Upgrading Danfoss controls to something smarter

[Sammy21]

Hi, I'm new here, and I'm new to central heating, but I'm keen to learn. I'm still working my way around the house trying to understand the current setup, and how it works. My aim is to replace the 2 Danfoss controllers (and sensor) with a smart control setup, such as Wiser or Tado, or even cheaper control tools from Meross. I also plan to replace all the old style TRVs with smart ones, probably as part of the same control system. As you can see from the diagram below, I've still got a long way to go in understanding how the whole system works, but from what I can gather (largely by reading other posts here on this forum), I have a 2-zone heating setup (upstairs TP5000 & downstairs TP9000) with a DHW tank upstairs (controlled by TP9000). Here's what I've learned so far:

So can I ask some dumb-ass questions?
1. If I'm going to be controlling the individual rooms with smart TRVs (eventually), do I really need 2-zone control? Wouldn't it be easier to just unify the 2 zones? Or, as the 2 flow valves for the 2 zones are already there, will it be smarter to control the 2 zones separately. Just seems a bit odd to set an overall schedule for the house, then a separate schedule for upstairs, and then individual schedules for the TRVs.
2. On the TP9000, the back plate looks like this:

The brown wire in terminal 4 goes to the wiring box and turns on the zone 1 heating valve, but where the heck does the orange lead in term 4 go (not the one going to the TS2 external sensor at terminal 5)?
3. Am I right in thinking that all the TP5000 does is open the zone 2 valve, and it does not control the pump? So the pump is switched on by the boiler, right?
4. What switches on the boiler (and pump)? I assume that's what the "switched live" does, is that right (black cable in the boiler)? But where does this come from, and what fires it up?
5. Bearing in mind my confusion, is there another junction box somewhere I haven't found?
6. the three switching valves for zone 1+2 and HW all have an orange cable that are all attached to the blue cable from the TP9000. What do they do?
7. There is a third cable going into the wiring box, I've labelled it "Mains??" in my diagram, because it seems to be live and might be necessary to power the switching valves, the TP5000. Is my assumption correct?

Sorry to be such a noob, and I'm doing my best to work all this out on my own, as much as I can. I probably don't need to know all this to do the job, but from experience it helps to know how things work before you start messing around with them. Any help will be greatly appreciated.

 

[ian1182]

I think you have a bit of a mix and match system. Not sure of the age of your house/heating system but in principle its very similar to my brothers house. The builders rather than installing a 3-channel programmer, put in a standard 2-channel programmer looking after hot water and the downstairs heating supplemented by a battery powered programmable thermostat for the upstairs. This lead to a small problem swapping out for a 3-channel Wiser system as the old programmer location did not have sufficient cores in the cables running to the wiring centre to support all the channels. He had to relocate the programmer next to the wiring centre which added to the effort.

It looks like you have made a good start in identifying the cables and their connections. Is the TP5000 battery powered?

If not already done, I'd recommend a look at

S Plan central heating system

S-plan central heating system operation and wiring diagram

flameport.com

which provides an excellent overview of how it all hangs togther.

What is the proximity of the TP9000 and wiring centre. The locations of the TP5000 and down stairs thermostat don't matter as they won't form part of a future smart system. Can you see any unused cores in the cables running from the TP9000 to the wiring centre? I suspect there may not as I can see a green/yellow core being used as a live in the "L" terminal on the TP9000 which is far from ideal. Is there space near the wiring centre to relocate the programmer if required.

 

[stem]

This seems to be quite a common set up. In fact someone else with a TP5000 / TP9000 set up wanting to move to a smart controls posted a few days ago. You can read their post here.

I'm guessing that your property is a fairly new build and the two zones are there because of the building regulations. From 2010 onwards Part L of the building regulations stipulates that different heating zones are provided for the living areas and sleeping areas. If you change it to one zone your home will no longer comply.

All 3 motorised valves contain a microswitch (orange and grey wires) to control the boiler. When any of the valves are open, the microswitch operates and start the boiler.

