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Radiator valve inspection & troubleshooting: here we explain the use, adjustment, diagnosis & repair of hot water or steam heating radiator valves & steam vents to control heat output from individual radiators.
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Guide to Using, Adjusting, Diagnosing & Fixing or Replacing Hot Water or Steam Radiator Control Valves & Vents
Traditional "Manual" Radiator Valves
Radiator valves are opened to allow hot water or steam to enter and heat a radiator, or closed to turn off or reduce heat output from the radiator. By "manual" radiator valve we mean that you have to turn the valve open or shut yourself. We discuss automatic (thermostatically controlled radiator valves and other radiator controls below.
At above left is a top-fed two pipe steam radiator at Google Headquarters in New York City.
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 or NO HEAT - FURNACE.
If your heating system radiators won't get hot, for hot water radiators or convector heat, see COLD HOT WATER BASEBOARD / RADIATOR; for steam heat see COLD STEAM HEAT RADIATORS for help in diagnosing the problem.
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). Cold heating baseboards are discussed at AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE.
Which Way to Turn the Radiator Valve
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". Usually turning a radiator valve "clockwise" or "down" closes the valve (turns the heat At COLD HOT WATER BASEBOARD / RADIATOR 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.
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 most radiator valves have been left in the "on" position - 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.]
Watch out: don't use excessive force to try to turn a "stuck" radiator valve. First, you may be trying to open a valve that is already in its fully-open position. 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.
Watch out: even if the radiator valve appears to be "open" - that is, turned fully counter-clockwise, if the radiator valve stem is broken internally you may be just turning the knob but the valve may be staying closed inside. If your radiator valve turns too easily or if it does not appear to raise (opening) or lower (closing) when turning, and especially if turning the valve makes no difference in the behavior of the radiator, the valve stem may be broken. (First check for air bound radiators or if your heating system uses steam, check for a steam vent that is not opening.)
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.
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, see AIRBOUND HEAT SYSTEM REPAIR by WATER FEED VALVE (hot water heat) or if a steam radiator valve is open but the radiator is still cold, the steam vent may not be working. See RADIATOR STEAM VENTS and also STEAM HEATING SYSTEMS for details.
Hot Water Heat Radiator Valves
In our photo at left you can see not only the radiator control valve, but lots more information:
This radiator is being fed from the top. We know that this must be either a hot water radiator or a two pipe steam heat radiator.
Now look closely at that air bleeder connector on the side of the radiator valve.
From this detail we can conclude that this is a hot water heating system, not a steam heat system
Hot water can enter a hot water (hydronic) heating radiator at the radiator top or bottom. Hot water radiators may have an air bleeder valve but never a steam vent valve.
Steam can enter a steam heating radiator at the radiator top too (most but possibly not all two pipe steam heat systems) or also at the radiator bottom (one pipe steam heat systems).
Steam Radiator Control Valves
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. Excerpts from that article are found below.
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.
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.
See STEAM RADIATOR PIPING CONNECTIONS for an explanation of different types of steam piping and steam-radiator piping connections.
On a heating convector unit there is usually an individual valve that lets the unit be turned down or off - but as our photo (left) shows, the valve can be a little harder to spot.
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.
Manually Setting the Radiator Valve
On hot water heating systems and two-pipe steam radiator heating systems you can adjust the radiator valve to:
If your hot water radiator is too hot or the room is too hot, you can partially-close the radiator valve.
If your hot water radiator is too cold, be sure that the valve is open and that the radiator is not air bound. Details are at COLD HOT WATER BASEBOARD / RADIATOR
If your steam radiator is too cold be sure that its supply valve is open. If it's a one pipe steam heat system (only one pipe comes to each radiator), be sure that the steam vent is working (you should hear it hissing when steam is rising in the system). Details are at COLD STEAM HEAT RADIATORS.
If you steam radiator is too hot in a two-pipe steam system, according to the U.S. DOE,
If your steam heating system pipes are noisy see BANGING HEATING PIPES RADIATORS wHere we explain steam condensate return problems that can cause banging clanging pipes.
There are additional methods for automatically controlling the heat output from individual heating radiators, for both steam and hot water heat: thermostatically controlled radiator valves and adjustable or thermostatically controlled steam vents. We discuss these controls beginning at Automatic or Thermostatically Controlled Radiator Valves - TRVs.
