Replaced Danfoss FP715 with CP715 now no hot water.

[danielfinlay]

I have a gas boiler in the attic and a cylinder water tank in the airing cupboard.
The programmer Danfoss FS715 started going faulty so I managed to buy a Danfoss CP715 to replace as its easy they just plug in to the backplate.

However after installing the CP715 and making sure the dip switches matched the FS715 I was unable to get the hot water to work. When I press for the hot water the central heating comes on instead. I presume its something to do with the wiring, I have attached a photo.

I don't seem to be able to buy a FS715 so can't do a direct swap, does anyone know if a FS715si would work? Or any other programmer with the wiring setup I have, thanks.

 

[Johntheo5]

Is it Y plan?

 

[CBW]

Can you post a photo of the dip switch selection for both? If you didn’t alter wiring, I’d suspect faulty timer or dip switch selection

 

[CBW]

Is it Y plan?

I’d say so, seems to be a hot water off in terminal 1.

 

[Johntheo5]

The CP715 shows CH on in terminal 4 (purple) and the DHW on in terminal 3

 

[danielfinlay]

Can you post a photo of the dip switch selection for both? If you didn’t alter wiring, I’d suspect faulty timer or dip switch selection

 

[danielfinlay]

Is it Y plan?

Thanks for your reply, how can I tell its a Y plan?

 

[Johntheo5]

You should find a motorized Mid position valve with 3 pipes probably located in your hot press near the HW cylinder.

 

[danielfinlay]

You should find a motorized Mid position valve with 3 pipes probably located in your hot press near the HW cylinder.
View attachment 312227

This is what I have by the cylinder

 

[Johntheo5]

Thats it, Y plan.

The wiring diagrams for the ("faulty") FP715 & the (new) CP715 are the same so I wonder was there anything wrong with the pogrammer and maybe the fault is in the mid position valve. Are you sure that when you request HW that the CH only is coming on and not both CH and HW?.
What fault were you getting with the FP715? if the baseplate is the same and unchanged, can you plug it back in and see what happens, ie, if you request HW does the CH come on?.

 

[danielfinlay]

Thats it, Y plan.

The wiring diagrams for the ("faulty") FP715 & the (new) CP715 are the same so I wonder was there anything wrong with the pogrammer and maybe the fault is in the mid position valve. Are you sure that when you request HW that the CH only is coming on and not both CH and HW?.
What fault were you getting with the FP715? if the baseplate is the same and unchanged, can you plug it back in and see what happens, ie, if you request HW does the CH come on?.

On the FP715 the two red lights are stuck on, nothing showing on LCD and buttons are unresponsive, I'm doing a test now to see if the water heats up.

 

[danielfinlay]

I'm getting no hot water, is there anything I can do? From what I have read the valve has probably jammed in the central heating position?

 

[terryplumb]

Manually latch the valve into its mid position ,but central heating would also need to be on to fire up the boiler ,that would give you hot water. Only a short term solution though. Don't you have an immersion heater in cylinder as back up ?
Did the system originally work ok ,before programmer went faulty ?

 

[Johntheo5]

The valve is spring loaded to to HW position with no power, if its stuck in the CH position then it may be possible to free it up by removing the actuator and moving it back and forth manually with a adjustable spanner but as above, may only be a temporary solution.

 

[James1991]

I know it might seem obvious, but did you try resetting the old one? The R/S button left of the HW select switch.