Burnham ES2-4 common wire output for Nest thermostat


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Old 05-15-16, 11:08 AM
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Burnham ES2-4 common wire output for Nest thermostat

We have a gas-fired Burnham ES2-4 furnace. On the IQ panel, there are five outputs - labeled 1, 2, 3 and T, T. The old themostat worked by connecting to the two T terminals. With Nest, I need to also have a common wire to provide constant power (according to Nest support when I called).

I need help figuring out which output on the Burnham would provide that common wire. Another post on this forum from a year ago that is similar in nature indicates that terminal 3 provides that common wire. But that does not work for me - the Nest says that things are not wired correctly.

Has anyone else wired a common wire out of the Burnham ES2-4 and which terminal did you use? If it should be terminal 3, are there any specific voltage measurements I could take to confirm if my system is outputting as expected?

thanks!
 
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Old 05-15-16, 11:41 AM
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Welcome to the forums.

Based on the advice I gave in the link...... you should measure 24vac from 3 to the next T.

1 - not used
2 - not used
3 - common - C
T - 24v - R
T - W

Do you have the same controller as in the other thread ?
 
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Old 05-15-16, 04:34 PM
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Hi PJmax- thanks for the reply. Yes, it appears that it's the same IQ panel as the previous thread. I've attached a photo of the panel as well as a closer picture of the 5 terminals.

The one thing I notice is that the order for the red and white is different in my wiring. The first T (position 4 counting from the left) maps to the White wire and second T is the Red. I did switch them to try matching the suggestion directly and Nest reports that there is no power to Rh. It appears to work okay temporarily in my positions until the Nest battery runs down (which is why I require the common wire in the first place). When I connect the C wire to terminal 3, Nest simply reports a miswiring.

I'll pick up a voltage meter tomorrow and check the readings.

thanks

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Old 05-15-16, 04:55 PM
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If you were only to use a two wire hookup..... the polarity (R-W) would make no difference.
It does when using a C connection as the C is cold in reference to the left T which is 24v high.

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Old 05-15-16, 09:13 PM
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Ah, okay that makes sense, thank you. I have updated my wiring on the IQ to match (position 3: Common; 4 (T): Rh; 5 (T): W)

The volt meter reads 24VAC across Common and Red.

When I hook this up to Nest with the Common wire, it says that there is no power to Rh. Nest support says this likely is because the common is not properly grounded. If I simply unplug the Common wire from Nest, it does power on fine and work for a while, so there clearly is power to Rh.

Any suggestions on what to try next? For example, is the "not properly grounded" a likely case as to why attaching Common causes problems? If so, is this something that requires a proper technician to fix or is it something easy on the furnace IQ panel I can do?

Thanks again the for input!

Tee
 
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Old 05-15-16, 09:18 PM
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Did you check for 24vac at 3 and the first T with the nest connected ?

The C does not need to be ground or to be grounded.
 
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Old 05-15-16, 10:07 PM
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Yes, it's reading 24VAC with Nest connected (but not actively heating). I notice the voltage tester also warns that there is hazardous voltage of 50V or greater at the same time I get the reading. Given that it reads 24VAC, that's a bit strange to me. I checked the tester on a few other circuits and the warning doesn't appear.

I think I'll just have someone professional come out and take a look unless there's something else obvious to check!

thanks
 
 

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