Problem with Danfoss FP715Si Programmer

[brianmoooore]

But no, wait, on second thoughts, I'd have switched to another brand by now - they use a standard backplate and should be a simple swap.

This was something dreamt up by British Gas, IIRC, but unfortunately, they didn't specify it closely enough.
The backplates are similar, but differ in detail, so in practice it rarely works. Most significantly, the order of the connections can vary.
You might get lucky with some swaps, but I can't remember one myself.

 

[Moley]

Thanks very much for the offer. I will add a note to my diary to remind me when the heating engineer has replaced the faulty Danfoss. The last time it broke was March 2021. Where are roughly located? I'm in Lincolnshire. However, I really would like a different make of programmer now, because the Danfoss seems to be very unreliable. I have no idea why a heating programmer should fail so spectacularly just because of a power outage. Must be a very poor design, either with the PCB or the software. It would seem to me, as a retired programmer, that the one thing the manufacturer should test for is resilience during/after a power cut!

I'm in S. Wales, just north of Cardiff so I assume would need to be posted unless you fancy a long drive ;-)

My own unit is a Drayton LP522. It's worked fine for me so far.
EDIT:
Just checked the wiring and it 'should' be a direct replacement.

 

[Avo Mk8]

I don't have a clue how to do that!

Simple on/off switch (or eWeLink)

or a wire

between Live in

which is the terminal marked "L" on the backplate (mains live!)

and central heating on

which is the terminal marked "4" on the backplate

will switch the heating on, (but not off if it's alrady switched on by the programmer).

 

[LittleTyke]

Based on the experience of fitting and servicing programmers over a lifetime of doing so, I came to the conclusion that the CP715 is the most reliable and easily programmable unit out there. Whatever the internet says, I've never had a problem with a single one, other than what I stated earlier in the thread.
Still have five of them in service in my own properties.

So how come I've had three go faulty in several years? And other users on the internet have reported the same problem. Maybe your properties have never had a power outage!

 

[LittleTyke]

I'm in S. Wales, just north of Cardiff so I assume would need to be posted unless you fancy a long drive ;-)

My own unit is a Drayton LP522. It's worked fine for me so far.
EDIT:
Just checked the wiring and it 'should' be a direct replacement.

Posting it wouldn't be a problem. I'll search for that Drayton LP522 right now. Thanks. By the way, did you ever experience an unplanned power outage in a storm? Because that's what kills the Danfoss here nearly every time. Only once did it recover when the power came back on. And here in rural (very!) Lincolnshire we get power cuts almost whenever there's a storm. Mostly, the National Grid (formerly, here, Western Power Distribution) fixes it in a couple of hours, but last week it took them 5 hours.

 

[Moley]

Not had power outages due to storms for a long time. It's pretty reliable around here. What part of Lincolnshire are you in?

 

[brianmoooore]

Maybe your properties have never had a power outage!

Extremely rural where I am. All 11kV distribution lines, with transformers rarely serving more than two or three properties. Lightning strikes cutting the power for a couple of seconds are common, but because I'm served by a section that also supplies a main TV transmitter (which handles comms for most of N Devon), the breakers are arranged so that, unless the problem is very local, our section stays on.

 

[LittleTyke]

Further question: In the airing cupboard there are two switches on the wall. The top switch is for the immersion heater. But what is the bottom switch for? It is always switched on. I believe my heating engineer once told me to never switch it off. However, I did switch it off just now and the Danfoss LEDs went out! Ooh, I thought. Maybe I've found the secret fix! But when I turned the switch back ON, the Danfoss, as ever, turned its LEDs back on and the display is still blank. So the switch must have something to
do with the programmer, but what exactly?

 

[brianmoooore]

This is likely to be the isolator for the whole heating system.

 

[LittleTyke]

I'm adding the following picture so that anyone new to the thread can recognise the problem: