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UPDATE:

I was able to wire a C-Wire to the Ecobee. So now I got 24 Volt at the Ecobee. But it still won't run.No sign of action at all. Maybe because I got no green connection? Any ideas?

We relocated from Germany to the US and with the upcoming Autumn I try to make improvements on our temperature management. Our house has three zones with two furnaces. The single zone I was able to connect to an ecobee, although there was no C wire. But the PEK terminal that came with the ecobee helped me with that.

The other two zones are connected to the Mastertrol Mark V. For I got very limited knowledge about this system I better ask:

There is a cable (5wire)connecting the MarkV and each Thermostat. I hope that RWY are connected according to the typical scheme in these systems. If so I need C and Green. The wires are there hanging around the Cable.

I wonder if:

I can grab C from 1 or 2?

I can get green by connecting to the green cable on the left?

Maybe a stupid approach but hey! 55 years we had a water based heating system - this is 100% new to me….

Ot another approach: any idea how to wire that?

Any help is well appreciated!

Wiring Diagram

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LarsN Reimann
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  • Don't connect up green at all. This system is not designed for that. It has the raw connections side on the left isolated from the connections on the right that connect to thermostats. – Kevin Cathcart Sep 29 '22 at 16:19
  • This whole thing basically looks like a normal thermostat to your heating and cooling system, but this box is responsible for opening and closing zone dampers, and passing through the command for heating and cooling as needed. (Likely alternating between zones if multiple are calling). – Kevin Cathcart Sep 29 '22 at 16:41
  • More modern versions like Honeywell truezone exist, which support passing though commands for the green wire, but there are damper compatibility concerns. You have 5 wire dampers, and honeywell is designed for 2 or 3 wire dampers. If you have Trol-A-Temp dampers they are probably not compatible. Special wiring would be needed if you have Zone-A-Trol dampers. – Kevin Cathcart Sep 29 '22 at 16:43
  • Ok, here you lost me regarding understand what you are talking about. As far as I understand I will need green to connect an Ecobee. Any way you can see to solve that? – LarsN Reimann Sep 29 '22 at 16:55
  • The green wire is for the fan control. You don't need it, as this zone controller handles that automatically. You simply lose out on the ability to set the fan to run continously. You really can and should leave the green wire unconnected. Trying to connect it to the green wire on the left will not have the desired result, as those connections are isolated from the ones on the right. – Kevin Cathcart Sep 29 '22 at 17:47
  • But when you set up the ecobee, it will complain about not detecting a green wire. That is fine. You simply need to manually configure wiring and lie and say the green/G wire is connected. This need to lie is a safety feature to avoid damaging more common setups where the blower is not automatically enabled when calling for cooling. In those common setups not having the green wire connected could damage the AC. This is not one of those setups, so telling it that the green wire is connected when it is not is safe, and harmless, except for inability to set the fan to always blow. – Kevin Cathcart Sep 29 '22 at 17:54
  • Alternatively you can upgrade to a newer zone controller that supports green wire connections for the remote thermostats. (Honestly I would be very tempted, as that system is quite old), but as mentioned your dampers may not be compatible with newer systems. You would really want to discuss that option with an HVAC technician. – Kevin Cathcart Sep 29 '22 at 17:57
  • Cool, thank you so much! For I am not the landlord here, I would need to ask him about that. Maybe I can convince him. If not this sounds as a way to go. Is there a way to double-check after installation? Damaging the system would be a bad result for me. And as you see: I am not very confident in what I am doing here... – LarsN Reimann Sep 29 '22 at 18:13
  • Yeah, after installation, set all other thermostats to not call for heat or cooling (either off, or set to a higher temp than inside for ac or a lower temp than inside for heat), and set the new one to call for AC. Wait a minute for things to kick on, then see if the blower fan is running. If it is running, then all is good. If the AC compressor (probably outside somewhere) is running but the blower fan is not running, that is the bad situation, in which case, turn off, and undo your changes. – Kevin Cathcart Sep 29 '22 at 18:29
  • Having it run w/o blower for a minute or two is not a big deal, but letting it run for say 15+ minutes could cause damage. – Kevin Cathcart Sep 29 '22 at 18:34
  • Kevin, thank you so much. I think I know what to do now! Happy feelings. In some days I come back here and tell what happened.... – LarsN Reimann Sep 29 '22 at 19:16
  • Naaa - doesn't work so far. I found 24V on #1. Connected blue as C-Wire and measured this at my cable before installing the Ecobee. Was ok, 24V between red and blue. But after installing the Ecobee remains dead. Any ideas? – LarsN Reimann Oct 01 '22 at 14:52
  • And just realized that the heater in the zone I am working on is running.... – LarsN Reimann Oct 01 '22 at 14:53

1 Answers1

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Yes, 1 or 2 should provide a C (measure for 24v against R in each zone). And G may be accessible from the left-sided terminals. But you need to provide more pics of the actual wiring and a better description of the entire set up for a more thorough answer.

There was also a previous thread with this system:

Connection for C wire on Mastertrol Mark V zone control panel

diy_coder
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  • Thank you so much! This will help me. I just uploaded more pictures...What I don't understand: "measure against R". Could you explain that for a dummie? – LarsN Reimann Sep 29 '22 at 14:47
  • @LarsNReimann Use a multimeter in volt mode to measure between the T5 terminal of the zone you are replacing the thermostat for, and the 1 and 2 terminals. One of the terminals should measure about 24 volts, and the other should measure 0 volts. You want to connect the C wire to the one that measure 24 volts. (If you connected it to the other one, you would just be creating a second R wire). – Kevin Cathcart Sep 29 '22 at 16:06
  • Ha! That is what I need: just for somebody with no clue.... Thank you! Regarding the Green Wire I would tend to separate it from the System (left side of the box) and connect both green Wires leading to the Thermostats to it. This way I would think I don't mess up with the System. What Do you think about that? – LarsN Reimann Sep 29 '22 at 16:41