Modular Hi-Rise Replacement Series – MIY
INSTALLATION, OPERATION, & MAINTENANCE MANUAL
22
SECTION FIVE — Routine Maintenance, Cont’d.
Electric Resistance Heater Assembly
Electric resistance heaters typically do not require periodic
maintenance when unit air filters are changed properly.
The operation and service life may be affected by other
conditions and equipment in the system. The two most
important operating conditions for an electric heater are
proper air flow and proper supply voltage. High supply
voltage and/or poorly distributed or insufficient air flow
over the element will result in element overheating. This
condition may result in the heater cycling on the high-limit
thermal cutout. The high-limit thermal cutout device is
a safety device only and is not intended for continuous
cycling. With proper unit application and operation, the
high-limit thermal cutout will not operate. This device only
operates when a problem exists, and ANY condition that
causes high-limit cutout MUST be corrected immediately.
High supply voltage also causes excessive amperage
draw and may trip the circuit breaker or blow the fuses on
the incoming power supply.
After proper air flow and supply power are assured,
regular filter maintenance is important to provide clean
air over the heater. Dirt that is allowed to deposit on the
heating element will cause hot spots and eventual element
burn through. These hot spots will normally not be enough
to trip the high-limit thermal cutout device and may not be
evident until actual heater element failure.
Electrical Wiring and Controls
The electrical operation of each unit is determined by the
components and wiring of the unit. This may vary from
unit to unit. Consult the wiring diagram attached to the
unit for the actual type and number of controls provided
on each unit.
The wiring diagram is affixed to the acoustical RA block-
off panel inside the unit. It is visible when the return air
panel is removed.
The wiring and controls are accessible through the flip-
down control box door (see Figure 15) located above the
motor/blower assembly. The door is also designed to be
removable by disengaging the spring-loaded pins found
on either side of the lower portion of the door.
Figure 15. Control Box Door
The integrity of all electrical connections should be verified
at start-up. Afterwards, all controls should be inspected
regularly for proper operation. Some components may
experience erratic operation or failure due to age. Wall
thermostats may also become clogged with dust and
lint and should be periodically inspected and cleaned to
provide reliable operation.
When replacing any components such as fuses, circuit
breakers, or relays, use only the exact type, size and
voltage component as furnished from the factory. Any
deviation without factory authorization could result in
personal injury or damage to the unit. This will also void all
factory warranties. All repair work should be done in such
a manner as to maintain the equipment in compliance with
governing codes, ordinances and agency listings.
Valves and Piping
No formal maintenance is required on the valve-package
components most commonly used with fan coil units other
than a visual inspection for possible leaks in the course
of other normal periodic maintenance. In the event that
a valve should need replacement, the same precautions
taken during the initial installation to protect the valve
package from excessive heat should also be used during
replacement.