This is a TH104 from Aube. Very good unit. I have some TH101 for at least 7 years and they still work fine. I have a few TH104 and they are even better.
FIRST: Check to make sure that the maximum watts rating is not exceeded (at 220V -- 3500 Watts). This is written in the booklet that come with the termostat (likely also visible in the back of the unit).
You seem to have two baseboard on the circuit. Don't forget to Add their rated power.
SECOND: The only thing you need to do is to replace the two black lead from your actual thermostat with the two black lead of the Aube (no particular order). Everything will be fine.
On a 220V circuit, both wire are LIVE. You can thing that each wire bring 110V (reference to ground) and that add-up to 220 V. (Bi-phase or something similar to that). This is the reason for two neighbor breaker in the panel.
When off, the baseboards always receive 110 Volts (reference to ground). This is the reason for always turning the breaker off when working on most 220 Appliance even when switch-off by the thermostat. Otherwise, this is not a problem since the circuit is not completed and therefore, it can't consume any electricity unless you were to deliberatelly short-it to ground using the bare copper wire or your body. The thermostat sit on the second phase (110 Volts) that get "switched off" by the thermostat. To start heating, the thermostat complete the circuit and that it, the baseboard can heat. This is that simple.
NEVER TRY any other type of connection. If you can find one that work without frying the thermostat, you are likely to bypass the "OVERHEAT" protection of the baseboard or the thermostat itself.
THIRD: After looking at your picture... I will recommend that you take extra care of your connection. With a good connection, you should not be able to see any copper. The "MARRET" must hide all the copper pretty wheel and the connection must be solid. If there is still some copper showing it face, use electrical tape to insulate them well. If your marret is too small, change them for larger one. Usually the RED Marret are good for 3 #12 wire. In case of doubt, hire a professional. This is no joke since these connection handle a lot of current.
I don't know about Ontario. But in Quebec, a standard heating circuit will have a RED and a BLACK wire (Usually #12, sometime #14 gage). That does not change anything except that it is easier to understand that both wire are actually LIVE.
FOUR: Check the documentation for the TH104. Some of these thermostats has two operating mode. If you have a BLOWER in any of the baseboard, the TH104 must be program for it (if you fail to do it, you are likely to burn the blower motor). If you don't have any blower... Check anyway: if the thermostat came preset for a BLOWER motor, it is best to reverse it to "Passive Baseboard" mode.
ATTENTION: If you have a blower and that the documentation of the thermostat does not mention any setting for it (or that it support them)... You have the wrong AUBE model. Don't connect it... Exchange it.
