY RECALLS CHIMNEYS VENTS HEATERS
SOLAR HEATING SYSTEM DESIGNS
SOOT on OIL FIRED HEATING EQUIPMENT
STEAM HEATING SYSTEMS
THERMOSTATS, HEATING / COOLING
VIDEO GUIDES: HEATING SYSTEMS
WINTERIZE A BUILDING
WOOD-OIL COMBINATION HEATERS
WOOD STOVE OPERATION & SAFETY
ZONE VALVES, HEATING
Troubleshoot cold radiators, baseboards, convectors in hot water heating systems: this article describes the diagnosis & repair of cold "hot water" heating baseboards, convectors, radiators, or "hot water" 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.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.
If your heating system uses steam radiators or steam convectors see COLD STEAM HEAT RADIATORS for help in diagnosing and fixing steam radiators that won't get hot.
This article series 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. Our page top heating system illustration is provided compliments of Carson Dunlop Associates.
If none of your heating radiators, baseboards, etc. are getting hot, start your diagnosis of the problem at NO HEAT - BOILER / FURNACE DIAGNOSIS. It may be that your boiler is simply not running, has lost power, is switched off, or that the thermostat is not calling for heat.
If you have heat in some areas but not others we discuss diagnosing baseboard heat problems below, followed by a discussion of radiators and convector unit problems for both hot water and steam heat.
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. (See THERMOSTATS.)
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 heat is provided by baseboards there will not normally be individual shutoff valves at those devices, but if your system uses one circulator and provides multiple heating zones (and thermostats) there will be zone control valves (usually near the boiler) that are opened or closed by the room thermostat(s).
Air-Bound Baseboard Heating Zone Diagnosis
Once your thermostat is calling for heat and the heating boiler has been running for ten minutes or more, just feel the baseboard. Don't cut your fingers on the fins, and don't bend them if you can help it.
If some sections of baseboard are not easy to access that's ok - you can simply feel the start and the end of a section of baseboard to determine where the loop of heat piping is hot and where along the system the baseboard piping first feels cold.
Our photo (left) shows an older finned copper tubing baseboard system with the end-cover removed - it's easy to just touch the copper pipe to feel its temperature - hot or cold, that's all we need to know.
If just some sections of an individual zone or loop of heating baseboard are not getting hot, feel along the piping entering and leaving each section of baseboard in each room to find which sections are hot and which are cold - this is a first diagnostic step in determining what's wrong.
If your heat is distributed entirely through one zone (one thermostat, one loop of heating piping & baseboards) and if part of that loop is warm (usually just the beginning portion of the loop), then there is a good chance that your heating zone or loop is air-bound.
We provide detailed, step by step procedures for diagnosing and curing an air-bound hot water heating system, beginning
Also see heating baseboard air bleed valves discussed
Since on many hot water heating systems a key air bleeding or air vent point is at the air scoop or air separator closer to the boiler,
Thermostat, Zone Valve, or Circulator Pump No-heat Diagnosis for Baseboard Heat
If your heating system is divided into multiple zones of baseboards or a mix of baseboards and radiators: If the heating boiler is running and some baseboard sections or rooms are hot but others are not, first check to see if your heating system uses multiple thermostats and multiple heating zones.
It may be that the thermostat controlling the "cold" rooms is not calling for heat or is not working. See THERMOSTATS.
If your heating baseboard is installed over a carpeted floor, be sure that the carpeting has not blocked the air inflow space under the bottom edge of the metal baseboard cover. Blocking this air intake will drastically reduce the heat output from your heating baseboards, thus increasing your heating bill.
If your heat is provided by individual hot water radiators or convector units, usually there is a control valve at each radiator or convector. Make sure that the control valve at the heating radiator is "open" or "on".
In the "cold radiator" diagnosis article below we include links to additional detailed articles that will help you correct a problem with heating baseboards or radiators that are not working:
Check the radiator control valve: If a radiator is not getting hot: (steam or hot water) first see if the valve that controls it has been turned off. Try turning the valve counter-clockwise to see if it will open. See details
In our photo (left), the heating convector control valve was found at floor-level under the heating convector. The "open" and "close" directions for this "radiator valve" were nicely marked by the manufacturer (click to enlarge the photo).
