Replacement Panel for EWC-ST-3E to run Nest

[Dhmike661]

Hi,

I have an Ultrazone EWC ST 3E on a forced hot air system with 3 zones and AC. I understand that the Nest Thermostat will not work with this control planet because it does not have the seperate O & B terminals.

Which panel would replace the ST 3E and gain me functionality to run a Nest Thermostat.

Thanks

[Erik W.]

You can upgrade to the NCM-300 panel.

[Dhmike661]

Eric,

That's what I figured. Look at the below response I got from a nest representative, do you think it has any merit?


I looked at the photo you sent and it looks like you are compatible. Congratulations!



Most of your wires will plug into similar terminals on the Nest, the only one that will be different is the blue wire in B, that will need to go into C on the Nest.


If you have any more questions, please give us a call at 855-4MY-NEST (855-469-6378) and mention your case number 00155736. We're open 7 days a week from 5am - 9pm pacific time.

Thanks for contacting Nest. Let us know if we can help with anything else.


- Charles

Nest Support

[Erik W.]

There is a way to be able to use the nest thermostat on the ST Panel, but not in the way the people at nest are telling you to wire it. You would need to install a summer winter switch at the zone panel for it to work. By upgrading the panel to the NCM-300 you would not need that switch and the nest would be compatible fo all of your zones.

[CColotti]

It looks like all that is needed is this switch:

http://www.ewccontrols.com/acrobat/090375a0222.pdf

For about $40 it seems easier and less expensive than changing the panel out. I live in NH and we have a clear line between heating and cooling so we don't usually flip real time between them. In that case do you think this is an okay route? Or is it better to change out the panel and can that be done using a picture of the original panel? Considering the NEST units are $249 each adding a new panel with labor could make this little project cost prohibitive

[CColotti]

So here is the thing I found. the NEST looks for Power on Yellow FIRST then white. If no power is on yellow it errors out. You only GET power on yellow if the summer winter switch is set to SUMMER, but in the winter the NEST sees power but only on the White and you need to remove the yellow wire for it to work. Is there a way to make this work for real with the switch for both AC/Heat without removing wires every season or changing the panel?

[CColotti]

Looks like I may have figured it out but wanted to check. After the switch is installed I need to run a Common from each now slave T-Stat to the NEST to provide power. In metering the lines the Y1 has no juice when the switch is set to HEAT and vice-vera, but this seems to avoid the NEST power issue. If this is in fact correct please let me know I'd love to blog about it.

[rajeevn]

Ccolotti, Can you please confirm if running the Common resolved the problem. I am thinking of making the same setup. Any other suggestions. Thanks.

[Bronx68]

How can I get the Nest generation 2 to run with a EWC st-3d panel?

[Paul Z.]

ST-3 will not support an NEST thermostat. A replacement board NCM-300 will be needed.