MPB question

[orbital]

R2 (long lead Nulled) test from MET to gas bond 0.78 ohms 10mm G and Y

What would you do

Length 15-20m

re running would be a significant challenge.

 

[ACDC]

Not Sure what the question is TBH, but a reading of 0.78ohms, on a 10mm earth conductor does sound a little high (Without looking at my book). Check your connections are nice and tight and that the connections are not made on painted surfaces e.t.c. Is your test equipment calibrated and in good working order?

 

[Guest123]

The resistance per metre of 10mm G+Y single core cable is 1.83 m'ohm per metre.

20M x 1.83 / 1000 = 0.036 ohms. Your value of 0.78 is way off. Check meter accuracy, lead connections, probe tips etc.

Did you disconnect one end of the conductor before you tested it???

 

[ackbarthestar]

The resistance per metre of 10mm G+Y single core cable is 1.83 m'ohm per metre.

20M x 1.83 / 1000 = 0.036 ohms. Your value of 0.78 is way off. Check meter accuracy, lead connections, probe tips etc.

Did you disconnect one end of the conductor before you tested it???

I'd agree with this comment. Most 'strange' continuity readings from a low reading Ohmmeters are due to
1/ Not zeroed
2/ Poor croc-clip connection
3/ poor connection of probes to point of contact
4/ high resistance leads
5/ out of calibration meters

Several ways of checking this is
1/ are the high values consistent?
2/ pressing the grip of the croc-clips or repositioning the probes
3/ taking more than one reading

other considerations can be
1/ the differential temperature of the instrument with the ambient temperature, is the instrument cold when first being used?
2/ are the batteries flat?

Simple check would be to get a 100m roll of known sized cable, I use 4mm2 grn/yell.
Knowing the Ohms per meter, the length and a correction factor for the ambient temperature you can then compare the calculated value with the measured value. If there is a significant difference then either you or your instrument is at fault.

 

[orbital]

Thanks for comments

Pretty happy that readings are correct. MPB to gas is to high should be equal lower than 0.05

So would you say that MPB needs to be re done?

 

[GLENNSPARK]

Thanks for comments

Pretty happy that readings are correct. MPB to gas is to high should be equal lower than 0.05

So would you say that MPB needs to be re done?

firstly take a look at post 3 mate (Lenny)......test leads are a known cause of high resistances on low resistance ohmmeters. You mentioned that you nulled out the leads so have you checked the plugs where the leads interface with the tester?...Dirt, dust or crap maybe in the plugs?....Try nulling out in the normal way then when zero`d properly just "waggle" the test leads then take another reading....see what you get..........

 

[Octopus]

Thanks for comments

Pretty happy that readings are correct. MPB to gas is to high should be equal lower than 0.05

So would you say that MPB needs to be re done?

If the existing cable is continuous you either have poor connections or need to recalibrate your tester leads. Have you got a few meters of cable to hand - then test that and see what readings you get.

 

[telectrix]

if a 10mm bonding cable is not open circuit ( broken ) then a reading of 0.78 ohms is not the cable. it's as lenny says:

1. connections. 2. leads. 3. meter. 4. you.

 

[orbital]

Well the bond is in a cupboard
The MET is 15-20 m away
who knows what goes on in between

I tested about 5 times.
New batteries, leads good and can;t see any 'user error' clean copper on clamp

But ultimately if you get a high bond reading, it has to be re done. right

Thing is R2 long lead to gas supply to boiler is good

 

[hercule]

I've seen nice shiny new 10mm green and yellow either end disappearing under the floor boards then not so shiny bell wire joining it together out of sight...

 

[GLENNSPARK]

can hide all sorts of nasties can floorboards n cupboards..........there was this house once where we had ripped out the kitchen and behind one of the units was this tatty old dirty pair of knickers...........

 

[ACDC]

can hide all sorts of nasties can floorboards n cupboards..........there was this house once where we had ripped out the kitchen and behind one of the units was this tatty old dirty pair of knickers...........

LOL, did you have a cheeky sniff

 

[Geordie Spark]

can hide all sorts of nasties can floorboards n cupboards..........there was this house once where we had ripped out the kitchen and behind one of the units was this tatty old dirty pair of knickers...........

Sounds like Wor Lass has been there !!

I kid you not, she "lost" a pair & we turned the house upside down looking for them to no avail. They turned up in her handbag .... :crazy: