Master venting vapor steam risers

Onepipe

I posted this question on an older chat but got no response so sorry for any redundancy.

I have Richardson vapor system that I am currently working on that was in pretty rough shape, luckily all original parts are there. The system is now running pretty good but the steam is taking a wile to get up to some of the upper radiators before the stat satisfies. I am going to be moving the stat as it’s in a poor location and also taking a few of the inlet valves apart for a rebuild as they are stuck in position. I am trying to keep the system under 6oz with out short cycling so as I have been thinking about it venting came to mind.

My question: can I add smaller main vents to the second floor risers (before the vapor valve) so that I can get steam to not only the end of each main but to each vapor valve roughly at the same time? Or will this not work with vapor?

My thoughts are if I do that I can then just adjust each valve as nessary to ensure no pressure drop, balance and keep my water seal. That way I’m not depending on that small bleeder hold in the Richardson elbow to vent all my air in the riser and let it only worry about the radiator once the steam is there. 

Read about this technique in lost art and have used it on one pipe systems. it has increased efficiency and control of heat 10 fold. 

I have gorton #2’s on the steam mains and dry return ends and was looking to install a M.O.M #1 with adjustable caps on the second and third floor risers. I would install a tee just below the vapor valve and place the vent off the branch of the tee. That way I could adjust the vent orifice as needed.  Goal is to have the mains fill before the risers but then all risers fill equally after.  Thanks for the help

Jamie Hall

Read my comment on steam venting -- a contrarian view. Yes indeed you can add vents to the risers or runouts before the valves (there are a few vapour systems where you can't or shouldn't -- Hoffman Equipped is one). But why go small? As I said in that other post, the question isn't what the maximum vent size is, but the minimum. And the bigger, in this case, the better -- within reason, of course!

Onepipe

@Jamie Hall thanks for the response and your reference post was great. I am going to definitely add those vents and look forward to the results. You mention in your post that some two pipe systems regulate steam flow with an orifice on the exit of the radiator? Is that a vapor style system? Lastly you mention that it is important to have one pipe steam boilers shut off at reasonable intervals to regain heat control in the building. ( May not be the exact quote). Are you referring to the system cycling on pressure or satisfied t stat….or both. I get the boiler needs to stop and let the steam collapse for the vents to open, but isn’t that the normal function of the one pipe system? Or am I over thing the statement. 

Thanks again for the info.

Jamie Hall

Some vapour systems use exit orifices. A number use what can only be described as patented widgets on the exit. Most, however, either use orifices on the inlet or calibrated throttling inlet valves -- a more satisfactory solution in my view. The cycling on one pipe systems to regain control could either be on pressure or on a thermostat -- or even, in very big systems, a timer. If it's on pressure, however, it is important that the pressure really drop to zero while the burner is off, and that may not be the case in many systems. It's usually really only a problem when one is using thermostatically regulated vents for control, although it is also a problem when recovering from a setback and the run is very long, as rooms which have slow vents and might not overheat normally may overheat rather badly.

Onepipe

Got it. And thanks for the recognition that I am on track to understanding steam like the greats. I work on a lot of one pipe systems(all residential 80-100years old) and the old guy that thought me made me read dans book cover to cover many times and taught me to vent all the mains including risers to the second and third floors as fast as I can so steam reaches all rad valves at the same time. Some times that hard to get the steam to the top riser before the first floor radiators start to take steam. Then vent each radiator as required by the home owner. Generally master bed is slow, bathrooms hot, dining rooms and living rooms hot exc. he used the make sure steam is at each valve and the run all over the house like a mainik and check steam flow through the house. He said that if you are master vented correctly you should not see any pressure build until every radiator is about 25% full. At that point you might see the needle lift off the pin. The systems were all designed before these high heat producing boilers so you have to adapt from the coal days. There are always variances but that’s what I try to do. Key is to beat out the thermostat before it shuts off heat when half the house is still not warmed up……hate those things some times.

thanks