Can I swap a Danfoss CP715 with a FP715-SI

[BobSpoons]

Hi

My central heating controller is a Danfoss CP715

From reading the Danfoss literature, am I right in thinking that it is a straight-swap for a FP715-SI without me even needing to do any wiring (assuming the original installer wired up the CP715 correctly as he made a mess of a lot of our CH system).

If Im right, this would give me a seperate set of timings for the HW as well as the CH.

Would appreciate if anyone has experience of these models to reassure me before I spend the £50

Many thanks

Bob

PS: As far as I can tell the "SI" added to the 715 above is simply the current version of the product (think it means service-interval, which is a new feature of the unit)

 

[D_Hailsham]

The FP715 is a direct swap for the CP715 - no wiring changes needed.

If you are buying new the Service Interval feature is switched off.

But if you are buying a second-hand one, check with seller that the SI feature is not enabled, as the only way of disabling this is to contact Danfoss, who will only give the info to Gassafe registered engineers.

 

[BobSpoons]

Thanks thats brilliant, screwfix here I come.

That should be an end to morning cold-showers without running the gas bill up too much

Thanks a lot

Bob

 

[Templar28]

Your query was a long time ago but my heating system is still controlled by a Danfoss CP715 controller. I'm making some modifications to the system which is pumped CH and gravity HW. I'd like the timing of the CH to be different from the HW but have been unable to get the controller to do this. From your query, would I be correct in assuming that the CP715 is not able to switch them independently but that the CP715SI is?

 

[stem]

The CP715 is capable of independent control of the heating and hot water.

However because your system has 'pumped central heating' and 'gravity circulation of the hot water' that means it is not possible to have the central heating on without the hot water being on as well. This is because of the restriction of the plumbing, not the controls.

The CP715 has a switch on the back marked gravity / pumped which is selected according to the system it is connected to. At the moment yours will be set to gravity to take the plumbing restriction into account and start the hot water whenever the heating is selected.

For independent control, the plumbing would need altering, to incorporate at least one motorised valve, and hot water cylinder thermostat.

 

[Templar28]

Thanks for your reply. My system is the old 'bog standard' type with a pump supplying the radiators from a Grant 'Gemini' boiler through 8mm small bore tubing and the hot water cylinder by gravity via 28mm tubing - there are no motorised valves in the system. Because the system is not very efficient, the radiators take most of the heat leaving the hot water cylinder cool. I'm in the habit of pressing the '1 hour override button' on the hot water side of my controller after the central heating has timed off. This gives the hot water cylinder a boost. The situation never occurs when I would want the central heating on without the hot water. I was trying to set things up so that the controller would switch off the pump, and thus the central heating, but leave the boiler on so that it would boost the hot water cylinder. Incidentally, the dil switch on my controller is set to 'pumped' - is this correct or could it be part of my problem? Many thanks for your help and sorry if it's all a bit tedious, I'm one of those DIYers I'm afraid.

 

[ianmcd]

no you need to set the switch to Gravity, then you will get HW on its own or CH & HW but not CH on its own