Use Honeywell VisionPro without EIM?

Question

I just acquired a Honeywell VisionPro TH9421C1004 thermostat but I didn't get the Equipment Interface Module (EIM) with it.  Can I still wire this directly from my furnace?  It only has 3 wire connections: Data, R, and C.

ThreePhaseEel · Answer

No, you can't
Unfortunately, the Honeywell thermostats that use an EIM rely on it to translate either RedLink (for wireless versions) or a proprietary protocol (for the wired ones) to the 24VAC signals that a furnace understands.  So, since Honeywell discontinued the wired versions in favor of their RedLink counterparts, you'll need to hunt down a secondhand EIM for your thermostat.

Use Honeywell VisionPro without EIM?

One Answer

No, you can't

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