# Ecobee3 with Carrier Wiring



## user_12345a (Nov 23, 2014)

This carrier edge, just based on the pics and your post appears to be similar to other high end controls in that it communicates digitally and there's a module that does the switching - applying 24v to the right conductors.

You could switch to conventional wires, but you should see what it's going first.

It may be controlling other things like air quality products- like humidifier, hrv, etc.

You'll have to have a lot of wires in the wall to use a conventional product with loosing features.

you'll need at least 6 wires for normal control with a common and whatever's connected to o/b/w2*, and better to have an extra 2 for future use. 

*what's confusing is that you appear to have a single stage furnace, so what's o/b/w2 controlling? do you have a heatpump as well?

ecobee is known to be a good product and offers stuff you normally would have to spend at least an extra hundred $ for.


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## beenthere (Oct 11, 2008)

Write down what wires are connected where on the Edge's base/EIM. Then wire nut them to the same color wires going to the thermostat location. Then connect those wires to the same terminals on the Ecobee.


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## supers05 (May 23, 2015)

The ecobee3 should be able to do everything that the eim is hooked up to. The outdoor sensor (oat) is not used for the ecobee3, as it uses the internet for that instead. 

If you have a heat pump, make sure that you configure the ecobee3 to dual fuel. 

As user mentioned, you'll need the same number of wires at the thermostat as what's connected in the eim. (minus the oat) so that's at least 6 wires. 

Cheers!


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## user_12345a (Nov 23, 2014)

I would see what's connected to w2/o/b before doing anything else.

the board is of a single stage furnace. What's it controlling?


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## plat00n (Feb 22, 2017)

Appreciate all of the responses!

From the comments above, it sounds like I can connect the 6 wires on the right side directly to the unused wires and then connect the other side to the Ecobee, bypassing the EIM entirely. There are 7 unused wires running between the EIM and the thermostat (plus the 2 for the Edge), so I should be good from that perspective.

It was mentioned by supers05 that the OAT is not required. On the EIM, there are 2 wires for OAT. One is labeled OAT and the other is OAT/RRS return {SRTN}. Do neither of those need to be connected?

Thanks for the point on the dual fuel, I do have a dual fuel unit but wasn't sure where that needed to be set. I can set that on the Ecobee.

For the last point regarding the w2/o/b, there is a connection on the Ecobee that reads O/B. I assume that is where this would connect? I will go back in tonight and trace out that wire to determine where it is going.


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## supers05 (May 23, 2015)

plat00n said:


> .. One is labeled OAT and the other is OAT/RRS return {SRTN}. Do neither of those need to be connected?


No. They will be abandoned. 




plat00n said:


> ..
> Thanks for the point on the dual fuel, I do have a dual fuel unit but wasn't sure where that needed to be set. I can set that on the Ecobee.
> 
> For the last point regarding the w2/o/b, there is a connection on the Ecobee that reads O/B. I assume that is where this would connect? I will go back in tonight and trace out that wire to determine where it is going.


Yes. That's where you connect it. 

For the settings, you'll set the system type to heat pump, and the backup heat as fossil fuel. Lockout temp will be determined by the sizing of your equipment and local conditions. You'll have to experiment on how well the heat pump does in the cold. If you're on NG, I'd set the temp in the upper range. If your on LPG or other expensive fuel, then it would be in the lower range. 

Cheers!


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## user_12345a (Nov 23, 2014)

w2/0/b is likely going to the reversing valve.

You'll have to read the ecobee instructions very carefully and configure it to run what way you'd like.

You have to decide if you want the heatpump to continue to run below the thermal balance point, and for it to shut off and for the furnace to cycle on when it's not cooking up.

Or, if you want it to shut down below the thermal balance point.

The latter is probably easier on the equipment. There may be some savings in your area below the thermal balance point where some backup heat may be needed to continue heating with the heatpump.

However, the potentially short cycles of the furnace, having to defrost in cold weather and cycle between heatpump and furnace will increase wear and diminish any savings.

Not sure if yours has an outdoor sensor. the ecobee probably uses online data.

Heatpumps are best left at a constant temperature in heat mode; the capacity to recover just isn't there. The recovery often occurs in the early morning or early evening, when the outdoor temperature is low; shifting operation to when it's less efficient will whip out any savings. Either it will run less efficiently, or the furnace will kick in above the thermal balance point.

Only straight gas, oil, and electric forced air furnaces work well with large setbacks. Heatpumps, hot water, ac? nope.


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## supers05 (May 23, 2015)

user_12345a said:


> ...
> Not sure if yours has an outdoor sensor. the ecobee probably uses online data.
> ....


The ecobee3 does use internet weather stations instead of an outdoor sensor. For better or worse..... 

The OP has wires for it. They usually don't get hooked up unless there's actually a sensor installed. 

