Data and power in the same flex to a boiler.

[wannocks]

Hi there. I'm a heating guy with a question for you sparks out there:
My question is regarding the situation where the 20v DC ebus data pair to a boiler is in the same 5 core flex supplying the 230v AC to the boiler. I know this can cause control problems due to induced voltages causing data errors. There is also the risk of someone in the future crossing a cable and frying all the DC components in the system.

My question is does this contravene any specific electrical regs?

Any advice will be appreciated.

 

[flameport]

Permitted provided that the cores within the cable are all insulated for the highest voltage, 230V in this case.
Standard 5 core flex will comply.

 

[ban-all-sheds]

I know this can cause control problems due to induced voltages causing data errors.

Does/do the boiler maker(s) advise against using a multicore cable in that way, for that reason?

There is also the risk of someone in the future crossing a cable and frying all the DC components in the system.

If the sort of person who cuts and/or joins cables without keeping the colours the same, or without knowing what they do, has been fiddling with a heating system it might be that the boiler no longer firing up is a good thing.

 

[ericmark]

We can not really plan for idiots, we can use enclosures which require a key or tool to open them, but after that there is very little we can do. Using optical isolators we can limit the damage, we did this with 7 core portable traffic light cable, if the cable was damaged causing the 110 volt and radar control cables to get joined all it did was blow a very cheap component not the whole board.

We don't design the boilers so it is down to the manufacturers as to how they protect the boiler.

 

[wannocks]

Does/do the boiler maker(s) advise against using a multicore cable in that way, for that reason?

Yes they do, there has been problems where the boiler is unable to be controlled due to this. Separating the cable has solved the problem.

If someone did cross the 20v side with the 230v it would damage multiple circuit boards causing an expensive repair that would not be covered by the warranty.

 

[EFLImpudence]

Yes they do, there has been problems where the boiler is unable to be controlled due to this. Separating the cable has solved the problem.

That, then, is nothing to do with the Electrical Regulations.

If someone did cross the 20v side with the 230v it would damage multiple circuit boards causing an expensive repair that would not be covered by the warranty.

That, then, is nothing to do with the cable type.

 

[wannocks]

I know the manufacturer doesn't allow it.
I wanted to know if the electrical regs did.

 

[ban-all-sheds]

Yes they do, there has been problems where the boiler is unable to be controlled due to this. Separating the cable has solved the problem.

That, then, is nothing to do with the Electrical Regulations.

Indeed not.

But the Q about the Wiring Regulations is moot, surely? Someone can't say "the Wiring Regulations do not forbid it, so I'm going to do it" if the maker says "you must not do it because it might affect the working of the boiler".

If someone did cross the 20v side with the 230v it would damage multiple circuit boards causing an expensive repair that would not be covered by the warranty.

That, then, is nothing to do with the cable type.

I would have thought that there was less chance of someone applying 230V to a 20V input if it was all in one cable, and therefore with all the conductors a different colour, that if there were 2 cables, and therefore a choice of 2 of each colour.

 

[EFLImpudence]

I know the manufacturer doesn't allow it.
I wanted to know if the electrical regs did.

Fair enough.

 

[JohnW2]

But the Q about the Wiring Regulations is moot, surely? Someone can't say "the Wiring Regulations do not forbid it, so I'm going to do it" if the maker says "you must not do it because it might affect the working of the boiler".

In this case, that's probably right, and makes sense. However, more generally, I need not tell you that manufacturers often warn against doing things (and say or imply that such action would invalidate a warranty) without any apparent rational reason.

I would have thought that there was less chance of someone applying 230V to a 20V input if it was all in one cable, and therefore with all the conductors a different colour, that if there were 2 cables, and therefore a choice of 2 of each colour.

I agree. As I see it, the potential problem with a single cable would be the possibility of impairment of functionality, not a greater chance of mis-wiring.

Kind Regards, John

 

[ban-all-sheds]

By impairment do you mean a core-to-core fault within the cable?

 

[JohnW2]

By impairment do you mean a core-to-core fault within the cable?

No - I mean capacitive and/or inductive coupling, leading to potential interference with data transfer.

Provided that all cores are insulated to the degree required for the highest voltage present, a core-to-core fault is no more likely to occur in a cable containing cores carrying both LV and ELV than in one carrying only LV.

Kind Regards, John

 

[ban-all-sheds]

Indeed, but you posted about impairment in reply to my comment about someone applying 230V to a 20V input, so it seemed reasonable to me that you were talking about an impairment which caused that.

 

[mattylad]

So Wannocks, are you now intending to do this?

 

[wannocks]

No. But I do have to deal with the problem it causes when others do it.