Electrical test procedure on gas boiler advice

[martineire]

Quick question regards electrical test procedure on a gas boiler. I've isolated the power via removing fuse from spur but the problem is when doing my earth continuity, short circuit test and resistance to earth checks I'm getting different resistance reading when the spur switch is turned on and off. Fuse is removed and all clocks and stats are calling for heat but with the spur switch on I'm getting difference reading than when it's switched off?? Earth continuity is grand it's less that 1 OHM but with the other two tests I'm getting confused and need advice

Fuse out with switch on

Live and neutral= 187 OHMS
Live and earth =186 OHMS
Earth and neutral = 000.7 OHMS

Fuse out with switch off

Live and neutral= 183 OHMS
Live and earth= OL
Earth and neutral= OL

My live test I'm getting

Live and neutral= 231V
Live and earth= 231V
Earth and neutral= 17V

Any advice and help thanks

 

[londonboy]

This would be better in the electrical section.

With the spur turned on, but with the fuse removed, you are switching the neutral 'on'. You will always get a low reading (in ohms) between neutral and earth, as these are connected together either beside the meter, or outside in the street.

 

[martineire]

This would be better in the electrical section.

A service engineer is meant to preform theses tests on a boiler prior to servicing/repairing. So was just thinking maybe there are some service engineers on here that could clear this up for me.
Thanks

 

[Dan Robinson]

Why?

 

[martineire]

Why?

why what? Why do I want to know is it? Because I just want to know if anyone can tell me? Just want to learn

 

[Dan Robinson]

But Why?

 

[martineire]

But Why?

because I preformed theses test on a boiler and theses are the reading I am getting and I'm confused to why I am getting theses different readings especially in relation to the resistance to earth test

 

[picasso]

edit

 

[Weedrip]

Your probably right about asking a sparky londonboy.

With the spur turned on, but with the fuse removed, you are switching the neutral 'on'. You will always get a low reading (in ohms) between neutral and earth, as these are connected together either beside the meter, or outside in the street.

How does that work with double pole isolation on a fused spur?

 

[martineire]

Lad the the problem I was encountering was only on the resistance to earth check Irrelevant as ye say it is I'm just interested in understanding why I was getting a resistance reading with the switch on. I'm not sure I still quite understand because I have the fuse removed from the spur so that's the live isolated from the main circuit. Now when I'm doing the resistance to earth test I am testing between Live and Earth. Now correct me if I'm wrong but as I understand by having the spur switch on but the fuse is still removed I have Neutral from the boiler connected to the main circuit but by having the switch off with fused removed I am now breaking the Neutral from the main supply, Correct??

Now this is where I'm getting confused. When I'm doing my resistance to earth test I'm testing between Live and Earth. Now I'm being told I'm getting a resistance reading when the switch is on because the Earth and Neutral are connected at the meter so that is creating a circuit hence that is why I'm getting a resistance as opposed to having the switch off (neutral broken) and not getting a resistance (testing boiler only). But with the switch on and fused removed I'm probing the Live and Earth terminals at boiler, how is that creating a circuit through my multimeter regardless of the Earth and Neutral connected at meter because one my probes is in the Live terminal at boiler which is broken (fuse removed) and the other in the earth terminal but how is the creating a circuit through my multimeter so that I'd be is pick up a resistance?

 

[AngelesPlumbing]

Why?

 

[martineire]

Why?

really what is the point in posting that. Not one bit helpful.