Generator back up for house

[littlespark]

Not so much an electrical question, but physically.

Got a customer out in the sticks who’s suffered with powercuts frequently during the recent storms.
Now, easy enough to fit a changeover switch, but in this case, the mains comes in in the centre of the house. Not a handy place to drill a hole to outside.

So, would you wire in a 32A (or 16, depending what genny they get) plug to the changeover, leave a long enough extension lead to reach a window, crossing their kitchen floor….

Don’t suggest a “widowmaker”

 

[pc1966]

I was thinking a 4mm T&E run behind the kitchen kickboard to an outside wall, drill through and a BS4343 32A plug on the wall.
He would want the generator, however to be sighted away from here, as neighbours bedroom window is only 2m away... So a trailing extension lead from here to the genny, roughly 10m away

Can you put the inlet socket closer to the desired final location?

Also I would suggest making up a suitable H07RN-F lead, or get them to buy one you have checked is OK for the job.

Also, the plug would be close to his outside oil boiler... there is a 10mm bonding conductor from the copper pipe back to the MET from here.
Bond between plug and pipe?

Maybe, but the real issue is you need an earth rod as:

• You cannot depend on the supply earth being present during power outage (a whole cable section could have been sliced)
• You cannot rely on service pipes to do that job

As it might well be TN-C-S normally you then need 10mm bonding to the rod so taking a properly installed earth to the generator is not OK as 4mm T&E CPC far too small, so really I would add an earth rod to the gas pipe bond cable (and of course verify it is sound, etc).

As the changeover switch needs to carry the load of the property in normal use, need to go with 100A, as i dont know the main fuse size...

So this?

100A 2 Pole Surface Mounting 3 Position Changeover Switch IP66

Insulated polycarbonate enclosure

www.cef.co.uk

Looks fine, or the other 100A+ models others have just pointed to.

With an enclosure containing a 32A MCB on the generator source... (although will the generator have that built in?)

You probably don't needs that as the generator should have overload protection and so long as no Muppet puts a bigger generator above 32A on a 32A female plug to power it then no issue.

I would double check the generator has an output MCB and RCD, though I expect by that size they would be properly equipped and a TN-S source.

There's already Henley blocks and a service isolator in the mains supply... and no problems with space.

And i'll mark up the existing CU to say which circuits are more vital than others.

Excellent!

 

[brianmoooore]

The generator RCD can give rise to further problems if the existing installation is protected by multiple RCDs/RCBOs. Existing earth leakage might be well below that required to trip any of the existing ones, but the sum of them might trip the generator RCD.
I know from experience that customers are not amused when this happens when they are struggling with rough weather and a power cut.

 

[pc1966]

The generator RCD can give rise to further problems if the existing installation is protected by multiple RCDs/RCBOs. Existing earth leakage might be well below that required to trip any of the existing ones, but the sum of them might trip the generator RCD.
I know from experience that customers are not amused when this happens when they are struggling with rough weather and a power cut.

Very true, and this is sounding like a big enough generator that it might be a problem, but often if you have to shut off 2/3 of the circuits due to tight load limits you might get away with it.

Certainly worth checking out the accumulated leakage before it is cold, dark, wet, and no mains!

 

[brianmoooore]

Unfortunately, the type of weather that results in 'no mains' is often the kind of weather that bumps up the leakage!

 

[Rockingit]

From experience, that type of small generator may also have a floating earth (I-S) and it's RCD configured such that it's the actual chassis/electrode being monitored through a CT and not the outgoing L/N inbalance - ergo if you have a fault to electrode downstream then it won't get seen.

 

[pc1966]

From experience, that type of small generator may also have a floating earth (I-S) and it's RCD configured such that it's the actual chassis/electrode being monitored through a CT and not the outgoing L/N inbalance - ergo if you have a fault to electrode downstream then it won't get seen.

Seems an odd thing to do when it is big enough to power multiple circuits, etc, but I guess they have their reasons.

Certainly worth checking the manual / asking manufacturer, or at the very least doing a bond check N-E at the generator outlet.

 

[Rockingit]

Seems an odd thing to do when it is big enough to power multiple circuits, etc, but I guess they have their reasons.

Certainly worth checking the manual / asking manufacturer, or at the very least doing a bond check N-E at the generator outlet.

The two things I mostly have to ‘correct’ on hired-in gensets in muddy fields are making a PEN link and reworking where the RCD fits in the system