danfoss SET3E contlolled heating system ?

We had a power cut when it came back on my danfoss set 3e didn't come back on

Mick
November 2021

My electric went out and when came back on again my danfoss set3e had not come back on I can't turn heat on there is no lights are timer working any ideas of to fix are do I intall new unit?

Barry
January 2017

Check the 2 switch wires are not mixed up ( in your programmer ) and it's always calling for heat instead of hot water . Possibly wired wrong ..

Michael ( electrician )
August 2016

OK, so: Is the controller telling the heating to run, when it shouldn't be telling it that, or is there a fault in the rest of the set up that means the heating runs?

There's a manual here:

http://www.gasapplianceguide.co.uk/Danfoss%20PDF/Danfoss%20SET%203E%20Install%20and%20User.pdf

You an check the switch with a battery and bulb or maybe a multimeter on ohms. Take the SET3 off the wall and check for a short between pins 4 and 5 on the back of the controller (see manual). If there's a short, get a new programmer.

The other possibility is if you have a diverter valve and it is stuck in "Heating" position. With that kind of set up, the controller calls for heating but that only makes the diverter valve run. When the diverter valve is in the right position it turns the boiler and / or pump on. If the valve is stuck in "Heat" the boiler will run all the time.

You 'll need to find it and check. There's usually a manual lever you can twiddle. There's some generic info here:

http://danfoss-randall.co.uk/PCMPDF/Introducing%20Motorised%20Valves%20Part%204.pdf

If you know what make/model yours is, you should be able to find info online. (It may be an integral part of the boiler)

XXX
July 2016