Can I run (Extra-) low voltage thermostat cable alongside 240 volt cable (Ed.)

[Mr.B]

Hopefully fairly straightforward ..... my installer is coming here on Friday to move the IDEAL Halo Smart Interface unit from the boiler (a Vogue 32 MAX 2nd Gen Combi - fitted three months ago) FROM the boiler TO a location within the house. The boiler's fitted in an attached garage, separated by a 9 inch wall and the wireless RF signal from the battery operated Halo wall mounted thermostat isn't enough to send a strong signal to the boiler ..... the signal does arrive but the Halo on the wall indicates it's displeasure by turning the strength indicator LED red instead of green. No amount of re-positioning inside the house gives us a good signal.

So he's moving the Interface unit FROM the boiler and repositioning it in the airing cupboard, which has a much better line of sight between the two components. Obviously it will be hard wired (with 1.5mm twin and earth cable) in order to take the 24 volt signal from the Interface in the airing cupboard all the way to the boiler in the garage.

As part of that cable run that I just described a short section of the 24 volt cable is sited in the same plastic trunking as the 240 volt cable that supplies the boiler itself. The two cables are tight up against each other in the trunking for about two metres.

My question is - is it recommended or permitted or advisable to have those two different voltage cables so close for two metres?

I could re-route it but would prefer not to as it means a bit of alteration, but nothing that can't be done. The installer is coming on Friday and I'd like to have it ready for him so would appreciate advice from someone who knows about these things.

For confirmation purposes - Ideal have sent their area engineer to me and he has replaced the two components and the problem has remained. The IDEAL BOOSTER that he recommended didn't do anything and this is his next recommendation. If this doesn't work they'll have to rip it out and fit something else. An EPH CP4 is a possibility. Or a Hive or something else??. But we haven't got there yet.

Thanks in advance

BY THE WAY ....... Maybe this would better in the Electrical forum. Am I allowed to post in two places?

 

[cross thread]

We used to have issues when Worcester had a similar situation ,we used screened cable for low voltage as advised by Worcester and it worked .I am not a electrician.

 

[Mr.B]

Right,o thanks.

 

[Mr.B]

Ideal Technical fella today said you can't run the thermostat hardwire if it's physically touching a mains cable. It has to be a couple of centimetres from the mains cable.

Ideal are sending their engineer to me again next week ( I have the NO WATER FLOW FAULT error message come up sometimes) .... so I'll see what he says. It's looking likely we'll swap the Halo for an EPH CP4

 

[ericmark]

I had a problem with my mother's central heating, this thermostat slowly got worse and worse, until it would only work when facing the sender. But same house, this

thermostat worked flawless. The other was simply a poor quality thermostat.

As to running wires close to each other, AC will always have some capacitive and inductive linking, but 2 meters should not be a problem, either the low voltage or extra low voltage cable can be screened, but over such a short run, it should not need it, but there are always exceptions.

 

[Mr.B]

Thank you, ericmark.

Have to admit this has occupied a disproportionate amount of time and effort.

The first Halo wall thermostat unit (I'll call it the "sender") developed a flickering screen hence the Ideal engineer replacing it (and the receiver - the Interface - too).

The problem manifests itself insofar as the heating turns itself on without being ordered to. This is because the Halo Interface has a 'failsafe' whereby if the Interface (I'll call it the "receiver') doesnt receive a strong enough RF signal it turns the heating ON. Thats how I became aware of the problem.

The Ideal "Booster" failed miserably. It did absolutely nothing.

My installer has used Halo's with Logics and they've been fine but he's not over the moon at the way mine is performing.

 

[ericmark]

The thermostat I showed

did the reverse, no signal and it turns off, seem to remember using one of these, and there was an option to select heating or cooling, with heating the normally open contact closed as it cooled, and with cooling the normally open contact closed as it heated, so it would fail safe, when battery went flat.

I just looked at paperwork for my Drayton Wiser thermostat, and there seems to be no option to change if normally open or closed contact is used for heating or cooling, normally open is always for heating. But both the Drayton Wiser hub and the Google Nest hub, both have manual start buttons, so with a non working thermostat you can activate the boiler manually.

Yes I have two thermostats, Nest in the hall does DHW if required, and generally turns on heating if needed in the house, but hall cools too slowly, so second one in living room, this time Drayton Wiser so I can add TRV heads to turn it on as well, so if living room too cold, it turns on heating even if hall still warm enough. Can't have just a thermostat in living room, as we have option for an open fire, which if used would cause rest of house to get cold.

It also means should one thermostat fail, we have a second one to turn heating on. Both thermostats have the option of analogue control, (OpenTherm) but the oil boiler does not, so using low voltage (230 volts) control, not extra low voltage. But not noticed anything saying how the extra low voltage cables should be routed, I do use extra low voltage between Nest Gen 3 hub and the thermostat, and to be frank not a clue where it runs, the whole reason for Nest was the three core and earth cable main house to flat where boiler is, changed colour, and had one core open circuit, so thought prudent to make it extra low voltage (12 volts) and also Nest Gen 3 also sends the info as to if boiler is to run and if motorised valve and pump should run, so all done with two wires.

The Drayton Wiser uses wireless linking, the Nest could, but I like the idea of at least one thermostat not relying on a battery, just a pity Nest did not do what it said on the packet, it does not connect to TRV heads, at least not in a useful way. So now have best of both.

 

[Mr.B]

The EPH CP4 I mentioned above also acts as yours and turns the system off, rather than on, as the Halo does.

