HARDY MANUFACTURING CO., INC (MODEL KB125) PAGE 13
SECTION III
CONNECTION TO CENTRAL HEATING/AC SYSTEM
3-1
Connection to Central Unit with Existing Blower Relay
This unit must be wired by a qualified electrician in accordance with the National
Electrical Code.
Turn off all power going to your central air handler system.
You will need to add a double pole / double throw relay to your central air handler. You
will also need a heat only thermostat added to the wall, preferably next to the existing
thermostat. Run a two (2) conductor thermostat wire from the air handler to the new
heat only thermostat that was added to the wall. The normal colors for this wire are red
& white.
NOTE: If you are not familiar with the control circuit of your central unit, do not continue
beyond this point. Call a heating and air conditioning serviceman to complete the
wiring. Improper wiring can cause excessive electrical usage or cause your blower
motor to over heat and burn out.
At the wall heat only thermostat connect the red wire to the screw terminal marked R
and the white wire to the screw terminal marked W.
At the central air handler where you added the relay, connect the white wire that is
going to the new heat only wall thermostat to terminal #7 of the new relay along with a
short jumper wire that will connect to terminal #6 of the new relay. Next find the red
wire going from the air handler control wiring to the original wall thermostat. Cut this
wire and connect the end that is going to the wall thermostat to terminal # 2 on the new
relay. The end of the red wire that is still connected to the control wiring of the air
handler will need to be connected to terminal # 1 along with the new red wire that is
going to the new heat only wall thermostat.
Locate the green wire going from the central air handler control wiring to the original
wall thermostat. Cut this wire. Connect the end of the green wire that is going to the
original wall thermostat to terminal #5 of the new relay. Connect the end of the green
wire that is still connected to the central air handler control wiring to terminal #4.
Locate the low voltage transformer that is providing you with 24 volt power. Find the
common lead of this transformer and connect a wire to this lead and to terminal #8 of
the new relay.