calculating vent size

Gary Myers

Hello,

I have a residential steam boiler with a 50 foot 2 1/2 inch main that wraps around the basement and arrives back at the boiler where there is a Vent-Rite #75 on a 6inch nipple. After the vent the main is returned down to the boiler. There is a 10 foot 2 1/2 inch run off this main with a Vent-Rite #35 at its end and that is working fine, but the #75 vent is not getting steam during a typical 15 minute heat cycle. The last radiators only heat up about 2 segments and the pressuretrol never seems to kick in even when I crank the thermostat. If I take the # 75 off I get steam out of the nipple in about 5 minutes from making steam. How do I calculate the proper size vent for this main? It seems like it is harder to blow through the #75 then the small Vari-Vents at the end of the radiators; should this be the case??

Thanks for any advice,
Gary Myers

Boonierat

Calculating vent sizes

Mr. Myers:

One foot of 2 1/2" steel pipe contains .03 cubic feet of air
(see page 27 of Dan's Dead Men's Steam School workbook).
If I read your posting corrcetly that you have a total of 60
feet of this then you're trying to vent 1.8 cubic feet per minute.
The only single steam vent I see available that has a rating higher than 1.8 cfm is the Gorton/maid-O-Mist #2. They're rated at 5.5 cfm. If a the vent in question is serving a radiator you need to include it's cubic contents also. The Gorton/Maid-o_Mist vents quite a bit at 5.5

Regards,
Nels

Gary Myers

Thanks Nels,

The #35 which is on its own leg is doing some of the venting as well as the #75 so I wonder if combined they might be sufficient? I think I may have another problem too, as I had an older boiler replaced 5 years ago with a new Peerless but the contractor retained the old near boiler piping arrangement which does not allow for any water backout to be separated. Two of the far radiators "pant" in and out which Dan lists as a symptom of wet steam, but the water in the sight glass does not go low during a typical heat cycle. Can anyone comment on this?

Thanks again,
Gary

Boonierat

The #35 & #75 Vents

The #35 & #75 steam vents from Vent-Rite are rated at .4 cfm each. Soooooooooooooooooooooooooooooo,combined it looks like they're capable of venting about 44% of the 1.8 cfm your looking to vent. By the by all these numbers are based on 2 oz steam I saw Dan at the NHPHCC trade show in Nashua, N.H. last Saturday and both agreed that steam is 4th grade math 'n 5th grade science. Most of the time the tooth pulling comes in getting the right data. I keep his Dead Mens Steam School workbook at my desk. Use it daily.
Regards, Nels

PS I don't work for him nor get royalties it's just a damned good book when I couple it with his videos.

Bob W._2

Each of my mains...

are similar in size and length. I use two Gorton No. 1's on each main. Each is equivalent to a Hoffman 75. I don't know what the venting rate of a Vent Rite 75 is. The Gortons are only $15-16 each so installing 2 is no big expense.

[Deleted User]

I second that

It's right beside MY desk, too.

on top of EDR, and Lost Art 1 & 2

Noel

Boonierat

\"Lost Art 1& 2\"

> It's right beside MY desk, too.

>

> on top of EDR,

> and Lost Art 1 & 2

>

> Noel



I don't dare leave "Lost Art 1 or 2" hangin' around...................them puppies will find walkin' legs. #1 is so dog eared and battle weary from the copy machine I've yet to see any other document/book/catalogue in our office like it. Always acknowledge the source when I copy.

Boonierat

\"Lost Art 1& 2\"

I don't dare leave "Lost Art 1 or 2" hangin' around...................them puppies will find walkin' legs. #1 is so dog eared and battle weary from the copy machine I've yet to see any other document/book/catalogue in our office like it. Always acknowledge the source when I copy.

[Deleted User]

I'm on my third copy of #1

They should last longer, now. They've retired indoors from the truck.

Noel

Gary Myers

I may need to hire someone who has the Book if it turns out I need to re-do the near-boiler piping! I am not in the business myself. I am in the Nashu NH area, are you a local heating contractor? If the boiler is throwing water into the steam would it neccessarily cause low water in the sight glass?

Thanks again,
Gary

Gary Myers

how fast?

Hi Bob W,

Approximately how long does it take for steam to hit the vent at end of main in your system? This will give me a point of reference for a good working system.

Thanks,
Gary

[Deleted User]

Gary, it should take....

One to two minutes for the steam to hit the end of main vents, AFTER the header first gets hot.

Noel

Unknown

Vent valves

Gorton # 1 Vent valves vent 4 Cubic feet of air per minute
Gorton # 2 Vent valves vent 16 Cubic feet of air per minute
Hoffman 75s vent 4 Cubic feet of air per minute and should out last all other manufacturers by 3 times


Jake

Steamhead

That long main

should have a Gorton #2 vent. If the long main then heats faster than the short one, put both Vent-Rites on the short main.

You want both mains to heat up in about a minute, measured from the time the boiler starts producing steam. The steam should reach the ends of both mains at about the same time. Once this happens, the steam will rise to each radiator simultaneously.

www.gorton-valves.com

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