Switch 1 – Relay Assignment; Switch 2 – Equipment Type; Switch 3 – Equipment Stages; Switch 4 – Reversing Valve Or Fan Mode - Smart temp SMT?770 Installer Manual

Switch 1 – Relay Assignment
The SMT‐770 is fitted with 5 relays capable of switching up to 24VAC @ 1Amp. Switch 1
sets the function of these relays as either 3 fan speeds with 1 heat and 1 cool operation
or single fan speed with 2 heat and 2 cool, in either HP (heat pump / reverse cycle) or
HC (heat with add on cool) mode.
Switch 2 – Equipment Type.
Both heat with add on cool or heat pump types of systems can be controlled by the
SMT‐770.
Heat Cool System uses the "W" terminal(s) only for heating and the "Y" terminal(s) only
for cooling.
Heat Pump systems use the "Y" terminal(s) for BOTH heating and cooling (the
compressor). The "W1" terminal to control the reversing valve which determines
heating or cooling mode.
Switch 3 – Equipment Stages.
When it is necessary to control a single stage A/C system fitted with auxiliary heating
elements, turn Sw3 OFF thereby selecting single stage mode. Heating elements
controlled by the W2 output are now assigned as stage 2 heat.
Switch 4 – Reversing Valve or Fan Mode
When the SMT‐770 is set for Heat Pump mode (Sw2 is on) then this switch sets the
reversing valve logic (O/B). When the SMT‐770 is set for Heat Cool mode (Sw2 is off)
then this switch sets the mode for the Heater fan logic (HG or HE mode).
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