If the radiator valve does not turn in that direction, try turning it in the other direction (clockwise or "closed") to see if the radiator valve is stuck. You may also find the same control valve at heating convectors (but not usually at heating baseboards).
While people sometimes turn off radiators in an un-used portion of a building we usually find that they have been left "on" - in fact turning off a hot radiator in some building areas could lead to its freezing and cracking. Steam radiators, on the other hand, can usually be turned-off with impunity since steam radiators do not normally contain water in its liquid form. [That's true at least so long as condensate has not become trapped inside of the steam radiator.]
Second, the valve may actually be jammed. Excessive force can break the valve or even cause a leak. If the valve won't turn at all counter-clockwise towards "open", try turning it the other way - clockwise, towards "closed". If the valve now turns you'll know it was already in its open position.
Thermostatically controlled radiator valves:
If you have to replace the control valve on a hot water or steam radiator or convector unit, consider installing a new valve that incorporates a thermostat as well, such as the automatic radiator valve shown at above left.
This (more expensive) radiator control valve lets you treat each individual radiator as a "heating zone". As long as the thermostat is calling for heat, each radiator can be regulated automatically.
If only some of your hot water radiators, hot water heating convector units, or hot water baseboard heating sections are not getting hot and the radiator valve is open,
Watch out: even if the radiator valve appears to be "open" - that is, turned fully counter-clockwise, if the valve is broken internally you may be just turning the knob but the valve may be staying closed inside.
Usually while turning a radiator valve to from "closed" to "open" position, if you look closely at the valve stem - the metal rod or shaft extending below the knob you are holding, and extending into the body of the valve itself - you'll see that as you "open" the valve the stem gets "longer" and often a less-oxidized, shiner part of the valve will become exposed as it moves upwards from having been inside the valve body.
That's a great way to convince yourself that yes, the valve is probably opening internally too, you're not just turning the knob. If the valve body has broken loose from the valve stem, that's an internal problem you can't see, but turning the radiator valve knob, even if it rotates, will not open a broken, stuck, frozen valve.
Unlike a radiator valve, a heating convector control valve may be hidden by the convector's steel cover, or it may be little and hard to recognize as we show here.
This valve, if it's not jammed by corrosion, is operated by a screw driver; it may be possible to get this valve working by gently loosening the lock-nut and then turning the control screw with a flat-bladed screwdriver.
Do not take apart this valve while the heating system is on and hot - you risk getting sprayed with hot water or you may start a leak that's hard to stop without making a mess and having to shut down the whole heating system.
How to Bleed Radiators of Trapped Air
If just some of your hot water radiators are not getting hot you may just need to bleed or remove air from the "cold" hot water radiator, baseboard, or heating convector unit,
Carson Dunlop's sketch (left) shows a common location for the air bleed valve on a cast iron radiator.
See AIR BLEEDER VALVES for details about how to get an individual cold radiator working again if it's air bound, and
Since on many hot water heating systems a key air bleeding or air vent point is at the air scoop or air separator closer to the boiler,
Hot water heating boilers, their inspection, diagnosis, and repair are discussed beginning at BOILERS, HEATING.
If your heating system uses steam radiators or steam convectors see
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.
Make sure that the control valve at the heating radiator is "open" or "on" as we describe just below. Details are
First check the radiator valve.
It's standard to ask first "is the radiator valve turned on or "open" (fully counter-clockwise)?
But other problems can cause a steam heat radiator to stay cold when you want heat. Here is diagnostic and repair advice.
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.
Steam radiator sloped the wrong way - steam condensate blockage
As our Carson Dunlop sketch shows (below, 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.
[Click to enlarge any image]
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.
Continue reading at AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE or select a topic from the More Reading links shown below.
Suggested citation for this web page
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
No FAQs have been posted for this page. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References