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How to replace a room stat

RF Lightings step by step guide No. 2

How to replace a mechanical room thermostat with a digital programmable room stat.

The photos are of a sunvic (Same as honeywell) stat being replaced with a Danfoss programmable stat.

Step 1

Select the stat you wish to replace.

Step 2

Switch off the mains supply to the stat.
Remove the front cover and dial knob.

Step 3

Carefully expose the connections by hinging the translucent cover open.
Use either a multimeter or voltage indicator to verify that all the connections are dead.

Write down which wire connects to each terminal, or take a digital photograph.

Step 4

Undo the terminals, and remove the old stat from the backplate.

Step 5

Disconnect the earth from the backplate, and remove the backplate from the wall.

Step 6

Fix the backplate of the new stat to the wall

Step 7

Connect the permanant live to the common terminal of the new stat.
(In this case the brown wire to terminal B)

Step 8

If the cores of your cable do not have coloured sleeving on to identify their function, then the black (switched live) should be sleeved brown, and the grey (neutral) should be sleeved blue.

Step 9

Connect the switched live (black wire with brown sleeving) to the normally open (N/O) terminal.
(In this case it is terminal c)

Step 10

Place the neutral wire into a piece of strip connector, as the digital stat does not require a neutral.
Make sure the connector is positioned so it does not foul any part of the stat when the front is put on.

Step 11

If your stat does not require an earth connection, then connect the earth wire into a piece of strip connector.
If your stat  does require an earth connection, then connect the earth wire to the earth terminal.
Make sure the earth wire is sleeved with green and yellow sleeving

Step 12

Clip the front part of the stat onto the back plate.

Step 13

Install the batteries.

Step 14

Fit the battery cover and programme the times.

Step 15

Switch back on the electicity supply to the boiler, and check for functionallity.

Step 16

Make your self a nice cup of tea. You deserve it!

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