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# Gerry Gill, Steve Pajek or Steamhead

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Bill should size his vents at 1 ounce pressure.

• Member Posts: 168
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Balancing Steam Systems...

I need help understanding how to use the Main Vents chart. For discussion purposes, there is 3.9 cubic feet of air in one of my steam mains. I normally operate my boiler at 10 oz. (cut-out).

The chart indicates that Gorton #1 and #2 vents will purge air at .33 and 1.1 CFM, respectively, at a boiler operating pressure of 1 oz. Question: Do I correctly understand that these vents would purge air at 3.3 and 11.0 CFM, respectively, at a boiler operating pressure of 10 oz? If so, that means that I would need one #1 and not be able to vent fast enough. Please help me understand how to use this chart.
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I'd like to try my hand...

I know they know this stuff a lot better than I do, but I want to see if I've got the hang of this.

When you start the system (and when the mains are filling up) you're not running at 10oz, you're probably running at close to 1oz pressure. Also since you want to vent the mains as fast as possible the 1oz column will give you a bigger vent than the 2 or 3oz colums.

Therefore to vent your main in 1 minute you need to vent 3.9 cubic feet in one minute, 3 Gorton 2's and 2 Gorton 1's will do the trick.

Once the mains are full (and those big main vents close) the radiators start filling... 10 minutes later when the air vents on the radiators are full and all those valves close that's when your system will work its way up to 10oz pressure and the vaporstat cuts-out. That's why you don't need to worry about the cut-out pressure when you're sizing main vents.
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going from one ounce to

ten ounces, you multiplied by ten..thats not what happens in reality..look at the difference from one ounce and three ounces..its not three times as much..vermonter is right on..

gwgillplumbingandheating.com
Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

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gwgillplumbingandheating.com
Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

• Member Posts: 168
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That proves my ignorance

Good thing that I asked. Okay, 3 #2's + 2 #1 = 3.96 CFM or 102% of the target of 3.9. Logical combinations of Gorton vents for my other mains (call them Two, Three and Four) come in at 96%, 103% and 113%. No problem with the overshoot on the last one?

Logical combinations of Gorton vents for four steam risers come in at 97%, 97%, 103% and 118%. No problem with the overshoot on the last one? A fourth steam riser has a volume of .16 cu. ft. of air, so I'll use a Hoffman #4 (.133 CFM) unless someone tells me that using a Gorton #1 (.33 CFM) would not be counterproductive.

Incidentally, this is a 2-pipe system.

By the way, a steam guy at a S. Philadelphia plumbing supply house told me that he uses Heat-Timer's main vents on both 1-pipe and 2-pipe systems. Their main vents are not listed in the Balancing Steam Systems chart. Conversely, Heat-Timer's website indicates that their main vents are for 1-pipe systems. Is there a difference?
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i don't think

heat timer makes main vents..i think he uses the radiator varivents on mains..and i do too..not on one pipe mains but on two pipe mains, by tapping the riser supplying the radiator..never ON a two pipe radiator..but BEFORE it..this way it performs the role of a main vent..thats probably what he's eluding to..i hope he's not putting them actually on the radiator of a two pipe system, or it will mask a bad trap someday, and cause the boiler to flood, or sit there like a land mine by allowing the radiator to fill with condensate and when someone takes the trap cover off, well, hope he has rags handy..

gwgillplumbingandheating.com
Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

• Member Posts: 168
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Heat-Timer

Yes, Heat-Timer's main vents and radiator vents are apparently the same thing. At www.heat-timer.com, click on Applications and then click on VARIVALVE Radiator Air Vents where you will read, "Adjustable Radiator and Main Line Vent Valves for One Pipe Steam Systems."

The S. Phila. guy advocates using these vents on 2-pipe system mains, but not such systems' radiators.

Still not sure why Heat-Timer's website does not indicate that the vents are appropriate for 2-pipe system mains. They replied to neither my voice or email messages. Oh well.
• Member Posts: 168
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I'm still looking for guidance

concerning how close a vent's purging capacity should be to the application target. For example, one of my risers has a volume of .56 cu. ft. of air. Two Gorton #1's will purge air from that riser at a rate of .66 CFM. That's .66/.56 = 118% of the target. Do you think that too-fast purging rate might unbalance things? I just don't know the allowable tolerances here although I'm guessing that purging too fast would be worse on a main relative to a riser.
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i'd feel the other way..

if it causes a problem venting to fast, it would be on the riser more than the main..parallel main anyways..there is no ''set'' tolerances..each system is unique..go for max venting.you could always slow it down if a problem is created.

gwgillplumbingandheating.com
Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

• Member Posts: 168
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Okay, I'll be careful not to install too much venting on the risers.

Please refine the objective of going for maximum venting on the mains. For example, if a main has 3.9 cu. ft. of air in it, should I install more venting than, say, three Gorton #2's and two Gorton #1's which would collectively be capable of purging 3.96 CFM? Generally, how far should I try to overshoot the air target on the mains? I'm just trying to get a feel for what the pros benchmark.

Thanks for your patience as I try to get this right. It is much appreciated.
• Member Posts: 21
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Ooh, Ooh, I want to try again...

Filling the mains quickly gets steam to the bottom of all the risers at roughly the same time. This makes getting steam up all the risers and in the radiators at the same time easier.

Installing more venting may not have any advantages, especially when the goal is to get the steam where you want it when you want it.

I'm curious how big the other 3 mains in your house are, but in the meantime let's take my own home for example.

One main has about 1.2 cu.ft. of air, one has about 0.5 cu.ft. and one has about 0.1 cu.ft. Convenient huh? Gorton 2, Hoffman 75, and a Hoffman 4A. All three mains full, and all in one minute.

Let's imagine I have a Gorton 2 on the smallest main, five on the middle one, and twelve on the biggest one. Not only have I just spent \$900 on vents, plus a pile of 3/4" fittings etc... but now I can vent my mains in 12 seconds!

I've vented the air out of the mains faster than the boiler can fill them with steam. My venting is still proportionate with the air in the mains but I don't have enough power in the boiler to do the work (filling and warming up the mains) fast enough to take advantage of all those beautiful vents. Forget about balance, the mains will just fill up however the steam decides to fill them up.
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your not giving me the most critcal

piece of information..that being the size of the tapping you want to put these vents on..

gwgillplumbingandheating.com
Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

• Member Posts: 3,078
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gwgillplumbingandheating.com
Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

• Member Posts: 6,688
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That's good

cause Vermonter can take up the slack when we're somewhere other than the Wall..... ;-)

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yup, and it will help

cause i only type with one finger..this threads been a rough one..hehe

gwgillplumbingandheating.com
Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

• Member Posts: 21
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May not be true, but it's nice to hear... [nt]

• Member Posts: 168
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other mains & tapping info

Vermonter asked about the other mains. Attached is an Excel spreadsheet that shows calculation of the air volume in the mains and risers and suggested vent selection. Advice welcomed because this stuff is all new to me (HO here).

Re Gill's question, available taps on the mains are also indicated in the spreadsheet.
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Nevermind...

Nevermind...
This discussion has been closed.