Nest Power Adaptor with external transformer on a Taco SR506 6 zone

Johstacy

I had a heating company come in and install an external transformer on to my Taco SR506. I only have two wires going to each zone so I have to use the nest power adaptors. They hooked up the power adaptors and the transformer. The Nest thermostats are all working however the issue is that when one turns on it turns the relays on for all zones not just it's zone. I think the issue is how they hooked up the red wire coming off of the transformer. In the first pic you can see they connected the red wire from the transformer to the red side of of the zone and the blue wire from the transformer is connected to the common for each power adaptor. If you disconnect the red wires they nothing works and I believe that is because there is no longer a complete circuit but I also believe that somehow connecting the red wire up like that is what is causing all the relays trigger when only one zone is supposed to be active. Does anyone know a better way to connect this up. I do not have the option of running more wires to the thermostats.

Jamie Hall

How are the white wires hooked up?

EBEBRATT-Ed

If you only have two wires to the Nest you're going to have issues. The Nests have batteries that need recharging.

STEVEusaPA

Why happened to the company you paid to install it?

Johstacy

Jamie Hall said:

How are the white wires hooked up?

One white wire (labeled C) is hooked to the blue coming from the transformer
The other two white wires (labeled R and W) are connected to the associated Zone
The grey wires (labeled R and W) are connected to the associated two wires going to the thermostat
A red wire from the transformer is connected to the R wire connected to the zone

Sorry if this isn't clear

Johstacy

EBEBRATT-Ed said:

If you only have two wires to the Nest you're going to have issues. The Nests have batteries that need recharging.

understood that is what the nest power adaptor is for

Johstacy

STEVEusaPA said:

Why happened to the company you paid to install it?

I will be talking to them on Monday

109A_5

Hello @Johstacy,
I think they have too many wires going to too many places. All the zones should be basically independent except the NEST power adapters connections to the additional transformer.

So all the wires that function as Red on the thermostat side get connected together and to the transformer.
The Blue (C or Common) goes to your 5 NEST power adapters and the transformer.
The output side of the NEST power adapter, R and W goes to the appropriate zones of the Taco SR506.

Notice on the NEST power adapters the thermostat side is a group of two wires and the output side is a group of three wires.

You may want to pick one zone and chase it out and see if there is any unnecessary wires and/or connections.

Seems like they have extra Red wires going to the Taco SR506 terminals, where I would expect only one wire to each terminal of Taco SR506.

Also when only the necessary wires are connected correctly you may have to reverse the R and W at the Taco SR506 TT terminals since it looks like yours is an older SR506 unit. Look near the end of this post.
https://forum.heatinghelp.com/discussion/178485/old-t-t-taco-sr506-with-5-zones-looking-to-convert-to-5-nests-transformer-questions

BTW if wiring changes are needed shut everything off and check that all the wiring is correct before re-energizing.

Here is 3 of the your 5 zones so you can get the idea.

Johstacy

109A_5 said:

Hello @Johstacy,
I think they have too many wires going to too many places. All the zones should be basically independent except the NEST power adapters connections to the additional transformer.

So all the wires that function as Red on the thermostat side get connected together and to the transformer.
The Blue (C or Common) goes to your 5 NEST power adapters and the transformer.
The output side of the NEST power adapter, R and W goes to the appropriate zones of the Taco SR506.

Notice on the NEST power adapters the thermostat side is a group of two wires and the output side is a group of three wires.

You may want to pick one zone and chase it out and see if there is any unnecessary wires and/or connections.

Seems like they have extra Red wires going to the Taco SR506 terminals, where I would expect only one wire to each terminal of Taco SR506.

Also when only the necessary wires are connected correctly you may have to reverse the R and W at the Taco SR506 TT terminals since it looks like yours is an older SR506 unit. Look near the end of this post.
https://forum.heatinghelp.com/discussion/178485/old-t-t-taco-sr506-with-5-zones-looking-to-convert-to-5-nests-transformer-questions

BTW if wiring changes are needed shut everything off and check that all the wiring is correct before re-energizing.

Here is 3 of the your 5 zones so you can get the idea.

Your a rock star... This is the correct solution Thank you