HELP ! bleeding out a bit...ST->NCM->Tstat options

Post your questions and comments here.
Post Reply
m303803
Posts: 1
Joined: Mon Jun 12, 2023 11:05 pm

HELP ! bleeding out a bit...ST->NCM->Tstat options

Post by m303803 »

Hi, I'm an engineer who isn't afraid to admit I am in over my head. Forced natural gas Hot Air/outside condenser AC, no water, 2 zone system today controlled by Building 36 system/thermostat.

I never thought this could/would be so complicated. Anyhow, through a series of interactions I have lost trust in the local dog petting HVAC company everyone here in suburbia CT uses. At one point they told me there were no other options than to use their $20/month subscription system in order for me to have a wi-fi enabled heating/cooling system. Turns out they may be right ! Rather than trying to get a relationship with a new HVAC company, I talked to my electrician about the upgrade to decouple myself from this subscription service knowing there should be plenty of other options. He was fine to help and said he has done this before many times. Somehow I now find myself almost $1000 dollars into this job and no closer to a solution ! There was a bit of ready fire aim on my part. What can I say I have two small children and am an engineering director at a major jet engine manufacturer and I'm grateful for enough time during the day just to use the rest room. My electrician trusts the fact that I'm an engineer who usually does good research and knows what i want - we have a good partnership that way. So I ain't gonna come down too hard on him for not thinking this out more - it would be uncharacteristic of our relationship. First thing first he tells me to do is to call EWC and find out what my options are for the board I have. They tell me i need to upgrade from ST-2E to NCM300. OK so i buy that. I then pick up two honeywell smart wifi Tstats and I think I'm going to be in business. Come to find out, my zone one tstat has 6 wires. My zone 2 tstat has only 3 wires. Literally only three wires plumbed up from cellar to 2nd floor. Honeywell says we can use their tstat in zone 2 if we use a power pack and only use heat. Well what good does that do for me ? I then go down the path trying to find a tstat that would be battery powered, wifi capable that only needs 3 wires to operate. Seems like it's a unicorn that only exists in Building 36 design space ? how can this be ? I could strangle the guy who only ran a 3 wire bundle up whenever they put this system in. House was built in 2005 but new furnace put in in 2018, I expect with existing control/wires. Anyhow...i am appealing to this community for any options that may come to mind with this set up. Which appears to be 'as designed' for the ST-2E........zone 2 only called for 3 wires on the wiring diagram and by God thats what they did. I did just almost for the hell of it purchase a Sensi ST55 mart thermostat as it seems to be the only battery wifi one i could find. I suspect the three wires will be limiting there as well however..... Am I on the path to the biggest semi-DIY mistake of my adulthood here ? Save me :lol:

Relevant pics attached.
You do not have the required permissions to view the files attached to this post.
Steven W.
Posts: 104
Joined: Tue Jun 25, 2019 9:13 am

Re: HELP ! bleeding out a bit...ST->NCM->Tstat options

Post by Steven W. »

When you have the time please give me a call.

--
Steven R. Weisneck

HVAC Zoning Technician
Tel: (732) 446-3110 Ext. #461
tech@ewccontrols.com
sweisneck@ewccontrols.com
www.ewccontrols.com
M-F 8:00am - 4:30pm
Steven R. Weisneck
Technical Engineer
Tel: (732) 446-3110 Ext. #461
www.ewccontrols.com
sweisneck@ewccontrols.com
Vishal5310
Posts: 1
Joined: Sun Feb 11, 2024 2:58 am

Re: HELP ! bleeding out a bit...ST->NCM->Tstat options

Post by Vishal5310 »

I am in similar situation. I have only 3 wires routed to second floor thermostat. I plan to use ecobee thermostat. I already upgraded my st2e board to ncm300. Installed ecobee thermostat on first floor because it had 5 wires I could connect my ecobee thermostat to. I just don’t know how to proceed with second floor thermostat with only 3 wires coming out of wall.
Post Reply