The mains supply is connected to all of the grey wires at terminal 2 as per your diagram below, so the grey wire is permanently live.

When the switch is made the orange wire also becomes live. This is connected to the boiler and starts it working.

The TP5000 is battery powered. However, the brown wire in terminal 2. will be a live, when the TP5000 switches the heating 'on', it will make the other wire in terminal 3 live. This will subsequently provide a live to its zone valve, which will now open. When it's open, the internal switch operates and the boiler runs.

Excellent info with your first post BTW. If only they were all as good.

 

[harrythefurrysquid]

If you change it to one zone your home will no longer comply.

Presumably this is not the case if you drop in something like Drayton Wiser?
That would have the effect of creating room-by-room zones if desired.

Or do the regs not really cover that sort of thing?

 

[ian1182]

This seems to be quite a common set up. In fact someone else with a TP5000 / TP9000 set up wanting to move to a smart controls posted a few days ago. You can read their post here.

I'm guessing that your property is a fairly new build and the two zones are there because of the building regulations. From 2010 onwards Part L of the building regulations stipulates that different heating zones are provided for the living areas and sleeping areas. If you change it to one zone your home will no longer comply.

All 3 motorised valves contain a microswitch (orange and grey wires) to control the boiler. When any of the valves are open, the microswitch operates and start the boiler.

View attachment 292032

The mains supply is connected to all of the grey wires at terminal 2 as per your diagram below, so the grey wire is permanently live.

View attachment 292033

When the switch is made the orange wire also becomes live. This is connected to the boiler and starts it working.

The TP5000 is battery powered. However, the brown wire in terminal 2. will be a live, when the TP5000 switches the heating 'on', it will make the other wire in terminal 3 live. This will subsequently provide a live to its zone valve, which will now open. When it's open, the internal switch operates and the boiler runs.

Excellent info with your first post BTW. If only they were all as good.

Whilst I stand to be corrected, I would have expected the TP5000 to be permanently live independent of the TP9000. Otherwise the upstairs heating would depend on the downstairs being in an "on period". I thought the point of device like the TP5000 was combining a single channel programmer and thermostat into one unit.

 

[stem]

Whilst I stand to be corrected, I would have expected the TP5000 to be permanently live

That's right it is..... But isn't that what I said?

The TP5000 is battery powered. However, the brown wire in terminal 2 will be a live.

The TP5000 has its own live to terminal 2, it doesn't get it via the TP9000 exactly for the reason you state.

Perhaps I confused the issue by saying it didn't need a live for its operating power.

 

[stem]

Presumably this is not the case if you drop in something like Drayton Wiser?
That would have the effect of creating room-by-room zones if desired.

Or do the regs not really cover that sort of thing?

Two zones is the minimum. There can be more, provided the boiler is shut down when all zones are satisfied.

"For wet heating systems in new dwellings with a floor area of 150m2 or greater, a minimum of two independently controlled heating circuits should be provided. System controls should be wired so that when there is no demand for space heating or hot water the heating appliance and pump are switched off"

I am familiar with a 5 zone installation (not Drayton Wiser) and in practice almost always at least one zone is calling for heat, so the boiler very rarely stops. Previously it was a 2 zone installation and they were both satisfied more of the time so the boiler was off quite a bit........Does that mean it is using more energy now that it's a 5 zone? If not using more gas, certainly it will be using more electricity keeping the boiler and pump on for longer.

 

[ian1182]

That's right it is..... But isn't that what I said?



The TP5000 has its own live to terminal 2, it doesn't get it via the TP9000 exactly for the reason you state.

Perhaps I confused the issue by saying it didn't need a live for its operating power.

you did. I need a lesson in reading.

 

[Sammy21]

This is great! Two replies, and both really useful. Thanks! I take that back. It'x taken me quite a while to write my response, and there has been quite a bit of chat since!

