17th testing

**clive jackson** · 14th September 2009, 12:36 PM

does 17th Ed let you test insulation resistance at 250v ?

**robbieforrest** · 14th September 2009, 03:05 PM

Yes if you look at table 61 on page 158 of the big red book, and read down from 612.3 Insulation resistance, it lays out when you may need to test at 250 volts, for instance when 500volts could damage electronic euipment.

**clive jackson** · 15th September 2009, 10:32 AM

cheers robbie,so i expect >99.9Mohms is ok to put on cert ?

**Central Scrutinizer** · 15th September 2009, 10:11 PM

Originally Posted by clive jackson

cheers robbie,so i expect >99.9Mohms is ok to put on cert ?

hate to be pedantic, but......nah i love to be pedantic

you dont expect >99.9Mohms!!!!

if you did, then you would have to fail a reading of, say, 98Mohms, or 97Mohms

you EXPECT >1 Mohms for a 230V circuit, you may get >99.9Mohms, and you may get 5 Mohms, and both would be a pass as per table 61

incidentely, i use this reg on exisiting circuits, and test @250V as a matter of course - if it passes (especially L-N) then i crank it up to 500V - saves popping that aeriel booster running off the lighting circuit in the attic!