IM 907 / Page 8 of 4
Installation
Piping
1. Branch piping to and from unit heater should be the
same size as unit connections and include swing
joints to allow for expansion and contraction of the
piping without placing a strain on the unit heater
element. On steam systems, the branch piping should
be taken off and returned above the center line of the
supply and return line.
2. Install pipe unions and shut-off valves in lines to
and from each unit heater to allow maintenance or
replacement of unit without shutting down and drain-
ing entire system. For hot water systems, include
a balancing valve in return line when possible for
water flow regulation. In areas subject to freezing,
a drain valve should be installed below each unit
heater to remove water from the heating coil.
3. In steam or hot water systems, rapid air removal is
required because entrained air is a cause of corro-
sion. Hot water systems should be equipped with
suitable air vent valves for rapid and complete
removal of air at the high points and ends of both
supply and return mains. Proper air venting for steam
systems can be achieved by use of a steam trap with
an internal air vent.
4. Traps must be located below the outlet of the unit.
Consult trap manufacturer for specific recommenda
-
tions. Each steam unit heater should be provided
with a trap of sufficient size and capacity to pass
a minimum of two times the normal condensate
released by the unit at the minimum differential
pressure in the system. Trap capacity is based on
the pressure differential between supply and return
mains. Steam systems should be equipped with a
float and thermostatic trap or an inverted bucket trap
with an air bypass.
5. It is advisable to use a pipe line strainer before each
steam trap draining a unit heater. This protection
will reduce the maintenance of the steam trap. When
strainers are used they could be installed between
the unit heater and the trap and be the same size as
the trap tapping. In order to catch dirt and scale, the
strainer should have a screen perforation size smaller
than the trap orifices.
6. On systems where the steam supply to the unit heater
is modulated or controlled by a motorized valve, a
vacuum breaker should be installed between the unit
outlet and the trap. If a vacuum breaker is used, it
should be in conjunction with a float and a
thermostatic trap.
7. Install a dirt pocket at the bottom of unit heater to
collect dirt and scale as shown in figures on page 7.
Pipe diameter must be the same size as unit
connections and about six inches long.
8. Provide adequate pipe hangers, supports, or anchors
to secure the piping system independently of the unit
heater.
Wiring Instructions
All wiring must be done in accordance with the National
Electric Code and applicable local codes. In Canada, wir-
ing must conform to the Canadian Electric Code. Power
supply to these unit heaters must be protected by a fused
disconnect switch. It is recommended that all wiring be
adequately grounded.
Electric wiring must be sized to carry the full load amp
draw of the motor, starter, and any control that are used
with the heater. All units with power codes B, I or L
(polyphase motors) must be provided with suitable over-
current protection in circuit supplying heater at instal-
lation. Overcurrent protectors should be sized based on
motor current rating shown on the unit serial plate, and
applicable national electric code procedures.
All units are provided with an electrical junction box.
Junction boxes are either integral to the motor or at-
tached to the unit casing. Units with explosion-proof
motors have an explosion proof junction box attached to
the motor.
Any damage to or failure of units caused by incor-
rect wiring of the units is not covered by standard
warranty. See page 22.
Location of room thermostat should be in the natural
circulating path of room air. Mount thermostat about five
feet above floor level where it will not be affected by
heat from the unit or other sources of drafts that would
prevent it from properly controlling room temperature.
See instructions packed with the thermostat. Speed con-
trollers furnished with specified unit heater fan motors
are packed separately and must be connected according
to wiring diagram with each controller. Controllers are
not interchangeable with different motor sizes or manu-
facturers and must be specifically wired to their respec
-
tive motors.
DANGER
Disconnect all electric power including remote
disconnects before servicing. Failure to
disconnect power before servicing can cause
severe personal injury or death.
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