Wiring Requirements For Generator Installation

[andy_spark]

[SIZE=medium]I have been asked to install some sockets in a scout hut, at a remote scout campsite, that is powered by a 6 kVA generator.  There is currently a  2 way CU with 25A 30mA RCD main switch, feeding a 6A light circuit with about 6 lights on it and a 10A socket circuit feeding 1 outdoor socket.[/SIZE]

[SIZE=medium]The generator has an arrangement of 16A sockets 110v and 240v for outgoing supplies all protected by a 20A c type mcb double pole.  The current cable is a 1.5mm flex running to the CU in a duct about 4 metres long about 6 inches under a path to the campsite hut. The generator itself is under a wooden shelter to keep rain off and the sides are half enclosed with covers.  It is used mainly in the evenings to provide light to the hut which includes toilets a dining area and a kitchen.  All cooking and water heating is gas with now plans to change.[/SIZE]

[SIZE=medium]The outdoor socket is in1mm and needs rewiring and about 4 new sockets to be added for using relatively low power kit ( phone chargers, radios, cleaning equipment and power tools etc). [/SIZE]

[SIZE=medium]I have not done a generator install like this before and have tried to understand it as best as possible form the books. I would appreciate any thoughts and comments or advice on my plan please.[/SIZE]

[SIZE=medium]My plan is to change the 10A to a 16A mcb for socket circuit and add new sockets, in 2.5mm T&E.[/SIZE]

[SIZE=medium]Fully test and inspect lighting circuit, it’s at least 15 years old[/SIZE]

[SIZE=medium]Install 10mm earth bonding to water supply which is in copper, connected to mains water (no bonding currently).[/SIZE]

[SIZE=medium]Rewire supply from genny to CU in 4mm SWA, (plenty adequate for 20A and also no plans to replace generator), it may not be possible to reach the CU with the SWA so the CU may have to be moved.[/SIZE]

[SIZE=medium]At genny end I will make off SWA in a IP66 box and finish the run to the genny in 4mm flex with IP66 16a socket, so it can be unplugged without stressing the SWA, unless anyone knows of a plug that SWA can be connected to.[/SIZE]

[SIZE=medium]Add an earth rod that will be connected to the earth lug on the generator.[/SIZE]

[SIZE=medium]Does an additional main earth from genny to CU need to be run in a larger size? I’m not that sure of the requirements of earthing so would grateful for any pointers.[/SIZE]

[SIZE=medium]The campsite managers understand the curernt install is not really up to scratch and there is a fair bit to do, budget is  not infinite but funds are available to do it properly.[/SIZE]

[SIZE=medium]Thanks Andy.[/SIZE]

 

[ProDave]

I'm not sure I like the rod going to the earth stud on the genny. Too much chance for it not being connected etc.  I would prefer to see the rod going direct to the MET.

Also look at 12V lighting from a battery (charged from the genny and a solar panel and even a small wing generator. Think the sort of stuff used by caravanners. Then they would only need to fire up the genny for big stuff. but that's probably outside the scope of what they want you to do.

 

[Sidewinder]

There is also the consideration of linking the N-E @ the genny depending on the install.

 

[Andy™]

most small genny's have floating earth.. so if you add an earth rod it isnt going to do anything unless its tied to neutral

 

[binky]

worth having a look at going 'off grid' couple of batteries and suitable controls to genny, would make big difference to running costs.

 

[andy_spark]

They have a solar panel and battery at a seperate toilet block on the site and are having charging problems due to tree cover. The site is in woodland and the buildings don't point south so there will be associated problems with that. 

They, customer, were hoping that it would be fairly simple to add sockets to existing set up, but understand the current set up is not adequate. I just want to get it right as the site will be hired out etc and there are liabilities to consider with that.

Am I right thinking that the rod is needed to Earth the generator but install a N-E link inside, is it possible that this is in place already?  I don't have the specification for the generator and would have to investigate that.

