Problem with Danfoss FP715Si Programmer

[BeatlesForever]

Re: Danfoss FP715Si Programmer
Anyone have any direct experience with this unit?

NB: There are quite a lot of posts online about this issue, but nothing I have found that has found the cause.

This Danfoss FP715Si Programmer that works fine.
But the following situation occurs from time to time:

The screen goes blank and both red lights stay on permanently,
and none of the buttons work, so the heating & hot water are powered continually.

I've not tried the reset, because this will change all the settings to default.
(NB: But those online who have used default say that it made no difference)

But if I power off (the main programmers power) for a while, then when I power back on, it usually works as normal for days.

NB: This unit’s install booklet says:

a: It has battery back-up, but doesn’t mention anything about how to change that battery,
or what would happen if the battery starts to fail.
No battery is visible, so I guess it's inside on the main PCB.

b: This also has a 'Service Interval Timer' (SIT) which when set to on, may do something similar to this issue?
Q1: Anyone used SIT and knows what then happens when a service is due?

NB: The SIT is used primarily for landlords, to force the tenant to seek a boiler service.
But this can’t be set to on, because this unit has been working fine for many years.

Q2 So is this issue a:
Symptom of a battery failure?
or something else,?
or a faulty unit?

Anyone know the solution?
Many thanks.

 

[brianmoooore]

Installed dozens of these, and never come across anything quite like you describe. What can happen is that any of the four push buttons can catch on the edge of the hole around them when pushed in, keeping the button in. Not obvious when it's stuck, and if more than one are, the strange things can happen.
Only other fault I've had with these (apart from the pathetically weak hinge on the flap) is that the display gets gradually dimmer over the years.

 

[BeatlesForever]

Installed dozens of these, and never come across anything quite like you describe. What can happen is that any of the four push buttons can catch on the edge of the hole around them when pushed in, keeping the button in. Not obvious when it's stuck, and if more than one are, the strange things can happen.
Only other fault I've had with these (apart from the pathetically weak hinge on the flap) is that the display gets gradually dimmer over the years.

Thanks Brian,
If you do a google search you'll see that it seems to be a common problem.

Have you ever set the SIT to on, if so, do you know what happens to it when it's time for a service?
The book says that it will disable all buttons, and the system will only operate for a portion of each hour.

 

[brianmoooore]

Thanks Brian,
If you do a google search you'll see that it seems to be a common problem.

Have you ever set the SIT to on, if so, do you know what happens to it when it's time for a service?
The book says that it will disable all buttons, and the system will only operate for a portion of each hour.

I knew I had the SIT instructions tucked away somewhere, which I downloaded after a google search a few years ago.
Found them, and see, to my surprise, that the source was this very forum, which I wasn't a member of back then.
A quick search of the forum comes up with this: service interval timer help! - https://www.electriciansforums.net/threads/service-interval-timer-help.100630/

 

[Jax_81]

Did you ever discover a solution to this problem, I’m having the same issue with mine!

Re: Danfoss FP715Si Programmer
Anyone have any direct experience with this unit?

NB: There are quite a lot of posts online about this issue, but nothing I have found that has found the cause.

This Danfoss FP715Si Programmer that works fine.
But the following situation occurs from time to time:

The screen goes blank and both red lights stay on permanently,
and none of the buttons work, so the heating & hot water are powered continually.

I've not tried the reset, because this will change all the settings to default.
(NB: But those online who have used default say that it made no difference)

But if I power off (the main programmers power) for a while, then when I power back on, it usually works as normal for days.

NB: This unit’s install booklet says:

a: It has battery back-up, but doesn’t mention anything about how to change that battery,
or what would happen if the battery starts to fail.
No battery is visible, so I guess it's inside on the main PCB.

b: This also has a 'Service Interval Timer' (SIT) which when set to on, may do something similar to this issue?
Q1: Anyone used SIT and knows what then happens when a service is due?

NB: The SIT is used primarily for landlords, to force the tenant to seek a boiler service.
But this can’t be set to on, because this unit has been working fine for many years.

Q2 So is this issue a:
Symptom of a battery failure?
or something else,?
or a faulty unit?

Anyone know the solution?
Many thanks.

 

[BeatlesForever]

Did you ever discover a solution to this problem, I’m having the same issue with mine!

Hi Jax,

I've discovered that the fault only happens if I have the heating & the hot water set to come on automatically together, eg:

Originally:
They were both set to come on about 6am,
and the water would go off after 1 hour,
(or sooner if the hot tank stat goes off)

But the fault doesnt happen if:
I set it so that only the heating comes on automatically, and then later, I manually switch off the heating, while I heat the hot water for 1 hour.

I've checked the PCB inside the programmer and there are no obvious problems.

If you look at the wiring diagram of the programmer, there is a connection via the cylinder stat's 'satisfied' contact, that feeds to the 'grey' terminal of the valve, and also to back to the HW 'common' on the programers first HW (off) terminal, so it may be that the fault is either with the valve or the programmer.
If its the programmer, then it may be a failed isolating diode etc, but it's difficult to know without a schemit diagram of the programmer.

 

[LittleTyke]

Re: Danfoss FP715Si Programmer
Anyone have any direct experience with this unit?

NB: There are quite a lot of posts online about this issue, but nothing I have found that has found the cause.

This Danfoss FP715Si Programmer that works fine.
But the following situation occurs from time to time:

The screen goes blank and both red lights stay on permanently,
and none of the buttons work, so the heating & hot water are powered continually.

I've not tried the reset, because this will change all the settings to default.
(NB: But those online who have used default say that it made no difference)

But if I power off (the main programmers power) for a while, then when I power back on, it usually works as normal for days.

