Only One Main Vent ?

Steamhead (in transit)

and they should be installed just after the last radiator takeoff on each main. No point in heating up the return. Measure the length and diameter of each main up to the last takeoff, and we can tell you what you need.

For your boiler, if you're using oil the Burnham Mega-Steam is the best one out there today. If gas, check out the Smith G8- it's a wet-base boiler with a power gas burner, which is a bit more efficient than an atmospheric unit. Slant/Fin has approved their Intrepid wet-base boiler for use with a power gas burner too, according to my friend Noel.

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Charlie Taylor

Only One Main Vent ?

I have a one pipe steam system with 4 mains leaving the boiler header. There is only 1 Main Vent in the system --installed on the longest main run,at the end of the condensate return line ( at top of vertical drip to wet return).
I have never been able to get the system balanced well adjusting the venting by the size of the radiators.There is only a single thermostat and the heating in the house always remains uneven.

Need some advice.....
Is there a way to get the existing system balanced better or should I have additional vents installed at the ends of the other 3 shorter Mains ??

My old boiler casting has recently develpoed a major leak in the off season and I'm facing replacing it ASAP.....so this may be the best time to get into the plumbing and resolve any venting problems also.

Charlie Taylor

Need More Vents + Boiler Replacement

Steamhead....I'll get busy measuring those mains & get back to you.

Thanks for the boiler replacement tip too. I've done some research this morning on the Burnham Mega Steam boiler----Very impressive.
Their largest capcity model(MST629) is rated at DOE 201,000/151,000 Net BTU.....My existing 30+ year old Weil McLain P766E had ratings of DOE 236,000/177,000 Net BTU---Not a direct match........but I decided to dig into calculating the total Net EDR radiator load on the system.
I come up with a total net load of 105,300 BTU ( re-ran it three times to confirm !!)The guidelines say the standard pick up factor is 1.33---which comes to 140,000 BTU.......and IF there is insufficient radiation or little pipe insulation, use a pick up of 1.5 for safety----that would calc. to 158,000 BTU.....And then choose the appropriate boiler from the DOE Rating.

Judging from these figures , it looks like my old W-M P766 boiler was way oversized for the system.Looks like the Burnham MST513 (DOE 164,000 / 123,000 Net BTU) would be a better fit for my system.

Is there anything else I need to consider to size this new boiler correctly when I sit down with the heating folks ??

Steamhead (in transit)

The pick-up factor

is already figured into the rating. You need not add to it. The MST513 has enough headroom anyway, you may end up down-firing it slightly to match the load more closely.

Just out of curiosity, how did you get your EDR load?

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Charlie Taylor

Radiator EDR Figures + Mains


Steamhead,
Searched the internet & got my figures following the "Cast Iron Radiator Heating Capacity Guide" on the Colonial Supply website(www.colonialsupply.com/resourses/radiator ).

Got out the tape measure over the weekend and attacked those mains as you suggested .Discovered that one run ( Main #2 ) is much longer when actually measured ......and I have a lot of heavy duty asbestos pipe wrap insulating ALL the the piping---Mains + returns.
Here goes:

Main #1- 22 feet of 1-1/2"dia reducing to 20 feet of 1-1/4" dia to last take off at end of main.Condensate return starts from this point back to boiler.This is the return with the one existing main vent installed---a Dole #3B (1/4 " thread) at the top of its' wet drop.

Main #2- 16 feet of 2" dia to condensate return fitting.24 more feet of 1-1/2" dia continues to last takeoff at end.

Main #3- 19 feet of 1-1/2" dia ending at a tee ( last two takeoffs).Condensate return fitting at one of the take off pipes.

Main #4- 17 feet of 1-1/2"dia terminates at last take off (-vertical riser to third floor radiator).Condensate return fitting only 2 feet from header on this one.

Thanks for all your assistance !

Steamhead (in transit)

You have some choices here

You can use either the Gorton #1 or Hoffman #75 main vent. If it's more convenient to drill and tap 1/8" holes in the sides of the pipes rather than 1/2", you can use the Gorton #D radiator vent- not the usual procedure, but it will work. All the above-mentioned vents have roughly similar capacity. Sizes were figured at about 1 ounce pressure.

Mains 1 and 2 should get two vents each.

Mains 3 and 4 should get one vent each.

Vents should be installed just past the last radiator takeoff on each main.

Then watch how well it works!

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Charlie Taylor

Thanks again for all your help

Let you know how it works out after the system gets up and running with the new boiler !!

Charlie Taylor_2

One Main Vent-More Main vents needed--followup for Steamhead

Hi Steamhead,
Following up after you advised I add more main vents to my system when the new Burnham MST replacement boiler went in ..well, all done and quiet as a mouse. The addition of those main vents as you suggested really works great on 3 of the 4 main piping runs in the system.
After 15-20 minutes of steaming time,the radiators on 3 of the mains are all heated halfway but, the longest main run is just beginning to get steam at the takeoffs and Main Vents ( 2 gorton #1's). This run has only 2 radiators at the very end with their takeoffs just before the main vents....By the time the boiler cycles off after 35-40 minutes, the rest of radiators in the system are fully hot and cookin' ,but the 2 on this long Main run are only about a 1/3 heated and the rooms cool.
Tried adding a third main vent to this run and even double vented the 2 radiators---But only a very slight improvement . Then took a listen to how the main venting compared between the runs....The other three vent air at a smooth ,steady rate ..But the problem mains' vents are pulsing /breathing air in bursts. There is NO water hammering going on at all throughout the entire cycle.But something is apparantly blocking the smooth flow of steam down this one main.
I do notice that this problem mains' piping is different coming off the boilers' header.....comes off its' feed riser at a right angle about 20" lower that the other three mains....then slopes very slightly upward ( confirmed w/ a level) for 10' --takes a 45 degeree elbow upward...rises another 4' to a 90 degree elbow ( highest vertical point of the run) ---from there, continues to slope downward for the 30' run to the radiator takeoffs and main vents...after the vents it drops into a dry condensate return run back to the boiler . There is no drip piping installed on that first 14 ' of pipe that's sloping back toward the header riser.

Do you think that condensate is splashing back towards the header in this run and causing the pulsing steam flow ??

Charlie Taylor_2

My apologies --this was my followup -to Steamhead--

Left the name & email at default--got so absorbed in putting the details down

Steamhead (in transit)

It might be

I'd repipe it properly, and see what happens.

"Steamhead"

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Charlie Taylor_2

Repipe it

Thanks for the reply.
I assume that the best way would be tie into the header riser like the other 3 mains are already piped .....get rid of way that first 14' of pipe connects currently....and not just adding a drip return to what's there now ??

Steamhead (in transit)

Correct

let us know how well it works!

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