MK SENTRY CONSUMER UNIT KITS

[cornish terrorist]

Just wondered if anyone has used theese MK kits with 10 breakers fitted supplied.

Lid slightly different and cheaper RCDS fitted to unit.

Had a situation today while doing a CU change when testing the ze at this unit to be 0.10 ohms as it is close to transformer TNCS i teasted a radial circuit 2m long wired in 2.5mm cable supplying one socket outlet i found the loop impedence to be 0.60 ohms.

this was with a megger MFT1552 tester on trip lock, i tested the RCD on the incoming side and found 0.10 ohms and on the load side o.38 ohms.

Has anyone found the extra resistance theese units add to the circuit.

I had this problem a few years ago with some old Hager BS4293 RCCB.S that did the same to the ircuit to such a large factor

 

[Andy™]

did you test on non-trip on the incoming side? almost every tester will give different readings between non-trip and high current

 

[cornish terrorist]

Yes the incoming side of the RCD the reading is 0.10 and on the out going 0.38 when the is set on the non trip setting.

With so much resistance its imposible to get an accurate reading so i added

thr R1 + R2 to the Ze to get a calculated reading.never had so much of a hidden resistance reading before

 

[sparkytim]

As Andy has said you will always get a higher reading on the no-trip setting. Try taking reading on both sides of RCD on no-trip settiing.

 

[steptoe]

agreed,

its not the resistance, its how your tester is taking the readings, try as tim suggests.