electrical - connect room thermostat to boiler (Bosch - 2 wire bus)

Seems a bit heavy.

Is there mains on this cable or is it (extra) low voltage? If low, I would see no harm in using any reasonably heavy signal cable - perhaps mic cable?

If mains, how about CY or SY[1] cable - common enough and the screening, whilst braid rather than wrapped foil, should be effective.

Thanks Tim - a huge help. Intelli roomstat guide say LV while boiler install. guide says ... am still trying to sort it out :-)

Perhaps SY would be safest.

To earth the braid, gather it and twist it into a "pigtail" and sleeve it with G/Y sleeving, then clamp it in the earth terminal. If the instructions specify an earth connection at either end, use a core in addition as the braid is designed more for screen and limited protection and it's cross sectional area may be less than what is needed.