[off topic] 2gig ct100 thermostat to buderus logamax heater connection


This is rather off-topic , but I need help and I thought someone here may have the answer.

I am trying to connect my 2gig CT100 Thermostat to a Buderus Logamax heater.

I can control the heater when the ct100 is powered with batteries but when I try to get the power from heater I fail.

First of all, the CT100 requires 24V (ac) to power and the heater has 24V
On the heater there are 4 connections on the control panel. Let me call them w1,w2,w3, w4 from right to left.
w1 and w2 are looped when there is no thermostat connected (original heater installation with no thermostat)
Today I realized that heater also heats when w1 and w4 are looped. So either w1-w2 or w1-w4 should be looped by the thermostat when in heat mode and target is set to something above measured.

when I measure ac (v) between w1 and w2, I read 26V. (w1 is +)
when I measure ac (v) between w3 and w4, I read 3V (w3 is +)
when I measure ac (v) between w1 and w4, I read 27V (w1 is +)
when I measure ac (v) between w1 and w3, I read 23V (w1 is +)


On the thermostat I have following connectors:


In my previous heater connection (Baymak) I was using the same thermostat with 3 wires.
W and RH were used to loop the heater. C was used to receive external power (I am not sure if GND or Live)

Now, I don’t know which connector on heater is for W, RH and C on the thermostat.
Any ideas ?


the model of the heaater is logamax U022-22K