20kVA single phase generator grounding question

[Chris Wilson]

How should grounding be made to a 20kVA single phase generator set feeding a domestic property via a manual change over switch? At the generator's alternator neutral is bonded to earth. The generator will be some sixty feet from the mains input box of the property fed by SWA cable. The property's mains is a "protected multiple earth system" according to the sticker in the outside box.

Thanks.

 

[pc1966]

There are other aspects of the care and feeding of a generator you need to consider. 20kVA is quite a bit of current (87A) so while you can get sockets for that, they would be the 125A 'commando' sort and really are a beast to wrangle, and not cheap either! For example (socket for supply end = generator mounting, should be plug for transfer switch end, so no live pins if anything unplugged and running!):

125A 2 Pin + Earth 230V Wall Mounted Socket IP67

IEC 60309 specification

www.cef.co.uk

As such a generator is anything but portable, you would be better having it hard-wired in SWA cable.

Also they need to be run regularly, say 15-20 minutes every week, to keep the engine in good condition and (if diesel) occasionally run on a high load to keep the valves and exhaust from oiling up ("wet stacking" in USA parlance).

That also helps keep the battery charged, as if that runs down you will find it won't start when you really need it! Our generator admittedly has ATS (automatic transfer switch) and a USB-network adaptor for remote monitoring, in addition to its own control panel, and that lots takes about 0.27A so in just over 6 days its 44Ah battery would be flat. Realistically we have maybe 3 days before reliable cranking in cold is going to be tough.

Usually ATS have a trickle charger to keep the battery full, even if you don't got for automatic operation, having and DC power and control lines run in to the property (separate SWA or similar) for a trickle charger and means to start it from indoors if blowing a storm outside are worth considering.

Finally fuel has limited life. You might already go through a lot of diesel and so can keep the generator tanks not much more than 6 months old, otherwise you need to think what to do. HVO or Shell GTL both have around 10 years shelf life (claimed!) but only available in bulk, and more expensive. LPG is another option but few generators available to use it, but bulk tanks are at least tricky to steal from!

 

[Chris Wilson]

There are other aspects of the care and feeding of a generator you need to consider. 20kVA is quite a bit of current (87A) so while you can get sockets for that, they would be the 125A 'commando' sort and really are a beast to wrangle, and not cheap either! For example (socket for supply end = generator mounting, should be plug for transfer switch end, so no live pins if anything unplugged and running!):

125A 2 Pin + Earth 230V Wall Mounted Socket IP67

IEC 60309 specification

www.cef.co.uk

As such a generator is anything but portable, you would be better having it hard-wired in SWA cable.

Also they need to be run regularly, say 15-20 minutes every week, to keep the engine in good condition and (if diesel) occasionally run on a high load to keep the valves and exhaust from oiling up ("wet stacking" in USA parlance).

That also helps keep the battery charged, as if that runs down you will find it won't start when you really need it! Our generator admittedly has ATS (automatic transfer switch) and a USB-network adaptor for remote monitoring, in addition to its own control panel, and that lots takes about 0.27A so in just over 6 days its 44Ah battery would be flat. Realistically we have maybe 3 days before reliable cranking in cold is going to be tough.

Usually ATS have a trickle charger to keep the battery full, even if you don't got for automatic operation, having and DC power and control lines run in to the property (separate SWA or similar) for a trickle charger and means to start it from indoors if blowing a storm outside are worth considering.

Finally fuel has limited life. You might already go through a lot of diesel and so can keep the generator tanks not much more than 6 months old, otherwise you need to think what to do. HVO or Shell GTL both have around 10 years shelf life (claimed!) but only available in bulk, and more expensive. LPG is another option but few generators available to use it, but bulk tanks are at least tricky to steal from!

Some great answers and I appreciate all the time and trouble.

This generator has what is to me a slightly unusual control panel by a very helpful company called Blandon. It constantly looks for a load on its output, and on sensing one (probably has to be resistive of maybe 100W minimum?), it self starts and after a settable warm up time energizes its output contactor and supplies power. If all loads are removed it goes through a settable cool down period and then switches off to await another load being presented.

My aim is the manual transfer switch in the MAINS position will of course present zero load, but when the mains goes down and I switch to GENERATOR, a load is seen and the gennie starts. Time will tell...

Yes, 125 Amp connectors weren't cheap! I did make sure it was impossible for a flying lead to have live male pins, but thanks for the warning, as you say, it's a LOT of current.

I intend to use a battery charger that won't overcharge, maybe a solar powered one? It's a bit too big for my needs, but came at the right price with a blown head gasket due to someone leaving a bolt out of the new water pump that goes through into the coolant jacket... Being in the race engine game it was a novelty to rebuild a slow revving, hugely heavy diesel! Perkins sure don't think of the weight or skimp on the cast iron Thanks again everyone.

 

[pc1966]

Some great answers and I appreciate all the time and trouble.

This generator has what is to me a slightly unusual control panel by a very helpful company called Blandon. It constantly looks for a load on its output, and on sensing one (probably has to be resistive of maybe 100W minimum?), it self starts and after a settable warm up time energizes its output contactor and supplies power. If all loads are removed it goes through a settable cool down period and then switches off to await another load being presented.

I have seen some generators that have the "intelligence" built in, while our one has that in the ATS panel and assumes a dumb generator.

Cool-down is especial important if its a turbocharged engine to avoid trashing its spindle bearings, but should be done anyway to avoid coolant boiling up, etc.

My aim is the manual transfer switch in the MAINS position will of course present zero load, but when the mains goes down and I switch to GENERATOR, a load is seen and the gennie starts. Time will tell...

Yes, 125 Amp connectors weren't cheap! I did make sure it was impossible for a flying lead to have live male pins, but thanks for the warning, as you say, it's a LOT of current.

I intend to use a battery charger that won't overcharge, maybe a solar powered one? It's a bit too big for my needs, but

Here in Scotland the problems is when you really need a generator in winter you can have very little average sunlight, not just low solar elevation but also lots of cloud cover. You might be best to look at a charger that comes from the same company:

The automatic generator battery charger always keeps your generators ready to start - Blandon Group

Our automatic generator battery charger trickle charges your generator's battery from the mains so that it is always full and your generator is always ready to start. It features a charger fail alarm and LED battery charge state indicators.

www.blandongroup.com

But check the generato's details to see how it is normally done. it is possible that is built in if it has some mains-sensing arrangement.

came at the right price with a blown head gasket due to someone leaving a bolt out of the new water pump that goes through into the coolant jacket... Being in the race engine game it was a novelty to rebuild a slow revving, hugely heavy diesel! Perkins sure don't think of the weight or skimp on the cast iron Thanks again everyone.

At least you can service it then!

That is another thing, our has first oil & filter change at 50 hours, then most stuff at 200 hour intervals. Typical for small engine (1.6L here) as if a car averaging 30-45mph then you are looking at equivalent of 1500-2250 miles first, then 6,000-9,000 after that. but if prolonged outage its only 2 and 8 days!