Danfoss Room Thermostat

18 May 2007
Reaction score
United Kingdom
Hi Guys,

I replaced an old Sunvic TLX 2259 Room thermostat with a Danfoss TP7000 RF and RX1 Receiver.

The original Sunvic thermostat was fed by two 2.5mm two core and earth cables coloured black and red. 1 red wire was connected to Terminal 1 on the Sunvic, I red wire was connected to Terminal 3 and two neutral black wires were connected to Terminal 4. Two earths were connected to the earthing point on the backplate. A Danfoss FP715 Programmable Timer set to 7 days looks after timing the CH Channel and the HW channel.

I looked up the Sunvic Wiring on the Danfoss Conversion guide for the TP5 Thermostat - on the basis it should be simlilar. I wired the RX1 in as follows: Red wire from Sunvic Terminal 1 (On) to Terminal 3 (Zone 1 ON) on the RX1, Red wire from Terminal 3 of the Sunvic (Com) to Live (Electronics) on the RX1 and the neutral paired with the red wire from Terminal 3 to Neutral (Electronics). The remaining Neutral, I have isolated on the assumption it is not needed. I have also run a red wire between Live (Electronics) and Terminal 2 of the RX1 as required by the wiring diagram.

Everything between the thermostat and the RX1 is fine. However when a demand for heat is established, although the Channel Light on the RX1 is lit, the boiler does not fire (The FP715 CH setting is 'constant' as advised by Danfoss). Also the Hot Water no longer works either.

Can anyone help? As far as I can see the wiring is correct but maybe the isolated neutral is an issue ?

I'd be grateful for your advice before I give up and put the Sunvic back!!
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