Boiler Facts...
George R. Carey, Jr.
Vice President, Fluid Industrial Associates
gcarey@fiainc.com twitter: @Ask_GCarey
Faulty Heating Systems
Due to Lack of Knowledge
During the past few months, we have been presenting
quite a few seminars on various heating
subjects. One of the subjects was Troubleshooting
Steam Systems, which concentrates on understanding
and troubleshooting the different types of steam heating
systems. Of all the systems we discuss, one-pipe systems
are perceived as being the easiest to understand. The
reasoning is very logical: there is only one pipe feeding
each radiator, what’s so difficult to understand? However,
as we got into the “hidden” aspects of one-pipe
systems, the contractors started realizing these systems
have certain rules that need to be followed if the system
is going to be successful. A typical one-pipe steam
system chugs along for years unnoticeably, until finally
the boiler needs to be replaced or the new homeowner
decides to remodel a kitchen or bedroom and needs to
move or relocate some radiation. If it is done correctly,
the system will continue to provide warmth to the house
but as soon as one of the “rules” is ignored, anything can
happen.
This is what was happening with a newly renovated
house with an old steam system. They were experiencing
cold radiators and spitting vents and a friend of
mine asked me to take a look. One of the first things I
check when troubleshooting a steam system that has a
brand new boiler is to make sure the boiler was sized
for the connected load. This means counting the square
foot equivalence of direct radiation (EDR) rating of all
the radiators in the house to see if it matches the boiler’s
rating plate. This is important for two reasons:
1. If the boiler rating is less than the connected load,
it won’t be able to heat all of the radiators in the house
because it is undersized.
2. If the boiler rating is greater than the connected
load, the system will experience velocity and counterflow
problems. This can lead to spitting radiator vents,
sloshing, gurgling and banging pipes and radiators,
boiler short-cycling and uneven heating.
It turns out the boiler was considerably oversized,
which created a lot of problems. Making matters worse,
during the kitchen remodel, they moved a couple of
radiators to the other side of the room. This seemed innocent
enough. Unfortunately, there exists another rule
governing the size, the pitch and the length of pipe run
used to feed each radiator and this is critical, especially
in one-pipe systems. The reason is basic; the pipe that
is used to deliver steam out to the radiator also brings
the condensate formed in the radiator back to the main.
This occurs simultaneously so it is important the velocity
of the steam (how fast it is traveling towards the radiator)
doesn’t exceed a maximum. If it does, the condensate
won’t drain back and in fact will be driven towards
the radiator, causing banging and sloshing noises. Think
of it this way—steam traveling in a pipe is like wind
heading in one direction, while the condensate is trying
to gravity drain back underneath this wind in the opposite
direction. So long as the tunnel is big enough and
there is sufficient pitch, things will work as they should.
When our contractor friends remodeled the kitchen,
they were not aware of these piping concerns. They used
the same size pipe that had worked for the last 60 years,
but with the oversized boiler and the additional length
of horizontal run from the main to the radiators, they
had nothing but cold, noisy cast iron decorations.
Another time, a contractor asked me to visit an
apartment building that was giving the property management
company a lot of headaches with nuisance
service calls. What we saw when we walked into the
boiler room was quite remarkable. The first thing that
got my attention was the six old pressure reducing
valves (PRVs) sitting on top of the boiler. The next item
of interest was the expansion tank or lack thereof; there
was a ¾" copper line piped off the top of the boiler and
it went straight up into the sheet rocked ceiling. However,
we couldn’t see any expansion tank, only a piece of
pipe! The final piece was the piping of the relief valve.
Connected to the bottom of the discharge line from the
valve was a piece of 6" flue pipe that was positioned by a
milk crate wedged against the boiler. From there, more
flue pipe was attached. The janitor had built a drainage
system using the flue pipe that ran from the bottom of
the relief valve piping in the boiler room to a back room
where a floor drain was located.
14 ICM/November/December 2017