I've had a thermostat(2xAAA powered) for my gas heater wired via two wires from the second to first floor.

My question is I'm looking into the actual wire that is in the wall and it looks like either an alarm/Ethernet cable that was used.

I would want to upgrade to a smart thermostat but most seem to need a power to be fed to it. Can't really find anything battery powered to align with what is actually already set up.

I found some info on the cable imprinted ELAN A.F. CEI 20-22 III CEI 36762 C-4 (U0=400V) searching around found some kind of a certificate perhaps detailing more about the cable from the manufacturer
Cert PDF. It has 8 color coded cables inside apart from that I really don't know if it can handle for example live current to power a thermostat?

If the wires are potentially too thin. Maybe using the rest 6 unused cables in pairs so that the current flows through not a single but multiple? I don't really know if electricity works like that sorry.

Just thinking of ways if this cable can be re-used for a potential upgrade or do I need to possibly look into a different solution?

Thermostat back panel

thermostat wiring

heater specs

heater wiring

Heater wiring diagram

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    Luke, with all due respect, and I really hate to say it, but have to this time....based on your post, you have no idea what you are doing. Except for line voltage T-stats controlling baseboard heaters or other electrical resistance heaters, nearly all are low voltage (like 24v), powered by the furnace, heat pump, etc. There is nothing wrong with someone using multi-conductor, small gauge cable for low voltage T-stats, they aren't very particular. If you want more help, provide the make/model of your furnace and the new t-stat you are trying to install. Maybe time to call a pro. Commented Sep 8, 2021 at 19:59
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    Hi George, thanks for the answer . Yeah never did advertise as a pro and dont really want to come off as one. The gas heater is a baxi duo-tec compat+ and the current thermostat is a Siemens RDE 100.1. I could attempt to get some photos of the wiring. I dont yet have a new thermostat as im trying to find out what might work with this current setup. Just that Ive seen some advertised with inputs for 230v . Thats why I was worried of the small gauged cables if they can handle it. But yeah Ill probaby need to find consultation if all else fails.
    – Luke Keude
    Commented Sep 8, 2021 at 20:18
  • Some baseboard heaters are controlled by thermostats that actually have to switch the 240v power with relays. But most HVAC/furnace equipment is controlled with a low voltage 24vac. It sounds like that's what you have because of the small wires, and in that case, almost any wire should work because its a low-current control voltage.
    – JPhi1618
    Commented Sep 8, 2021 at 21:42
  • Can you open up your boiler and post photos of how it is wired? Commented Sep 8, 2021 at 23:30
  • Thanks for the answers. JPhi1618 yeah that is what I am hoping for that the current wires can be reused. @ThreePhaseEel I have added the photos to the bottom of the main post.
    – Luke Keude
    Commented Sep 9, 2021 at 5:32

1 Answer 1


Bad news: it appears that your boiler is using 230V controls

The bad news is that from your current boiler wiring, we can tell that your boiler is using a 230V control scheme. This means that you'll need a thermostat that's capable of line voltage control, as well as to replace the existing wiring with wiring that's suitable for line voltage use in your country, unless you wish to switch over to using Baxi's own proprietary remote control.

  • Understood. Im then going to have to look into some wireless solution then as there is no real way to redo it currently. Or I can find a similar thermostat like this one that works on batteries and sends the signal via the same wires. Unless Im wondering if I can perhaps find maybe a thermostat that works ona 24V range and power it via a separate source? So then it just still sends the signal via the two wires but gets power from somewhere else?
    – Luke Keude
    Commented Sep 10, 2021 at 5:15
  • @LukeKeude -- most line voltage thermostats will want either batteries (like yours) or a line voltage power source Commented Sep 10, 2021 at 11:40

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