No switched live to boiler?

CheshireH · Oct 18, 2020

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

Aquarius · Oct 19, 2020

Which Intergas model is it? Do you have a Honeywell thermostat?

CheshireH · Oct 19, 2020

Intergas Compact HRE 40 SB. I do not have a thermostat for CH - I have a standard two channel programmer that switches CH and HW on and off. HW has a thermostat of course (and I fixed the issue I mentioned with hot water, it was wrong wiring on the thermostat). What I do not understand is why there is no switches live to the boiler from the wiring centre. The boiler does come on when a valve opens, I would just like to understand why...before I make changes for my smart heating project!

Basher · Oct 19, 2020

I don't understand either!
I'm not suggesting you to go into the boiler (strictly GasSafe territory), but if you've looked at its wiring tray underneath, is there a wire in pin1 of connector X2, and if so where does it go? That's supposed to be switched live.

snowhead · Oct 19, 2020

If the Boiler fires when the Valve opens then the valve has control of the boiler.
If there is only a single Live (and Neutral and Earth), then the Valve must be switching that and it must be linked within the boiler.

Basher · Oct 19, 2020

snowhead said:
If the Boiler fires when the Valve opens then the valve has control of the boiler.
If there is only a single Live (and Neutral and Earth), then the Valve must be switching that and it must be linked within the boiler.

Which presumably means there is no fan overrun or pump overrun - is that not a bad thing?

CheshireH · Oct 19, 2020

Basher said:
I don't understand either!
I'm not suggesting you to go into the boiler (strictly GasSafe territory), but if you've looked at its wiring tray underneath, is there a wire in pin1 of connector X2, and if so where does it go? That's supposed to be switched live.

Definitely not wire going into boiler, other than power supply (brown, neutral, earth), which is connects directly to mains supply!

EvilDrPorkChop · Oct 19, 2020

Basher said:
Which presumably means there is no fan overrun or pump overrun - is that not a bad thing?

Won't do the boiler much good.

Sounds like it hasn't been wired up quite right. When there's nothing switched on, HW or CH or UFH is there any lights on the boiler?

CheshireH · Oct 19, 2020

EvilDrPorkChop said:
Won't do the boiler much good.

Sounds like it hasn't been wired up quite right. When there's nothing switched on, HW or CH or UFH is there any lights on the boiler?

Yes the boiler is in stand-by when all valves are switched off. To be honest, it does exactly what it is supposed to do, it kicks in a bit after the valves open and I believe it also runs a bit longer when they close. But there is definitely no electrical connection - in fact the UFH valve is connected directly to the UFH wiring centre (which has no connection to the boiler), it is not even linked into the S Plan wiring! And of course in the wiring centre, there is no switched live out from the terminal anyway where the orange wires from the valves connect to (no 10). It looks to me as if the opening of the valves create a flow (?) that starts up the boiler, perhaps there are sensors of some kind in the boiler! Unfortunately I know nothing about plumbing, but I understand electrics a bit, and there is only mains power to the boiler!
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Not a great picture but you can see the 3 core from the boiler kn the right, which goes straight across into 1,2,3 mains supply, and the orange cables from valves with no wire connected to them - where The switched out should be.

John.g · Oct 19, 2020

Maybe the boiler is just cutting in/out on its own stat, the zone valves opening and closing are simply speeding up the process by circulating water through it, it should also start/stop occasionally if the zone valves never open.

Murdoch · Oct 19, 2020

Are you sure the green and yellow cable isn’t the switched live .... seem it A LOT

CheshireH · Oct 19, 2020

No goes into earth connection in wiring centre..

Murdoch · Oct 19, 2020

so the boiler man couldn’t be bothered to run a new cable to the boiler with a SL?

CheshireH · Oct 19, 2020

Murdoch said:
so the boiler man couldn’t be bothered to run a new cable to the boiler with a SL?

Possibly. I don’t know. Just wondering why it is working now...
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I have a bit more information that will hopefully yield an explanation from someone!

