boiler in a vacum

anthony_12

TRUE OR FALSE "A STEAM BOILER IN A VACUUM IS NOT A GOOD THING"[NO VACUUM PUMP IS INVOLVED}

nicholas bonham-carter

vacuum question

when steam condenses, it develops a vacuum. this usually at the end of a burner cycle, and will persist until the main vents have let the air back into the pies, rads, and boiler steam chest.

if you are seeing a vacuum at other times, then you may have:

1. a vacuum system, or

2. a plugged pigtail/faulty gauge.--nbc

Jamie Hall

Generally speaking,

false.  What harm is it going to do?  In fact, some steam systems in the old days deliberately ran a vacuum at some points in the cycle.



As NBC notes, though, nowadays the vacuum shouldn't be very deep, nor last very long.  Not because it is bad for the boiler -- it isn't -- but it usually indicates a problem somewhere else in the system.  Unless... you have a system intended to run that way, and they are out there.

Ted_4

Maybe yes, maybe no

A steam boiler that runs a vacuum in a system not designed for vacuum risks sucking make-up water in through the check valve, producing a flooded boiler.  I've seen this happen in two-pipe systems with zone valves that shut off all the mains when there is no call for heat.  The fix is to install a vacuum breaker above the water line to relieve the vacuum.

One-pipe systems with main and radiator vents should never run a vacuum.

See "The Lost Art" for details on vacuum systems.