Boiler Room Learning Center
The boiler room or area where the heat source is located is one of the most important parts of any
heating system. The boiler room commonly houses the heat source, distribution pumps, zone valves or
actuators, manifolds, and acts as the main point of distribution in many systems. This page is
designed to educate our customers about these vital parts of a heating system.
Heat Sources
There are many different heat sources that can be used for heating systems. For radiant heat
and hydronic heating systems the two most common heat sources are boilers and hot water heaters.
Boilers
There are many different types of boilers available on the market today. These boilers may be
broken down into several classifications. One way to categorize boilers is by the fuel that they
burn. Boilers can use oil, natural gas, propane, or wood as a fuel source.
Another way to classify boilers is condensing vs. non-condensing. A boiler that takes advantage
of the condensing gases that accumulate in a boiler is considered a condensing boiler. This type
of boiler makes use of the extra heat that is created when the gas turns to liquid. This liquid
is very corrosive and therefore the boilers are created to withstand corrosion. These boilers can
operate at up to 99% efficiency. A non-condensing or conventional boiler must be protected from
flue gas condensation.
Water Heaters
Water heaters may be classified as either tank type or tankless. Tank type water heaters
store hot water in a tank so it is available whenever needed. Conversely tankless water heaters
are on demand, and create hot water instantaneously. Tankless water heaters are gaining market
share due to higher efficiency levels. The main drawback of these tankless water heaters is their
flow rate limitation. The required flow rate must be found prior to installation and an appropriate
water heater should be used.
Water heaters are generally created to be used for domestic plumbing systems. When they are used
as heat sources several parts must accompany them. These include a pressure relief valve,
circulating pump, and potentially several other items. When using a water heater as a heat source,
the required flow rate of the heat system must be found prior to installation and an appropriate
water heater should be selected.
Distribution Pumps
Circulator Pumps play a pivotal role in hydronic heating systems. A circulator pump is
responsible for moving the fluid throughout the system. Pumps must be sized correctly in order
for a Radiant Heat System to work properly. The two factors that are used to determine pump size
are flow rate and pressure loss. Flow rate is measured in gallons per minute (gpm). Pressure loss
is measured in feet of head. When both of these measurements are known a pump may be accurately
selected.
Most manufacturers offer a pump curve that can be used to size a pump. Below is the Taco pump curve.
On the y-axis is head loss and on the x-axis is flow rate. Taco offers a full line of pumps that
can meet the needs of hydronic heating systems. The ideal pump meets the exact flow rate and
pressure loss that is required. However, if a Taco Pump doesn't meet the requirements exactly, the
pump that meets the requirements and is the closest match should be selected.
Zone Controls - Mixing Valves - Transformers
Many of the controls involved in hydronic or radiant heat systems are located in the boiler
room. These include zone controls, mixing valves, and transformers.
Pumps as zone controls:
Pumps can be used in combination with a switching relay to control the flow of heat to several
different zones. Switching relays control the on/off functionality of pumps. Relays such as the
Taco SR series come in 1 pump, 2 pump, 3 pump, 4 pump, and 6 pump models. Therefore you can use the
SR506 switching relays and 6 007-F5 pumps to control six separate radiant heat zones.
Zone Valves:
Another way to control different radiant heat zones is with zone valves. Zone valves act as an
on/off control for each zone in a radiant heat system. This is a popular way to zone a radiant
heat system. Each manifold can be tied into a zone valve which is used to control a certain zone.
Zone valves come in many different varieties, sizes, and have many different manufacturers. We
carry several different models of zone valves from Taco and Honeywell. A zone valve controller can
be used in conjunction with zone valves to ease installation and allow for a greater level of
control in a heating system. Remember that if you are going to use zone valves, you will still
need a single pump to create a flow of water. This pump must be large enough to account for the
head loss from all of the loops in the system.
Actuators:
Actuators are able to control the flow of water for an individual loop in a radiant heat system.
An actuator is screwed onto a radiant heat manifold and subsequently controls the valve on the
manifold. In this way the actuator can open or close the valve and thus turn a zone's heat on or
off. Remember that if you are going to use actuators, you will still need a single pump to create
a flow of water. This pump must be large enough to account for the head loss from all of the loops
in the system. The main advantage to using actuators is that they allow installers the ability to
create multiple zones on a single manifold. For example, on an 8 loop manifold with the use of
actuators you can have one zone with 3 loops and one zone with 5 loops, or any combination that is
desired. Think of actuators as zone valves for the individual loops in a radiant heat system.
Actuators come in two different models: motorized and thermal. Motorized actuators are fast opening
and actually have a motor that opens and closes the valve on a manifold. Thermal actuators are slow
opening and don't contain a motor. Both types of actuators accomplish the same task sufficiently.
Mixing Valves:
Mixing or tempering valves act to adjust the water temperature received from the boiler to the
desired temperature needed to operate a radiant heat system. For example if a boiler is producing
water at 200 degrees and the radiant heat system requires water that is 130 degrees, the mixing
valve will mix the boiler water and cold water to create the desired temperature. Nearly every
heating system requires a mixing valve. Mixing water can actually become quite complicated with
the use of motorized mixing valves and injection-mixing, installers are given several different
options. However, a simple mixing valve may be used as well.
Transformers:
Transformers act as the source of electricity for components in a radiant heat system. When the
wiring of a heating system is being done, one of the central components is a transformer. As the
name implies, a transformer can change electricity at one voltage to electricity of another
voltage. The Wirsbo 50 VA transformer works well with radiant heat systems.
Expansion Tanks
Expansion tanks play a crucial role in hdyronic heating systems. The expansion tank controls
the pressure in a closed system. Because of the properties of air and water, pressure changes
will occur in the system. If an expansion tank is not used this pressure can get to dangerously
high levels.
Air Separators - Air Scoops
Air separators and scoops are designed to remove air from a hydronic heating system.
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