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”

 

[buzzlightyear]

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

why dont you put the cable over the kitchen table why at it.you could make it a skipping rope for a dog.

 

[pc1966]

Why not a 32A socket next to the change over switch and a suitable long lead plugged in as needed?

Ideally you would put a suitably IP rated socket outside somewhere so there is nothing trailing around, and then they bring the generator out as needed and a short patch-cable.

 

[PEG]

Hi, it might be better to start with what loads are required to be met,and what size/type of generator is going to be used?

 

[littlespark]

Hi, it might be better to start with what loads are required to be met,and what size/type of generator is going to be used?

Like I said, it’s the physical layout of the house that would be the issue.
They only really want lights and supply to the boiler to give heating. 16A will be enough.

It’s running a lead to an open window, instead of running a cable outside if the CU was on an outside wall.

 

[Spoon]

They only really want lights and supply to the boiler to give heating. 16A will be enough.

Do they not want any more basic amenities like to keep their fridge/freezer up and running? Maybe have enough to make a brew and watch tv?
I suppose it depends on how long the power cuts are for.

 

[Rockingit]

Find somewhere convenient to fix a 16/32/63A appliance inlet (male commando) and wire back to a changeover box. If the genset has electronic ignition then you can also use the same MF box and a cable alongside the mains to have an internal switch for it.

 

[littlespark]

Freezer. Good point, @Spoon

Wiring the thing isn’t a problem… it’s where to place the wires when it’s in use.
The commando socket would be in the cupboard, next to changeover…. Next to CU.
There’s already a service isolator, and Henley’s… so no problem reconfiguring for a changeover.

I’d have to lay an extension lead across the floor to reach outside, leaving a trip hazard.

Although… new day- new thoughts.
I can run from the cupboard, behind kitchen units kickboard, right along to a wall. I don’t know what’s behind the wall though… garage or outside.

Maybe it’s not going to be a huge problem after all.

 

[timhoward]

It’s amazing how a night’s sleep opens up new wiring route possibilities - happened to me many times!

 

[pc1966]

You can also use the likes of this to reduce trip hazard for temporary cables:

https://uk.farnell.com/vulcascot/ro7-b-3m/cable-protector-30-x-10mm-yellow/dp/3376514

26101115 | Vulcascot 3m Black/Yellow Cable Cover, 14 x 8mm Inside dia. | RS

uk.rs-online.com

 

[buzzlightyear]

it would be better to put the cables up the wall and through the joists and on to the cut out area so will be no trip hazzard if it could be done.

 

[pc1966]

A friend of mine up near Aberdeen has been having similar issues but no idea if anything being done to allow such a temporary supply. Now she has a new BF I don't hear much from her!

So I might also bee looking in to exactly the same sort of situation at some point.

 

[brianmoooore]

It's not just the trip hazard. If the genny inlet is in the middle of the house, there's a chance that sometime someone will decide to run the generator in the middle of the house, on a short lead, as well.
Some of the latest generators, designed for use with the likes of motorhomes, are all enclosed in a casing and run almost silently. They still use up O2 and pump out CO though.
Edit: It's just occurred to me, that as a result of building work in the last couple of decades, my own generator port is now more than a whole room inside the house.

 

[Spoon]

Now she has a new BF I don't hear much from her!

That's understandable. The excitement of having a new Balanced Flue doesn't leave a lot of time for chatting.

 

[pc1966]

That's understandable. The excitement of having a new Balanced Flue doesn't leave a lot of time for chatting.

I was assuming it was down to me being a cad and a bounder.

Drat, drat, and double drat!

 

[pc1966]

It's not just the trip hazard. If the genny inlet is in the middle of the house, there's a chance that sometime someone will decide to run the generator in the middle of the house, on a short lead, as well.

Very true!

Another very good reason to have a commando male inlet outside the building.

Incidentally anyone else feel they are not really waterproof enough if sloping down for easier cable access? Seems water can run down the gap between male socket and the female plug. Having it is some sort of shelter / box would be a good idea to keep the rain off once mated.

 

[brianmoooore]

Incidentally anyone else feel they are not really waterproof enough if sloping down for easier cable access? Seems water can run down the gap between make socket and the female plug. Having it is some sort of shelter / box would be a good idea to keep the rain off once mated.

That's what my gut feeling is as well, but having used them with my touring caravan for decades often two cables plugged together and lying on the ground, I've yet to see any evidence of any water penetration whatsoever

 

[Lucien Nunes]

Down-angled appliance inlets and couplers of less than IP67 are not good for permanent connection outdoors as the coupler does collect water. I have one on the boat, but with a sneaky drain hole drilled from the 'moat' of the coupler to outside at the lowest point when in position, to let the water back out. Upgrading it is one of those 'round tuits' that never seems to get a look-in because it works at the moment and there are always 1001 more urgent maintenance tasks on a boat that whatever it is you want to upgrade. For occasional use with a portable generator it is unlikely to be a problem as any water collected will escape when the coupler is removed.

 

[buzzlightyear]

That's understandable. The excitement of having a new Balanced Flue doesn't leave a lot of time for chatting

unless you are a fish wife .

 

[Rockingit]

Down-angled appliance inlets and couplers of less than IP67 are not good for permanent connection outdoors as the coupler does collect water. I have one on the boat, but with a sneaky drain hole drilled from the 'moat' of the coupler to outside at the lowest point when in position, to let the water back out. Upgrading it is one of those 'round tuits' that never seems to get a look-in because it works at the moment and there are always 1001 more urgent maintenance tasks on a boat that whatever it is you want to upgrade. For occasional use with a portable generator it is unlikely to be a problem as any water collected will escape when the coupler is removed.

