UK Inverter Generator to power house

[Wicked]

Hello - I'm not an electrician but I like to understand what I'm possibly asking an electrician to do - so please be gentle with me

I have a nice 7KW Inverter Generator which has a floating neutral - i.e. it is an unbonded system so the frame an the earthing stud is not connected to the neutral. In the 32A commando socket on the generator, the Earth pin connects to the generator frame, but not to the neutral. OK so far.

I propose to connect this to my house distribution board via a manual generator transfer switch. The one I have to hand is rated at 120A (easily big enough) and will switch both the Live and Neutral between mains and generator.

Inside the metal changeover switch box there is a small bus-bar - which I assume must be grounded to the main fuse board connection AND the earth connection coming in from the generator cable.

The Ground connection for my house looks like it is provided via the incoming cable from the sub station - so I assume that the N-E connection happens at the sub station or locally where the cable comes in.

I understand that there must only be one point of grounding.

So - given that this is Unbonded generator and I am switching Live and Neutral - am I OK with the green earth connections being permanently connected all the way through from the generator frame to the substation as this connection won't be broken by the changeover switch?
or:
Should the Generator be changed to Bonded, an earth stake added to the generator frame and my changeover switch replaced with an expensive one one that also breaks the earth connection? (I don't really want to do this unless I have to).

Seems like everyone on Youtube has a different view - so just asking the experts!

Thanks

Dave

 

[plugsandsparks]

Can you take a photo of the service head so we can work out what earthing system you have from the grid.

 

[Wicked]

Photo attached of incoming mains and the changeover switch.

 

[James]

Hello - I'm not an electrician but I like to understand what I'm possibly asking an electrician to do - so please be gentle with me
This really is a job for an electrician as it involves main earthing and possibly removing the tails from the distribution board.

I have a nice 7KW Inverter Generator which has a floating neutral - i.e. it is an unbonded system so the frame an the earthing stud is not connected to the neutral. In the 32A commando socket on the generator, the Earth pin connects to the generator frame, but not to the neutral. OK so far.
Check the generator manual, most will allow the N to be bonded to earth(generator frame). this would normally be done at the 32A socket. A ground rod would be needed to ensure that it is bonded to true earth.

I propose to connect this to my house distribution board via a manual generator transfer switch. The one I have to hand is rated at 120A (easily big enough) and will switch both the Live and Neutral between mains and generator.
Ok.
Inside the metal changeover switch box there is a small bus-bar - which I assume must be grounded to the main fuse board connection AND the earth connection coming in from the generator cable.
Correct
The Ground connection for my house looks like it is provided via the incoming cable from the sub station - so I assume that the N-E connection happens at the sub station or locally where the cable comes in.

Certainly looks like that is true.

I understand that there must only be one point of grounding.

Many buildings have more than one point of grounding.
some of them listed below,
suppliers earth connection
Gas bonding
water bonding
Steel frame bonding (not normally in domestic)
Earth rod in ground.
All of these when in the same building, should be joined together
you can't rely on any of them other than the rod or (sometimes the building frame) to provide a reliable connection to earth in the event of a power cut.
the supplier may cut the cable as part of the work to restore power
gas and water may be converted to plastic at any point without your knowledge or control.

So - given that this is Unbonded generator and I am switching Live and Neutral - am I OK with the green earth connections being permanently connected all the way through from the generator frame to the substation as this connection won't be broken by the changeover switch?
or:
Should the Generator be changed to Bonded, an earth stake added to the generator frame and my changeover switch replaced with an expensive one one that also breaks the earth connection? (I don't really want to do this unless I have to).

Both and neither.
I would bond the N to earth.
leave the connection to suppliers earth permanently connected
add an earth rod.

there should be no switches in the earth conductors

Seems like everyone on Youtube has a different view - so just asking the experts!

Thanks

Dave

 

[plugsandsparks]

https://electrical.------.org/wirin...is again is a myth,connected to Earth or not.

Have a read at the above, it basically explains why you are having issues getting an answer. Apart from the earth, there is also the downstream protections which may or may not be in place to make the installation safe.
Your earth maybe TNS, if so, unlike TNCS where the neutral is used for earth, when you disconnect the N from your changeover switch you automatically loose the earth on the grid connections.

Suggestion is to choose a genny you like, get hold of the installation manual, give manual to electrician who can also survey your house for suitability and what may or may not be required, i.e. NE connection, RCDs, a rod etc.
Just seen James' reply - which is basically how i connect larger non inverter gennys, got spooked by one genny configuration where an NE link blows it up, lol

 

[James]

https://electrical.------.org/wirin...is again is a myth,connected to Earth or not.

Have a read at the above, it basically explains why you are having issues getting an answer. Apart from the earth, there is also the downstream protections which may or may not be in place to make the installation safe.
Your earth maybe TNS, if so, unlike TNCS where the neutral is used for earth, when you disconnect the N from your changeover switch you automatically loose the earth on the grid connections.

Suggestion is to choose a genny you like, get hold of the installation manual, give manual to electrician who can also survey your house for suitability and what may or may not be required, i.e. NE connection, RCDs, a rod etc.
Just seen James' reply - which is basically how i connect larger non inverter gennys, got spooked by one genny configuration where an NE link blows it up, lol

Please note, not all electricians are competent in installing secondary supplies such as standby generators.
try to find one that has some experience in that field.

 

[Wicked]

Please note, not all electricians are competent in installing secondary supplies such as standby generators.
try to find one that has some experience in that field.

Thank you both - you have certainly clarified things for me.

I have spoken with the manufacturer of the Genny who says that it is OK to perform the N-E bond in the commando plug of the extension lead - and it must be clearly labelled. That way I needn't mess with the generator and invalidate any warranty - plus I can still use it as floating neutral for some other application by reverting to a standard extension lead.

I'll deploy an earth stake, and the earth cable from the generator will connect all the way through to the earthing termination in the meter cupboard and will not be broken by the changeover switch (this will just switch over the Neutral and Live). I think I've been confused by looking at American youtube videos where they get very emotional about having multiple ground connections - but as James says - there are probably already several local paths to earth via gas pipes, water pipes etc.

I assume that with the Generator bonded and grounded that RCDs should work ok with the Generator switched in circuit.

Thanks again for the advice - and yes I'm getting a qualified electrician to wire this in at the same time as he swaps out my split dis board for all MCBO breakers

Regards Dave

 

[DefyG]

grounded

Ground connection

grounding

I think I've been confused by looking at American youtube videos

Please Please - This is not America ........ The words 'Ground - Grounding' are NOT recognised in BS7671

 

[James]

Please Please - This is not America ........ The words 'Ground - Grounding' are NOT recognised in BS7671

I didn’t think it worthwhile to add in the terms Earth, earthing, bonding, circuit protective conductor.

At the end of the day, they are all green/yellow striped cables that are attached to the ground in some way