Strange thermostate wiring?

[felixrosbergen]

Hi All,

I'm looking into my thermostate wiring and found something odd that i wanted to get some input on. I don't know if the installer did this on purpose or if it's just random.

I have a 2 zone single stage heat/cooling system (Lennox system with EWG control and Honeywell simply T-state.

Zone 1 and 2 are different wired.

For zone 2 the R (Red), Y (Yellow), G (Green) and W(White) are indeed wired as such.

For zone 2 a blue wire is used instead of the W.

At the panel it all seesm to connect as normal so they just used the blue for whatever reason. Is this normal to use a different color for the different zones perhaps?

I think i can easilly swap the blue for the white on each end and it would be just as intended.

For thr 24V to the Aprilaire, can i take this from the furnace controller board? The 8811 protocol adaptor doesnt seem to have this output.

Also looking into what colors of the cat5e to use for which conneciton between the 8811 and the 8870 T-stat.

Any input greatly appreciated.

 

[felixrosbergen]

I just noticed the white wire was stripped...maybe they had a wire break and took the blue as an alternate...

 

[felixrosbergen]

ok...when try to put the white where it should go my HVAC control panel coughs and resets...so i'm guessing something is not right there...there is also an extra brown wire, but using that one resulted in the same problem. Taking a resistance reading between the white and brown while they are both not connected to anything shows close to 0 ohms...so the white and the brown appear to be shorted to each other somewhere...but it seems a stretch that one or both would also be shorted to another conductor...

So i guess i'll be using some conductors from the cat5 that runs from the ELK to the thermostate to get the 24v to the 8870. I have however no 24V anywhere near my alarm panel. I don't really want to introduce another transformer since i'd be building in more potential points of failire into the critical HVAC system. The HVAC and alarm panel are also not near each other.

I supposed i can run a new wire from the HVAC transformer to the ELK panel and from there send the 24V to the T-states.

Anybody know how much a T-state draws? Can i just run cat5 for it's 24v? Since the aprilaire protocol adapter only uses 4 wires i have 4 conductors in the cat5 available for 24v.

 

[dBeau]

Anybody know how much a T-state draws? Can i just run cat5 for it's 24v? Since the aprilaire protocol adapter only uses 4 wires i have 4 conductors in the cat5 available for 24v.

I'm not sure about the power draw for an 8870 (probably in the manual) but I do run power to mine over the cat5. Since two pairs were available I used both just to be sure.

At your current tstats, you might not have both a constant source of power and a common. Sometime you'll see this but most tstats dont need it. In heat only systems you'll usually just see the two conductors. For heat/cool, you'll see at least four in use but a five wire cable is pretty common. Checking both ends is really necessary. The colors are pretty standard but no guarantee.

In my set up, since I had to run the cat5 anyways, I used the existing tstat wiring to pull both the cat5 and a new 18/7 from the tstat location back to a can in the basement. I then ran new control wires from the hvac units to the same can. Now with everything in same can, the rest was easy. I used terminal strips to terminate and connect the controls and I used the aprilaire distribution panel to terminate the cat5.

 

[Lagerhead]

Thermostat draw ought to be quite small as it's just the electronics and the relays -- a few watts each.

If you do tap the 24VAC transformer for thermostat power, consider putting a small fuse somewhere in the line, but close to the transformer, just in case.

It's probably not a good idea to take power (parasitic) from the EWC controller itself. And if you did, you would still have to run a common wire anyway, because normal HVAC control switching does not require it, and so the wiring does not bring the common terminal out to the thermostats.

 

[felixrosbergen]

Hey Laged,

Ofcourse i read you post after i completed the tastk....

The EWG control does have Common output for each Zone. The wiring that was already in place had some issues but was essentially 18-7 which is what would be necesarry for a 2 stage heat/coolng system. Since i only have 1 stage i have 2 extra conductors in there.

I took the common from the EWG control and so far both stats have been working fine. The power supply for the EWG seems pretty heavy duty (actually hardwired to a box), but then again it's also driving the air valves for the zone controls.

Appreciate your input. I'm gonna leave it as is for now unless i run into issues.