Steam radiators and air vents (for homeowners)

JohnNY

Here's a thermal image I took last year in a customer's home in Park Slope, Brooklyn.

Areas of higher heat energy are shown in lighter (yellow) color while cooler areas are shown in purple shades.

This picture shows a steam heating radiator with steam entering through the valve at the floor at the bottom left, rising immediately in the first section to the top of the radiator and straight across the top. The steam is being drawn in by the cooler metal and the air vent mounted about 2/3 the way down on the right (the air vent is that little bump on the side).

This is the right way to do it. The steam will now work its way down toward the air vent, the vent will close in the presence of heat, and the radiator will be full of steam which will heat the room nicely.

If you have air vents near the top of your steam radiator, you've got it wrong. Heat will get to it too quickly and stop the flow of steam.

Fix it and you'll get the most out of the heat you pay to produce.

Rod

IR Picture of Radiator

Thanks John for posting the IR picture!  Very interesting! It sure backs up the old saying "One picture is worth a thousand words!"

- Rod

JohnNY

Thanks, Rod.

To compare, look at this picture where the air vent is on top. Notice the uneven heating of the radiator. Steam has shot across the top, closed the air vent (that little nub on the top right) and now all the steam is backing up in the first couple of sections. It looks like a good 1/3rd of the radiator is practically not being used at all.

ChrisJ

How long

Did it take for the steam to work its way across the top like that?



By the way,  do you have any more pictures like these? 

JohnNY

Duration

I'd have to guess and say about a 20-minute run time once steam was made. This is a 4th-story radiator.



I have a bunch of pictures like this.



Here's a hot water radiator:

Gerry G

water to steam conversion

John, these pics are great. I think they explain what's going on in my system. I recently got a two pipe hot water radiator on ebay. I closed the exit loop and put in the steam vent where the old air relief valve used to be. But that opening was at the top of the radiator about four columns in from the intake. The heat works only in heating the top and outer sides of the radiator. Middle and back are cold. After reading this thread I'm guessing the valve location is the culprit.



So, do I tap a new vent opening on the side 3/4 up as is standard on steam rads or can I put the vent at the old water return at the bottom of the Rad on the opposite side of the intake?



Thx in advance.

JohnNY

Location, location, location

Don't put the vent at the bottom. It'll foul up with crud in no time. Tap the radiator to accept an 1/8th inch thread in the middle of the end section.

Steamhead

And

there should be a "boss"on that end section in the proper place for the vent, that you can drill and tap. 

Gerry G

No easy place to tap

Because this was a converted slim profile water radiator, there are limited places to drill the tap opening.  Plus, I understand that it's a pain to drill through cast iron.

How about creating an alien looking contraption of nipples & elbows coming off the water return pipe at the bottom, so that the air vent would be raised about one foot up and not pick up any condensate crud? The way this radiator is made is that the vent riser would sit behind the columns and be out of sight.