Radiator vent placement

jeff_50

What if some of the largest radiators in this system
needed more venting; where would the second
vent be placed? Or simply should a larger/faster vent
be used? And, how difficult is it to drill and tap
where there is no boss?

jeff_50

I've read in Dan's books that air vents on
radiators should be 1/2 to 2/3 up on the height radiator.
Are these too low?

michael_15

they're fine

I believe those radiators probably even have a built-in tapping hole where they're placed; that is, they were built with the intention that air vents could be added in that spot.

-Michael

Dave_12

Air vent placement

You do not want the air vents too high because you want steam to enter the radiator, force the air out through the vents, then stop venting when the air is out of the radiator.

If you install the vents near the top of the radiator, the thermostatic vents will close when the steam gets down to the level of the vent. The bottom of the radiator will still have non-vented air, blocking more steam from coming into the radiator. The result will be a partially cold radiator.

Steamhead (in transit)

Right on both counts, guys

by the time these "large-tube" radiators came out, it was standard practice to cast a "boss" into the radiator so one could drill and tap an opening for a vent. This way all you had to do was drill where the manufacturer wanted you to, and the radiator would work as designed.

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David Efflandt_2

Venting

If you have Dan's book "The Lost Art of Steam Heating", read Chapter 8 about venting. Do you have enough main venting in the right place?

Sizing radiator vents may take some experimentation to get everything balanced. If you cannot vent the slow ones fast enough, an alternative is smaller or adjustable vents on ones that get too hot. But if upstairs risers are too small, too large of a vent can result in gurgling, sloshing and spitting, because rapid condensation from a cold radiator may be fighting the steam.

I had that problem with a north 2nd floor radiator (riser too small, most distant from boiler). It previously had a Dole C vent which had become inoperative. A Dole 1A set wide open plugged up in week and stopped venting at all (other Dole 1A's that came with the home still work fine). Now I have a Hoffman 1A throttled down, and it has worked fine for a couple of years. The radiator does not heat completely in mild weather (shorter run time), but fully heats without spitting in cold weather.

I do not have main vents (yet), but have a large vent on the 1st floor under the problem radiator, to get at least get steam to the riser quickly. And that 1st floor rad. is near an open stairwell, so its surplus heat can rise upstairs. Even though the radiators and risers are not perfectly sized, balancing the venting keeps everything at a fairly even temperature.

Steamhead

Jeff, regarding your main vents

measure the length and diameter of your vents and we can tell you what you need. Proper main vents will make balancing the system very easy.

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