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JamesI, Handyman
Category: Appliance
Satisfied Customers: 2086
Experience:  I have repaired and maintained numerous items over the years, from fridges to freezers, radios to TV's.
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My Danfoss thermostat controller device used my bolier will

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Hi my Danfoss thermostat controller device used for controlling my bolier will not respond to commands input on the keypad at all... it is a CP 175... there are LED display setting showing the date and time but the red lights will not come on when selecting the programs for heating or water

Hi thank you for contacting Just Answer, my name is ***** ***** I will assist you today.

There could be a number of causes of the fault (faulty controller, faulty wiring or corrupt configuration).

I have struggling to find the technical specs for a Danfross CP175, can you confirm if this is a wired or wireless controller, and if there are any symbols other than the date and time displayed on the controller display?

Customer: replied 1 year ago.
it is hard wired, and there are symbols for the selected programs (off -heating, Auto - hot water) , but I am unable to change the selection using the buttons on the device ... it is not responding to the commands I input at all...The device is a CP175 2-Channel common timebase programmer for heating and hot water...
Customer: replied 1 year ago.
my mistake it is a CP715
Customer: replied 1 year ago.
further update the hand book I have is for a FP715Si

Thanks for the quick response, restarting the timer should clear any common fault.

The engineer manual can be found here, you could try placing it in the engineer mode by holding down the top 3 buttons (PROG, + and DAY) under the cover for 5 seconds, press the next button to cycle through the settings and it should go back to user mode.

The good news is this shouldnt be a boiler fault, the controller is just a relay which tells the boiler when to start, and would be unlikely to cause this issue, so the focus should be around the controller itself.

If placing it in engineer mode didnt work, the next step would be to check the dil switches on the back of the panel encase they have somehow changed, see section 3.2 of the attached manual. If SW1 and SW2 are both as per the manual diagram this is correct, and would suggest a hardware failure in the controller itself, as you will see by the manual its not a big job to change the controller, the important thing is to switch off the mains power before going need the cables.

Please let me know if you manage to get the unit working or need further guidance on replacing the controller.


Customer: replied 1 year ago.
Thanks James, I tried holding the buttons, but that didn't work then I noticed when I tried to remove the unit from the wll that the hot water selector lamp went on and off I have somehow managed by manipulation to get the unit working again and all selections are working as desired.... thanks for your help....

This sounds like a potential lose connection then.

With the power off check all the wires are secure within the screw terminal block on the back of the controller, if they are its likely to be a lose contact inside the controller.

Appreciative if you could rate the service received to date so I may close this case, unless you have any further queries.



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