The radiator control valve opens or shuts to allow hot water or steam to enter and heat the radiator. An automatic or thermostatically controlled radiator valve allows you to set the desired room temperature.
The automatic hot water or steam radiator valve, thermostatically controlled, will automagically open or close to attempt to control room temperature to the desired level. Keep in mind that with any heat control installed right at the radiator, the control will be sensing temperature in that location, not across the room, so some experimenting to find the best setting will be needed.
Armstrong Corp. provides the RV-4 One-Pipe Steam Radiator Valve that operates as a room thermostat suitable for residential low-pressure steam heating systems. By installing a thermostatically controlled steam vent at each radiator, every radiator can be controlled or set to the desired temperature.
There is a central advantage of thermostatically operated steam vents over swapping out the actual radiator control valve for a thermostatically controlled radiator valve, that is, they are easier and less disruptive to control. The original steam vent is simply unscrewed and the new thermostatically controllable steam vent is screwed in at the same location.
Watch out: it's safer to install or change steam heating system parts when the system is not calling for heat and when the steam boiler and radiators are cold. Don't be fooled. If your heating system is on and the steam boiler is hot, unscrewing the steam vent on a "cold" steam radiator will allow steam to rise into the radiator (forcing air out of the steam vent opening) and you could be seriously burned by rising steam.
Replacing Manual Radiator Valves with 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.
Several companies provide thermostatically-controlled radiator valves including Armstrong, Danfoss, Hoffman Specialty, Jacobus (Maid'O'Mist) and others. The automatic radiator valve shown at left was observed on a typical modern European installation in Molde, Norway.
This (more expensive) radiator control valve lets you treat each individual radiator as a "heating zone".
As long as the room thermostat is calling for heat, each radiator can be regulated automatically when a thermostatic radiator valve (TRV) is installed..
This topic has been moved and consolidated at STEAM VENTS - home, where we discuss other steam vent problems such as spitting water, clogging, steam valves that do not open or close when they should, etc. and at STEAM VENT TYPES, SELECTION - where we identify the different types of steam vents use on 1 pipe and 2 pipe steam systems.
This text has moved to GUIDE TO CHOOSING & INSTALLING STEAM VENTS.
Watch out: If the radiator continually makes noises (whistling or wheezing) at the steam vent, there is a problem that needs to be fixed: a bad steam vent, steam piping problem, steam pressure set too high, or boiler oversized for the heating distribution system.
Watch out: to be sure your steam heating system and its controls are properly adjusted excessive steam pressure can be dangerous.
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Frequently Asked Questions (FAQs)
Question: where do steam pipes enter steam radiators: top, bottom, or both?
I had a question about the article at RADIATOR VALVES & HEAT CONTROLS.
I’m looking at the sub-section “Types of Radiator Valves: Hot Water vs. Steam” and here is a copy of the 1st paragraph; the writing becomes nonsensical and near the end and it may turn out that some of the information is incorrect: “In our photo at left you can see not only the radiator control valve, but lots more information: we can conclude that this is a hot water heating system, not a steam heat system because first, the valve is mounted at the top of the radiator (water, not steam - steam enters at a radiator bottom but sometimes so does not water; the reverse is never true).”
Photo at left: two pipe steam radiator fed from top right end. [Click to enlarge any image]
I was trying to make sense of what was written and discovered another article (which also has nonsensical syntax- it must be hard to describe these hot water and steam heating systems) which seems to indicate that in fact steam DOES often enter a radiator at the top. At this point I am just lost. We don’t have many residential systems with radiator systems (steam or hot water) so I am trying to educate myself but don’t have anything in front of me to compare what I think I understand.
Kind Regards, -Doug
Reply: Up-feed - Down-feed, One-pipe - Two-Pipe Steam Piping & Radiators - What's the Difference?
Doug, the other page (not at InspectApedia) that you gave provides information from Dan Holihan - probably the most-expert fellow alive when it comes to steam heating systems. Dan's text includes these two statements:
Dan is right again. Most two-pipe steam heat systems will show up with the steam entering the radiator at one end at the radiator top (below left), and the condensate return will exit at the bottom of the radiator at its opposite end. 
All one pipe steam radiators are fed with a pipe connection to the bottom of the radiator.
In response to your question we have added an article to help clarify the different types of steam heat piping - to - radiator connections and where valves will occur. Please see STEAM RADIATOR PIPING CONNECTIONS
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