A spur or not ?

[dsnd_medic]

I'm been scratching my head over a problem I got this week. I have 4 heater circuits in the main DI. 3 are ring circuits and checked out OK but the 4th circuit is really odd. The r1 checks out at the DU but when I check it out at the heater end and break the loop I don't get any continuity (the r1 ends are connected back at the DU). When I energize the cct I measure 240Vac. I picked another nearby heater and found the same thing. If I hadn't checked the r1 at the DU I'd say it was a radial cct. All four heater ccts seem to disappear into a old mechanical timer for switching them on and off.

I guess I'll have to pop the lid off of all the isolator switches now and do it the hard way :-(

Anyone got any ideas how else I could attack this ?

Thanks guys

Andy

 

[telectrix]

think TREE. FIR to be exact.... Further Investigation Required. did you get rN and r2 readings?

 

[Richard Burns]

The ring is possibly joined together in the timer and then one section of the ring is broken between the heaters.
If you long lead one of the legs from the DB to each heater then you should be able to find where the break is or at least between which two points.
It would be best to check if there is a ring interconnection at the timer first!

 

[bf03yvd]

I hate Spurs. They got no chance of making the top four.

 

[robd]

Can you R1+R2 it (cross connect the live and earth conductors at the cu then go round and check readings) higher readings at individual points indicate a spur