Boiler Wiring - 230V and 24V

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imroberts

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I have a Vaillant boiler and at the moment have a single 5-core cable running into the boiler, providing power (L,N,E) and two 230V connections for my thermostat.

I'm looking to replace the thermostat with a Vaillant model which uses a 24V "ebus" connection which transmits data back to the boiler to adjust flow temperatures etc, rather than relay switching the boiler on and off.

Is it acceptable to use the same 5-core cable to carry the mains power into the boiler, along with a 24V connection, or should separate cables be used for the two voltages?
 
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Cables carrying different voltage bands need to be insulated for the highest voltage present. So in this instance, you can use that 5-core to carry both 230V and 24V. It's quite a common practice for e-bus connections to have it that way.


Lucia.
 
Thanks Lucia.

I thought that was the case but wasn't sure if there was any regulation I'd missed which stated that multiple voltages couldn't be carried within the same cable.

:)
 
The vaillant manual specifically says not to though. The ebus carries a supply voltage for the controller and also all the data superimposed over the top of the voltage. The mains AC can disrupt this superimposed data.

We have an ebus controller on our boiler, and it is great for telling you the status of the boiler and allowing you to control everything, but not exactly user friendly! I can use it now I am used to it, but the wife hates it!

[edit]The recent manual for their latest controller words it differently[/edit]
In locations where eBUS lines run parallel with 230 V
lines over a distance in excess of 10 m, they must be run
separately with a distance of at least 25cm.
Click to expand...
 
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The 5-core cable from the boiler only runs about a meter, it then separates off to the 230V feed, and the thermostat cabling runs off in the opposite direction. So I guess this would be within Vaillant's current recommendations :)

Thanks for the feedback re: the user-friendliness of Vaillant's controls. I'm looking at the VRT392, one of their newer thermostats, it looks fairly user friendly from pictures, however I appreciate it is VERY minimal in terms of buttons, which generally means quite tedious to use.

I'll get used to it I'm sure :D
 
If the flex is just a tail from wall to boiler I am sure it will be fine.

Ours in the model previous to their current one.

What annoys me is that you turn the knob to adjust the temperature, but can easily accidently press it too, which then enters the menu.
 
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