Underfloor heating controls - a conundrum

[SimonH2]

Yes. See the time clock that's scribbled out, and the blue line that's scribbled out - you want to be using that arrangement. Omit the hand drawn clock on the right and leave the WCs permanently powered.
Basically, if you cover up the lower WC in that diagram - that's how each should be wired. For your two wiring centres, you need to connect the supply L&N and timer signal (use the 3 core & earth) in parallel to both wiring centres, and parallel the boiler contacts between both WCs. Then connect the pump for each as it's shown for the top WC in the diagram.

 

[abbadon]

I'm not familiar with the schematic for the current timer, would it be a different set of connections to trigger the timer connection than I am currently using, or the same pins?

 

[SimonH2]

Try this.
For L&N for the timer, you can take these from the L&N terminals on the block you connect the output to - shown here as the right hand one but you can use any spare block. Note the separate pumps, each connected only to it's wiring centre and not the other one.
Use the 3C+E link cable - Red=L, Blue=N, Yellow=Timer signal.

Same for the timer, use the 3C+E that goes to it, same colours as above.

The boiler connections are already in place.

 

[abbadon]

Try this.
For L&N for the timer, you can take these from the L&N terminals on the block you connect the output to - shown here as the right hand one but you can use any spare block. Note the separate pumps, each connected only to it's wiring centre and not the other one.
Use the 3C+E link cable - Red=L, Blue=N, Yellow=Timer signal.

Same for the timer, use the 3C+E that goes to it, same colours as above.

The boiler connections are already in place.

View attachment 152795

Could you please please clarify this a bit, it's the bit about the "on the block you connect the output to" that confused me!

 

[abbadon]

Ok, here we go again, I'm determined to nail this once and for all... Wiring is my nemesis!

Upstairs heating isn't working at all now, and since we're still living the previous wiring nightmare, diagnosing what's wrong is currently impossible...

So I'm going to try and print all the info out so I can have a stab at making sense of the last suggestion, I think it makes sense but I still fear I'm short a core to enable it!

Watch this space...

 

[abbadon]

OK so here is the next update, seems it is possible to still get power to upstairs, but im not sure I can write down the conditions.... dont ask.

However, with a bit more poking about, and reading the older comments over and over, looking at the diagrams, wiring etc.. it became apparent to me that it looks like the thermostat in the living room, and the main controller (next to it) are possiblt using the same 3 core + earth cable, whereas between them they should need 5 cores... I suspec there is something really screwy going on here now, but I need to pull off both devices from the wall later today and see what the hell is going on there.

In my previous images, its the wire ive dotted in green thats an earth core, but with a sleeve in brown at this end, that I think is going to one of the thermostats, and the other wire going to that stat is the blue one from the same cable. The red and yellow cores from that cable, i think, are now going to the programmer, and thats where is making or breaking power to the whole system by joining or not joining the yellow to the red at its contacts (tbh this does seem a bit sketchy?).

So now I need to confirm my suspicions. If this turns out to be the case (there might still be some full sketchy wiring at the stat and programmer end, im not assuming anything here as I cant quite work out how the stat can do anything without its third wire.... ) then I think the first step would be to wire that stat in correctly, as well as moving the controller near the cupboard where this all is, so i can use a new piece of wire to connect it correctly. Ill also have to then remedy the connections from this box, to the upstairs wiring centre, but I think that will just involve removing a link not needed, and connecting that pump link, instead as a new link feeding the switched live to the timer rail, that provides the power when the system is on, to the thermostats and the actuators.

 

[ericmark]

It seems odd that a property in South Wales has a system designed in North of Scotland, and I can see how it would be hard to get them to pop in and fix it, however I can also see why no one else wants to fix it, had it with central heating in this house, simply could not work out how it would ever work as it was, so used existing cables, but rewired from scratch.

So some pointers, one is you can't possibly remember it all, you will need to make a plan, but I did not twig it was an old post, until I saw @ban-all-sheds reply and he has been gone for over a year, so I started to read from the start.

My first thought was with my myson fan assisted radiator the fan was switched on/off by water temperature, and there was no electrical connection between the radiator and central heating boiler, it is possible the pumps were the same, when it detects hot water it runs and when water is cold it stops.

So it seems not all UFH is the same, but basic idea is when running the local pump circulates the water and as the water temperature drops it allows some water to be replaced using a second pump. Since in your case all UFH in theory there is no need to do this, the idea of the two pumps was so water at 70°C could be supplied to radiators or DHW while the UFH was limited to around 30°C.

So if I am reading is correct you never got it to work proper, but now you have extra faults? Pictures and diagrams don't match, so two options, make and as built diagram, or label as best as you can, and start from scratch. Neither will be easy.

You have been trying to sort this for two years, I wonder how long the previous owners of this house had been trying to sort out the heating in this house? I wonder if that had some bearing on it being sold? I am lucky, I have found some local tradesmen, who have done the plumbing for me, very lucky as my Welsh is rather poor, taught in school but never used. However I am Welsh and they seem to have accepted me even if I am a gog (gogledd which means North it seems) like you in the South are named after a river the Taff. But I can't see the chances of you working it out without some one local to help being very high after all this time.

Major problem is the Pubs are closed, normally we would ask in the Pub, and find some one who knew his stuff. However it says your an engineer, I assume that does not mean the driver of a steam train, so you do have some skills. But as to your electrical skills we must assume since being trying to fix for 2 years not that good?

So what had you thought as to the way forward? Swansea is one too far for me to travel and two Covid 19 much higher there than here in mid Wales so I am not willing to visit, but still want to help if I can, so it would seem all I can do is bounce ideas with you, and some times that helps.

