I have a small (2KVA) generator for running my oil fired cooker boiler, and possibly a couple of lights. Can I connect an earth to the main house earth. There will be no other connection to the house electrics, the genny supply being just a permanent extension lead.
Small generator earthing.
- Thread starter maltaron
- Start date
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I don't think you are meant to rely on the DNO earth if that is what you mean. If you are on a TT supply then yes.
Also, small generators usually provide an electrically separate supply meaning the neutral is not earthed, you often need to put a link in - something you need to check.
Also, small generators usually provide an electrically separate supply meaning the neutral is not earthed, you often need to put a link in - something you need to check.
Thanks Spark, I am not on TT and am not sure about the neutral arrangement of these new invertor generators, certainly the older genny's I have used have specifically stated that the neutral must not be earthed. This caused problems with testing RCD's connected to them. So, probably best to put an earth spike in.
If you weren't going to connect the earth rod/spike to the neutral, what would you connect it to - just the frame of the genny? (which would not achieve much). The generator supply really needs to be earthed.
Kind Regards, John
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Seen this discussed elsewhere and the outcome was follow the instructions that came with the generator.
Why?
If it is single phase there is no risk of voltage issues and if you think carefully about the "return circuit" if unearthed and a fault occurred there is no risk from a live (or live equipment to earth) fault.
Forget the books, which there is a predilection to refer to, go back to basic electrical circuits!
Similarly with an RCD, if unearthed and a fault occurs it isn't going to trip! What is the circuit back to the generator for the leakage? So how would a shock occur?
Why?
If it is single phase there is no risk of voltage issues and if you think carefully about the "return circuit" if unearthed and a fault occurred there is no risk from a live (or live equipment to earth) fault.
Forget the books, which there is a predilection to refer to, go back to basic electrical circuits!
Similarly with an RCD, if unearthed and a fault occurs it isn't going to trip! What is the circuit back to the generator for the leakage? So how would a shock occur?
There is an earth terminal on the generator and instructions say that this must be connected to earth. As Westie suggests if the live is not referenced to earth then you cannot get volts to earth if you touch the live! As far as suitability to run the boiler this invertor type generator is claimed to be stable enough to run computers, whether it is remains to be seen. For further info the unit is a Draper Expert 2Kw invertor generator. Thanks for the responses so far.
My comment was not primarily anything to do with books or safety - but, rather, experience. Like Spark123, my experience is that some electronic equipment (and I presume the boiler may well contain electronics) does not like a 'floating' supply.
As for safety, one would need at least two faults for a non-earthed genny supply to create any hazards, so maybe that's not too much of a concern.
However, the question which does seem to beg itself is if, as the OP says, the genny's instructions insist that 'it' (presumably it's frame/metalwork) should be earthed (but not connected to N), what on earth is that all about? As I said in my original post, that would not seem to achieve anything useful.
Kind Regards, John
Perhaps maltaron could ask the maker?
Indeed he could - and I. for one. would be very interested to hear of the answer!
In the OP's case, and on the assumption that this 'generator earth' is connected to the earth pin of its output socket, 'the generator' will almost inevitably be connected to the house's TN earth via the boiler/pipework/bonding - a path to earth almost inevitably of lower impedance than any rod local to the genny would provide - but, again, to what end I find it hard to imagine!
Kind Regards. John
Giving a little more thought to this, as the primary reason for generator is to power the cooker/boiler in power outage situations, then the cooker/boiler will be earthed to DNO earth via the water pipe bonding, so I would think that another earth via the supply cable from the genny would be inadvisable.
Indeed, as I recently observed whilst you were typing
As I said, I certainly don't think that a TT earth local to the genny would achieve anything (if earthing the genny frame alone ever would!), since the path to earth via the DNO's TN earth would almost certainly be much lower impedance. However, although you'll see discussion/argument about this, I really don't think there is anything particularly 'inadvisable' about connecting TT rod(s) to a DNO TN earth - after all, it's no different from what happens via bonding conductors and water/gas supply pipes in the great majority of houses. People might talking about 'vast currents' flowing between 'the two earths' in the event that a failure of the DNO's neutral, but the reality is that you'll never get much more than an amp or three to flow into a standard earth rod!
However, as I've said, it would be interesting to know what point the genny manufacturer sees in earthing its frame if there is no N-E link.
Kind Regards, John
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