Wiring Nest Into Furnace Control Board AND Oil Burner Control

[BenRacicot]

I have an Existing Oil Furnace

• Thermoflow "low boy" (model: CLB-105-DD-R-S2) manual
• no AC equipment
• GeniSys 7505 120V Oil Burner Control - 2 wire terminals (Tw and Tr) manual
• Main control board, has 4 wire terminals labelled C, Y, G, R

My Nest 3rd gen thermostat is now wired into the furnace's main control board, wires labelled C, Y, G, R. (not shown below)

However the old analog two wire thermostat was wired directly into the GeniSys 7505 120V Oil Burner Control. It has front-mounted, 24 VAC thermostat terminals compatible with both mechanical and many power stealing thermostats.

How do I wire my Nest thermostat to properly use the 4 connectors and or the 2 burner control terminals?

CYGR (left) and Tw, Tr (right)

[Patrick_Caezza]

@BenRacicot 

Can you post a picture of the control board terminal's wiring?

[BenRacicot]

Hi @Patrick_Caezza thanks for responding. I've added a full pic to showcase the description.

My research is consistently telling me that I'd need a relay to properly wire this. The CLB manual (page 14) shows diagram and does kind of allude to that we'd need to inform the Oil Burner controller.

[AxelD]

Hi BenRacicot,

Thanks for posting in the Community! I'm happy to help with your wiring configuration. To provide the best assistance, please answer the following questions:

1. Is your Nest Learning Thermostat already installed and working?
2. Did you use the Nest thermostat compatibility checker?
3. Is this system for heating only?
4. Do you want to connect both systems to the Nest Thermostat?
5. Do you want to connect the main control board with four wires or only the T wires for the oil burner control?

Keep me posted.

Regards,
 

Axel.

[BenRacicot]

Hi Axel, thanks for responding.

yes we used the compatibility checker. We’re compatible.

I’ve disconnected the nest so that I can connect it correctly with guidance.

wed like to connect the nest the way we should. It appears the furnace has applicable terminal connectors but that is not powering the thermostat when wired.

looks like I may need a service technician.

[AxelD]

Hi BenRacicot,

Thanks for replying! Based on the information provided about the wiring you have currently in your system, here you have these recommended wiring configurations:

If any of these wiring configurations still don’t power up your Nest Learning Thermostat, you may need to contact an HVAC local technician or a Nest Pro to check if your system needs to be rewired.

Let me know if you have any questions.

Regards,

Axel.

[BenRacicot]

Hi Axel,

For others who see this, that diagram is not correct. It MAY be correct in variation if there's active AC equipment. As mentioned we have none so we wouldnt sire the way you've outlined.

We did get the Nest to function but it was causing the oil control to repeatedly call for oil... would have burnt out if we kept it.

We've moved away from Nest, several AC service guys wont even work with them.