NB: This unit’s install booklet says:

a: It has battery back-up, but doesn’t mention anything about how to change that battery,
or what would happen if the battery starts to fail.
No battery is visible, so I guess it's inside on the main PCB.

b: This also has a 'Service Interval Timer' (SIT) which when set to on, may do something similar to this issue?
Q1: Anyone used SIT and knows what then happens when a service is due?

NB: The SIT is used primarily for landlords, to force the tenant to seek a boiler service.
But this can’t be set to on, because this unit has been working fine for many years.

Q2 So is this issue a:
Symptom of a battery failure?
or something else,?
or a faulty unit?

Anyone know the solution?
Many thanks.

This has happened in my house at least three times over the past few years. My Danfoss programmer is the CP715, very similar. It ALWAYS happens after a sudden/unplanned power outage during stormy weather. It happened yesterday, Thursday 21/Dec/23. The power was off for 5 hours due to a high voltage line snapping somewhere.

What happens is, when the power comes back ON, the Danfoss shows no LCD display and both LEDs are permanently on. THERE IS NO RELIABLE WAY I HAVE FOUND TO FIX THIS PROBLEM. The reset button does nothing, doesn't even click. If I switch off the circuit breaker in the consumer unit, wait for 10 minutes, then switch it back on, the problem is the same: blank LCD and both LEDs on.

The heating engineer comes and fits a new CP715 and the problem is fixed. It's a right pain, and expensive, in the proverbial.

Once, it so happened that the power came back on, the LEDs were on, display blank, and then the power went off again! However, when it next came back on, the Danfoss started working correctly, i.e. display back, both LEDs off, and I could press the manual 1 hour override button for water and/or heat. Right now, it's impossible just before Christmas to contact my heating engineer. Gee, thanks, Danfoss!

 

[LittleTyke]

Installed dozens of these, and never come across anything quite like you describe. What can happen is that any of the four push buttons can catch on the edge of the hole around them when pushed in, keeping the button in. Not obvious when it's stuck, and if more than one are, the strange things can happen.
Only other fault I've had with these (apart from the pathetically weak hinge on the flap) is that the display gets gradually dimmer over the years.

Please see my reply to BeatlesForever in this thread. This issue has happened with my Danfoss CP715 at least three times in 5 years.

 

[Avo Mk8]

If I switch off the circuit breaker in the consumer unit, wait for 10 minutes, then switch it back on, the problem is the same: blank LCD and both LEDs on.

No guarantees, but you might try switching it off for longer than 10 minutes, at least double that! There might just be a big enough reservoir capacitor that stops the dc supply dropping to zero in 10mins? Long shot though!

 

[LittleTyke]

No guarantees, but you might try switching it off for longer than 10 minutes, at least double that! There might just be a big enough reservoir capacitor that stops the dc supply dropping to zero in 10mins? Long shot though!

I'm doing what you suggest. It's now 21:53 on Saturday and I've switched off the relevant circuit breaker. The Danfoss LEDs have gone out. I'm going to bed now and will switch the circuit breaker back ON tomorrow morning. Fingers crossed!

 

[LittleTyke]

No guarantees, but you might try switching it off for longer than 10 minutes, at least double that! There might just be a big enough reservoir capacitor that stops the dc supply dropping to zero in 10mins? Long shot though!

It didn't work, unfortunately. I left the circuit breaker off for 10 hours overnight, but when I switched it back on this morning, the Danfoss CP715 still has both LEDs on and no LCD display. I'll just have to wait until after Christmas now.

 

[SJD]

If I had a heating programmer that routinely failed, I'd have a new spare in the cupboard, ready to swap it next time it failed.

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.

 

[Avo Mk8]

If I had a heating programmer that had failed, I'd add a link to the wiring to make the heating come on so I wasn't cold!

 

[brianmoooore]

If I had a heating programmer that had failed, I'd add a link to the wiring to make the heating come on so I wasn't cold!

And, in my case, that link is a simple and cheap eWeLink wifi switch ,so that I can turn the heating on half an hour before I get home, independently of the programmer.

 

[Moley]

It didn't work, unfortunately. I left the circuit breaker off for 10 hours overnight, but when I switched it back on this morning, the Danfoss CP715 still has both LEDs on and no LCD display. I'll just have to wait until after Christmas now.

I know this is no use to you at the moment but it could be something simple. I assume it will be using a dropper capacitor to supply the low voltage and to recharge the battery. Capacitors over time can 'age' and the unit won't charge or operate correctly. When you get a new unit if you can get the faulty one to me I can take a look at both the battery and capacitor for you. Not making any promises as I've never seen the inside a Danfoss unit before but if it can be fixed it would be a useful spare for you.

 

[LittleTyke]

If I had a heating programmer that had failed, I'd add a link to the wiring to make the heating come on so I wasn't cold!

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

 

[LittleTyke]

If I had a heating programmer that routinely failed, I'd have a new spare in the cupboard, ready to swap it next time it failed.

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.

Yes, I'm thinking about an alternative make, because the Danfoss brand is really peeing me off now. I've seen Honeywell mentioned elsewhere on the internet. Is that a more reliable manufacturer? And would it involve new wiring or simply installing a Honeywell programmer on the Danfoss mounting plate?

 

[LittleTyke]

I know this is no use to you at the moment but it could be something simple. I assume it will be using a dropper capacitor to supply the low voltage and to recharge the battery. Capacitors over time can 'age' and the unit won't charge or operate correctly. When you get a new unit if you can get the faulty one to me I can take a look at both the battery and capacitor for you. Not making any promises as I've never seen the inside a Danfoss unit before but if it can be fixed it would be a useful spare for you.

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!

 

[brianmoooore]

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

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).

 

[brianmoooore]

Yes, I'm thinking about an alternative make, because the Danfoss brand is really peeing me off now. I

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.