Indy School Unit Ventilator Steam

SpeedCity

I am working on a school hose, three story building, 38 old Herman Nelson unit ventilators (with TRV) and some cabinet heaters, all steam. System is two pipe mechanical return. The 16 section Burnham boiler was replaced earlier this year due to a clogged/cracked section. Among other issues with the system it was noted that after cranking the pressure down the water hammer out in the system became unbearable so the owner increased the pressure to stop the hammering. It is also noted that the system is making up 10 gallons of water or more each day. There are no buried returns, if returns were leaking they would see the water. Water has been observed coming out of the boiler feed tank overflow from time to time. Also, the first floor return main is having some rotting problems on one end of the building. Any thoughts would be appreciated.

Rod

Need a Steam Pro's Advice

Bump- Since you didn't get an answer I'll bump your question back to the front.

SpeedCity

OK

OK, its actually a school house, not a hose. Maybe that confused people. : )

Jamie Hall

A bit beyond me, however...

if you are making up 10 or more gallons of water per day, you have a significant water loss somewhere.  Steam heating systems are closed loop; that is, in principle it should never be necessary to add water (in practice, a little is always needed -- but 10 gallons a day is NOT a little!).  It would be helpful to find that water loss, to put it mildly.



Cranking up the pressure should not have changed a water hammer problem (if anything, it usually makes it worse).  What could be creating a hammer problem, which could possibly be improved (I'm speculating here) by cranking up the pressure, is water backing up from the boiler feed tank into a steam main somewhere -- and the additional pressure pushing that water back out.  So is the condensate able to flow freely back to the boiler feed tank?  Do you have an F&T trap somewhere with a stuck float?  Do you have a very badly clogged return?  Just a few thoughts...

gerry gill

Is it possible that

the radiator units are holding up the water long enough for the feeder to feed? I'm seeing possibly bad traps, or trv's closing and creating a vacuum in the radiator holding up the condensate...just a thought...eventually the water comes back and spills out the tank overflow..higher pressure is also compressing steam which could cause the feeder to eventually feed..something else is wrong tho if the system won't run under low pressure.



P.S. there is a company here in Bedford Ohio that rebuilds those herman nelson units and fabricates replacement bearings for those unique shaft bearings should you ever need that service.

SpeedCity

Interesting

that the increase in steam pressure resolved the hammer problem. It is true although it doesn't make sense. The building is three stories and the return on the first floor has had several rotten sections replaced (no pitch in these sections). I am thinking thats where the condensate is stacking up and then overflowing the receiver when it does come back. Good information on the UV repair services too. What is the rule or pitch of condensate return lines back to a feed pump?

gerry gill

as long as the line has

some pitch, (any pitch at all) it should drain into the feed tank just fine..