So ian1182 the house is around 10 years old, and I think all the houses on the estate have a similar setup. I don't know if there are any spare cables from the controller (downstairs utility room) to the wiring box (upstairs water tank cupboard) and they are not close, though I would have though there is plenty of room for the programmer in this cupboard if required. The TP5000 is battery operated. Just watched the video and it was really useful. I'd already worked most of it out, but along with STEM's explanation above, at least I know what the last remaining unknown wire is, and how the boiler is switched on.

Thanks for the explanation STEM, that makes sense. But surely if I was replacing a 2-zone system with 8 zones (one for each room, controlled by wireless stat or smart TRV) surely that wouldn't mess up the building regs?

Here's my updated wiring diagram:

1. Where does the mains in my wiring box come from? Could it be all the way from the boiler?
2. There still seems to be a few mysterious missing connections. The 5-core cable which was labelled TP9000, and is now labelled TP9k+boiler, clearly has wires going to the TP9k (DHW 3, HTG 4) and the boiler (pump & boiler SL). So is there another junction box somewhere where this cable splits in the 2 directions (or is it in the wall behind the TP9k)? And I still have no idea what the orange cable is in junction 4 of the TP9k, wired in with the brown. Any ideas?
3. Here is the layout of the boiler and the frost protection

Is this fused switch supplying the whole system, including the pump, and valves? The two cables from the frost protection and the boiler go up and through the wall....somewhere! Any ideas where? Again, it suggests there's another junction box somewhere where all these are sorted out, unless it all happens behind the tp9k mounting plate?

Much of the discussion above has been about whether or not I need to keep the 2 heating zones if I have TRVs (or wireless thermostats) in all the rooms. Doesn't seem like there is a definitive answer to this? If I do keep the 2 zones, will the upstairs TRVs then control the zone 2 water valve?

Thanks again for all the help. My understanding of how all this works has jumped dramatically in 24 hours!

 

[ian1182]

That is an exceptionally neat installation. Good to see conduit rather than tacking cables to the wall.

Hopefully the switched spur has one 240V "input" connection going to the boiler and a second up to the wiring centre. Unfortunately your orange line has obscured the view of the round junction box, but there should be a cable coming down containing the boiler switched live & pump live cores. In general the "wiring centre" instructs the boiler to start which then kicks the pump into operation. You probably notice the pump runs for a few minutes after the boiler ceases to fire (pump overrun).

You said "I don't know if there are any spare cables from the controller" - I meant cores within an existing cable. In my house there are 2 x 4-core cables running from the boiler, programmer & fused spur to the wiring centre. All 8 cores are in use (although 2 are earths). That said it may be straight forward to locate your new programmer next to the wiring centre.

Personally I would retain the existing 3 physical channels (Hot water, downstairs & upstairs). The number of logical zones you have by implementing smart TRV's is just a layer on top.

 

[stem]

Thanks for the explanation STEM, that makes sense. But surely if I was replacing a 2-zone system with 8 zones (one for each room, controlled by wireless stat or smart TRV) surely that wouldn't mess up the building regs?

The regs say "a minimum of two independently controlled heating circuits" so 8 would still satisfy the requirement.

1. Where does the mains in my wiring box come from? Could it be all the way from the boiler?

Yes, that it should come from, the 3A fused spur that supplies the boiler. The FCU is for the entire heating system it is usually mounted next to the boiler [easier for the engineer to isolate it when servicing the boiler] The permanent mains supply to the wiring centre can then either come from the boiler 230V terminals or directly from the fused spur itself. For safety, the same fused spur should isolate the boiler and all of its associated components. I suspect that in your case the mains supply may go from the FCU to the TP9000 N & L (as there are 3 wires in each terminal) and from there it goes to the boiler and wiring centre. If so, slightly unusual but nothing wrong with it.

2. There still seems to be a few mysterious missing connections. The 5-core cable which was labelled TP9000, and is now labelled TP9k+boiler, clearly has wires going to the TP9k (DHW 3, HTG 4) and the boiler (pump & boiler SL). So is there another junction box somewhere where this cable splits in the 2 directions (or is it in the wall behind the TP9k)? And I still have no idea what the orange cable is in junction 4 of the TP9k, wired in with the brown. Any ideas?