Reading through the boiler instructions, I realised that the boiler never goes into 'Waiting Mode', it stays on '1 Boiler shutdown when require temperature reached'. So I assume that the boiler controller essentially shuts the boiler down when it reaches a set temperature. Closing the valve will probably lead to reaching the temperature limit.

What I do not understand is why, in this case, the boiler does not switch itself back on when its internal temperature is reducing, even if there is no demand for heat. Or perhaps it does do that for a few minutes, before it reaches temperature again - I just might not realise?

Any advice? I am puzzled why one would not just connect a simple four core cable with a switched live to control the boiler. The wiring centre is right next to the boiler, and the installation was done from scratch, involving four core cable in various places, so there ws no pre-existing three core that somebody could not be bothered to replace. It must have been done lie this intentionally. Does anybody understand why?

John.g · Oct 20, 2020

I think that's what is happening as I mentioned in my other post, if you monitor it after cut out it should be easy to catch it firing back up as normally the cut in temperature is SP-5C. (Cut out SP+5C)

CheshireH · Oct 20, 2020

John.g said:
I think that's what is happening as I mentioned in my other post, if you monitor it after cut out it should be easy to catch it firing back up as normally the cut in temperature is SP-5C. (Cut out SP+5C)

Thanks John, is there any logic to this set-up? Is it acceptable? Will it do damage to the boiler? The installer is no longer trading, but I have had a boiler inspection from somebody else since who did mention that he would have wired things differently, but otherwise did not raise a concern.

What is SP by the way?

Basher · Oct 20, 2020

Cheshire - in you original post you mention two S-plan valves and a UFH Valve.
In your wiring centre (Terminal 10) you have just two orange wires, presumably from the Heating and HW zone valves, but should there be a further wire to call for heat for the UFH?
Maybe the boiler was connected up with switched live common with permanant live (ie 'on all the time') so that UFH has heat available even when the S-plan is not calling for it?
or maybe it's plumbed in a way that doesn't require a UFH Only demand.

John.g · Oct 20, 2020

CheshireH said:
Thanks John, is there any logic to this set-up? Is it acceptable? Will it do damage to the boiler? The installer is no longer trading, but I have had a boiler inspection from somebody else since who did mention that he would have wired things differently, but otherwise did not raise a concern.

What is SP by the way?

IMO, no logic in the way its configured, it should be configured as the S plan suggests.
SP = Set Point.

CheshireH · Oct 20, 2020

Basher said:
Cheshire - in you original post you mention two S-plan valves and a UFH Valve.
In your wiring centre (Terminal 10) you have just two orange wires, presumably from the Heating and HW zone valves, but should there be a further wire to call for heat for the UFH?
Maybe the boiler was connected up with switched live common with permanant live (ie 'on all the time') so that UFH has heat available even when the S-plan is not calling for it?
or maybe it's plumbed in a way that doesn't require a UFH Only demand.

Basher, the UFH valve is connected directly to the UFH wiring centre (just live, neutral, earth - grey/orange not used but GR/OR terminals are connected together in UFH wiring centre). Just as with CH and HW, the boiler starts up when the valve opens, without an electrical signal (no switched live).

John, if there is no logic in the set-up, can I just connect a switched live from the terminal with the two orange wires to the X2 connector no 1? Can I then also make a link between the live wire of the UFH valve and the same terminal where the switched live would come from (no 10 in my setup, which already holds the orange wire of the other two valves), so that the UFH valve opening would also activate the boiler?
Does this connection of one single wire need a qualified installer?

John.g · Oct 20, 2020

I think using somebody qualified is the proper/best way to proceed.

CheshireH · Oct 20, 2020

Another piece of information: I indeed just 'caught' the boiler switching on for a few moments without any valve being open - it went back to status '1' in the matter of perhaps a couple of minutes, with some 'banging' in the pipes. This really feels like something undesirable, can it damage something?

I would greatly appreciate anybody commenting on the possibility of connecting the UFH valve in the way I suggested. There is also a 'boiler enable in/out' on the UFH wiring centre (not 230V), which is unused, but I would need to run a cable across the garage - the UFH controls are not close to the valves and boiler - which has just been plasterboarded for use as a gym...

