# Nest with Honeywell HZ311



## yuri (Nov 29, 2008)

Your furnace has a 24 volt power transformer with R and C wires which go to the furnace circuit board.

Try hookup the Nest C to the C on that board.

Beware we have has LOTS of problems and complaints here about Nest and especially trying to get them to work with zoning panels.

EcoBee seems to be a better brand but zoning panels can be tricky and finicky with wi-fi thermostats and any using a C wire. If it was mine I would use conventional battery operated thermostats.


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## hamedalonso (Nov 3, 2017)

Do you think I should be able to Wire up the C wire at the HZ311 panel rather than the furnace circuit board ?


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## yuri (Nov 29, 2008)

The problem is the C side of the furnace transformer is grounded ( don't ask me why ).

I am not sure if the C from the zoning panel hooks up with the C AND grounding of the furnace properly and lots of people are having problems because of that.

Nest did not factor that into their design and it seems to cause problems as they designed for a standalone furnace.


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## yuri (Nov 29, 2008)

I found install info for that panel and it uses it's own transformer. However the C may not be grounded on it plus hooking up 3 Nests to the C may cause a conflict or some type of feedback.


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## hamedalonso (Nov 3, 2017)

Since each thermostat in the HZ311 Panel has a C port, You're thinking that the 'C' coming from the 24 Volt transformer and going to the red power section in HZ311 panel isn't grounded ?


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## yuri (Nov 29, 2008)

I get a lot of posters on different forums having problems with Nests and zoning panels.

The extra transformer is usually mounted on a wall and may not have it's secondary side grounded like in a furnace.

It seems like when 3 Nests try share a common C and transformer they can "bump into each other" and have problems. When each one is operating one furnace only they work OK.

My point is it may or may not work and based on all the bad reports of Nests and problems most people like EcoBee.

IMO these thermostats are designed and like to operate one furnace and AC only on it's own transformer.


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## Handypaddy (Jul 4, 2019)

I had the exact same situation with the Honeywell and the Nest thermostat. The nest draws power from the AC unit and when it needs to recharge it will stop the AC. This means a constant on off cycle and a very small decrease in temp.
I did as you suggested with the blue wire on the Nest and on the Honeywell and it has solved the problem. The unit has a dedicated power supply and does not need to interrupt the AC.
Thank you for the suggestion


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## husky1055 (Jun 3, 2019)

Please help me understand. The Nest blue wire is connected to the HZ311 tsat blue input. From the Trane furnace there is a C connection, I can connect a spare blue wire to it leading to the HZ311 panel. Where do I connect this blue wire to have the C power on the Nest. I do not see any C connection of the HZ311 equipment panel.


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## 57TinkerMan (Jun 17, 2018)

husky1055 said:


> Where do I connect this blue wire to have the C power on the Nest.



Nest issues aside, the proper location for the C wire termination (one zone thermostat) is pictured below. As others have said, you may have some problems with the Nest, but worth a try.


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## husky1055 (Jun 3, 2019)

Perhaps I did not explain my question clearly. I connected the Blue wire from the tsat C to the hz311 thermostat C (where you circled). What I need to do is to connect the C from the furnace to the hz311 to complete the circuit. I have the extra blue wire from the furnace to the hz311. Without this connection there is no 24v C wire power on the thermostat. There is not enough length to go from furnace to thermostat directly as my tsats are on the right side and the equipment panel is on the left. In addition I have 2 Tsats which needed C wires. Thanks for your quick reply.


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## user_12345a (Nov 23, 2014)

> What I need to do is to connect the C from the furnace to the hz311 to complete the circuit


No you don't.

The zoning panel t-stat and damper circuits are electrically isolated from the furnace's control circuit.

C at panel thermostat connection internally goes back to the panel's transformer. R is power from that same transformer.


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## husky1055 (Jun 3, 2019)

I do not have C wire power in either of my Honeywell tsats. But I did connect both tsats to the hz311 c wires. See attached pics.


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## rcp90 (Oct 8, 2020)

You would recommend ecobee for this situation? Can you run the ecobee at the base unit, mine is in my basement and then have a temp sensor on each floor? They are telling me they can't send wires upstairs


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## user_12345a (Nov 23, 2014)

^The ecobee can do that, but you would need a stat for each zone and it would get extremely expensive.

It can be set up to only read the sensor.

Start a new thread because this one is old.


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