Quick synopsis: I just purchased a house built in the 1830's it's been through several owners and just before we bought it had A/C added but not a new thermostat wired in.

The old thermostat had no cooling option, I'm having an issue wiring the new thermostat.

There are three wires, a red wire I have going to “R” a white wire going to “W” and a Blue wire going to “Y.

The fuse in the air handler(?) is not blown and power is turned on at the inside breaker, outside breaker and switch on the side of the furnace.

Question from user IDONTLIKEDICKS at hvacadvice at reddit.

Answer:

Based on the information provided, it seems like you are encountering difficulties wiring a new thermostat in your recently purchased house. The house, built in the 1830s, had air conditioning added at some point, but the thermostat was not replaced.

To wire the new thermostat correctly, you mentioned that you have three wires available: a red wire connected to "R," a white wire connected to "W," and a blue wire connected to "Y." Here's a general guide on how to proceed:

1. Ensure the power is turned off: Before working with any electrical connections, it's crucial to turn off the power to avoid any accidents.

2. Identify the wires: Verify the function of each wire in your HVAC system. While the red wire is typically the power wire (R), the white wire is commonly used for heating (W), and the blue wire usually connects to the cooling system (Y). However, it's always recommended to double-check the wiring and consult the manual or documentation of your specific thermostat and HVAC system to confirm the wire functions.

3. Match the wires to the thermostat terminals: Once you've identified the functions of the wires, match them to the appropriate terminals on your new thermostat. In this case, connect the red wire to the "R" terminal, the white wire to the "W" terminal, and the blue wire to the "Y" terminal. The specific terminals may vary depending on the thermostat model, so refer to the manufacturer's instructions for accurate labeling.

4. Secure the connections: Ensure that the wires are securely attached to their respective terminals. Tighten any screws or connectors as necessary to provide a stable connection.

5. Restore power: After double-checking the wiring and ensuring all connections are secure, you can turn the power back on.

6. Configure thermostat settings: Once the power is restored, you may need to follow the instructions provided with your new thermostat to configure the settings, such as setting the desired temperature range and programming schedules if applicable.

If you encounter any difficulties or have further questions, it is advisable to consult a professional HVAC technician or an electrician who can provide on-site assistance and ensure that the wiring is done correctly and safely.

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