 

[abbadon]

ericmark, thanks for taking time to reply

I am materials/mechanical engineer by training, I work in medical devices these days, but im not totally unskilled at electronics, its just "not my thing" . Reading back over the posts over the last few years, some of the things pasted in 2018 made a but more sense, and also, around that time I was always working away, and we only moved to the house in 2016, I never had much time to sit at the system with some of the info printed or on phone/laptop and really think hard about it/move wires aside and try and work out how the system was actually able to work. Nor did I ever get time to shut the power off to it and probe it with the multimeter to learn some more and try to work out where each un-labelled wire was going!

One thing that I hadn't grasped was the timer track in the board, was responsible for powering the stats, and once I realised that when i spent more time looking at the diagram, and reading back, then it became more clear why the upstairs system behaved weird, and also why the downstairs pump stayed powered - there was a route from a live back to the downstairs pump even when the relay was open downstairs.

I also couldn't work out how the stat and programmer were sharing cores - but i found out last night that the programmer is making and breaking the power as expected, but they have also powered the stat off that switched live locally at the wall plate, which will work, and gives a live when require to the stat, and allows it to send 240v to the central "make hot/close relays" line in the W.C.

Once I knew that, I was more confident that side doesn't need meddling with, so last night, i shut it all down, and pulled the link between the two pumps, and used that link to join the "timer 1" rail between the two W.C. I also re-made a few connections which were sketchy where 2 or 3 wires were in one side of a choc block - not nice. Why they didn't make better use of the large Live track and free connections in each zone block, or the Neutrals along the bottom, Ill never know!

That seems to have sorted a lot of the problems, but generated a new one! The boiler initially wouldn't fire up, if it wasn't late at night and I was worried about today, id have left it longer, and it may have just been it going through siphon prime mode or similar, but I also noticed that the downstairs W.C. was using the wrong relay block, so I switched that around, so the right relay was used for pump and boiler trigger respectively, and also that the polarity was the same on both WC for the boiler relays, I couldn't see why that would be the issue but seemed best practice...

And that seems to have fixed it. I did also stick the boiler on comfort always mode, and it seems to be switching in and out when demanded by the underfloor system. I did learn last night that the big combi I have, R40 , is known for not being the easiest to control, although I couldn't find any real info to qualify that it is/is not, just a bit of hearsay on a few other threads about whether or not external controls work with them or not, it seems to work fine in this install, at least now it does.

So I have essentially followed quite a bit of the recommendations from SimonH2, although for now the power will remain made or broken using the controller to both W.C., and the "hot" link will provide 240v to the timer line, instead rather than the timer powering those on both boards. Is it clean? No, does it work better than before.... yes, 100%. Will it remain like this? probably not, as there are a few changes we need to make to the house, and it will end up involving the heating at some stage, but at least I understand the oddities it has now, and that means I can label the wires up, so next time someone looks it will be clear whats what...

 

[ericmark]

I now use an oil boiler, but before I moved my mothers old house used a modulating gas boiler, and I realised the control system was clearly not suited to the boiler.

It seems there are two ways to control the boiler, connection to the ebus with likes of OpenTherm and the return water temperature. And the Worcester Bosch boiler my mother had did not have the option for ebus control so was controlled by return water temperature, with a radiator system this is done using TRV heads and a by-pass valve, so as the heads close the by-pass valve opens, and so hot water arrives at the boiler return which first turns down flame height and then causes the boiler to cycle, and the length of the mark/space is often adjusted with what is called anti cycle software, but it clearly can never turn off the boiler completely, as it needs the water to circulate to work out output required, so a simple on/off thermostat is added often in a ground floor room, with no alternative heating, and no outside door, to switch the system off in the summer.

But the thermostat the installers had fitted used a mark/space ratio to reduce hysteresis, so this was messing up the boiler, it worked but did not work in an efficient way.

I would guess your system also has a by-pass valve and so the return water to boiler is likely hotter than the return water from the UFH system, but it seems some boilers are designed for UFH as take advantage of the low return temperature of the water. However around this area there is no gas, we all use oil, some do use LPG, but all the UFH systems I have seen use oil boilers and also use radiators as well. So sorry can't really help you.

 

[SimonH2]

Could you please please clarify this a bit, it's the bit about the "on the block you connect the output to" that confused me!

I had to think - it's two years and I don't remember stuff like that
If you follow the switched output of the timer, it connects to one of the unused "stat + valve" zone connector blocks. There's a L&N on that block you could use to power the timer - just needing a 3C (+E) cable from the WC to the timer.

In the WC, the N, clock1, clock2, and L terminals are all commoned across the zones. So you can use the L & N of any of them for anything needing L&N. The clock1 and clock2 take the output from one or two time clocks and use them to feed the stats for each zone - as shown in the example connection on the left hand block.
Then the terminal with the arrow in takes the switched line from the stat, and connects it to the L connections for the valve actuator(s). There's two L & two N connections in case you want to control two valves from one stat - nothing more complicated than that.

Anyway, as I altered the diagram for you, the yellow core of a 3C&E takes the clock1 line from one wiring centre to the other. What I'd be doing is connecting the timer to one of the zone connector blocks (using the L, N, and clock1 terminals), and connect the yellow core of the linking cable to the clock 1 of another spare zone connector block. In fact, to make the wiring easier (less wires stuffed into one terminal), just connect each end of the link cable to a zone connector block (red to L, blue to N, yellow to clock1).

Hmm, been back and read things again. Do the time clock and room stat share one 3C&E cable ? If so, then that complicates things a little as it's not possible to (safely and regs compliantly) wire that up to work properly - it's not acceptable to oversleeve the bare CPC and use it for anything but an earth. If that's the case, I'd simply move the time clock to be adjacent to either of the WCs so it can have it's own cable.

Simon