WLCG/WLHG
High-Wall Air Handlers
• Installation, Operation and Maintenance Manual •
Comfort where it counts
38
P/N 240008111, Rev. G [06/18/10]
Low voltage controls —
cooling-only units
Cooling-only units utilize low volt intercon-
necting wires between the indoor unit, out-
door units and thermostat.
For air handlers with unit-mounted con-
•
trols, wires designated Y (yellow) and C
(brown) of the indoor air handler should
be connected to the corresponding Y (yel-
low) and C (brown) wires or terminals of
the outdoor condenser.
Other wires or terminals, such as R(red)
•
or O (orange), may not be needed and
should be protected by a wire nut to
prevent contact with the junction box or
other metal surfaces.
Interconnect wiring
Unit-mounted controls — see (Figure 36,
•
Page 36).
Wall thermostat applications — see (Fig-
•
ure 37, Page 36).
Checking voltage
A 24V transformer located in the indoor air
handler unit provides low volt control power
to both the indoor air handler and outdoor
condenser.
The 24v power supply can be measured
•
by placing a meter across the R and C low
volt terminals of the air handler.
The air handler will switch the condenser
•
on and off through the yellow (Y) wire.
When the air handler is calling for cool-
•
ing, 24V can be measured between ter-
minals Y and C.
Electric heat applications
Units with electric heat utilize a control relay
located on the circuit board in the control
box.
As a safety feature, an auto-reset limit switch
located on the heater end plate or on the
heater assembly will interrupt power to the
heater should an overheat condition occur.
Each electric heat assembly is also equipped
with a one-time fuse link. Should electric heat
temperatures rise above the auto resetting
limit switch, a non-resetting, the one-time
fuse link will open and the heater will remain
off. To restart, a new fuse link is required.
The following current values apply when the
unit is connected to a 230V power supply.
These values include fan motor current. (If
the supply power is different, the amperage
will change.)
5 kw = 22.3 amps
3 kw = 13.5 amps.
Low voltage controls —
optional heat pump with electric
heat applications
Heat pump units with electric heat utilize
four to six interconnecting, low volt wires de-
pending on control setup and/or thermostat
selected. Refer to the low volt interconnect
section and figures 1 & 2 for your particular
unit.
A 24V transformer located in the indoor air
handler provides low volt control power to
both the air handler and condenser.
With high volt power supplied to the
•
condenser, 24v can be measured across
the red (R) and brown (C) wires at all
times.
Cooling
The air handler will cycle the condenser
on and off through the yellow (Y) wire. To
check for a condenser signal, select cooling
mode on the indoor unit or thermostat and
place the setpoint temperature below room
temperature. Then, with a voltmeter, check for
24 volts across the yellow (Y) and brown (C)
wires. If no signal is found, then re-check all
wiring connections to ensure that they match
the low volt interconnect diagram. Check the
Troubleshooting
(continued)
