No switched live to boiler?

[CheshireH]

Hi

for a few reasons (problem with hot water, possible smart heating installation), I familiarised myself with my heating system and wiring. Looks like a standard S-Plan with magnetic valves for hot water, central heating and UFH. Valves are controlled by normal standard backplate programmer, thermostat on unvented hot water cylinder, and a John Guest wiring centre for the UFH. However, the boiler (two year old Intergas system boiler) is only connected with a three core cable to permanent power supply - 1,2,3 in wiring box. There is no switched live wire from where the valve orange wires are connected (10). I googled forever but I cannot explain why the boiler starts up when a valve opens ( which it does - small delay in firing up and closing down), without receiving a switched live signal. It works, but since I am considering a smart installation, I need to know why...

Unfortunately, the hot water valve does not open automatically and needs to be opened manually. Possibly a faulty valve, as I checked the wiring. Or a faulty thermostat on the cylinder. Is it dangerous to keep the valve in manual open mode until fixed?

Thanks, Henrik

 

[Basher]

Thanks Basher, why would there still be a live wire from the boiler? The only live wire not switched off by the boiler switch would be the feed to the UFH zone valve, but the microswitch (grey to orange) would no longer close as grey would not receive a live feed any more, and thus no orange would be live. Again, I may be missing something?
But to be fair, you have a very valid point, as there is a safety concern around the wire to the UFH valve, which could be live even when the boiler switch is triggered. This problem is already in place today, of course, and made worse by the fact that the connection between the UFH valve and the UFH wiring centre is made through the terminals 11 and 12 in the S-Plan wiring centre!!!

This may be a reason to actually pursue the thought of wiring the valve fully into the S-Plan, and only connect to the UFH wiring centre via the 'volt free' boiler enable link. So if no current exists in the S-Plan wiring centre, no current will ever flow back from the UFH wiring centre. I have contacted John Guest for advice on this, but I am more and more certain that this is the right way of doing it. It would be easily executed, as I could use the existing cable to the UFH valve for the boiler enable link, and connect the UFH valve locally to the S-Plan wiring which is right next to the valve!).

Hi Cheshire
I didn't get that there is already a direct connection between the UFH wiring centre and the boiler wiring centre!
The scenario I was concerned about was when boiler/kitchen circuitry left on, garage UFH locally isolated for maintenance. But no point in debating as they are already interconnected wiring centres!

Sorry I may be misunderstanding your suggestion. If you implement the 'volt free' signalling from UFH to boiler but still have orange wires terminal (10) to boiler switched live, the UFH can surely only come on when one of the others demands heat as well, and when the UFH goes off, it all goes off!
I hope I'm wrong!

 

[Brambles]

From your initial description, the most likely scenario is that your boiler has been wired without any external control switching into X2 (volt free) or X3 (240v) Consequently the boiler is just operating 24/7 on the flow temperature thermostat. A rather inefficient mode of operation.

The motorised valves have presumably then been wired independently, to allow boiler output to flow into the heating system.

The easiest way to check this is to ask your installer to ckeck or confirm if the boiler X2 and X3 terminals are both bridged across the input pins.

Thereafter, it can be conventionally (S Plan?) rewired to respond to room thermostat inputs.

Alternatively to test this therory, turn all room thermostats to their lowest setting and the boiler thermostat to its highest setting. Even with no hot water demand and no heating demand, as the boiler flow temperature cools, the boiler will fire.

 

[John.g]

Hi Cheshire
I didn't get that there is already a direct connection between the UFH wiring centre and the boiler wiring centre!
The scenario I was concerned about was when boiler/kitchen circuitry left on, garage UFH locally isolated for maintenance. But no point in debating as they are already interconnected wiring centres!

Sorry I may be misunderstanding your suggestion. If you implement the 'volt free' signalling from UFH to boiler but still have orange wires terminal (10) to boiler switched live, the UFH can surely only come on when one of the others demands heat as well, and when the UFH goes off, it all goes off!
I hope I'm wrong!

The signal from the UFH would have to operate a relay with one set of contacts wired like the zone valve "end switch" ie a grey permanent live to one side and a yellow (switched) from the other side to terminal 10, that way all three zones are independent.??

 

[Basher]

Hi John.g
As I understand it, the grey and orange wires on the UFH 2-port valve are currently unused, so could be connected directly to L and terminal 10. Simples!

 

[John.g]

Grand so, that's the way to do it alright.

Does the boiler still need a permanent live though as well as the (proposed) switched live, most boilers do for overrun etc.

