time it takes to vent the 1 pipe steam mains

Steve Garson_2

Are you firing at a low rate for the boiler? Can you hear the air coming out of the vent?

mike jones_2

time it takes to vent the 1 pipe steam mains

researching on here has led to a 1 to 3 minute time to vent the 1 pipe steam mains, but the posters did not show how long or thick their piping was.

we have 2 mains each 20 feet long of 2 in. pipe before they branch off to the 4 risers, each 2 in. and 5 stories tall in a 5,500 sq. ft. new york building 10 apartments.

even with a gorton 2 on the north main and a gorton 1 on the south main, it still takes 10 minutes for them to get hot at the same time which seems way too long. i am also suspicious since the gorton 1 does not know its on the warm side of the building since its in the cellar and the sun obviously affects the upper floors.

does anyone ever put 2 gorton 2's on a system this small for the north side of the building, or is something else suspect here?

we keep fine tuning the system but are a bit stuck here on this one. help would be warmly welcomed!

Brad White_185

Comparing apples and Buicks

Your 20 foot main at 2 inches is the least of your issues, if that is what you are venting with the #2. That segment has less than one-half a cubic foot of volume. A Gorton #2 would vent that at an ounce of pressure, in under 30 seconds.

If you are talking about getting your risers vented, that is another matter entirely.

Each riser, if say 50 feet, ten feet per story, have about 1.5 cubic feet per.

You have to vent these either at their tops or via the radiators if you have no other riser-top venting place. (Sometimes the highest apartment radiator has an off-branch to a master vent. Maybe it is in a closet or capped off long-ago- just one thought.)

I am not a fan of venting the mains through the radiators but sometimes you have no choice. Let me assume that here.


Assuming that you have five radiators on each riser, a Gorton D (equal in venting to a #1) at the top radiator would vent that main (not the radiator yet), in about 3.5 minutes at one ounce pressure and a 1:40 at three ounces pressure. (This is presuming that the other radiator vents are not contributing any venting, just for illustration here of what a single higher capacity vent can do.)

I would suggest that, if there are five radiators on a typical riser, starting from the top, a Gorton D, a C, a #6 on the bottom three of each riser. This would vent the main and get the radiators warm in about a minute at three ounces pressure. Chances are you will be higher than that, not that it is recommended.

I would make each riser the same; that relatively short main does not make a whole lot of difference.

Your notion that the Gorton #1 does not know it is on the warm side is correct. It does not. The placement of these is by your determination to suit how the building might heat.

kpc_16

let me ask...

are these pipes well insulated? that would make a difference. kpc

mike jones_2

time it takes to vent the 1 pipe steam mains

the firing was just adjusted based on a combustion analyzer so
i have been assuming it is firing properly. it will run for over half hour usually before the heat timer shuts it down, so it is not short cycling, if that helps answer the question.

the vents are very quiet, can't hear the hissing, the whole system is pretty quiet, no knocking, only 1 inch bouncing in gauge glass. should i ever hear or feel the hissing? i am only used to that on broken vents stuck in the open position which we have deep 6d.

mike jones_2

time it takes to vent the 1 pipe steam mains

ok i am digesting your 411, interesting.

i would note that we have old windows and hi ceilings with large old heavy old fashioned radiators on the lower floors, so these have gorton c's and d's. the upper floors have c's and d's also, even though the raditors are more modern with more tubes since these are the upper floors and the windows are new up there.

we have been sizing the gortons on the radiators mainly based on how cold the rooms are, under the theory that radiator size and distance from boiler come together with wanting the bigest vents in the coldest rooms. i hope that is not backfiring on us!

ps. most of your assumptions are pretty accurate in your post, but it takes 20 minutes for the top floor radiators to get hot, after the 10 minutes for the mains, for a total of 30 minutes. the good thing is they stay warm longer too.

Brad White_185

Still a ways to go though

I agree with Kevin (kpc's) point about insulating the piping. If not that is a good drag on speed even once warmed. Glad he asked!

Now, the way over-venting can hurt is if doing so creates such a low pressure that it draws steam right by other more restrictive outlets. The Gill and Pajek book on venting (#300 in the online store) has such a story, so FYI.

I suppose it would not hurt to move some vents around and see what difference might be made. But first, I would want to make sure that your piping is insulated, your pressure is low (a pound or so should be fine, even less) and your near-boiler piping is what the manufacturer recommends.

I think that your "following the colder rooms with faster vents" is a reasonable first approach though, but I am sure others will have more substantive opinions as to why

mike jones_2

time it takes to vent the 1 pipe steam mains

the pipes are insulated, especially in the cellar where they are fully exposed and easily wrapped. the fittings upstairs are rarely insulated.

the pressure is so low it is hard to read, rarely even reaches the 1 lb mark.

the above boiler piping has been checked as good which i know is important considering this was probably coal 100 years ago, then oil, and now gas, and we do have the hartford loop below.

i will read up on this potential overventing since i am not sure what is meant by passing the more restrictive areas.

my gut was that the faster the venting the better so long as the vents close properly when hot.

it just seems goofy that the mains are so slow to vent, and the risers even slower. maybe the risers are even slowing down the mains somehow. thank you guys for giving this your thoughts, i can't plead cold weather, i just want to get something right for a change!

Unknown

Say Mike,

not to be critical, but you really have to think like steam,,, do you have a copy of LAOSH?,, if not I would highly advise-it.

Dave