Getting Ecobee3 Lite to work with an old fan coil system

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Old 08-29-19, 09:06 PM
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Getting Ecobee3 Lite to work with an old fan coil system

Hi everyone, I'm having a difficult time trying to figure out how to get Ecobee3 Lite to work with an old 120v fan coil system through a 24v relay. Its a Whalen unit with similar configuration as this Innoline Fan Raiser Coil from the same company ( https://whalencompany.com/products/f...riser-fan-coil ) except mine is from late 70's. Heating and cooling is regulated by the building depending on seasons, and the only thing my unit does is run the fan to blow through the cold/hot radiator.
It has 3 wires running from the fan which I connected to RC840T-120 24v relay. Then, there is a small external temperature sensor connected to the heating/cooling pipe, which used to be hooked up directly to my old Siemens RAB20 series thermostat which I don't think I need for this to work. I have tried several configurations on Ecobee3 terminals and every time the thermostat boots up, I hear the relay switching, but the fan doesn't spin up. Not much help from ecobee support either - they said I have a complicated setup and I should just call a certified hvac installer...
I would be grateful to hear input from anyone who had experience with installing a smart thermostat on a 120v fan coil system. Hopefully these images help to clear some things up.
 
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Old 08-30-19, 05:22 AM
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Hi, how did you power the RC840T-120 24v relay? the relay will power the Ecobee as well as switch the fan coil ON/OFF follow the Dia. On the relay.
Geo
 
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Old 08-30-19, 08:40 PM
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Welcome to the forums.

That Aube unit may or more than likely not power the Ecobee correctly. They have a very limited 24v supply in them. The only thermostat that works 100% reliably with that unit is the nest as it has it's own battery.

Is there 120v on that temperature sensor ?
The diagram would suggest it but that is not 120v wiring.
Typically a fan cool has a blower that is 120v and directly run thru the thermostat.
 
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Old 09-01-19, 10:50 PM
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Geo, I powered the relay by connecting it straight to load, line and neutral that are coming off the fan. I followed the diagram but unfortunately that didn't work.
 
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Old 09-01-19, 10:53 PM
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Pete, glad to be here. Yes the temp sensor has 120v connected directly to it.

Its just strange that the Ecobee powers on and looks to be working without any issues. The relay also switches on and off depending on temperature settings, but the power doesn't seem to be passing through to the fan.
Do you think that I need to jump terminals despite of what Ecobee support suggested?

And this bit of information probably doesn't change anything, but there is a manual switch for high, medium and low fan speed on old thermostat.

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Last edited by PJmax; 09-02-19 at 07:19 PM. Reason: added relay pic
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Old 09-02-19, 07:18 PM
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You're switching 120v thru that control but there is no neutral shown.
Actually there is not "hot" to the switch shown either.

Your blower has one wire to neutral and looks like three speed wires.
The neutral from the RCB goes to the same neutral as the blower motor.
The black wire from the relay goes to always live/hot.
The red wire from the relay needs to go to one of the blower wires.

I can't find the manual and wiring that matches your thermostat.
 

Last edited by PJmax; 09-02-19 at 07:50 PM.
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Old 09-03-19, 03:41 PM
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OK, I think I'm beginning to understand. Initially when I used a multimeter I assumed those were line neutral and load because the wiring here is messy and without any labels, with mixed color wires. I have access to another unit with a different thermostat (TC-195). I can take a picture of its wiring and post it here as a comparison. Meanwhile, I will take the wall unit apart to see if there are any other wires tucked in under the fan compartment behind the blower.
 
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Old 09-05-19, 06:01 PM
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As promised, a couple of pictures of TC-195 wiring and its sensor.
 
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Old 09-05-19, 06:15 PM
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I have also taken out the blower (which had a diagram on its label) and I want to apologize in advance for posting so many images; I think this way I'll have less of a chance to confuse anyone. Here is what I found:
 
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Old 09-06-19, 01:56 PM
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Hi, itís pretty hard to tell whatís going on there in the pics , is that cable coming in from the side feeding that motor? If it is the white from the relay will connect to whites, the black will connect to the black of the relay, the red will connect the motor lead for the speed you want.
Tstat will connect to R C W, not sure how the temp sensor fits into the circuit.
Geo
 
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Old 09-06-19, 04:37 PM
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Pictures are extremely helpful. The more the better. I've been swamped with work so time has been short. We'll get this figured out soon.

The temperature sensor isn't critical. It's set up for hot and cold pipe temperature monitoring so that depending on the season.... the blower won't operate unless the pipe is cold or hot.
 
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Old 09-07-19, 02:42 PM
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I know the feeling, Pete. There aren't enough hours in the day to get everything done without an overlapping schedule.
Geo, I think I should update my initial diagram to reflect the correct wire arrangement.
 
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Old 09-08-19, 04:32 PM
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After rewiring I followed Geo's suggestion - connected relay's red to one of the wires controlling speed of the motor (red in this case) and left the other out. Ecobee is now able to turn the blower on, but only in heat mode. So only when the temperature falls below a threshold will it spin the blower. It doesn't seem to trigger the fan when rising above a set temperature.
I'm guessing now the problem lies in finding the correct settings and terminal wiring combination.
This is what I have so far:
 
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Old 09-08-19, 10:34 PM
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Excellent job with that diagram. That shows everything. Probably could do without the pipe thermostat.

If the thermostat used relays..... you could connect W1 and Y1 together. Either will turn the blower on.
You could try it with the EL3...... It should work.

Ultimately you'll need to put a switch between the red wire on the relay and the blower wires.
Typically you want high speed for A/C and a lower speed for heat.
 
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Old 09-08-19, 11:45 PM
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A quick correction to my last diagram. C from relay was meant to go to C on ecobee, not to G.
 
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Old 09-09-19, 12:03 AM
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Connecting W1 and Y1 together was right on point . Now the fan is triggered with both, heating and cooling modes.
Do you think there could be a way to have low and high speeds work independently with that relay?
 
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Old 09-09-19, 11:31 AM
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You'd need a second relay..... like an 840 relay to control a second speed.
 
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Old 09-09-19, 04:25 PM
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Hi, your going to have to incorporate that temp sensor somehow I believe, what I don’t get is what that control is that has Y G3 etc. that all appears to be line voltage switching for the fan speeds.
Paralleling Y1 & W1 is not the answer, what temperature is the water, you could be circulating Hot water for cooling and vice verser.
Geo
 
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Old 09-10-19, 12:10 AM
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That is a one line loop. That means they are circulating hot water in the winter and cold water in the summer from the plant.

The clip on thermostat keeps the blower from running during those switchover days in the spring and fall.The old thermostat only switched the blower on and off at the different speeds. It did nothing to control water flow. (Y switched the blower on at high speed and W on at a lower speed))
 
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Old 09-10-19, 09:32 AM
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Thank you for helping me figure this out and I appreciate all of your suggestions. I used the same process on the second system and they are both working flawlessly using that setup.
 
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