George R. Carey, Jr.
Vice President,
Fluid Industrial Associates
gcarey@fiainc.com
twitter: @Ask_GCarey
Boiler Facts
High-Efficiency
Equipment is Here to Stay
The landscape in the heating industry has drastically
changed. Over the years, when you entered
a typical boiler room in the Northeast, it was very
common to find a sectional cast iron boiler(s) and usually
some type of indirect heating appliance for domestic hot
water. It could be a side-arm heat exchanger with a storage
tank or a storage tank with the heating coil installed
directly inside.
Nowadays, it has become quite common to find highefficiency
modulating and condensing gas-fired boilers
(either liquefied petroleum LP or natural). These boilers
are not your average “run of the mill” atmospheric
gas boilers, either, because their efficiencies range
between 90%–96%. They use a Neg/Reg gas valve and
fan assembly, which means the amount of gas that flows
into the burner for combustion is regulated by the fan
assembly’s blower speed. The blower speed is controlled
by an on-board micro-processor that is performing
several internal calculations to determine the appropriate
amount of British thermal units (BTUs) needed to
satisfy the call. Hence the modulating part—it only uses
the amount of gas necessary to satisfy whatever load it is
currently seeing.
Most of the residential models have a “turn down”
ratio of 10:1, meaning they can fire down to 10% of their
total capacity and, of course, all the way up to 100% of
their capacity. It has become quite common in larger
residences to install two or more small “mod/con” boilers,
that, when combined, can handle the home’s total load.
However, more importantly
during the
normal course of the
heating season, when
the home is operating
at “part load,” the
boiler plant consumes
just the amount of energy
needed to satisfy
the current load that
the house is seeing.
The same holds
true for commercial
applications such
as apartment buildings,
condominiums,
churches and schools.
The larger commercial
“mod/con” boilers also
offer turn down ratios
10:1. That means with a couple of commercial boilers,
you can fire down to 5% of the total BTU capacity of the
boiler plant. With this type of turn down, building owners
are experiencing fuel savings in range of 35%–40%
and higher!
Unique features
Another unique feature of these boilers is the venting
options. The blower motor is designed to not only bring
combustion air into the burner assembly but also vent
the residual products out of the building. Most of the
“mod/con” boiler manufacturers have approved their
boilers to use several different vent materials. They are
approved to be vented with PVC, CPVC, polypropylene
and stainless steel vent pipe.
Each manufacturer provides very detailed instructions
on the dos and don’ts of how to properly vent their boilers.
Following these instructions is critical to allow the
boilers to operate efficiently. Of course, all of this piping
needs to be sealed tight to meet the venting codes.
These boilers encourage the condensing of their flue
products, which is the exact opposite of traditional boilers.
Their heat exchangers are designed to withstand the
corrosive nature of the condensate that forms when the
combustion products are condensed. Of course, this condensing
action is where the additional efficiency points
are obtained.
Some of the by roducts of this condensing can gather
in the boiler’s heat exchanger. If allowed to accumulate,
they will negatively impact the boiler’s efficiency performance,
which is why most manufacturers suggest an
annual inspection and cleaning of the heat exchanger, if
necessary. Also, the venting should be inspected to make
sure nothing has changed that could negatively impact
the operation of the boiler. This means every “mod/con”
boiler needs to be inspected every year.
One of the oilheat industry’s shining stars has been
its reputation for service and maintenance. The need for
these high efficiency boilers to be maintained is a perfect
opportunity for a company that has a service department
to offer service contracts to homeowners, commercial
property owners and management companies. Most of
the boiler manufacturers or their local representatives
offer classes on servicing these new “mod/con” boilers.
ECM circulators
A new style of “smart” pump has made its way into the
Cast iron sectional boilers
used to be the norm.
20 ICM/March/April 2021