Main Steam vents - What size and how many.

Don10000

The Header pipe attaches to a "T" splitting two Steam Mains of 60' each so a total of 120' Stream Mains, (not Including the piping to the radiators.)
The Steam Mains are 1.75" in diameter. The Main vents are located on the return lines over the boiler. Thank You!

nicholas bonham-carter

Are you having problems with slow steam delivery?
What sort of main vents are on there now?
If you have a good low pressure gauge, (0-3 psi), you can see the resistance to the escaping air as back pressure. Two ounces is a good target.
Are the main supply pipes insulated?—NBC

Don10000

The heating delivery time is ok. I have a 75-year-old American Standard Boiler. There are 2 very old Dole 3A -No. 1933 Vents. The pressure gauge is built into the boiler and doesn’t work. The pressuretrol is set at 2 psi. and differential at 2.5.
The 10’ long 2.0” diameter header tees off into two branch mains (1.5”D) of 60' each. Each Main has 6 radiators. One main works perfectly. The other main has problems with the last two radiators on the line.
Even if I remove the radiator vents from these last two radiators, no steam enters. But if I intentionally close off the radiators before these last two radiators, they work fine. Meaning, if I close off radiators 3 & 4, then 5 & 6 will heat up fine. My thought was to first install new main vents.

Jamie Hall

My first thought is to turn your pressure down. WAY down. Your cutoff, assuming the usual pressuretrol, is now 4.5 psi. You could try resetting your cutin to 0.7 psi with a differential of 1.0 If nothing else you'll burn less fuel.

Now your last comment gives you the tip: reduce the venting on radiators 3 and 4. I have no doubt that adding main vents might shorten the delivery time, but since you indicate that that is acceptable you may not really need to. But you do need to rebalance those 4 radiators, and you have done the experiment and have the results you need to do that.

Don10000

Thank You, NBC. The main supply piles are not insulated. Is it best to insulate them?

Don10000

Thank Jamie. I turned down the pressure on the pressuretrol with the same results. You are definitely on to something with the vents sizing. When I move one vent, it will affect other radiators. So I guess radiators 1,2,3and 4 are hogging up the steam not leaving any for 5 and 6? When I try to reduce the venting on the beginning radiator/s it it doesn't just reduce the venting. It shuts if off completely. The air vents that I have do not seems to be precision enough to reduce venting a little. The vents I have are Dole 3A, Watts, and the adjustable Ventrite #51. Can you suggest any vents that will regulate how much steam is let into the radiators so I can reduce the ones in the beginning of the line?

Steamhead

Put a Gorton #2 vent at the end of each main. This should get the steam to the ends quickly, so the last radiators will have a chance to heat up.

Don10000

Thanks Steamhead!

bobbob

Is it possible on a one-pipe system to have TOO MUCH MAIN VENTING? I mean, would that cause any kind of problems?

ChrisJ

bobbob said:

Is it possible on a one-pipe system to have TOO MUCH MAIN VENTING? I mean, would that cause any kind of problems?

Only when trying to balance mains like in my situation where one is 32' and the other is 10'. 

In that case I have the long one vented as fast as possible and then the short one is vented at whatever speed I needed to make them match. 

Otherwise I had radiators on the short one starting too soon.  I have a single Gorton 1 on the short one vs five Gorton 1s on the long one.