DIAGRAM 4 – BOILER WITH AC (TWO TRANSFORMERS) |
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| APRILAIRE MODEL |
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AIR HANDLER |
| 8870 THERMOSTAT |
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| 120 |
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| C |
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| R |
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L2 | VAC | L1 |
| RC |
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| SEE |
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| RSR |
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| RH |
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| 24 |
| R |
| REMOTE SENSOR(S) | RSA | NOTE |
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| C |
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| RSC |
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| VAC |
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| RSB |
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FAN |
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| G | O |
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| REF |
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RELAY |
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| COMMUNICATION | TERMINALS A+ |
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| 1ST STAGE |
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| Y1 | G |
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| B- |
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| COOL |
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| B+ |
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| W1 |
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| A- |
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AIR CONDITIONER |
| Y1 |
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| W2 |
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1ST |
| Y1 |
| Y2 |
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| B |
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STG |
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COOL |
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| C |
| BOILER |
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| 1ST |
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IMPORTANT! | W1 |
| STG |
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| HEAT |
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| C |
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| The thermostat B |
| 24 |
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terminal is for reversing |
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| VAC |
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R |
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connect the B terminal | L1 | 120 | L2 |
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to common side of |
| VAC |
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| transformer. | NOTE: HVAC installer may need to connect |
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| 24V AC to the R and C terminals to check the |
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| HVAC operation. If the Automation system |
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| 24V FIELD WIRING | is to be installed after the HVAC installation, |
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| leave the R and C terminals connected to |
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| FACTORY WIRING | ensure the HVAC system operates. If the |
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| OPTIONAL 24V | automation system is installed before the |
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| HVAC wiring, then DO NOT connect HVAC | 19 | ||||||
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| FIELD WIRING (SEE NOTE) | |||||||
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| wires to R and C. |
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