RCD Trip times

[gselectrical]

would agree with the over 50v touch voltage shutting down your meter,if the RCD is tripping out at 1X then it should be tripping at 5X by logic,

it is a fairly high Ra you have,

you really need to try get it down a bit, couple of hundred ohms hopefully,

how many rods installed, what sort of ground is it?

you can get some crystals to help, or salt water, or the ubiqutious wet around the rod(just dont get seen )

Slate ground. (again) The house is far up in the countryside. Transformer supplying house is 500m away on a pole. There are 2 rods installed. 3 metres apart.

GS

 

[Andy™]

what about deeper rods?

 

[a1]

My meter shows +40ms if the touch voltage is more than a set limit - can you remove this preset from your meter?Also - wet around the rod to retest; just to prove your meter is fine.

http://www.talk.electricianforum.co.uk/downloads.php?do=file&id=164

Should you need the Fluke 165X series Manual.

 

[a1spark]

Interesting post plumber mate....thanks .

a1spark.

 

[gselectrical]

Hi GsDone some thinking:coffee

It is your meter, 50v limit, so in essence 50v divided by 150 mA gives us a maximum of 333.333 ohms any value higher the meter wont work due to the 50v limit.

Ive spoke to several people about strapping the rcd as Andy and others have suggested, IEE, Manufacturers(RCD), Nic , Megger and they would not confirm this as an appropriate method of testing the rcd in this instance, but all stated it should be a code 1.

In a TT we have the 50v rule, hence 50/.03mA= 1666

and

The disconnection times need to meet 411.3.22 or 411.3.2.4

Additional protection requires 30mA or less and must trip within 40ms at 5 x idelta n.

So we can test our 30 mA rcd at time 1/2 and 1 times to make sure it operates for fault current verification as per ch41 bs7671 because 50/.03 = 1666 ohms

but

for additional protection(5 x 30mA) 50/.15= 333.33 ohms, so if this is all the meters will test too(because of the 50v) then the regs may as well say that if additional protection is required then the zs should be no greater than 333 ohms as we cant verify above this.

Good post plumer

Went back to the house the other day. Put another rod down. Got it down to 340 ohms (dry). Still would not trip on 5X. Knowing this reading was a little high, I returned the next day. It had been raining, tested Ze out of interest. 321 ohms. Tested fine on 5X. So as suggested by others, its defo the meter.

Anyway, took rod out (eventually) Hammered a bigger one down. Ze down to 185ohms. Im happy with that concidering the circumstances.

GS