Basher · Oct 20, 2020

CheshireH said:
Another piece of information: I indeed just 'caught' the boiler switching on for a few moments without any valve being open - it went back to status '1' in the matter of perhaps a couple of minutes, with some 'banging' in the pipes. This really feels like something undesirable, can it damage something?

I would greatly appreciate anybody commenting on the possibility of connecting the UFH valve in the way I suggested. There is also a 'boiler enable in/out' on the UFH wiring centre (not 230V), which is unused, but I would need to run a cable across the garage - the UFH controls are not close to the valves and boiler - which has just been plasterboarded for use as a gym...

This sounds like a job for a wireless link rather than a cable.
I think your added wire suggestion (If you mean hard-wired) would result in the S-plan valves actuating the UFH valve, ie a demand for HW would open the UFH valve. A relay can be used to isolate, but again a wireless link would overcome this issue.
Also if by any chance the UFH electrics is on a separate circuit from the boiler, there could be a further complication of 'borrowed neutral' which could trip rcb's/rcbo's. A wireless receiver that connects tag (10) to (L), with a transmitter, either a thermostat for the UFH, or the contacts you describe, might do it.
Maybe a bit of design work is required to map out a preferred Thermostat/sensor scheme etc.
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Basher said:
This sounds like a job for a wireless link rather than a cable.
I think your added wire suggestion (If you mean hard-wired) would result in the S-plan valves actuating the UFH valve, ie a demand for HW would open the UFH valve. A relay can be used to isolate, but again a wireless link would overcome this issue.
Also if by any chance the UFH electrics is on a separate circuit from the boiler, there could be a further complication of 'borrowed neutral' which could trip rcb's/rcbo's. A wireless receiver that connects tag (10) to (L), with a transmitter, either a thermostat for the UFH, or the contacts you describe, might do it.
Maybe a bit of design work is required to map out a preferred Thermostat/sensor scheme etc.

Suggestion instead of cable;

https://plumbbox.co.uk/product/mains-switch-rf-solution-alternative-to-cabling/

or

RF Solutions MAINSLINK Remote Control System,869.5MHz | RS

uk.rs-online.com

CheshireH · Oct 20, 2020

Basher said:
I think your added wire suggestion (If you mean hard-wired) would result in the S-plan valves actuating the UFH valve, ie a demand for HW would open the UFH valve. A relay can be used to isolate, but again a wireless link would overcome this issue.

Thinking about this...yes, it would put the orange wires to the other valves live, yes, but without the motor of the HW/CH valve running (i.e. being activated by the programmer and thermostat), would these valves really open? Perhaps I am missing something...

I have been looking around, and really the right way of doing this, I believe, would be to run the (not 230V) boiler enable cable to the boiler. John Guest calls this a 'Voltage Free' connection, what does this mean? Could this connection be made wirelessly?

Murdoch · Oct 20, 2020

OP you really need to get a decent heating / spark involved and make sure they understand what you are trying to achieve before they tamper with it

Basher · Oct 20, 2020

CheshireH said:
Thinking about this...yes, it would put the orange wires to the other valves live, yes, but without the motor of the HW/CH valve running (i.e. being activated by the programmer and thermostat), would these valves really open? Perhaps I am missing something...

I have been looking around, and really the right way of doing this, I believe, would be to run the (not 230V) boiler enable cable to the boiler. John Guest calls this a 'Voltage Free' connection, what does this mean? Could this connection be made wirelessly?

OK, sorry, I misunderstood what the UFH valve was. If it's the same sort of valve, generally speaking, as your S-plan valves, with microswitches operated by actuation, you are right - there's no 'back feed' issue, and your wire suggestion would work.

A 'voltage free' option is effectively a set of relay contacts, generally a single pole double throw 'switch', so you can choose to use the 'normally open' or 'normally closed' as you need. The relay contacts typically capable of switching mains, but wise to check.
Yes I think you could make a connection wirelessly, either from the volt free contacts switching a transmitter on, or from the orange wire if that can provide the necessary. Then a receiver by the wiring centre connecting (10) to (L)

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