Understanding installation voltages, particularly Vne

[ringer]

Believe that I am (mostly) up to speed with electricity as applied to appliances (n.b. just realised as I wrote this, that is where the word appliances comes from, never occurred to me before!), so I am now trying to understand installation voltages. My aim is to learn/train eventually to become domestic installer, maybe more. Anyway, the point of this post is...

So I have my Fluke 6500 appliance tester plugged in and the home/idle screen shows the voltage/frequency of the supply as measured by the instrument. Current readings are:
VLN = 248.6v
VNE = 0.3v
49.9Hz

VLN is varying over time (over the last two minutes) from 247.7v up to 249.3v though I have seen it as high as 250.4 and as low as 239.8
VNE varies from 0.0 to 0.3, though does not constantly change like VLN does, just slowly.
When I switch on a toaster or microwave on the same circuit VNE jumps to 0.4v and VLN drops (sometimes) by up to 2v
When I switch on the kettle on the same circuit VNE jumps to 0.8v
Plugging the Fluke into another circuit, VNE remains constant (albeit non-zero) whether the kettle/toaster/microwave are on or not.

I can (sort of) understand that incoming voltage may vary. My main query/concern is about Vne

So my question (finally) is - are these readings 'normal', or does this indicate some sort of fault with my installation (or perhaps with the Fluke)?

 

[Golden_Boy]

Believe that I am (mostly) up to speed with electricity as applied to appliances (n.b. just realised as I wrote this, that is where the word appliances comes from, never occurred to me before!), so I am now trying to understand installation voltages. My aim is to learn/train eventually to become domestic installer, maybe more. Anyway, the point of this post is...

So I have my Fluke 6500 appliance tester plugged in and the home/idle screen shows the voltage/frequency of the supply as measured by the instrument. Current readings are:
VLN = 248.6v
VNE = 0.3v
49.9Hz

VLN is varying over time (over the last two minutes) from 247.7v up to 249.3v though I have seen it as high as 250.4 and as low as 239.8
VNE varies from 0.0 to 0.3, though does not constantly change like VLN does, just slowly.
When I switch on a toaster or microwave on the same circuit VNE jumps to 0.4v and VLN drops (sometimes) by up to 2v
When I switch on the kettle on the same circuit VNE jumps to 0.8v
Plugging the Fluke into another circuit, VNE remains constant (albeit non-zero) whether the kettle/toaster/microwave are on or not.

I can (sort of) understand that incoming voltage may vary. My main query/concern is about Vne

So my question (finally) is - are these readings 'normal', or does this indicate some sort of fault with my installation (or perhaps with the Fluke)?

Voltage drop is dependant on current in that circuit only. measuring the voltage on another circuit will not show the drop, just the input voltage to the board.

Read up on ohms law.

THe NE you are measuring is the voltage drop on the neutral ONLY

 

[Adam W]

Those readings sound 'normal' to me.

 

[Golden_Boy]

Those readings sound 'normal' to me.

me too

 

[ringer]

I can understand the VLN varying, but not the VNE. Why would that increase when an appliance is working? I would have expected that to remain constant.

 

[Hawk81]

I can understand the VLN varying, but not the VNE. Why would that increase when an appliance is working? I would have expected that to remain constant.

the reason that the vne increases when using an appliance is because your appliance is leaking a small bit of voltage from the neutral to the earth.

 

[pmac10]

the reason that the vne increases when using an appliance is because your appliance is leaking a small bit of voltage from the neutral to the earth.

leaking current mate, giving rise to a voltage

 

[Hawk81]

leaking current mate, giving rise to a voltage

thats what i meant to say thanks for the correction

 

[Golden_Boy]

leaking current mate, giving rise to a voltage

My college work from donkeys years ago just popped back into my head... I may be wrong but..

The current in the neutral will give rise to a voltage with respect to earth due to the resistance of the neutral cable. As the neutral and cpc are connected at the transformer and there is only current in the neutral there will be a voltage developed between the two. The measured voltage will be dependant on the resistance of the neutral and the current through it.Or has my head remembered it wrong???