And sadly, very hard to find (and expensive to buy when you do!)

 

[littlespark]

We used to get a lot of waterlogged 16A plugs on the caravan park. Couldn’t see where the water was getting into the hook up units, but somehow would get into the socket on the bottom of the box and run into the plug.

Some of the blue plugs came with clear covers so you could see the level of water inside reaching the terminals.


I’m going to look at the genny job this week, so will see where the route under the kitchen units comes out.. either outside or through garage.

 

[littlespark]

I’m going to look at the job on Saturday morning, and now I’m looking at other threads about genny backups… it’s a little more complex than I thought… and expensive.

The changeover switch needs to be rated to carry the full load when on mains power… so 60A at least.. some switches are £200 plus from CEF


Then there’s the earthing. Will I need to stake next to where the genny is, or does the genny give its own as part of the neutral… does it have to be a specific type of generator, or just a standard building site machine?

Indicator lights at the changeover to show when mains power was restored… or is that a “nice to have”?

 

[brianmoooore]

The changeover switch needs to be rated to carry the full load when on mains power… so 60A at least.. some switches are £200 plus from CEF

Fitted many tractor driven 5kVa and 15kVA generators on dairy farms, and of course, they always came with a switch rated for the genies output. Cue argument with the farmer every time as to why he had to fork out for a big, expensive switch, when one was supplied.

Indicator lights at the changeover to show when mains power was restored… or is that a “nice to have”?

Always fitted them, usually to the mains isolator alongside. If they know when power has been restored, it discourages them from switching the changeover switch under load, "just to check".

 

[pc1966]

I’m going to look at the job on Saturday morning, and now I’m looking at other threads about genny backups… it’s a little more complex than I thought… and expensive.

The changeover switch needs to be rated to carry the full load when on mains power… so 60A at least.. some switches are £200 plus from CEF

Yes, can be expensive! Our ATS was a shade over £1k

This might be worth a look:

Manual Changeover Switch 63A 4 Pole Metal Enclosure

Our range of enclosed changeover switches are available in plastic enclosures from 25-40A and steel from 25-1000A. They are manufactured to IEC standards and feature other approvals, Data sheets can be provided on request.As always we select products with the ease of installation in mind so...

www.generator-man.co.uk

Then there’s the earthing. Will I need to stake next to where the genny is, or does the genny give its own as part of the neutral… does it have to be a specific type of generator, or just a standard building site machine?

It depends.

Most smaller 'site' generators are isolated / IT supply so not suited as such for multiple circuits. Larger ones usually have the N-E link internally so just need a suitable rod, most have 30mA RCDs so have the accumulated leackage risk (less if only a sub-set of cirucits powered) but then only need a rod with Ra <= 200 ohms.

Indicator lights at the changeover to show when mains power was restored… or is that a “nice to have”?

I don't think is is required by any regulations, but is such a good idea to have anyway!

Some indicators say they don't need a fuse but if in doubt then a small HRC fuse feeding it would make sense. Some use the usual 20 x 5mm fuses but they are lucky to meet 1.5kA breaking, or you can look for the BS88 style as they are often >= 50kA rated.

 

[buzzlightyear]

Then there’s the earthing. Will I need to stake next to where the genny is, or does the genny give its own as part of the neutral… does it have to be a specific type of generator, or just a standard building site machine

for that the loading a descant one is needed ,it depends on the generator.

 

[littlespark]

Had a look this morning, and the customer isnt adverse to spending a few bob.

He's going to be ordering a genny at £1500 anyway... One like the pic on Buzz's post above.
6kW, with 32A hookup on the 230v side.

They work from home, so there would be computers and broadband hub over the general lighting, fridge freezer and possibly electric hob... which i said, use only one, and not at the same time as kettle.

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
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?

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

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

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.

 

[SparkySy]

They used to do a 100a twin or 4 pole main switch change over assembly that was two main switches linked together, one was upside down to the other so when one was on the other was off as a change over switch. I haven't seen one for ages and not sure how safe this set up is?! A 3 position switch is a much better option!

 

[sinewove]

They used to do a 100a twin or 4 pole main switch change over assembly that was two main switches linked together, one was upside down to the other so when one was on the other was off as a change over switch. I haven't seen one for ages and not sure how safe this set up is?! A 3 position switch is a much better option!

TLC Electrical do a 125A c/o switch for £82.80 plus vat.It comprises a 4 pole 125A switch with suitable links.
Comes in a metal din enclosure.
Regards,
S

 

[littlespark]

Something to consider.
Thanks guys

 

[SparkySy]

Thanks @sinewove hadn't seen them on there! I found one here

FuseBox 125A Changeover Switch and Busbar (SCO125SWB) | UKES

Great deals on FuseBox, including this 125A Changeover Switch and Busbar (SCO125SWB)! Shop now, FREE DELIVERY over £75.

www.ukelectricalsupplies.com

The only thing I don't like about them is there is no proper off position. On the rotary ones I have fitted they have on mains off Center and on generator, I prefer this as there is a definite off between the change over.

Ps just remembered that I fitted the TLC 63a rotary one some time ago on a farm and it was good quality and nice to fit too!
This one

63 Amp 3 Pole Change Over Switch - IP65 | Klockner_Moeller (T5B37I)

Should imagine the 32a one is of a similar standard!
Sy

 

[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