Fast Venting mains

Jim_64

I thought the main vent should be on the end of supply line before the elbow that leads to the return? Or am I wrong and that the main vent should be on end of return line before it goes back into the boiler?

George_47

Fast Venting mains

I have a one-pipe steam system which I am trying to balance. I currently have an uneven heat issue. My first project is to vent the mains as quickly as possible.

I have two feeds:
First is a 2 1/2 inch pipe that is 61 feet long.
Second is a 2 inch pipe that is 56 feet long.

Any recommendations on the size of the end of line air vents needed?
Is any brand of air vent better than the other?

Supply House Rick

vents

i would choose a gorton #2[ pexsupply.com] for each return. also i would keep the pressure low with a 16 oz. vaporstat, and a good low-pressure gauge [gaugestore.com 0-3 psi.] i think you will notice the difference. don't forget to mount them in a location on the end of the dry return protected from water-hammer.--nbc

Kool Rod

Perhaps # 2 Grotons on the 2 main feed lines and smaller vents on the return lines before entering the boiler?

Kool Rod

Getting confused


From the reading I have done on heatinghelp it appears that the size of the rad determines the size of the rad vent. When you visit www.gorton-valves.com they say this:

"Larger sizes of Vapor Equalizing Valves should be installed on radiators farthest from the boiler and-in the coldest rooms. The small sizes are for radiators closer to the boiler and affecting the thermostat."

Is it a combination of both distancce from the boiler and rad size? Or is it strictly rad size?

I guess if it was easy to balance a system, no-one would be having uneven heating problems.

Kool Rod

What Gorton is proposing is that all rooms reach temperature at the same time.

If the room where the thermostat is located, reaches the set heat, the burner shuts off and if the other rooms are still cold, this obviously creates a problem as the other rooms would never warm up. On the other side of the equation, some rooms may get too hot while waiting for the room where the thermostat is located to reach the set heat.
Using different size vents balances this all out.

The general feeling seems to be to deal with the mains and radiators separately. Get the steam into the mains as quickly as possible hence the need for maximum venting at the ends of the mains to let the air to escape. When that is accomplished then the next stage is to deal with the individual radiator venting.
Your options here are balancing the system using fixed / adjustable vents or going to maximum venting and using TRVs in rooms to control any over heating. On the downside - maximum venting the radiators may create problems with water hammer as the pipes going to the radiators are a counterflow (1 pipe system)so some radiators may not tolerate too fast a venting and you'll have to adjust for this. I've found the Heat Timer Vari-valves very beneficial if you need to adjust the venting speeds.

If you don't have it already, I'd highly recommend Gerry Gill and Steve Pajek's e-book on venting.

http://www.heatinghelp.com/shopcart/product.cfm?category=2-138

- Rod

ttekushan_3

Confusion

On a single pipe system the vents go at or near the ends of the steam mains. The mains then drop into the wet return. Wet returns are below the boiler water line and have no air to vent.

Two pipe systems have a dry return which handles air and condensate. This return is above the water line until the boiler room in most cases and is vented just before dropping into the hartford loop area. The end of the main is typically vented into the dry return with a steam trap.

These are the general forms of steam heat found in homes. There are endless variations, especially when you get into institutional and industrial steam heating.

Even on two pipe systems an end of steam main vent really accelerates and evens out heat distribution.

The idea is to vent the mains fast enough that the main acts more as a manifold that feeds steam to radiators all at the same time rather than a linear pipe that feeds radiators sequentially based on their distance from the boiler.

You're doing the right thing, and put the vents towards the end of the steam main. You could put two vents on the larger main and one on the smaller one due to the difference in volume of the two lines.

-Terry

George_47

Terry,

Thanks for the input. Strangely enough even though the main pipes are 2 and 2 1/2 inch pipes respectively - the steam reaches each end at the same time. At exactly 14 minutes from burn start - pretty poor effort that - so any venting should help in this case.

I just bought the place so its a steep learning curve for me.

Any thoughts on the insulation that is best suited for the pipes - 1/2 inch or a full inch fiberglass pipe insulation? Do the returns also need insulation of a full inch or would half inch do? None of the suppliers really advertise the R values of this type of insulation.

scrook_2

Mains volumes, R values, etc.

61' of 2.5" pipe's about double the volume of 56' of 2" pipe (2.875" ID vs. 2.067" ID for Sch 40 pipe) so you might put two Gorton #2's on the 2.5" main and one on the 2" main to vent both in about the same time.

Insulate steam mains w/ full 1" fiberglass, may as well use 1" on returns too, price difference for 1/2" vs. 1" thick is fairly small, at least in the larger diameters.

At 200°F fiberglass thermal conductivity is about 0.28 to 0.30 BTU inch/hr ft^2 °F, (smaller values are better!), regardless of thickness (so you have to know/account for that).

R value is resistivity (inverse of conductivity), and has factored out thickness (so you can compare R-values w/o knowing the thicknesses).
1" fiberglass would be about R-3.6 to R-3.3 (bigger is better) and 1/2" would be half (about R-1.8 to R-1.7).

nicholas bonham-carter

what vent's what

in the ideal system, the main air vents allow the air to be pushed out by the steam rushing into the pipes from the boiler. the volume of this air is the total of the horizontal steam pipe capacity PLUS the volume of the boiler steam chest-quite large!

the radiator vents let the air out of the vertical riser serving the radiator, and the radiator itself, a smaller volume.

if you have a tall top floor [3+], i always recommend using the SAME size larger capacity vents on each radiator at the top. intermediate floors can have lower capacity vents, because they are only doing the radiator and not much riser.

if finances are tight, spend money only on the main vents, as they are doing most of the work. it's a choice of one payment to mr. gorton, or continuing payments to your fuel co. most of the time, the rad vents are still functional even after decades!--nbc