WiFi/internet replacement for a Danfoss FP715Si programmer

[JBM]

I have a Trianco Contractor 50-90 Oil Boiler that heats water for a central heating cylinder.
Hot tap water is provided by running the full pressure mains supply through a heat exchanger coil in the central heating cylinder.
Side question: Is this setup unusual and does this setup have a recognised name?
I have replaced a Danfoss FP715Si programmer with a Drayton WT724R or WV724R (not sure of the difference or which I have). Nothing else has been touched!
With the old Danfoss programmer, when CH is demanded, both the CH pump and the Boiler are activated (there was no room thermostat, only radiators with TRVs and 2 radiators without TRVs).
With the new Drayton programmer, when CH is demanded only the CH pump is activated, the Boiler is not activated (the Drayton kit included a wireless room thermostat).
The main question:
Is there a way to make the New Drayton behave like the Old Danfoss or do I need a different model or programmer altogether?
The aim is to achieve WiFi remote control of the CH over the internet. The Drayton is achieving this but only if I switch the HW & CH on individually at the same time)?

 

[ericmark]

It seems the old unit and the new Wiser hub use the same backplate and connections, so turning the old thermostat to maximum and fitting Wiser or for that matter Hive two channel hubs should be easy. However, reading the text it seems you only need CH, so may want to change things.

There are some rather complex systems around, the big question is if the cylinder is fed from header tank or direct on mains, the latter needs annual tests, and seems to me to be the work of the Devil to get tradesmen an annual income.

In theory, there is no need for a wall thermostat, the TRV heads can report direct to the hub which tells the boiler when to run, but the Wiser system does allow one to use both wall and radiator mounted thermostats.

I am sure there is a way to make it work, boilers vary, my thermostat links to a hub, the hub links to the motorised valve, which links to a relay, which fires both the pump and boiler. Reason for relay is I have two pumps, also the hub can connect direct to the boiler, for DHW, I am using a C Plan, but it unlike most C Plans has motorised valves, so I can select if it heats main house or flat.

It sounds as if yours is what we call a combi boiler. However, I know the Hive system you can set it up, so one set of contacts works the boiler, and the other set the pump. With the basic C plan, just the boiler runs for DHW, and boiler plus pump for CH. What the oil combi has done, is takes parts normally outside the boiler, and fitted them inside.

The old programmers had dip switches and blocking device, and with a fully pumped system you would have 16 programs, but with C Plan only 10, and you could not select CH without DHW. From the installation manual

this is not found with latter programmers, I did not work much on domestic, but as an electrician remember coming across them.

 

[JBM]

Thanks for the reply and including the diagrams, a couple of notes and updates…

There is no old thermostat.

I do need control of CH and DHW.

The cylinder does have a header tank.

All TRVs are the old ‘dumb’ type.

The Boiler is not a Combi boiler.

Looking at the old Danfoss programmer, does changing the Sw.2 DIL switch from Gravity to Pumped control whether or not the Boiler is fired when CH is demanded?

Can I add a simple relay between the CH line and the DHW line to make the Boiler fire when CH is demanded?

 

[stem]

does changing the Sw.2 DIL switch from Gravity to Pumped control whether or not the Boiler is fired when CH is demanded?

With the switch in gravity mode, whenever the CH is on it also switches the HW channel on as well, and by doing that it does start the boiler.

If you had gone for a Hive Thermostat they do have a gravity setting, and Nest Thermostat has slightly different connections so can be wired to provide the same control. The Wiser unfortunately doesn't have a gravity setting, or be wired for such.

Can I add a simple relay between the CH line and the DHW line to make the Boiler fire when CH is demanded?

Yes you could.

 

[ericmark]

This house on move in had one of these it is marked as DHW and CH, but in fact all it did was turn the boiler on/off. Down in flat found one of these but never found the thermostat that should go with it,

was missing, there were two pumps clearly one for the flat and one for the main house, but the only way to turn on one for main house was to go down steps into the flat and plug it in. The old thermostat still controls the flat, the power did not only come from different fuse/MCB, it came part from a fuse box and part from a consumer unit.

I had one major problem, only two of the triple and earth wires had continuity, so I did not like the idea of relying on a battery, so installed Nest Gen 3 as only two wires required hub to thermostat, I found selecting pumps did not work, the water circulated in reverse, so got a plumber to fit motorised valves so I could shut of flat, but I did the rewiring of the heating. It was C Plan, and I was advised that with C Plan on an oil boiler the DHW allowed the boiler to cool, and to leave it as C Plan. This is the basic Nest Gen 3 C Plan, it is not in the Nest instructions. Common becomes an out, and with Wiser Common is linked internally to Line feed, so this will not work.

If someone was to try and describe my system on a forum, likely they would fail, it needs to be one site with it, and to make out a wiring diagram, but in most cases type of motorised valves if any give us a good idea. So there are exceptions but in the main.
1) No motorised valve = C Plan
2) Two x two port valves = S Plan
3) A three port valve = Y or W plan
I used the boiler for DHW in winter, but solar with an immersion heater in the summer. With a C Plan the pipes are so large, that each time boiler fires most of the energy goes to heat the pipe work and boiler, so cheaper to use electric in summer, but cheaper to use boiler in winter.

 

[JBM]

Thanks for all the info.
I’m going to add the relay to the existing system and all should be well.

 

[DP]

Honeywell lyric T6 or T6R