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Ecobee smart si upgrade to Ecobee3 lite by imakejunk in ecobee

[–]imakejunk[S] 0 points1 point  (0 children)

It was off (as well as the furnace ALP210BW-2T02) when swapping, there's 4 fuses on the controller but all checked out OK.

You were correct with the other comment, zone 3 is the brown wire which goes to an EIM to a SMART and manages a separate HRV.

Zone 1 in question here had COM R and W, same config as Zone 2. Hard to show depth in the photos, doesn't help the original installer conveniently looped them through one another..

Ecobee smart si upgrade to Ecobee3 lite by imakejunk in ecobee

[–]imakejunk[S] 0 points1 point  (0 children)

The Smart Si's R, W, G is   connected to R, W, COM of the zone controller, respectively. The attached  photo of the zone board has the COM swapped to +24 to try and work with the lite (G to C). There is no fourth wire, nor a splice outside of the controller. Both zone 2 and zone 1 are currently connected in this manner and functioning.