Atmos Energy HE26 - Manual (Page 21)

Controller Label and Associated Terminals
Note: Terminals X4/11 & 12 are available for OpenTherm modulating stat.
5.3.1 24V dc Electrical connections
24V dc Terminals X4
Description Connector X4 Remarks
Room stat 6 - 7 6= +24Vdc
Outside temp
sensor 8 - 9
OpenTherm
modulating stat 11 - 12 6 - 7 not used
Frost stat 6 -7 Parallel through
room stat
Power 24Vdc
(3VA) 6= +24Vdc, 9= -.
Notes
1. Under no circumstances must any electrical
power be input to the room thermostat terminals.
It is a volt-free switch.
2. Care must also be taken to avoid induced
voltages caused by the running of the thermostat
cables along side mains voltage cables.
5.3.2 Volt free Room thermostat on/off
1. Connect the room thermostat. See § 5.3.1.
2. The terminal block for the connection for a volt free room thermostat, or time clock, is X4 on the control panel. The terminals
are wired to the input circuit of the control unit, which has its own 24V dc ‘wetting voltage’ .
3. If using a room thermostat with heat accelerator, this must be set at 0·1A.
4. The maximum permissible resistance of the room thermostat circuit and cable is 15 Ohms.
5. Where a 'wireless' room thermostat is employed, consult the manufacturer’s instructions for installation.
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