Installing NEST Thermostat with Power Connector

[DaveR]

I have an oil fired hot water heating system.
It is heating only. There is no air conditioning.
It was installed around year 2000.
The system has 3 zones.
I am trying to install a NEST thermostat on the primary heating loop.

The primary thermostat only has red and white wires coming in. The GOOGLE home application said I needed a POWER CONNECTOR installed.

The Honeywell control box (Triple Aquastat-relay type L8124A,C L8151A)for the primary zone contains:
a boiler temperature control (206625A 206625AA)
a relay
transformer to produce 25 VAC for the thermostat.

Here is the wiring list:
Black and White wires come in on L1 and L2 with 120 VAC
Screws T go to the thermostat with green and cream wires
Does polarity does no matter on screws T?
B1 red wire to conduit for circulator pump control
C1 white wire goes into conduit for circulator pump control
ZR black wire goes into conduit for circulator pump control

Screws with no connection
B2
C2
ZC

[DaveR]

How should the Power Connector be connected?

[JuliCL]

Did you ever find a solution to this?  I have the same exact set up as you and trying to install the power connector.  Thanks

[jonhoo15]

did anyone ever figure this out?  I have this exact setup and just got the power connector.

[DaveR]

I think the answer is in the NEST Power Connector Pro Installation Guide pages 10 and 11. The guide is available as a PDF. You will need to buy a 120 VAC to 28 VAC transformer, which has to be powered from an outlet. I have not tried it yet.

[B788556]

Also need help here. Is B2 common 24V? Is that where you would connect C from the nest power connector?

[DaveR]

I found a manual for a Honeywell Aquastat L8124A. It covers several different related models. My impression is that B1 and B2 are burner power supplies. Of the 5 models, listed in table 1, 4 of them were 120V. Only L8124E used a 24 V supply. See figure 4.