Problem with Danfoss FP715Si Programmer

[Moley]

I had a bit of spare time today so had a look at the Danfoss that @LittleTyke sent to me. I only had a X2 capacitor and not the X1 that was in there originally but what the hell, let's live life on the edge Anyway, I chucked the new cap in, soldered on some fly leads (DON'T DO THIS AT HOME FOLKS), plugged it in and, well, let the picture talk for itself. Just got to order a correct X1 capacitor now.

 

[LittleTyke]

I had a bit of spare time today so had a look at the Danfoss that @LittleTyke sent to me. I only had a X2 capacitor and not the X1 that was in there originally but what the hell, let's live life on the edge Anyway, I chucked the new cap in, soldered on some fly leads (DON'T DO THIS AT HOME FOLKS), plugged it in and, well, let the picture talk for itself. Just got to order a correct X1 capacitor now.
View attachment 112623

I replied to Moley separately by email. What a great contribution he has made to our knowledge of the Danfoss CP715 ! I just wonder whether this capacitor got overloaded when the power went out during the storm.

By the way, just as a matter of interest, can anyone point to the faulty capacitor in question? If another user gets the same issue and takes the unit to an electrician, maybe they can get it fixed cheaply. I don't think capacitors are expensive.

 

[brianmoooore]

@Moley Is the capacitor the main volt dropper for the PSU? If they're prone to slowly failing, I wonder if they could be responsible for the dimming LEDs?
I have one where the LEDs are almost out. I might just open it up and check that capacitor.

 

[Moley]

By the way, just as a matter of interest, can anyone point to the faulty capacitor in question? If another user gets the same issue and takes the unit to an electrician, maybe they can get it fixed cheaply. I don't think capacitors are expensive.

In the photo it's the square(ish) yellow block. The original was a grey colour.
I'm having problems finding a supplier that will supply single caps at a reasonable price. RS want £2 each but minimum of 5, Farnell minimum of 10, CPC want an order of 5. I've looked on Ebay and they are all £5 +. A class X2 is much cheaper.

 

[Moley]

@Moley Is the capacitor the main volt dropper for the PSU? If they're prone to slowly failing, I wonder if they could be responsible for the dimming LEDs?
I have one where the LEDs are almost out. I might just open it up and check that capacitor.

Yes, it's the main volt dropper. I don't know about dimming the LEDs. In the case of the one I have here the LCD went before the LEDs.

 

[LittleTyke]

Yes, it's the main volt dropper. I don't know about dimming the LEDs. In the case of the one I have here the LCD went before the LEDs.

Having just read a bunch of stuff about capacitive dropper power supplies, is Danfoss going the X1 route to avoid the cost of a proper switching power supply to drop 230V to 5V? In one video the guy says near the end "That is why capacitive dropper power supplies are super dangerous and should always be positioned inside a closed housing."

 

[Moley]

I would say 'super dangerous' is a bit of an exaggeration. They don't isolate the output from the mains input so yes, they should be enclosed. Apart from that they are no more dangerous than any other. It's not just Danfoss that use them. Dropper caps are used quite a bit in enclosed equipment. I would imagine you will have quite a few scattered around the house especially if you have LED light bulbs, remote sockets etc. If a switch mode power supply was used it would increase the size by quite a lot too.

 

[Moley]

I've just checked the cap I took out. It should be 474nF. It's reading 327nf with an ESR = 3.4ohm

 

[LittleTyke]

I would say 'super dangerous' is a bit of an exaggeration. They don't isolate the output from the mains input so yes, they should be enclosed. Apart from that they are no more dangerous than any other. It's not just Danfoss that use them. Dropper caps are used quite a bit in enclosed equipment. I would imagine you will have quite a few scattered around the house especially if you have LED light bulbs, remote sockets etc. If a switch mode power supply was used it would increase the size by quite a lot too.

"If a switch mode power supply was used it would increase the size by quite a lot too."

Yes, I did wonder about that.

 

[The Winetaster]

Excellent review and guidance, just read the whole thread as my programmer has just set the same issues:
1) Fixed screen with set time
2) Unresponsive selection buttons.
3) Red LED’s for DHW and CH permanently on

Will now order a replacement as this CP715 is 25 years old and I think it’s had its day!!

Thanks for the detail.

Especially like the "Never take a sleeping tablet and a laxative at the same time!!" comment from Moley