Is it worth it to enlarge my vent tap or not?

jalubarsky

Four years ago I bought a house with steam heat and with this sites help I have improved my system significantly - thank you all. Recently my daughter bought a house (vintage 1890's) with steam heat so another challenge affronts me.
A brief system summary:
3 mains:
#1 main 70 feet in total, 1st 50 feet is 2 inch pipe, last 20 feet is 1 1/2 inch pipe. Single vent with a 1/8 inch tap. Not sure what kind of vent it is. Time to get steam to vent is roughly 18 minutes. There are 9 rads hanging on this main.
#2 & #3 main start as a T with one side 18 feet the other 22 feet. Pipe is 1 1/2 inch. There are no main vents. 4 Rads on these mains. Time to heat to end roughly 15 minutes from cold start.
Total number of radiators equal 13 and all of them have Durst A884 vents. These are not getting it done, many of the rads take a long time to get fully hot if at all.
Having read We Got Steam Heat I fully believe in fast venting so -

Question #1: On Main #1 - I calculate that there is roughly 1.43 cubic feet of air in this main. Since a 1/8" tap at full open can deliver 1.1 cfm @ 1 oz. should I put three Gorton D's on and call it a day? Or should I enlarge the tap to 1/2" and add a Gorton #2 or more? I am not a plumber so the first option is far easier.
Question #2: On Mains 2&3 with no venting. Since they are so short I calculate one has .252 cubic air the other .308. One has a 1 1/2 inch plug at the end so I can downsize to 1/2" without drilling. The second there is no way to get a vent other than drilling the pipe. Any suggestions what makes the most sense?
As for the radiators I am going to replace the poor functioning Dursts with most likely Gorton D's, 6's, or 5's depending on distance from boiler.
Any input would be greatly appreciated as always.

nicholas bonham-carter

If you can put decent sized main vents on each leg, then use Hoffman 40’s on each radiator. This follow the principle of venting the radiators slowly, and the mains fast. In this advice, I show my difference of opinion with the advice from Gorton’s website.
You are trying to balance the aggregate resistance to the escaping air (back pressure), of the all the radiators on a line with the resistance of the main vents. A higher radiator vent resistance will enable steam to fill fully the main lines before creeping upto the rads. If you can vent the mains at 2 ounces on a 0-3 psi gauge, you are good to go.—NBC

Jamie Hall

Honestly, I'd bite the bullet and open that tap on the long main to half inch and put a Big Mouth on it. A bit of a nuisance, but I expect you'll get better results that way. And I agree with @nicholas bonham-carter on the rest.

jalubarsky

I appreciate this feedback - thank you.
I reached out to Barnes & Jones about their large main vent and they are available including the 1/2 inch version.

EBEBRATT-Ed

From a fuel savings standpoint alone you should probably bite the bullet and do what you have to do to install larger main vents. It will be worth it.

also if possible, locate the vents 18" back from the end of the mains. Put the vents on as long a nipple as possible

New England SteamWorks

jalubarsky said:

I appreciate this feedback - thank you.
I reached out to Barnes & Jones about their large main vent and they are available including the 1/2 inch version.

Be advised that the 1/2" version does not have the venting capacity of the 3/4" version, being limited by the 1/2" orifice. Change the bushing, well worth it. Bushing won't budge? Might entail cutting into the returns and starting over. Also well worth it.

gerry gill

Don't forget that Barnes & Jones make a kick **** adjustable main vent that is small in size but big in venting capacity and is 1/2'' ips.