I suspect that the orange wire at the TP9000 is from the frost protection system. When the frost protection system kicks in, it will need to open one of the motorised valves to start the boiler and allow water to circulate. The orange wire in terminal 4 of the TP9000 could be that, because this terminal is what starts Heating 1 when the TP9000 switches it on. The pipe thermostat at the side of the frost stat is to switch the frost protection off once the water in the flow return to the boiler is warm enough to stop the pipes freezing.

I can't see the wires at the TP9000 that clearly, but I would expect the 5 core cable at the TP9000 to be:

1. L Permanent live (L)
2. N Neutral (N)
3. E Earth (E)
4. HW control (3)
5. CH Heating 1 control (4)

Remember. There are no boiler or pump control functions done by the TP9000 (that's all done via the switches in the motorised valves.) All the TP9000 does is open the motorised valves for Heating 1 and Hot Water.

So if my theory is correct, you may have something like below. Although it would need checking to be sure, and the use of a green/yellow wire as a live wire indicates some cable sharing, rather than the use of separate cables for each of the functions [Earths omitted for clarity]

 

[Sammy21]

Hi guys, so we're nearly there, I think.

Ian, here is the top round junction box next to the FrostStat. Fat white cable (5 core, mains + pump+ SL) plus smaller white cable from FrostStat, going somewhere, presumably to the tp9k on the other side of that wall.

The bottom round box just contains mains in (from the fuse) and the fat white 5-core out and up. The second image is the boiler wiring, showing how the 5-core is wired:

But here's the interesting thing. The two cables going into the wiring box are a 3-core (mains) and a 5-core (dhw, htg, sw/l, pump, earth). so, somewhere in between the boiler and the wiring box, perhaps behind the tp9k, there's some clothes-swapping going on, right?

Sammy, thanks for answering my next question about the wiring of the Froststat. Makes a lot of sense, though the cables int he Froststat doesn't have a hint of orange, so I'm guessing the earth with the brown sleeve is the switched live which connects to term 4 of the tp9k (htg) via a junction and a piece of orange wire...? Or is that far fetched? Bugger...I'm going to have to take the back off the tp9k aren't I and have a good rummage...darn it.

I think it makes sense to keep the discussion of how to wire up a smart system as a separate thread, once I've got the basics covered. I'll put the link here when I'm ready to open that can of worms, but I'm no clearer as what the "right" strategy is re 1 vs 2 zones. I mean if everyone is out except me, I don't need the heating on. But if I'm in the upstairs office, and decide I want the radiator on, then turning it up at the radiator should turn on the boiler and send heat to my office radiator only, so it should really only open zone 2 valve and pump water around the upstairs circuit....sorry, I said I wasn't going to talk about this! Let's save it for later...


Thanks guys.

 

[ian1182]

If you have a multi meter it's probably a good idea to check out the continuity across the various cables so that you can match the unknowns. That's probably something to do once the weather is slightly better and you have adequate time.

 

[Sammy21]

And here we have it, the final few pieces of the puzzle. I took off the back-plate to the tp9k and there behind it were 3 cable joints solving the last few questions.

The so-called orange cable was, in fact, light brown and went to the Froststat as you suggested. There was a cable joiners changing the boiler SL from blue to black, the missing grey wires for the pump were both back there too.

Thank you all for your enormous help. I'm going to wait a day or two to think about what I really want from a smart system, and then I'll start a separate thread on that. I hope you'll join in!

 

[stem]

Well done with your investigations, it's always good to understand how things actually work rather than just seeking advice about which wire goes where and not understanding what they do.

In reality, usually with a smart upgrade on a system like yours, one unit will replace the TP9000 to control Heating Zone 1 and the Hot Water, and a second unit replaces the TP5000, controlling Heating Zone 2. In which case, there isn't a need to modify the wiring centre anyway.

An additional benefit for you is because the TP9000 has it's own TS2 temperature sensor as part of it, there isn't an existing wired room thermostat that needs to be decommissioned requiring any additional wiring modifications.