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I am installing the Honeywell VNT5150E1000 ERV. Here is the information sheet: https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Honeywell-VNT5150E1000-Submittal-Sheet.pdf

Going from the following wiring diagram in the installation instructions:

ERV wiring diagram

Is it possible to use the G and C wires on the furnace terminal block (G to G, C to R) as the ventilation contacts such that whenever there is a call for fan the ERV activates too? To be clear, my thermostat has no specific contacts for the activation of an ERV or similar device.

I know the terminal block in the furnace operates at 24vdc, however I do not know if that is going to be too high for the board and it requires something in between to step down the voltage, like a wall control.

What gives me pause is there is a second wiring diagram that describes an interlock which does specifically reference using the terminal block:

Interlock diagram

Since this diagram does directly reference the use of the terminal block to achieve an interlock, it makes me think the G and R REMOTES contacts will not directly accept wiring from the furnace terminal block.

In short, is what I propose doable or must a wall control be used here? Thanks.

Andy Hall
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1 Answers1

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No, because R is supplying power from the ERV's internal transformer

What you describe will not work, and will blow the fuse inside the ERV. This is because the ERV's R terminal is a supply of 24VAC power from the ERV's own transformer.

You'll need to whack a fan relay in, with its coil connected from G to C on the furnace block and its NO contacts connected from G to R on the ERV, to adapt the G signal from your thermostat into a dry-contact closure for the ERV to read.

ThreePhaseEel
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