Nest thermostat incompatibility with new furnace

[genejames]

New HTP boilers. Efficient, expensive and quite smart. They require dry contact closure to fire up. Nest and 2-wire power adapter are working correctly, but nest power adapter does not close circuit enough to light up furnaces because it uses, probably, opto-isolator transistors. so I have a 24 V transformer (running the power adapter )and a 24 V AC relay for the power adapter to drive, then the 24 V relay contact will light up the furnace. Even if I run three wires to thermostat, I don’t know how to connect the transformer and relay to W, C, R, RH, etc, terminals. Trouble is furnace and thermostat businesses talk in terms of color codes and arcane cable lettering. Does anyone have a schematic so I can make this look to the power adapter like a furnace. Does Google publish a schematic of the power adapter?

[pereztzum]

Hi @genejames,

I understand you're facing an incompatibility issue between your Nest thermostat and your new HTP boiler. Here's how we can approach this:

Nest Thermostat Compatibility:

• Double-check Nest's compatibility list: While your boiler might be efficient, Nest thermostats might not be compatible with its specific firing mechanism (https://support.google.com/googlenest/answer/9246656?hl=en).

Alternative Solutions:

• Consider a relay solution: Your idea of using a relay to simulate the furnace behavior is a potential workaround. However, wiring modifications require caution.

Caution and Professional Help:

• Unless you're comfortable with electrical work, it's strongly recommended to involve a qualified HVAC technician. Improper wiring can damage your furnace or thermostat and even pose safety risks.

Information Gathering:

• Furnace manual: Look for a wiring diagram in your HTP boiler's manual. It should show how the original thermostat connects.
• Relay wiring: Research online resources for specific relay models you plan to use. They should have wiring diagrams for the relay itself.

Nest Power Adapter Schematic:

• Google doesn't publish schematics for the Nest power adapter due to safety concerns. Modifying it is not recommended.

Next Steps:

1. Verify Nest incompatibility.
2. If considering the relay solution, research relay wiring diagrams specific to your model.
3. Consult your HTP boiler manual for its wiring diagram.
4. If unsure about any step, contact a qualified HVAC technician to ensure safe and proper installation.

Remember, safety is paramount. If you're not comfortable with electrical work, prioritize professional help.

Additionally we'll need to look for more information please fill out our Contact Us Form and a specialist is going to contact you to look into this further, please keep in mind this is going to be based on your HVAC system.

Regards,

Brandon.