main vents

Steamhead

would require 4 Gorton #2 vents. Maid-o-Mist doesn't make anything that big.

How did you arrive at the 18.29 cubic feet? Did you measure the whole system?

Steam mains need to be vented quickly so all radiators have an equal chance at the steam. But on Vapor, the vent on the dry return is often the only vent in the entire system. In a water-seal system like the Mouat, the vent holes coming out of the radiators are rather small. You might be able to get by with one or two Gorton #2 vents on the dry return, depending on how much radiation the system has.

Also, the Mouat system illustrated in Lost Art has the dry return vent line going into the chimney. The flue draft was used to pull air from the system. This arrangement works very well, but there must be a way to keep steam from getting into the chimney. A ceiling-mounted radiator or long pipe was used for this. You could also use a large thermostatic trap which would close if steam reached it.

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steve_6

main vents

how many main vents do I need to vent 18.29 cubic feet of air in a two pipe Mouat vapor system? Does anyone know how much air a maid-o-mist air vent vents?
Thank you, steve

steve_6

venting

18.29 is the amount of air in the whole system. Used a chart from a printout I have. There is 488 sq. ft. of column type radiation in the system. There was a Hoffman 75 added to the system. No chimney vent or condensing radiator. I assume it was aborted years a go. Someone also emailed me with a venting rate of about 16 cfm on a Gorton #2. Not sure what pressure that rate was at.. Another chart I have shows a gorton #2 or maid o' mist vents @ 5.5 cfm @ 2 oz. through a 1/2" vent size. How fast should the system be vented. There are 14 mouat traps in the system with 7/64" vent holes in trap. If I'm understanding what steamhead is saying that equates to an area of 1.5" that vents into a 1" dry return. how many vents do you think I need?
thanks Steve

Steamhead

Two Options

The first, and easiest, is to change the Hoffman #75 to a Gorton #2. The #2 should be mounted on the dry return, where it will vent air from the entire system. You could also install a tee and continue using the #75 along with the #2.

We normally express venting capacities at a pressure of 2 ounces. At this pressure the Gorton #1 or Hoffman #75 will vent 1.4 cubic feet of air per minute, and the Gorton #2 will vent 5.5. These vents will pass more air at higher pressures, but we don't see higher pressures when a steam system is venting air.

The second option is to re-activate the dry return vent into the chimney. This will require some device to prevent steam from reaching the chimney if any should make it past the water seals. A long pipe, a condensing radiator or a large thermostatic trap will accomplish this. Since this setup will pull air from the system, less steam pressure will be needed which may reduce your fuel consumption.

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