Radiator Valve Types: Hot Water vs Steam
What kind of heating radiator & valve do I have?

Hot Water Heat Radiator Valves

In our photo just above 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

Above: a typical inlet control valve found at the bottom inlet end on a one pipe steam heat radiator. Our photo shows one of two common locations for steam radiator valves: at the radiator bottom at one end:

Below: a thermostatically controlled steam inlet valve at the bottom inlet of a two pipe steam heating system radiator.

On some steam radiators, particularly some two pipe steam system radiators, you may find the steam inlet control valve at the top of one end of the radiator rather than the bottom, as you can see in our photo below.

We describe automatic steam radiator control valves

at AUTOMATIC RADIATOR VALVES

If your steam radiators won't get hot 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.

See STEAM RADIATOR PIPING CONNECTIONS for an explanation of different types of steam piping and steam-radiator piping connections.

Also see STEAM VENTS since some of these, like the Dole steam vent shown below, are adjustable and so provide additional control over the steam radiator heat output.

In-Line Hydronic Heat Control Valves - Pneumatic or Vacuum or Electric

Question: identify this hot water heating control valve

2020/11/24 Kristina said:

Hello, Could someone help me identify what kind of valve this is?

It is part of a 1957 hydronic heating system. It is in one of the bottom kitchen cupboards in the basement apartment of a triplex.

The metal wire coming out of the top is connected to a knob further down on a baseboard heater that doesn't seem to work in adjusting the temperature.

This Q&A were posted originally at CHECK VALVES, HEATING SYSTEM

Moderator reply:

Shown here: a pneumatic or vacuum-operated steam radiator control valve.

Kristina

I think that is either an electrical (low voltage) OR a pneumatically-controlled (air-operated or in some models, vacuum-operated) steam valve (or hot water control) that was connected to a room thermostat or other temperature sensor.

Is it possible that your building's heat was originally a steam heating system later converted to forced hot water ? If so, this control could be a left-over.

Look closely: is that metal "wire" coming out of the top of the valve actually a wire or is it a rigid copper tube?

[Click to enlarge any image]

Both types of controls have been used on both hydronic (hot water) and on steam heating systems (wires and pneumatic or copper tubing).

If my guess is right or "sort-of" right, the control in your photo is a cousin to the pneumatic/vacuum operated steam control shown in my photo (above) of a steam radiator installed in Rockefeller Hall on the Vassar College campus in Poughkeepsie NY.

If your heater control no longer responds, the valve itself may be jammed (in which case it will need to be removed entirely or replaced perhaps with a zone valve) or the thermostat or wire that controls it needs to be found and repaired or replaced.

Below we show the Davis patented air valve, one of the earliest air-controlled valve patents that give insight into the history of this device.

• Davis, George M., AIR VALVE [PDF] U.S. Patent No. 404,963 issued June 11, 1990.
  Excerpt:
  This invention relates more especially to the class of air-valves used on radiators in the system of steam-heating for the purpose of allowing the air to escape and to trap the steam. The valve may be set to act automatically or be adjusted by hand and Worked on the expansion principle.

Above is an example of the type of thermostat that operated pneumatic steam heat control valves described by Joesting's 1953 patent. .

• Joesting, Frederick D. TEMPERATURE RESPONSIVE CONTROL APPARATUS [PDF] U.S. Patent 2,564,222, issued August 14, 1951.
• Joesting, Frederick D. SELF-CYCLING PNEUMATIC CONTROL APPARATUS [PDF] U.S. Patent 2,651,468, issued September 8, 1953.

Hidden Manual Radiator Control Valves on Heating Convectors

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.

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.

Problem getting the old corroded air bleeder valve out? Or trouble removing a cast iron or steel plug on a radiator where you want to install an air bleeder valve?

See RADIATOR PLUG REMOVAL for a suggested procedure as well as for steps to recover your radiator if the vent mounting hole threads are badly corroded or stripped.