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replacing zoning board with new EWC and Honeywell Thermostats: questions

replacing zoning board with new EWC and Honeywell Thermostats: questions


Old 06-28-20, 07:46 AM
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replacing zoning board with new EWC and Honeywell Thermostats: questions

New member here but I found the forum while searching for this very topic, so here is the deal. I am dealing with a 2500 sq ft (1250/floor) residential area that currently operates an oil burning furnace (forced air) and an AC system (both single stage as far as I can tell) via an EWC ST-3E zoning board. As it all sits, there are 3 thermostats connected, though only one controls the furnace, blower fan, and AC (master/slave setup, normal behavior for this board from what I understand). What I would like to do is upgrade the zoning board so that I can install matching honeywell 5+2 thermostats in all 3 locations, and operate the zones independently rather than relying on the master. As far as I can tell, the damper controls are already in place for this, and I only need to swap the zoning board and the thermostats.

My initial thought was to get an EWC NCM-300, which seems to be the go-to board to update these older ST-*E boards, and I may still do that. However, it is worth noting that there is a spot on the wall with some thermostat wiring sticking out which I presume is a 4th zone (in a room with vents that I never had blow air). I will need to check in the furnace room if I can find those wires to verify, as well as verify if there is a 4th damper. In the case that the wiring is there for the 4th thermostat and damper, I'm thinking of going with an EWC BMPLUS-3000, plus the additional daughterboard for extra zoning. From the looks of both boards, it seems the hookups are almost the same.

I'm sure I have some other questions, but right now I just want to make sure either of those boards will work for my application without major work that will require I call an HVAC tech. As far as wiring goes, it looks fairly straightforward, with some extra wires on the old board I'm not sure yet where they will go.

1. Besides the ability to add the extra zoning board to the BMPLUS, what differences do the NCM-300 and BMPLUS-3000 have?

2. Are either of these boards direct drop-ins for my ST-3E?

3. Do these boards require I update the thermostats at the same time with ones with heat-off-cool ones? I already have the honeywells ready to install, just wondering.

I'm sure I will have some more Q's as I learn more about the process. Here is a picture of my board for reference:

I haven't investigated the wiring beyond taking that photo, but I will take a closer look next time I'm in there to see if I can trace those wires to where they go, and figure out what that wire nut is doing. Thanks in advance!
Old 06-28-20, 12:08 PM
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1) I've never used an expansion board to go over three zones.
2) pretty much direct drop in.
3) When you change the board at least put in the #1 stat.

Looks like nine cables.
There are three for the dampers.
There are three for the stats.
There is at least one that goes to the equipment.
There should be one that goes to the transformer.
All cables must be marked.

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