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ELECTRONIC OR ELECTROMECHANICAL THERMOSTAT
POWER:
1- The A55 Unit Controller energizes the thermostat components with 24VAC via J/P297-1.
OPERATION:
2- The A55 Unit Controller proves the optional N.O. filter switch S27 (indicates dirty filter when closed) and optional
N.O. air flow switch S52 (indicates no air [i.e. broken belt] system shuts down).
3- The A55 Unit Controller receives data from the supply and return smoke detectors A171 and A172, blower motor
overload relay S42, discharge sensor RT6 and return air sensor RT16.
4- The A55 Unit Controller receives data from the electronic thermostat A2 (Y1, Y2, W1, W2, G, OCP)
and the CO
2
sensor A63 (if economizer is used). A55 energizes the appropriate components.
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