Danfoss FP715 Si >> Drayton Wiser Kit 2

[MarlieChiller]

Hi,

I have recently moved into a 3 story terraced house built in 2011. When I moved in, the house utilised a danfoss heating system that I wasnt familiar with. Inside the airing cupboard (which is situated on the top floor) was a danfoss FP715 Si 2 channel programmer for heating and hot water. On the wall outside of the airing cupboard was a TP5000 Si thermostat. On the ground floor there is a simple danfoss dial to set the temperature. This setup seemed to work ok heating the house and controlling the hot water.

My problems arose when I decided I wanted to upgrade from a fixed programmer to a newer app controlled system. I removed the FP715 inside the airing cupboard and replaced it with a drayton wiser (kit 2). The base plate connections for these two systems seemed to suggest this would simply be a plug and play replacement.

(Danfoss on the left, Drayton on the right)

I also decommissioned the TP5000 thermostat by removing the batteries and capping its electrical cables with electrical tape. Once I made this change however, I lost the ability to control the heating to the upstairs of the property. The hot water and downstairs heating continued to work fine. I realised that the wiring that plugs into the TP5000 thermostat seemingly controls the upstairs heating. This was confirmed when I wired the two connections together in the on terminal (shown below).

Once power was reenabled, the heating upstairs immediately came on... but not under the control of the drayton wiser. What do I need to do to the system to fully cede control of the upstairs, downstairs and hot water to the drayton wiser? To my layman knowledge, this sounds like a 3 channel system which would require a drayton wiser kit 3 rather than a kit 2 however the danfoss system is clearly labelled as a 2 channel programmer. At this point im not sure if im 1 simple fix away from solving this, or actually need to do significant work rewiring and paying for an electrician. If the latter, I will simply fallback to the danfoss as I only really want the ability to control via the app. The original system worked, I just had to go upstairs to hit boost sometimes - im starting to kick myself... "if it aint broke..."

Heres a couple of extra details in case handy:
Base plate (no modifications made)

airing cupboard setup:

 

[stem]

The Danfoss FP715 Si which is a 2 channel programmer controlled the downstairs heating and hot water, and the TP5000 being a programmable thermostat [which has time and temperature control in one unit] controlled the upstairs heating and was not linked to the FP715 Si at all, as you have discovered.

So as it stands, you can reinstate the TP5000 programmable thermostat and use it to control the upstairs heating as it was, or change the Wiser you have for a three channel version and rewire the upstairs heating to use the 3rd channel. This may not be as easy as it sounds as the existing thermostat wires will need to be traced back to their origins and re-routed to the three channel wiser. However, from your comments above you seem to have a good grasp of how it works, unlike some.

As the downstairs heating is working, it appears that you have managed to decommission the downstairs dial thermostat OK.

 

[MarlieChiller]

Thanks for the detailed response. I havent decommissioned the downstairs thermostat but given its just a dial, I think all it does is set the max temperature rather than dictating when to come on - the Drayton must have taken control in that case as it comes with its own digital thermostat to place in a given room.

I have two further thoughts based on you confirming my fears

1) Looking at my current base plate configuration above, it looks as though I have a L, N, CH ON (3) and (4) ON connection, but no HW OFF (1) connection. Lets say hypothetically I can reroute the landing thermostat wires to the programmer base plate. If I were to do some rewiring how would I translate my current base plate config to the three channel youve highlighted? Its not clear to me what (4) is used for in the two channel set up. Additionally why is there no HW OFF wiring? Is my hot water is being controlled by the (3) or (4) connection erroneously? Do I even have a HW ON connection?

2) Ive noticed I have two uncapped wires behind my base plate that have been bent back down the socket hole to be kept out of the way (brown and black below). Could these be backup connections in case of a instance like this to prevent significant rewiring? Would there be significant harm in trying to hook these connections up in the hope that they are the upstairs channel?

 

[stem]

Thanks for the detailed response. I havent decommissioned the downstairs thermostat but given its just a dial, I think all it does is set the max temperature rather than dictating when to come on

Not exactly. It should either be set to its maximum setting (so that effectively it's permanently 'on') or, the two live switching wires joined together so that the new Wiser thermostat has full control and the old thermostat won't interfere with it. Anything else and you run the risk of the old thermostat switching the heating 'off' and the Wiser thermostat trying to switch in 'on'.

1) Looking at my current base plate configuration above, it looks as though I have a L, N, CH ON (3) and (4) ON connection, but no HW OFF (1) connection. Lets say hypothetically I can reroute the landing thermostat wires to the programmer base plate. If I were to do some rewiring how would I translate my current base plate config to the three channel youve highlighted? Its not clear to me what (4) is used for in the two channel set up. Additionally why is there no HW OFF wiring? Is my hot water is being controlled by the (3) or (4) connection erroneously? Do I even have a HW ON connection?

Some systems that have a 3 port motorised valve require a 'HW OFF' for them to work, so it's there for them. However, a 3 port valve cannot be used on systems with two or more heating zones because it can never be totally closed (either the HW or the CH port will always be open) As a 3 port valve can't be used on multizone heating applications the HW OFF would never be used, so isn't supplied on multi heating zone controllers.

If you follow the line diagrams for the Wiser Two Channel internals carefully, you will see that actually terminal (3) is HW ON and (4) is CH ON, so yes, you do have a HW ON connection to terminal 3.

2) Ive noticed I have two uncapped wires behind my base plate that have been bent back down the socket hole to be kept out of the way (brown and black below). Could these be backup connections in case of a instance like this to prevent significant rewiring? Would there be significant harm in trying to hook these connections up in the hope that they are the upstairs channel?

It would be very unlikely they would be connected to anything, it's more likely the wires aren't connected at their other end either. But you should find out before attempting to use them for anything though. Connecting 230V to a wire that you don't know where it goes would be very risky.

With the 3 Zone Wiser:

Terminal (1) controls the Downstairs Heating
Terminal (2) controls the Hot Water
Terminal (3) controls the Upstairs Heating

Terminal 3 of the 3 Zone Wiser would be connected to the live of the upstairs heating motorised valve, so when Wiser switches on the upstairs heating, terminal 3 becomes live and opens the motorised valve.

 

[MarlieChiller]

thanks, time to investigate the possibility of rewiring then!