Problem with Danfoss FP715Si Programmer

[LittleTyke]

Simple on/off switch (or eWeLink) between Live in and central heating on will switch the heating on, (but not off if it's alrady switched on by the programmer).

It's not the central heating I need, but hot water, as it's costing a fortune to heat the cylinder in the airing cupboard with the immersion heater. It's mild enough still to use small-ish oil-filled radiators to heat just one room. In winter I spend most of my day in the south-facing kitchen anyway, which keeps fairly warm from cooking, the TV and even the weak sunshine streaming through the glass patio doors.

I've done a lot more research into the programmer, and programmers in general, and they really are simple. I even took the Danfoss off the backplate, after isolating the power, just to see what was inside. It's just a matter of pins that engage with spring clips on the backplate. No disconnecting of any wires needed. And a plug compatible alternative such as the Drayton LP722 should just swap out no problem. Toolstation locally even have one in stock for £89.98, which is probably more expensive than one could find elsewhere. But they are not open today.

This (you already know this!) is the internal wiring of the backplate/programmer:


So if I connected a temporary wire from Live to connector #3, that would switch on the hot water, yes? I would do this via a temporary inline switch e.g. off one of my table lamps, e.g.



Sounds doable?

How would I switch the hot water to OFF? If the DHW connector is N/C, which it apparently is, then just switching off the temporary inline switch should cause it to switch off the boiler?

 

[Avo Mk8]

So if I connected a temporary wire from Live to connector #3, that would switch on the hot water, yes?

Yes

How would I switch the hot water to OFF? If the DHW connector is N/C, which it apparently is, then just switching off the temporary inline switch should cause it to switch off the boiler?

Yes.
You don't need to use the "off" contact to turn the HW off. Once power is removed from 3 the HW will go off, so your suggestion should work.
The "off" contact is sometimes used with system boilers to provide power to boiler/valve(s), if heating & HW shouldn't be on at the same time.

 

[LittleTyke]

Yes

Yes.
You don't need to use the "off" contact to turn the HW off. Once power is removed from 3 the HW will go off, so your suggestion should work.
The "off" contact is sometimes used with system boilers to provide power to boiler/valve(s), if heating & HW shouldn't be on at the same time.

I decided to get a new programmer instead. I ordered the Drayton LP722 yesterday from Screwfix. It was delivered (for free) earlier this afternoon. I isolated the power, removed the Danfoss, checked the gravity/pumped link on the rear of the Drayton (it was already set to pumped), installed it, switched the power back on. Bingo! The clock was 4 minutes out, so I adjusted that. Then I used the Boost feature to switch on the heating and the boiler is now running and the radiators are nice and hot! I am one happy bunny, I can tell you!

 

[Moley]

Glad you are back up and running. Do you want me to take a look at the old unit and see if it's the simple fix that I think it probably is ? If it's fixable then it might be useful as a back up for you.

 

[GBDamo]

I wonder if these are getting fritzed by the power outages or over voltages.

Do you have surge protection @LittleTyke ?

Could be these Danfos controllers are acting as a canary, it possible other more expensive items are at risk of damage.

 

[LittleTyke]

Glad you are back up and running. Do you want me to take a look at the old unit and see if it's the simple fix that I think it probably is ? If it's fixable then it might be useful as a back up for you.

Glad you are back up and running. Do you want me to take a look at the old unit and see if it's the simple fix that I think it probably is ? If it's fixable then it might be useful as a back up for you.

Hi, Moley. Know what? I want shot of Danfoss! I now have the Drayton and it works just fine. However, I know you are keen to inspect the Danfoss CP715 and possibly find what went wrong with it during/caused by the power outage on 21/Dec/23, so I'm quite willing to post it to you on my dollar (second class, so that it won't cost me and arm and a leg), but I do not want it back! If you find something wrong with it, you could add a note to this thread to kind of round off the whole saga, so others coming here will maybe be enlightened. If you fix it and it is of any use to you, keep it and use it as you wish. I don't want any payment! The thing is pretty light, so it shouldn't cost me more than a couple of quid to post. Think of it as my thank you to this forum for all the good advice I've received over the past week. If you want to do this, I'll need your postal address, but don't post it in an open public forum. Send me a message to a temporary email address I created earlier: [email protected]

As soon as I receive an email in that inbox, I'll delete the email address. If you want, you can first send a dummy message so that I know it's you. I will then respond from my real email address.

Any problems, add another message in this thread.

 

[Moley]

That would be great. I love looking into faulty stuff and (try to ) fix them. I'll drop you an email now.

 

[LittleTyke]

I wonder if these are getting fritzed by the power outages or over voltages.

Do you have surge protection @LittleTyke ?

Could be these Danfos controllers are acting as a canary, it possible other more expensive items are at risk of damage.

This is the first I've heard of surge protection for domestic dwellings in the UK, so I did a quick Google and found out about it. As far as I know, my house does NOT have surge protection. Nor did my previous house in another part of the country. The 40 houses and bungalows on this estate were constructed by a local builder between 2003 and 2004.

Now whether surge protection would have helped in this case when there was a sudden, unplanned power outage due to the effects of Storm Pia, I don't know. However, none of the other items of electrical equipment in my house suffered. All came back in working condition when the power was restored 5 hours later. The equipment I'm talking about is: Samsung TV anno 2011, microwave, cooker, several computers (which actually in this instance were switched off), radios, approximately 30 LED downlighters in various rooms, the oil boiler itself. None of them took a hit. Only the Danfoss programmer stopped working.

I've yet to see how resilient the new Drayton LP722 programmer is in the event of another sudden power outage. Hopefully, it will survive okay.

When the power outage happened, it wasn't instantaneous, but intermittent. I happened to be standing next to the double oven and I noticed the time display flickering madly. Then the downlighters also started flickering. The TV went into standby mode, then came back on, then back into standby mode. And finally the power went. So any electrical susceptibility in the Danfoss could well have blown its PCB or something.

I do, however, have a UPS for each of my PCs, as we do get frequent power cuts out in the sticks, although the power supply has got better in the last five years or so.

 

[LittleTyke]

That would be great. I love looking into faulty stuff and (try to ) fix them. I'll drop you an email now.

Yep, got your email and have replied to you. I'll send that faulty Danfoss tomorrow, Saturday.

 

[brianmoooore]

Went into one of my properties with a FP715 today, to switch it permanently 'off', since the property will be empty for a couple of weeks.
Both red LEDs on, screen displaying time, but totally unresponsive to all the buttons. Don't know how long it had been like this, as the occupants hadn't mentioned anything.
Quick examination revealed that the 1 hour timer button for the hot water was stuck in, and after releasing it, full normal service was resumed.

 

[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.