Pressure in 14 story steam system

MWSASSO

I live in a 14 story building with a circa 1929, 2 pipe steam heat system with a 1970's or 80's replacement boiler. Condensate used to run through the pad of the building but the pipes went bad in the 50's and the condensate returns were moved to the ceiling of the 1st floor. No longer any radiators on the 1st floor. Our system is lumpy and we have spent the last few years adjusting the slope (no longer possible to run downhill etc) and adding vents  etc etc. We seem to be in pretty good shape now, much less noise, banging etc. The current pressure is set at 2psi and we get plenty of heat to the 14th floor. Would it be a good idea to lower the pressure to 1.5 or 1 psi? Would that be likely to help with noise?

Also the original plans for the steam system had vents and we have reinstalled them which made a big difference. We use steam vents on each main steam line and air vents on each main condensate return line. the steam vents got the steam to move and the condensate air vents seem to have helped dramatically with noisiness. Do you have any input on types of vents to use?

We do not use a vacuum or condensate return pump.

In the literature I was somewhat confused by the height requirements for steam traps in the main pipe and also for the psi in terms of condensate flowing back smoothly. For example the steam main rises vertically out of the boiler for several feet before it turns horizontal. Is the measurement taken where the pipe turns horizontal?

nicholas bonham-carter

modified 2-pipe system

if you have any venting problems with such a drastically modified system, you should seek steam-professional help. remember that the air must leave the pipes before the steam can arrive.

if none is available, can you post a diagram of the new piping layout?--nbc

Dave in QCA

Height Reguirements

There are two height requirements that are explained in The Lost Art of Steam Heating.  Pages numbers are noted.

Dimension A, is the distance between the normal water line and the bottom of the lowest steam carrying main. For a boiler with a pressure that does not exceed 2 psi, Dimension A is 28".  Pages 24 & 25.



Dimension B, is the distance between the normal water line and the lowest steam trap.  Dimension B is 30" per pound of pressure in the boiler.   See page 127.

Jamie Hall

See also...

Steamhead's response on the duplicate thread, below somewhere...



2 psi is OK, though, as a maximum, although it might be better to turn it down to 1.5 -- but only if your particular pressuretrol is reliable at 1.5.  Keep in mind that whatever the maximum is set at, most of the time -- if the system is properly vented -- it will run at a good deal less pressure (just ounces at the boiler).  However, the A and B dimensions Dave mentions are related to the maximum pressure.



Banging is caused by water (condensate) collecting where it shouldn't, or in quantities that can't drain out.  Lowering the maximum pressure can help in some situations but, honestly, not in most -- provided it is at least reasonable (yours is).  It can, however, take a good deal of thought to track down banging.  The first consideration is when does it happen?  If it is right at the beginning of the cycle, when steam is hitting the mains and risers, the usual culprit is excessive condensate not being able to drain -- sometimes because of a sag or a poorly pitched pipe, but sometimes because there is simply too much condensate trying to go one way in a runout while the steam tries to go the other way.  Increasing the slope or the pipe size are the only solutions, and sometimes they aren't feasible (in a one pipe system, this can sometimes be cured by the simple but non-obvious solution of reducing the venting on the offending radiator(s)).  Later in the cycle the problem is often wet steam -- or excessive pressure.  But the bottom line is thinking like condensate.  Can it drain adequately?  If not, why not, and fix it!