Nest power connector - help needed to connect to oil burner

[jkd2390]

I'm trying to set up a Nest smart thermostat with my heating only system. I have a 2 wire system without a C wire, so I purchased a Nest power connector to set everything up. I have a Carlin EZ-1HP oil burner and I'm trying to figure out where the C wire on the power connector is supposed to go on the panel on the burner. All I have are the R/W wires (which connect to the thermostat) and 2 yellow wires. Would it be the second from the right?

Any help is appreciated! Photos of the panel on the burner plus my existing thermostat is attached. Confirming this is a 20-30 VAC system so it is compatible.

[CoolingWizard]

Jkd2390,

The Carlin 28245 primary controller (and your model) do not present common output from the step down transformer inside the case. The two yellow wires go to a CAD sensor in the burner box. Now, if you have access to a Volt Ohm Meter (VOMj, sometimes called a multimeter, we might be able to find a way to get you to your goal.

Sometimes those Carlin control systems connect the common side of the transformer to the chassis ground. To check this, you need a Volt Ohm Meter. Set the VOM to AC voltage. Put one meter lead on the Red wire on (the red wire T on the controller), and put the second meter lead on unpainted metal chassis below the control box. If you your meter shows approximately 24Volts, your in business! Your common wire of the Power Connector would simply be attached to the metal controller chassis. I hope this helps you.

If you find my answers helpful, please provide a “Kudo” and if it was the solution, click the “recommended Answer”.

Ken, The AC Cooling Wizard

[jkd2390]

Hi Ken

Thank you so much for the reply!

Would something like this work for reading the voltage?

Two other amateur questions for you:

1. When you say "put the second meter lead on unpainted metal chassis below the control box," what do you mean?
2. You mention that if it reads 24V, we just connect the power connector C wire to the "metal controller chassis" - which is this?

[CoolingWizard]

Hello JKD2309,

First, yes indeed that digital multimeter is perfect and nice tool have in your toolbox.
Second, look at the picture below.



If you do not want to wait, a simple test is good enough. Just install the power connector with the common wire on that box screw, and see if the Nest thermostat can see the power connector. If it can see the power connector the COMMON is indeed connected to chassis ground.

Ken, The AC Cooling Wizard

[jkd2390]

This is very helpful, thank you!

What are the two chassises to the right of the yellow wires? They are marked as "alarm" on the panel it seems.

[CoolingWizard]

When the device detects and error or a problem, it can be wired to a Fire alarm system using the terminals. Basically the fire alarm sends power on one of the A and looks for the power on the return A if I sees the power coming back, it sets an alarm status.

Ken

[Markjosephp]

Hello folks,

I appreciate your expertise here, Ken. big help!

@jkd2390, I wanted to ensure that everything was covered here. If you're still in need of assistance, feel free to let us know.

Best regards,

Mark

[EmersonB]

Hi everyone,

@jkd2390 I wanted to follow up and see if you are still in need of any help. Please let me know if you are still having any concerns or questions from here, as I would be happy to take a closer look and assist you further.

Thanks for lending a hand, Mark and Ken.

Regards,
Emerson

[Jhonleanmel]

Hi there,

I'm just checking in to make sure that you've seen our response. Please let us know if you have any other questions or concerns as I will be locking this in 24 hours.

Thanks,
Mel