 

[SimonG]

In cases like this I tend to go in, identify all the inputs and then disconnect everything before starting from scratch.
Then I know it's right.

 

[Basher]

Grand so, that's the way to do it alright.

Does the boiler still need a permanent live though as well as the (proposed) switched live, most boilers do for overrun etc.

Yes, that is the proposal.
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You are right Basher, the orange ones are on 10! And of course I could check whether there is voltage on 10 (I am just a bit reluctant to open an electric panel before switching off supply, I never usually do that...), although I am totally convinced that there is, following all the logic of a standard S-Plan. But the voltage on 10 is not taken anywhere, so I am now convinced that the solution would be to connect terminal 10 on my S-Plan wiring to the Switched Live terminal on my boiler (x2 connector no 1 on the Intergas Compact HRE). Question 1: Would you concur from what you can see?
I have also thought about how the UFH zone valve could be brought into play, as this valve is directly connected via L, N, E, only to the UFH wiring centre. If I connected the grey wire from this valve (currently unused) to terminal 1 permanent live (alongside the grey wires from the other two valves), and the orange wire (currently unused) to Terminal 10 (alongside the orange wires from the other two valves), I believe that the microswitch in the UFH zone valve would close when the valve is activated, and provide a live to the no 10 terminal, just as the other two valves do via their orange wires. Question 2: Does this make sense to you?
I have read the boiler instructions, and connecting one wire from the wiring centre to one connector in the boiler is a 5 minute job. No other wires would have to be changed. I may have to take out the link between 6 and 7 on the x4 connector, which I believe makes the boiler think that it needs to be permanently on. I would obviously do this with the power supply turned off. This should then result in the boiler coming on and off when valves are opening or closing. Question 3: Does this make sense, and would this require any other setting change to the boiler?
Thanks for all the help, it is all clear in my head now, would just appreciate some additional views!

Hi Cheshire
The consensus seems to be that what you described earlier is the way to go.
ie get electrician to:
Replace present 3 core cable to boiler with 4 core to carry both a perm live, and a switched live from terminal 10
wire UFH valve grey wire to live
wire UFH valve orange wire also to term 10 (there may be a spare core to implement that?)
job done!

 

[CheshireH]

OP .. you seem to have made up your mind what you are going to do so crack on with the bang test

AND you shouldn’t have 2 points of supply to your central heating system - it tends to irritate the guys who service them as they don’t like getting shocks ..

I think I will rather continue to seek advice than do a bang test - very grateful for the hints and tips, which is exactly what helped me discover the two point of supply issue. It was not me who wired it up in the first place!
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Yes, that is the proposal.
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Hi Cheshire
The consensus seems to be that what you described earlier is the way to go.
ie get electrician to:
Replace present 3 core cable to boiler with 4 core to carry both a perm live, and a switched live from terminal 10
wire UFH valve grey wire to live
wire UFH valve orange wire also to term 10 (there may be a spare core to implement that?)
job done!

Indeed, all of that, plus I believe replace power supply to UFH valve with power supply from wiring centre (solving the two supply source issue, I do think this needs to be done for safety), and use cable between UFH wring centre and S-Plan wiring centre to connect to boiler enable on the UFH wiring centre, wiring it into S-Plan like a thermostat for another zone.
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Regarding power supply: I noticed that switching the boiler feed off near the boiler does not switch off the power to the central heating and hot water programmer (which is in the kitchen). Clearly the programmer is connected as without a live signal from it nothing central heating and hot water would not work. If the programmer is still on when the boiler feed is disconnected, does this not mean that the wiring centre may still get a live feed?
I might be wrong here, but if not, I am starting to wonder how this was all signed off - which it was, I remember the electrician going round for almost a day with another electrician who certified it all.
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I had a look into all the wiring today, including inside the boiler. All as expected and supporting the solution above. However, this also confirmed that the power supply to the programmer is indeed made locally in the kitchen (same consumer circuit breaker, but not isolated by boiler switch). So a live feed could be sent even when boiler switch is off. Luckily I isolated the consumer unit circuit breaker at all times when investigating the system.
The cable running from programmer to S-Plan wiring centre is only three core plus earth. So if I wanted to supply power to the programmer from the S-Plan wiring centre as it should be done, I could not run a neutral wire. In this context, would it be acceptable to use the neutral from the local supply?

 

[Basher]

the dreaded 'borrowed neutral'
before answering, I wondered what model the programmer Is, and how it is wired. If it just switches the wiring centre via 'volt free' contacts with the live coming from the wiring centre and returning via the appropriate core, there would not be a hazard in the way you describe.

