Ecobee3 Lite and HRV

[Jrostek]

I'm having the same issue with the 3 amp fuse blowing on the control board when hooking up the Ecobee3 lite.  I noticed an extra wire back wound around the tstat wiring.  If I hook this up and use it as the c wire can I hook up the ecobee3 lite this way and avoid the PEK? 

I followed the diagram Admin had provided in earlier posts and it worked for a few hours but then still blew the fuse. I had pigtailed the G/NC wire before the PEK and plugged the pigtail into G on the PEK, maybe this was the issue causing the fuse to blow.

I would like the HRV to continue to operate normally and do not want to connect it to the smart thermostat.

Agreed, that diagram should be packaged and sent out with the Ecobee products, it's invaluable.   

[Admin]

The Ecobee 3 Lite can't control an HRV anyway, but it does sound like the HRV interlock wiring is causing the fuse to blow anytime the HRV starts.

The PEK is wired differently depending on which version of Ecobee is being used.  I believe the Ecobee 3 Lite and Ecobee 4 use the same PEK wiring, but the Ecobee 3 PEK wiring is different.  The Ecobee 3 Lite PEK terminal is wired to the PEK adapter Y terminal and the Ecobee 3 Lite C terminal is wired to the PEK adapter G terminal.

If you have a 5th unused black wire then eliminate the PEK and connect it to C on the Ecobee and C on the furnace.

Assuming you're using a single stage furnace follow the attached wiring diagram.  Make sure there is only 1 wire on the furnace G terminal if you're using the 3 wire HRV interlock method.

[Admin]

It sounds like you wired things as shown in the first diagram below, which is wrong.  The C and G would create a direct short.

If you're using the PEK follow the second diagram.

I also recommend using 3 wires to connect the HRV interlock wiring, not 2.

[Admin]

If you only have 2 wires for the HRV interlock then follow the first wiring diagram below.

If you only have 2 wires for the HRV interlock and want to use the PEK adapter then follow the second wiring diagram below.

[Jrostek]

Thanks for the info.  I definitely wired it in the way you show in the "wrong" diagram the first time.  I'm surprised it ran for as long as it did if it caused a direct short. 

Since I have the dedicated C wire to use, I will use the first diagram you sent and will hope all is well.   The interlock is a 2 wire, the nc and G wires are maretted together from the HRV and tstat as shown in your diagram. I'm hoping to leave that interlock alone if I can.  The furnace is a Lennox Merit series unit.

[Admin]

Your HRV must not turn on very often.  It would only short when the HRV started.

I'm not sure how that system is working.  The NC terminal is only used with the 3 wire interlock method.

Does the HRV have 3 wires connected to NC, NO and C?

[Jrostek]

Yes, apologies, it is a 3 wire interlock.  NC to G, C to G, and NO to R.  If I make that spare wire the 'c' wire and connect as per your first diagram, everything should work perfectly.

[Jrostek]

The C wire really does the trick with powering these thermostats.  Once the C was connected on both ends and everything else left the same, the stat powered right up and has ran without issue.  The HRV continues to run off it's own controller and calls for the furnace fan when needed.  Also nice to see that the installers had the wiring in correctly to start.  Thanks again for the invaluable advice.

J

[Admin]

Glad to hear.  Many thanks for the donation, that's much appreciated!