Danfoss CP715Si error codes



Hi. I have a Danfoss CP715Si which has been working fine for years but recently I came back from holiday and the hot water wasn’t working. I reset the controller by poking the reset button and it worked, but it flashed up 706 n02 before the clock came back on. The next day again the hot water didn’t come on (even though the red light was on in the controller) and I reset it again and then it worked again, but with the same message 706 n02.

I assume this is an error code but I can’t find out what the different codes mean. Any ideas, as I can’t keep resetting the device every time I want hot water?!!

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I wonder if that is initialisation code prior to dusplay.
Is the other channel working?
If it is then possible relay is knackered
I seem to remember that n01 is the initialisation code, so I would imagine that n02 is possibly just confirming the 'reset' that has taken place and if so has no relevance to the fault.

There several faults that could cause this symptom. Here are some I have found:

On a couple of occasions, I have seen this if the programmer is controlling an 'S Plan' type system where the hot water is controlled by a 'two port motorised valve' the programmer operates the valve but the microswitch inside the motorised valve is intermittent, so it doesn't always start up the boiler. Switching the hot water on and off a few times (or performing a reset) can cause the valve to move enough to get it to operate the the microswitch and the boiler will fire up. However, you haven't given any details about the system the programmer is connected to. So, you may not have an 'S Plan' in which case this is irrelevant.

The CP715Si may be faulty, so that whilst the red light is coming 'on' the internal relay isn't actually providing an output that does anything.

So the first step is to determine whether the CP715Si is actually providing a switched live hot water output when the hot water should be 'on' or not. This is not a difficult job for someone who has a basic understanding of electrical circuits and is competent in the use of a multimeter.

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