Changing a Central Heating programmer (Danfoss to Drayton)

[Payney1238]

Please help..

I have a problem swapping over a central heating programmer. Right, at the minute i have a Danfoss CP series programmer (and to be honest it's old fashioned and not the best!!) sooo i though i would change it to a new 'all singing all dancing' Drayton Tempus series (7) - i made sure i got one that was compatible so it would only be a 10 minute job!! - According to the packaging both have a grade A which means they are compatible without the need for any additional wiring. So i change them over, switch the fuse spur back on and set the new programmer timing up..all appears to be good. But then once all set up within a few seconds, the boiler starts up.. even though the programmer is showing CH OFF & HW OFF, both lights are also off.. the radiators at this point are starting to get warm. i then checked the time settings, and all are correct.

Why could this be, please help!!!

Any ideas?

p.s - i then put the old danfoss one back on and everything worked fine.

 

[gas4you]

Sounds as though they are not really compatable.

Check the settings on any dip switches.

Can't stand Drayton controls, you would have been better off replacing it with a new Danfoss FP715Si.

 

[Aquaheat]

Hi, i have checked the compatability of the programmers and it does show that they should be a one 4 one swap, the only difference being that you no longer need an earth. Is it possible to supply the exact model of the existing programmer?

Also it could be a faulty new programmer. Test to see if you have continuity across the pins on the back of the programmer. With it removed it should read:

L - 1 = continuity
L - 2 = continuity
L - 3 = no continuity
L - 4 = no continuity

If you get continuity across 3 or 4 then the boiler will fire and the programmer is faulty.

 

[Payney1238]

Thank you very much, apprieciated. well my first thoughts were that it was a faulty programmer but just wanted a second opinion.. the actual model of the existing programmer is the Danfoss CP715 and the new model is the Drayton Tempus 7. As you say, i've made sure it's compatable so this shouldn't be a problem. I will test to see if there is continuity and if not replace the programmer. It does seem very strange that the existing programmer works fine, but this one doesn't so this would suggest that the wiring is fine and no changes are needed as i first thought.

Let me know if you have any flashes of inspiration!!