Boiler Basics
My Boiler won’t
start - what to do
first!
Nothing can be more
frustrating than a
nonfunctioning boiler on
a cold day.
Fortunately, noticeable
changes in boiler
performance precede most
mechanical failures. If
you notice a change in
boiler performance such
as new noises, smells,
rising stack
temperatures or
continually resetting
safety devices, call
your boiler professional
for help.
Although unexpected
mechanical failures do
occur, it is likely that
one of the boiler’s
safety or operational
devices is preventing
your boiler from
starting. Most safety
devices have manual
reset buttons that need
to be reset before
boiler operation can
continue. Continual
resetting of safety
devices is an indication
of unsafe operating
conditions. Prompt
attention by your boiler
technician is required.
Locate all devices
that can prevent your
boiler from starting.
They include:
Burner controller:
The controller is
usually located in
front of the burner.
On a call for heat the
controller starts a
sequence of events
that ensure safe
operation before the
burner is allowed to
start. The controller
continues to monitor
burner operation while
the boiler is running.
If for any reason the
controller senses an
unsafe operating
condition it will shut
the burner off.
Pushing the manual
reset on the
controller will often
restart the boiler.
High pressure or
temperature switch:
This device is a
safety backup to the
“operator”
control. It has a
manual reset which
when pressed to start
the boiler indicates
that the
“operator” control
has failed.
Gas pressure
switches on the fuel
train: The natural
gas fuel train usually
has two pressure
switches. The low
pressure switch locks
out the boiler when
too little gas is
available for
operation. The high
pressure switch locks
out the boiler when
the regulator is
allowing too high a
gas pressure. Both
switches have a manual
reset.
Low water cutoff:
The low water cutoff
may have a manual
reset. When reset
indicates a low water
condition existed in
the boiler.
Other devices that
may prevent the boiler
from starting:
Time clocks:
Time clocks or
other energy
management devices may
restrict boiler
operation during
weekends, evenings or
other times of the
day. Check their
operating schedule.
Outdoor
temperature limits:
These devices sense
outdoor temperatures
and prevent boiler
operation above
certain outdoor
temperatures, usually
65 degrees.
If resetting these
devices does not start
your boiler call your
boiler professional for
assistance.
Reminder: Do
not bypass any safety
devices in an effort to
start your boiler.
Causes of Boiler
Room Accidents
Boiler systems are
designed for safety and
efficiency. The
key to safe boiler
operation is the
operator. Armed with
some basic knowledge
about boiler systems and
maintenance the boiler
operator can ensure
years of safe, reliable
service.
History has shown
that without proper
operation and
maintenance, boiler
conditions and safety
deteriorate, causing
potential hazards due to
neglect and
misunderstanding.
Routine maintenance
is well within the
ability of most boiler
operators. Boiler
tune up and repairs
however are best left to
trained professionals.
Understanding when to
turn to qualified
professionals for
assistance is an
operators first
responsibility.
Here are some
problem areas where
trained professionals
are needed:
Leaking
pressure relief valves
Continuous make up
water to boiler
Steam leaks or
steam vented from
condensate tank (steam
systems)
High stack
temperatures (greater
than 350 degrees)
Insufficient heat
to building
Condensate dripping
down stack or out the
front of the boiler
Constantly
resetting controller,
high pressure or
temperature limits or
low water cut off
switches
Common Boiler Room
Accidents
Dry Fire
Accidents: Dry fire
accidents are also
called boiler meltdowns.
These accidents occur
when the boiler is
allowed to operate
without adequate water
in the boiler.
Functioning low water
cutoffs are essential to
preventing dry fire
accidents. Boiler
damage can run from
severe buckling and
deforming of the boiler
to complete meltdown or
potential boiler
explosion.
Excessive Pressure
Accidents: Excessive
pressure is potentially
the most lethal form of
boiler accident. These
accidents occur when the
boiler can no longer
contain the excessive
pressure allowed to
build in the boiler. The
operator control, high
pressure limit, and the
pressure relief valve
need to fail before
these accidents can
occur. Excessive
pressure accidents, even
in small boilers, have
been known to completely
destroy a building.
Fuel Related
Accidents: Fuel
related accidents
usually occur when the
operator fails to purge
combustible gases from
the fire box before
ignition is attempted.
Never bypass
safety devices with
jumper wires to restart
your boiler.
Unintended ignition of
unburned combustion
gases in the fire box is
possible.
Leaking fuel valves
can also be the cause of
these accidents. If the
operator notices any gas
odor the boiler should
be shut down and the
fuel supplier called
immediately.
Water Treatment
Basics
Boilers are filled
with water that contains
naturally occurring
impurities. Common
impurities such as
calcium, magnesium and
oxygen can, if they are
not controlled, effect
boiler performance and
durability.
All water contains
dissolved minerals such
as calcium and
magnesium. If these
minerals are allowed to
reach high enough levels
in the boiler water they
will come out of
solution and form as a
hard shell on the hot
surfaces of the boiler.
This hard shell is
called scale and is
often found on the
outside of the fire
tubes. Scale insulates
the heating surfaces
reducing the ability of
the fire tubes to
transfer heat from the
hot combustion to the
boiler water. High stack
temperatures or ruptured
fire tubes are common
problems related to
scale build up.
Boiler water also
contains dissolved gases
such as oxygen or carbon
dioxide. These gases in
the presence of water
and metal can cause
corrosion. Corrosion
eats away the metal
effecting the durability
of the boiler.
Water treatment
strategies:
Boiler heating
systems lose water
through steam and water
leaks. Additional water
called "makeup
water" is added to
the boiler to replace
these losses. The amount
of make up water and the
level of naturally
occurring impurities in
the water will determine
the type of water
treatment required.
Boiler heating systems
that have very few leaks
will require simple
water treatment
programs. Your boiler
inspector or water
treatment professional
can assist you in
developing a water
treatment program. Steam
and hot water boilers
typically require
different water
treatment programs.
Steam boilers:
Steam boilers are
usually treated to
prevent scale and
corrosion. Scale
producing dissolved
minerals accumulate in
the boiler water when
mineral rich make up
water replaces mineral
free steam and
condensate leaks.
Strategies to prevent
scale attempt to keep
the components of scale
such as calcium and
magnesium suspended in
the boiler water or to
reduce their
concentrations in the
boiler water. Draining
water from the
boiler (bottom blowdown)
is a common method for
reducing the
concentration of solids
and to discharge sludge.
Corrosion is reduced
by adding oxygen
scavenging chemicals to
the boiler water. Boiler
water testing is
required to ensure that
conditions suitable for
scale and corrosion are
not present.
Hot water boilers:
Scale build up is
usually not a problem in
hot water boilers.
Although make up water
contains dissolved
minerals, system leaks
discharge water with an
equal amount of
dissolved minerals.
Since as many minerals
are leaving the boiler
system as enter it;
minerals do not have the
opportunity to
accumulate in the boiler
water.
Corrosion remains a
problem so oxygen
scavenging chemicals are
added to address the
problem.
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