Generator earthing
- Thread starter PaulAH
- Start date
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Me or Spark123? From memory (haven't got the machine here) ours is a Workzone 240V 2.2kVA. Probably made in China at that price. The manual recommended earthing the chassis but we havent got a suitable earth on the expanse of solid concrete where it sits.
In the absence of anything better, a 2.5mm wire connected to the earth pin of a mains plug would tie it to the local earth. Not as per regs I know, but it would make it safer. If you also connected the output through a RCD that would help.
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I was getting worried in case my personal experience of small genneys was not typical so I emailed a manufacturer from the web to ask them.
Luckily they agreed with what I had said here! Here it is:-
"""The neutral is earthed.
----- Original Message -----
From: [email protected]
To: [email protected]
Sent: Monday, October 24, 2005 5:41 AM
Subject: small single phase generators
On your single phase small generators is the phase / neutral usually both floating or is the neutral linked to the chassis and earth connection of the output?
Regards
T Glazier"""
Luckily they agreed with what I had said here! Here it is:-
"""The neutral is earthed.
----- Original Message -----
From: [email protected]
To: [email protected]
Sent: Monday, October 24, 2005 5:41 AM
Subject: small single phase generators
On your single phase small generators is the phase / neutral usually both floating or is the neutral linked to the chassis and earth connection of the output?
Regards
T Glazier"""
If the neutral is earthed, why when I put my insulation resistance tester (500v) across N-E (and L-E) on my generator outlet it read 999Mohms> ?
How do you get around when a generator has no earth electrode, under a single fault condition the L becoming attached to true earth, the chassis of the generator becoming live with respect to true earth?
How can they say anything is earthed without a connection to earth, wether it be an electrode or system earth?
Do you understand the theory of electrical separation? Electrical separation means separate from earth (and other systems). If the alternator winding is electrically separate from earth, it has no reference with earth and hence there is no path for current to flow to earth. Under single fault condition, the L or N can oscillate around earth. Danger should only arise under double fault condition as discussed earlier in this thread.
Other examples of electrical separation can be SELV systems, bathroom shaver supply units, and in a majority of cases batteries.
My generator, for the reasons above is electrically separate. It does not have a permanent link between N-E because with it fitted and under single fault condition whilst using it as electrically separate it can cause danger. I have a facility to fit a N-E link if so desired in the form of a specially adapted lead (with RCD) to make it a TN-S system when I have ensured the electrode is fitted if a TN system is required.
How do you get around when a generator has no earth electrode, under a single fault condition the L becoming attached to true earth, the chassis of the generator becoming live with respect to true earth?
How can they say anything is earthed without a connection to earth, wether it be an electrode or system earth?
Do you understand the theory of electrical separation? Electrical separation means separate from earth (and other systems). If the alternator winding is electrically separate from earth, it has no reference with earth and hence there is no path for current to flow to earth. Under single fault condition, the L or N can oscillate around earth. Danger should only arise under double fault condition as discussed earlier in this thread.
Other examples of electrical separation can be SELV systems, bathroom shaver supply units, and in a majority of cases batteries.
My generator, for the reasons above is electrically separate. It does not have a permanent link between N-E because with it fitted and under single fault condition whilst using it as electrically separate it can cause danger. I have a facility to fit a N-E link if so desired in the form of a specially adapted lead (with RCD) to make it a TN-S system when I have ensured the electrode is fitted if a TN system is required.
Agile said:
Agile, I think you have been wrongly advised.
I just checked my Generac ED4000, "neutral" is not connected to frame.
Also checked my Honda Ex1000, same.
Spoke to Generac Technical, they advised that all their Generators are "floating Earth"
Suggest you double check.
I was only quoting my ( limited ) experience of small generators mostly 2-6 kW used to power test and survey vehicles.
The company I emailed is a manufacturer I found via the web.
Obviously different manufacturers take a different view.
If the genny is just used to power a portable tool or other single item then it would seem to be safer for it to be floating.
On the other hand if its to be used to power a house or caravan or small building with a distribution system with a wired earth then my view is that it would be safer if the neutral is linked to the earth at the generator.
Tony
The company I emailed is a manufacturer I found via the web.
Obviously different manufacturers take a different view.
If the genny is just used to power a portable tool or other single item then it would seem to be safer for it to be floating.
On the other hand if its to be used to power a house or caravan or small building with a distribution system with a wired earth then my view is that it would be safer if the neutral is linked to the earth at the generator.
Tony
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