 

[SPECIAL LOCATION]

[SIZE=medium]I have been asked to install some sockets in a scout hut, at a remote scout campsite, that is powered by a 6 kVA generator.  There is currently a  2 way CU with 25A 30mA RCD main switch, feeding a 6A light circuit with about 6 lights on it and a 10A socket circuit feeding 1 outdoor socket.[/SIZE]

[SIZE=medium]The outdoor socket is in1mm and needs rewiring and about 4 new sockets to be added for using relatively low power kit ( phone chargers, radios, cleaning equipment and power tools etc). [/SIZE]

[SIZE=medium]The generator has an arrangement of 16A sockets 110v and 240v for outgoing supplies all protected by a 20A c type mcb double pole.  The current cable is a 1.5mm flex running to the CU in a duct about 4 metres long about 6 inches under a path to the campsite hut. The generator itself is under a wooden shelter to keep rain off and the sides are half enclosed with covers.  It is used mainly in the evenings to provide light to the hut which includes toilets a dining area and a kitchen.  All cooking and water heating is gas with now plans to change.[/SIZE]

[SIZE=medium]I just want to get it right as the site will be hired out etc and there are liabilities to consider with that.[/SIZE]

Ignoring the generator side of things for the moment...

Just considering the installation & its typical uses....

Youngsters, evening, strangers in a hired out building in the dark...

someone trips the power off...

I wouldn't want a single RCD...

Use some of SBS Dave's mini RCBO's in a small enclosure.

I would also be wary of someone overloading & losing the socket power.... 

May be better with 2x 10A sockets rather than 1x 16A socket circuit..

Scout hut...

Is it ever hired out to Guides..?

do they have teenage girls using it..

Hair dryers / Hair straighteners can take a lot of juice..

Although you say only low power stuff....

Some pratt is sure to plug in something too big....

How stable is the genny output??

Need to be aware of volt drop when under load...

evening lights on...  someone tidying up with a vacuum cleaner & electric kettle...

Just wire the whole place up as if it were a grid supplied TT installation with a back-up generator..

meeting all your disconnection times, bonding etc..

circuit distribution minimising inconvenince..

IP ratings etc...

Then check the speck of your generator and any special requirements that may have.

:coffee

 

[Marvo]

........Am I right thinking that the rod is needed to Earth the generator but install a N-E link inside, is it possible that this is in place already?  I don't have the specification for the generator and would have to investigate that.

Check the manufacturers literature regarding the winding arrangement. If the genny is V-O-V wound the neutral must float at 110 wrt to chassis and earth, you'll damage it by linking the N and E.

 

[steptoe]

Im thinking like a 110 Tx where its 55v - 0v - 55v  , ie, Voltage - 0 - Voltage

where the neutral actually has potential, and is NOT tied to 0v like a normal star point

 

[andy_spark]

Thanks I see the point being made about the winding, I'll try and find out about any literature for the generator.

Thanks for the advice so far.

 

[Marvo]

Is V - O - V a foreign thing ?

Is V meant to be Y ?

Im thinking like a 110 Tx where its 55v - 0v - 55v  , ie, Voltage - 0 - Voltage

where the neutral actually has potential, and is NOT tied to 0v like a normal star point

I meant as Steptoe said. Generator chassis centre tap connected so both L & N at potential to earth. Site type generators are sometimes configured this way and aren't suitable for permanent installation.

 

[Adrian41uk]

Think you may have overlooked something here .....

Your genny is 6kVA so is capable of delivering around 6000/230 = 26A at full load..... but you are only connecting it to your distribution system using a 16A connector so you can only access 16 * 230 = 3680 VA ...... in effect your design only allows you to access 3680/6000 = 61% of the generators capacity.....

 

[andy_spark]

That is the only socket the generator has with 230v output.  There are 32A & 16A 110v sockets and 16A 230v sockets.  The inbuilt generator overcurrent device is a 20a mcb c type. I can't see what I can do to change this.