HVAC incorporates steam coil

David L. Taylor

We are nearly finished having our plumber install piping for our HVAC system for an entire floor of our office building.  In addition to air cooled units, there are two (2) 5 ton water cooled a/c units.  During the winter these water cooled units also provide heat to the floor by operating the fan across a steam coil installed in the duct work.  The steam is supplied by a riser from the building's heating plant and steam condensate is drained into a return line riser back to the heating plant.  It's a 2 pipe system (seperate steam and return line risers)

I (Building Supt.) reviewed the plumbing work and found a few problems:

* the steam supply line is very close to the (concrete slab) ceiling and consequently the air vent and the solenoid modulating valve on the supply line piping are installed with a tilt.  They cannot be installed upright because the ceiling is in the way.  Also, the vent is installed into a tee on the supply piping and has no height above the supply line.  The plumber insists he can correct the problems by installing the solenoid modulating valve upside down and by using a smaller, special type of air valve which won't get damaged by water hammer.

* Because of an obstruction, on one of the units the supply line piping from the riser is pitched in part towards the riser and in part towards the steam coil.  The plumber says the supply line pitch won't make a difference because it's a 2 pipe system.

Is the plumber resolving the problems or will (could) there be problems as a result of his proposed solutions?  I appreciate any advice you could provide.  Thank You.

Empire_2

Hello David:

I think that posting this topic in the Strictly Steam heat category may yield quicker response.  "Stem head is a "WIZ" at these specifications.  No quick answer can I respond to as this is why I direct you to above.  You are in the right place though.  Being the weekend, I'm sure even someone here could answer you question better than I.



My .02



Mike T.

JStar

RE

Motorized steam valves should not be mounted upside down or sideways. They must be vertical within about 22 degrees either way from top dead center. Look for the literature on your particular manufacturer and you will see the acceptable mounting arrangement.



There is no such thing as an air vent that won't get damaged by water hammer. And smaller venting is almost never the right choice. The air vent should also be on the return side of the steam coil before (if any) trap. There should be more room there for the right air vent with proper height.



The supply pitch isn't totally critical on 2-pipe steam. You just want to make sure there isn't any piping that will cause condensate to form and puddle. Any condensate that's produced has to go somewhere. Typically, it should drain back to the supply main.