You can't really defrost and use the furnace for reheat. It's too harmful to the compressor. It's either a straight defrost or you switch over before defrost is needed.


Cheers!


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## user_12345a (Nov 23, 2014)

> You can't really defrost and use the furnace for reheat. It's too harmful to the compressor. It's either a straight defrost or you switch over before defrost is needed.


Yet a lot of guys will do it that way and it's even in dual fuel control manual. Rather than risking complaints due to cold drafts.


It can be done with a plenum t-stat that shuts down the call for furnace heat if the supply air gets too hot, but then again the short cycling of heat during a defrost that last minutes wouldn't be good for the heat exchanger at all.
*

All the more reason to not run it below the thermal balance point. *At today's gas prices there may not even be any savings running a heatpump.


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## beenthere (Oct 11, 2008)

supers05 said:


> The ecobee3 does use internet weather stations instead of an outdoor sensor. For better or worse.....
> 
> The OP has wires for it. They usually don't get hooked up unless there's actually a sensor installed.
> 
> ...


Down here we always run the furnace, whether gas or oil during defrost. Oil almost always needs a bonnet sensor to shut the furnace off. To prevent over heating the indoor coil right after the heat pump switches back to heat mode. On gas furnaces, only seldom is a bonnet sensor required. And usually only on the grossly over sized ones.

On York heat pumps with the Yorkguard defrost board. If a bonnet sensor is used. 30 seconds before the heat pump goes into defrost. It will bring on the gas furnace. So that the burner comes on shortly after the heat pump starts defrost. And will stop calling for the furnace heat if the bonnet sensor senses 101°F temp before the coil.


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## supers05 (May 23, 2015)

beenthere said:


> Down here .....


Interesting.... The things we do to prevent complaints. 

Cheers!


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## beenthere (Oct 11, 2008)

supers05 said:


> Interesting.... The things we do to prevent complaints.
> 
> Cheers!


LOL, yep. A happy customer, is a customer that will pay. Usually, ROFL.


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## user_12345a (Nov 23, 2014)

install some strip heaters downstream of the coil use for defrost. that would be easier on the equipment. would only need 5 to 10kw in most 3 ton and lower applications.


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## supers05 (May 23, 2015)

beenthere said:


> LOL, yep. A happy customer, is a customer that will pay. Usually, ROFL.


[emoji23] indeed, getting paid is always nice. 

If they only knew how hard it was on is on the compressor.... First stage isn't so bad, when the furnace is sized close enough. 

Cheers!


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## beenthere (Oct 11, 2008)

user_12345a said:


> install some strip heaters downstream of the coil use for defrost. that would be easier on the equipment. would only need 5 to 10kw in most 3 ton and lower applications.


Not actually easier on the heat pump. 

When a furnace runs during defrost, the compression ratio is lower. Then when a heat pump has electric aux heat. Plus with a furnace, the defrost cycle is shorter. Of course I'm speaking about a furnace that isn't grossly over sized, or is equipped with a bonnet sensor.


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## user_12345a (Nov 23, 2014)

Not certain it would lower it because the head psi would good up too.

i don't think blasting an evaporator with 120 to 140f air is good for the compressor in defrost mode, considering it normally gets 65 to 80. especially if it's piston metered so return gas would be greatly superheated leading to less winding cooling especially with the low head on a frozen/cold coil. 

whatever - you do what works in the field.


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## beenthere (Oct 11, 2008)

user_12345a said:


> Not certain it would lower it because the head psi would good up too.
> 
> i don't think blasting an evaporator with 120 to 140f air is good for the compressor in defrost mode, considering it normally gets 65 to 80. especially if it's piston metered so return gas would be greatly superheated leading to less winding cooling especially with the low head on a frozen/cold coil.
> 
> whatever - you do what works in the field.


On the average gas furnace, it takes a good long while for the heat exchanger to gt up to 101 when the fan is already running before the burner ignites.

Head pressure doesn't rise as much as often thought, since the coil is frosted up, and that frost is absorbing the heat very quickly.

On time and temp defrost boards. When they go into defrost needlessly, the defrost cycle is too short to build up a high head pressure. Since many of those boards terminate defrost at 50 to 70°F.


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## supers05 (May 23, 2015)

Head pressure is greatly suppressed when there's any water on the coil. Even more so when it's frozen. 

Defrost doesn't last too long, so slightly warmer suction for that short duration isn't too bad. It does however increase compressor loading, which can be quite hard on recips. Scrolls handle it better, but it's still hard mechanically and electrically. 

Cheers!


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## plat00n (Feb 22, 2017)

I was able to connect the Ecobee last night based on the discussions and everything came up properly, so thanks for the assistance!

A lot of discussion around some of the settings, so I'll need to take some time go through all of that and see how some settings should be applied.

Appreciate the guidance!


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