Chapter 9
Near Boiler Piping
ALL steam heating systems MUST be properly
piped exactly according to manufacturer’s
instructions.
Excuses like:
“I’ve always piped them this way and
never had a problem.”
“That’s the way the old one was piped.”
“The customer just wanted a cheap price
and didn’t care.” ...are not acceptable.
Improperly piped steam boilers will not
provide efficient, trouble-free operation. Far
worse, they can be dangerous and cause severe
harm to people and property.
For a steam heating system to operate properly
it’s imperative that both the “near boiler
piping” and system piping be properly sized
and connected.
Near Boiler Piping
Every boiler manufacturer provides detailed
installation instructions which must be followed.
Most manufacturers require that the bottom
of the header on a gravity system be a minimum
of 24" above the boiler’s water line. The
higher the header, the dryer the steam.
All manufacturers require a Hartford Loop
when connected to a gravity return. The loop
is normally connected between 2"– 4" below
the boiler’s water line. This prevents water
from being pushed out of the boiler because the
steam pressure pushes equally on the supply
and return (through the equalizer.) The Hartford
42 National Oilheat Research Alliance
Loop also prevents a leaking wet return
from draining the boiler.
The system return piping must be connected
to the equalizer with a close nipple to minimize
water hammer if the boiler water line drops
below the top of the nipple.
Some manufacturers require an offset header
to prevent damage caused by expansion.
Figure 1.
Figure 1
Smaller boilers (usually below 145,000
BTU’s/Hr. and under 450 sq. ft. steam) require
at least one supply riser to the header. Larger
boilers generally should have two supply risers
to the header.
In general, two supply risers are always better
because they allow the exit velocity of the
steam to be cut in half and greatly reduce the
chances of wet steam making its way into the
supply main. The slower the steam, the better
the steam.