But we're deviating somewhat from the main point of my post which was in connection with running the smart thermost hardwire alongside mains cable.

As I said, Ideal Technical say you definitely can't. but their engineer is coming here next week so we'll see what he says.

 

[Mr.B]

Not much in the way of responses. To be honest that seems to be par for the course for most of my threads. They're obviously pretty darn boring.

I'd move this to the electrical section if I could, but I can't see how.

 

[RandomGrinch]

Basically, whether 'extra low voltage' (<50V AC or <120V DC) cables can be run next to 'low voltage' (mains voltage etc.) cables, depends on a number of factors.

Ideally, the cables should be in separate containment.

However, from a safety point of view, if both the cables are rated to take a voltage in excess of the mains, then it is difficult to argue that they couldn't be mounted together.

From a non-safety point of view, the cable should be specified to cope with the voltage drop of the long run.

There may also be induced voltages in cables running close to each other, that could be damaging to any extra low voltage equipment the cable is connected to.

Additionally, the Halo is sending data down the cable, as well as power. This might require a screened cable, if it is run close to other electrically noisy cables.
The cable joining the Nest heatlink to the thermostat has been known to be susceptible to noise - a screened cable like this, is often recommended...

0.75mm² 2 Core CY Control Flexible Cable (Cut Length Sold By The Mtr)

Plain copper conductors

www.cef.co.uk

So,

Can I run (extra) low voltage thermostat cable alongside 240 volt cable

I'm afraid, it depends and will be down to the installer, to specify an appropriate cable for the situation.
And I think my main concern for your long run of cable, would be voltage drop.

I'd move this to the electrical section if I could, but I can't see how.

If you wish to move this thread to the electric forum, press the report button, and ask a mod to move it.

 

[Mr.B]

Thanks, RandomGrinch ... that was helpful.

As of today, I can report that I took the bull by the horns and spent a very long day yesterday re-routing sections of the hardwire between the boiler and the distant Zigbee Halo Interface and its respective mounting bracket which will hopefully soon be moved in to the airing cupboard within the house. To repeat, the cable run is something like 12 or 15 metres and the cable itself is 1.5mm three core plus earth (of which only two conductors will be used) and the cable is now no longer run alongside sections of mains 240v cable. The Interface unit will be powered by its own 24volt power supply sited adjacent to the Interface unit in the airing cupboard. The cable wasn't specified by anyone, it just happens that I fitted it several years ago thinking it might be needed for any anticipated change of boiler with a view to providing cabling for a boiler over-run - it turns out it wasn't needed for that purpose but seemed appropriate for the job in hand.

At the risk of further repetition the boiler (and the associated Halo Zigbee Interface unit) is currently mounted within the boiler - which is in the attached garage separated by a 9 inch block wall (which is impeding the signal from the wall mounted Halo programmablr thermostat sited in the hallway of the house) .... and by moving it to the airing cupboard it's hoped the signal will be improved and the red LED on the Halo wall stat will turn green.

A final repetition is that IDEAL Technical have said, quite plainly, that the cables must not be touching and should be separated by at least one or two centimetres. They did offer a technical reasoning but I confess i only picked up a small percentage of it.

The Ideal Engineer is coming next week for something else and I hope he'll take time to swap the Interface over whilst he's here otherwise the installer will return to do it.

Fingers crossed.

Ta.

 

[RandomGrinch]

To repeat, the cable run is something like 12 or 15 metres and the cable itself is 1.5mm three core plus earth (of which only two conductors are used) and the cable is now no longer run alongside sections of mains 240v cable

Ok, from your previous posts, it wasn't clear that the three core + earth was a pre-existing cable.
That should be adequate from a safety and voltage drop perspective.
Where it may fall down, is with electrical noise and induced voltage - however, with a shared run of only a couple of meters, it should probably be fine.
Hopefully the installer will give it a try.

 

[Mr.B]

Ok, from your previous posts, it wasn't clear that the three core + earth was a pre-existing cable.
That should be adequate from a safety and voltage drop perspective.
Where it may fall down, is with electrical noise and induced voltage - however, with a shared run of only a couple of meters, it should probably be fine.
Hopefully the installer will give it a try.

Just to clarify, I'm not aware that, since my re-routing endeavours yesterday, there are now any close encounters with any mains cables, certainly no touching that I'm aware of.

If the Ideal engineer doesn't move it next week then the installer has said he will give it a go and if it still doesn't send a strong signal then he'll take it out and fit something else, He suggested Hive but I think I favou EPH Combi pack CP4 on the grounds of simplicity and the fact that it uses Opentherm. Apparently Hive doesn't (which seems odd). Maybe Honeywell T6 is anothewr alternative.

Anyway, I'll update.

 

[ericmark]

Wiser used the same back as Hive, there are three versions, single, twin, and triple, it has OpenTherm, and it would seem to connect to a room thermostat or TRV heads, not confirmed it will work without a room thermostat, but note is sold as hub with 6 TRV's.

I can't get it to work with a PC, only phone and tablet.

 

[Mr.B]

Wiser used the same back as Hive, there are three versions, single, twin, and triple, it has OpenTherm, and it would seem to connect to a room thermostat or TRV heads, not confirmed it will work without a room thermostat, but note is sold as hub with 6 TRV's.

I can't get it to work with a PC, only phone and tablet.

You've lost me there, ericmark. Am I missing something? Help me out.