Manual
9. Heater Electrical Wirinq
Electrical shock hazard.
Shut OFF electric power at unit disconnect or service panel
before making any electrical connections.
Unit MUST be grounded before making line voltage connec-
tions. Do NOT fuse ground or neutral conductors.
Failure to follow this warning can result in property damage,
personal injury, and/or death.
NOTE: All electrical work MUST conform with the requirements of local
codes and ordinances and in the United States with National Electrical
Code ANSI/NFPA70-1990 or current edition. Provide line voltage power
supply from a separate protected circuit with a disconnect switch (when
required) located within sight ofthe unit. Supply voltage, amperage, fuse
and disconnect switch sizes MUST conform with all technical specifica-
tions in this manual and on the unit rating plate and local codes.
Wiring MUST be protected from possible mechanical damage and MUST
NOT interfere with removal of access panels, filters, etc.
All exposed wiring or connections MUST be made with weatherproof
cable or wire unless installed in conduit.
All line voltage connections and the ground connection MUST be made
with copper wire.
The power supply wiring MUST have overcurrent protection. This can be
either fuses or circuit breakers. The maximum size for the overcurrent
protection is shown in the column labeled "Max. Fuse or NEC HACR
Breaker (Amps)" in the Electrical Data Table in FIGURE 10 or on the unit
rating plate.
Grounding
Permanently ground the electric heat accessory in accordance with local
codes and ordinances and in the United States with National Electrical
Code ANSI/N FPA70-1990 or current edition. Use a copper conductor of
the appropriate size from the electric heat accessory to the ground lug on
the circuit breaker panel as shown in FIGURE 9.
Adjusting Thermostat Anticipator
Set theheat anticipator of the thermostat to the propervalue. See instruc-
tions provided with the thermostat before making this adjustment.
Model Number Anticipator
Setting
AMMK05AHB/A .18
AM MK07AH B/A .36
AMMK10AH B/A .36
AMMK15AH B/A .36
AM MK20AH B/A .54
Limit Controls
The limit controls are mounted on the face of the heater and are wired into
the supply wires to each element. If there is not enough air flow through
the heater, the limit will open and break the power circuit. The limit will re-
set when the electric accessory cools down.
Time Delay Operation
The heater elements are switched ON and OFF through one or more con-
trois which operate through the low voltage thermostat circuit.
These controls consist of a number of time delays depending on the spe-
cific heater model. An electric heat accessory has 1,2 or 3 of these con-
trois. The first time delay is activated when the thermostat contacts close.
Approximately 1 to 20 seconds later the indoor blower and the first heater
bank are energized. Approximately 70 seconds after the first heater bank
is energized the remaining time delays and heater banks are energized.
Staging
Some electric utilities require staging on electric heaters larger than 6 kilo-
watts. Therefore, the heater elements are turned on in 5 or 10 kW incre-
ments under control of the sequencers.
If staging based on heat loss or demand is required, the use of accessory
outdoor thermostats is recommended. The heat sequencer wiring is de-
signed to be staged by breaking the 24V "Common" Leg (normally brown
or gray). Outdoor thermostats available through your wholesale supplier
allow the control of two or four stages of electrical heat.
Some indoor electronic thermostats may provide for multiple stage of
electric heat. When this type thermostat is used, it may be necessary to
break the 24V"Hot" leg of the sequencer (as fed from the "W' circuit at the
thermostat). This will require field modification of the control wiring and
should only be done by an experienced controls technician/or electrician.
Installing Wiring
1.Shut OFF electric power at unit disconnect or service panel.
2.Install the appropriate field supplied conduit fitting into the heater
knockout located in the rear panel of the unit. The wiring entrance
hole is sized for 1" conduit.
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