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Steam boiler piping

FredR Member Posts: 62
Sorry for the double post. I could not get past the code process.

Thanks Christan:

1- single boiler- Church, minimum usage, two zones.
2-system was originally D/B Vari-Vac.
3-system had boiler and cond tank replaced.
4-the tank has an air switch to run the air pump with
(jet type ejector)which creates vac on the returns.
5-tank also has water pump which is float controlled and pumps to boiler regardless of boiler level.


  • FredR
    FredR Member Posts: 62

  • FredR
    FredR Member Posts: 62

  • Christian Egli_2
    Christian Egli_2 Member Posts: 812
    Hey, that's me! Hi Fred

    Two ideas pop to mind

    It's very possible the new boiler is too small in inside volume. Being flat chested is often the plague of modern steamers. But everything is relative.

    Small volume boilers are only a problem with slow returning condensate, in a sprawling layout for instance.

    Your church has a vacuum pump, you seem to say it works. I think you need to figure out if it really does and if it is critically necessary. Go find any lift stations on along your returns, if you have any, then you must run the vacuum pump at all times along with the steaming.

    Otherwise, vacuumizers are still a great thing. They make start up steam deliveries instantaneous, and thus save you fuel. It's worth it checking out it's performance. Cleaning out the machine and scraping dirt out of the jet tube is about all it takes, and the occasional pump seals and bearings.

    If you determine the vacuum is not necessary for lift purposes, try temporarily shutting it off, just to see if your boiler water problem is related to a sneaky vacuum going where it isn't supposed to. There is an all important anti-deeper-vacuum-in-the-boiler-vs.-the-return-lines connection that has one check valve on it pointing into the boiler. Check this one way valve to see if it is clean and check if there is a shut valve on the line, and open it.

    Once all this out of the way, and if you have no lift stations, see that the vacuum pump operates only for 10 minutes (or whatever is needed to empty the system of air) on the start of a call for heat. Use a timer relay. This should be all you need from the vacuumizer, but it's like clipping coupons, you don't need to do it all day long.

    The varivac control, if you still have it, was meant to work on steam modulation. A little bit over the top as far as complexity and chances are the system was (simplified) a long time ago. Maybe not, and if so, make sure you keep all the parts there, going back to varivac operation could be a next step down the road.

    Meanwhile, to solve the boiler flat chestedness problem, usually what it takes is either an accumulation tank in parallel with the boiler, right at the normal water line, or the use of a feed tank. The former has no moving parts and is a very attractive solution.

    But, you have a condensate tank right now, so, I would convert it to being a feed tank. All it takes is rewiring the pump control. Easy.

    Easier yet is to modify the current on off float level at which the pump kicks in an out. This fiddling alone might solve your problem.

    Make sure also that your radiator traps are working. Dunham traps are very robust, it's not unusual to see real old ones in place. If you need new ones, get replacement Dunhams rather than any other brand - just to keep the vacuumed system homogenous.

    Check the system also for any tempestuous one pipe style air vents that may have been added to this two pipe radiator trap system. If you find any, think hard and long about what they're doing - they're probably a bad afterthought attempt at fixing another problem that hasn't gone away either.

    Do you have pictures of this beauty? Where are you located? Sounds like a cool job.
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