 

[CheshireH]

the dreaded 'borrowed neutral'
before answering, I wondered what model the programmer Is, and how it is wired. If it just switches the wiring centre via 'volt free' contacts with the live coming from the wiring centre and returning via the appropriate core, there would not be a hazard in the way you describe.

It’s a bog standard one, mine is iflo but the Drayton ones look identical. Definitely not volts free...it is the live feed going through for CH and HW. I am puzzled how this could be wired up like this only two years ago. As I said, luckily I removed circuit breaker before looking at wiring and did not touch anything before building up a through understanding, but the wiring centre could definitely be receiving a live feed from programmer even when boiler switch is off!

 

[Basher]

That is a pain. I agree you need another wire!
The system should have been done to the wiring regs, so I don't understand why you've ended up like this, unless due to 'organic growth' of the heating.

The 'borrowed neutral' is not the proper way as I'm sure you appreciate. In this instance it would work because both loads are on the same breaker, but not recommended - those more knowledgeable might like to comment?

Would it be practical to move the programmer to be nearer the wiring centre?

Alternatively if you were considering updating the system, eg to control individual radiators, then wireless could solve the issue.

 

[CheshireH]

Thanks Basher, I am not going to pursue the borrowed neutral idea. I am not quite knowledgeable enough to really understand why this would be problematic, but it would certainly be confusing.
I will indeed go wireless for the heating control, which would leave me with a spare wire to the boiler wiring centre to connect the neutral correctly for the hot water control. Most probably, I will even move the entire programmer to the garage next to the boiler, we do not really need to access hot water controls all the time, this runs on a timer and rarely gets changed. And my wife would rather like an extra socket in the place of the apparently very ugly programmer, and the fact that the programmer is locally supplied, with power not linked to the boiler, will allow this to be done!
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Deciding whether to move and keep the programmer next to the boiler and keep a manual on/off option available or go wireless and just connect the wireless receiver. I will be using a Lightwave RF boiler switch (as I have loads of Lightwave TRVs already) for CH, but not sure what to use for HW. Thinking of a wireless relay but worried about no manual override option. Any ideas?

 

[Basher]

Deciding whether to move and keep the programmer next to the boiler and keep a manual on/off option available or go wireless and just connect the wireless receiver. I will be using a Lightwave RF boiler switch (as I have loads of Lightwave TRVs already) for CH, but not sure what to use for HW. Thinking of a wireless relay but worried about no manual override option. Any ideas?
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No immediate bright ideas. It's a shame Lightwave don't do a combined heating and HW link. There are other brands doing this, but I guess would't integrate with what you're suggesting.
I used a Lightwave electric switch LW934 to control a water heater, and scheduled it with the app, but that won't integrate with a Lightwave thermostat controlling the boiler switch. And the boost button would be your phone!

If you decide to put a 13A socket where the programmer is (make sure the cable is 2.5mm) don't you then have a spare 3 core to the boiler wiring centre? In which case you could buy an electronic boost button and hard wire it! This sort of thing: Sangamo Powersaver Electronic Boost Timer 30min to 2 Hour - https://www.tlc-direct.co.uk/Products/SGPSB.html . I understand if this doesn't appeal!

 

[CheshireH]

I used a Lightwave electric switch LW934 to control a water heater, and scheduled it with the app, but that won't integrate with a Lightwave thermostat controlling the boiler switch. And the boost button would be your phone!

Oops, why does it not integrate with boiler switch/thermostat? I just put a saved search on eBay for the LW934 as it is no longer sold anywhere. Is it not just like a timed switch that you can schedule, activate via app, or indeed press manually?

 

[Basher]

Oops, why does it not integrate with boiler switch/thermostat? I just put a saved search on eBay for the LW934 as it is no longer sold anywhere. Is it not just like a timed switch that you can schedule, activate via app, or indeed press manually?

it does all those things - schedule, activate by app, and press manually, yes. Sorry, the integrate comment is misleading - I was thinking you might want to 'talk to it' via the boiler switch/thermostat.
The one thing about it, is that it has a temperature sensor, and turns off once the set temp is reached. It goes up to 40 or 45 deg C. So if you set it to max, the room never gets to that temp. so it continues switched on until the schedule activates 'off'.
I've got an unused LW934 if you want one! It was one of the few first series Lightwave devices which were Homekit compatible. I hope they don't stop supporting it.