New FCU for bathroom floor heating

How can I tell whether my combi boiler is connected direct to the main ring or as a spur (I can't trace the wiring back as it's hidden).
I'm hoping to use a spur from the combi's FCU in the airing cupboard to connect underfloor heating, but presumably you can't run a spur from a spur?
Thanks

You say that the boiler is on an FCU - opening that up will tell you whether it's on a spur or on the ring.

1 cable = spur
2 cables = ring, or possibly on to another device (which it shouldn't) - you'd need to disconnect both cables on the supply side and see if one or both are live.

IMHO it is 99.9999999999999999% certain that the FCU is not directly on the ring, and yes, you're right, you can't spur off a spur to power something else.

What is the load of the U/F heating?

longbloke said:

How can I tell whether my combi boiler is connected direct to the main ring or as a spur (I can't trace the wiring back as it's hidden).
I'm hoping to use a spur from the combi's FCU in the airing cupboard to connect underfloor heating, but presumably you can't run a spur from a spur?
Thanks

Click to expand...

The heating circuit and immersion should be on a dedicated circuit back to the consumer unit