one pipe venting

lanceL

Hi Guys,
Great site, I've learned a lot, but still have some questions. I have "Lost Art.." and have read it several times.
I just got a 2 story bldg with 3 comml on the first and 4 apts on the second. The boiler is a gas Weil, installed in 05, output about 330k. New header, welded, no drop, but looks right. Just insulated the header, big difference. Honeywell pressuretrol, 1/2 to 1 1/2 psi, down from 2-4. Setback thermo in one store. New Hoffman 75 at the end of primary main where it goes to a dry return. All other main vents are at the end of the dry returns where they drip to the wet line, usually on a 2' riser, and are hoffman #4. No spitting or hammer present.
OK, here's the problem: The stores don't heat well. They each have a radiator with many thin sections, and are 18" h x 12"d x 60 to 72"l. They only heat 1/3 of the way with temps in the 20's. I've tried new hoffman 1-a, and leaving the vent out (better). All pitch 1/2" to the valve, and the feed is at least 1/2" to the ft back to the main. I haven't removed the valve cap yet, cause if it ain't broke..
Should I repipe to put the main vent at the end of the store steam supply before it drops to the dry return, it's about 25' before it drips down? Any suggestions greatly appreciated, I don't know what else to try!
Thanks, Lance

gerry gill

you need a heck of a lot

more venting on your mains...one hoffman 75 is like invisible to the steam.

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lanceL

Thanks gerry,
I thought the 75 was the biggest available. There are about 5 #4's also on this main where the branches drip back. Maybe I should do the riser vent before the valve, but I'm trying to avoid surgery in a 12" crawl space.
Lance

nicholas bonham-carter

more venting

i second that- you need a # 2 gorton on each dry return [in a protected location].
the hoffmans 4 and 75 are too small to do anything much.if you get the venting chart from here you will see how small they are-ever try to breathe through a small straw?

it would also be better to get your pressure down below 1 psi. as i am sure you have read the low pressure steam travels more quickly through the pipes.

check your thermostat anticipator and location, and don't use much setback, until you know how effective everything is--nbc

Unknown

Gerry is too much of a gentleman to recommend his own book so I will do it.

Lance, you need to get:

"Balancing Steam Systems
- Using a Venting Capacity Chart"
by Gerry Gill & Steve Pajek

As Dan as given a far better description of their booklet than I could, use the following link:

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

I found their booklet very useful and enlightening. If you want to know about venting and see a comparison of the venting capacity of different Make/Model vents, this is the book for you. It's available as a download E-Book.

lanceL

Thank you all, I will get Gerry's book on venting. It seems you like the Gorton better than the Hoffman. There was a Gorton 1 where I installed the 75.
What about the pressuretrol vs. the vaporstat? Lower operating (and more accurate) pressure gives faster steam travel and better fuel economy? Is the Honeywell 408J1017 what I want?
If the system is working, but I know the mud leg has never been cleaned, should I touch it?
Thanks again, Lance