Paging ARW - generators bla bla

You've been told 3 times not to use a cable with a plug at each end. Is there some significance of being 3 times?

Indeed have no idea why you have felt the need to mention you don't have PME. Do you know what earthing arrangement you have? I can assure you that in the UK, even without PME, neutral should only be a few volts different from earth potential. Do you know the normal potential on each conductor?

Additionally, if you don't understand the concept of earth bonding, protective conductors, PME supplies, earth spikes and centre tapped supplies, I would give up now and get help from someone who does.

NT

The supply earth is one the supplier supplies, along with L and N.

Do you have an earth rod (TT install) instead?

In which case, that part is easy - connect your generator chassis plus its N to your house earth.

Assuming it is a regular single phase generator.

Yes, that's pretty much it.

That's (most likely) because the two terminals are the ends of a winding that's having a voltage induced into it, it's floating.

Do you have the manual for the generator?

TBH I know nothing about the Spanish electrical distribution system; what happens if you try the neon screwdriver test on your fixed sockets.

At the moment the output of the genny will be floating - all you can say is that one side will be ~230V with respect to the other, but where either are with respect to true earth earth potential is undefined.

(Neon screwdrivers are not really the tool for working out what is going on here).

Typically you would use an earth spike, and connect that to both the generators earth terminal. and also to one side of the genny's output. That is now your neutral.

(you can make a link in the plug that goes into the generator - with a link from its earth pin to one of the others).

From your description of your house earthing you have what we would call TT earthing[1]

(you can read about the alternatives and how to identify them here[2])

If you connect the house earth to the genny earth, the earthed output of the genny to the house neutral, and the other to the house live you should be there.

That does not follow.

Indeed.

If you start with the genny powered down and disconnected. Use your multimeter on a resistance range to check the resistance between both outputs and the earth connection on the socket. If you get infinite or a very high resistance reading (>= megohms) between either output and the earth terminal, then you are good to go, since you now know there is no internal earth connection between either side of the generator winding and the earth terminal. Follow the instructions in my other post about how to connect it up.

A "supplier earth" is what some electrical supplies will include - they will supply three connections live, neutral, and earth. Common in the UK. With these there is no need for additional earth spikes etc at the property.

See the TT earthing article I pointed you at elsewhere.

That will happen even with PME in most houses, since its common for the neutral voltage to rise a little above the earth when connected to a load. That will allow enough current to flow to earth when the are connected to cause a RCD trip.

If C, its also not really suitable for connection to a house electrical system. Restrict its use to feeding a few appliances via separate extension wires etc.

If the winding is centre tapped toearth, both poles will be live with respect to earth. At half the voltage that appears between the poles. In effect a "two phase" output with the phases at 180deg.

I was too... by your use of three different usenet identities (Paul, Paulus and Paul Carmichael).

However, leaving that aside, once I managed to find the posting with a dropbox link to your photo of the generator panel, it would seem to be the sort of small portable emergency generator sold by the likes of Aldi from time to time back in blighty.

These are designed to power incandescent lighting and fridges and freezers. Unfortunately, when it comes to supplying electrical loads with anything more than a microfarad's worth of excess leading current, the generator itself reacts by overvolting despite any AVR controller circuit's best efforts to maintain the correct voltage level. IOW, you might find problems if you have much in the way of computer kit in your office, especially if you have a UPS or two in the mix.

What appears to be the model number (GG2500C) suggests that it's a

From your description, it appears that the two 110v windings have been permanently linked in series in the generator head itself rather than brought out to a voltage selector switch on the panel to cover both mains voltage options as in the case of the Aldi 115/230v 2.8KVA genset.

It's standard practice to leave the stator windings floating on single phase gensets. The splittedness of the stator windings makes for a very balanced floating supply, hence being able to detect voltage using a neon tester on either outlet socket pin (live and neutral as you referred to them. Are they actually 13A sockets hidden under the flaps?).

If you're going to use it to provide emergency power to fridge / freezer and incandescent table lamps, you're safest method is simply to run an extension cable or two to where your appliances are and transfer their plugs from the house sockets to the genset extension sockets.

However, the floating output could still represent a hidden danger in the event that items like fridges or freezers with their earthed metal casings were to develop a live to casing fault which on its own represents no immediate danger of electric shock (other than a mild sensation of 100Hz tickle when lightly touched due to leakage paths to earth , largely capacitive leakage when everything is nice and dry).

A worst case fault scenario is when a fridge adjacent to a freezer develops respectively a live to case and a neutral to case fault. The lack of a path to earth in the former case (because the neutral is isolated from a good safety earth) means that the usual fuse protection against such faults is rendered ineffective (the neutral to case contact isn't normally a shock hazard[1]).

An obvious way to get around this problem is to use an rcd breaker between the genset and the extension socket but you need to strap what's marked as the neutral pin on the genset sockets across to the earth and make sure to connect to a reasonably good earth connection.

With domestic electrical supplies, there are already enough ways to create dangerous/lethal shock hazards. Adding an emergency genset into the mix multiplies this risk management considerably. It can be done with properly installed equipment and wiring practice by an electrician who specialises in such installations.

For more casual use of such emergency gensets, limit your hook ups to simply transferring the appliance plugs from the house sockets to the genset sockets and stay mindful of the potential danger in using a floating 220v supply[2].

You could make up a connecting lead to go from the genset, normally kept outside, with a suitable inline socket (a 10A IEC female socket as used by the detachable mains leads used by PCs would be fine for this where you plan to trail the lead into the house. The associated permanent panel mounted shrouded plug will only give finger access to the house neutral and earth connections and a dead "live pin" connection.

A technically better (and marginally safer) option would be to use an external weatherproof 16A IEC connector designed for such usgae on the outside wall of the house handy to where you plan to run the emergency genset.

Whichever method you use to connect to the special genset 13A sockets, you gurantee that one of the generator terminals is connected to neutral leaving the other connection to act as a live phase and the genset framework earthed to the house earth which is generally an order or three magnitude better than an earth spike alone.

However, it won't do any harm to provide the genset's frame an additional connection to an independant earth spike connection. It will keep it safe if you're using it to power external electrical tools or just running it up for testing (or simply if someone pulls the plug whilst the genset is still running).

That is correct - but see below

That is because the neutral is not tied to ground.

You may already have an earth rod for your house electrics. if so then there is no need for another earth rod rod for the genny.

Sometimes I link the neural and earth in the lead from the genny - it is sometimes needed to do this to fire up boilers.

Is that the house RCD or the genny RCD? If the genny has an RCD then you cannot link the N&E together on the output - you would have to do it on the internal wiring - if indeed you need to do it at all. I did Scraggys genny with a NE link and added an earth rod (to the house and not the genny) to ensure that his boiler would fire up should the cause of a powercut at his place be caused by a cut supply cable to his house.

House. Genny has a simple 16A trip as far as I can tell.

This house has the mother of all earth setups.

Missed that 3 times, as I've not even mentioned such a possibility.

Yup. As mentioned "several times". Six 1.5m earth spikes.

One has to know all that stuff to connect a simple generator to a house? Blimey.

The generator might be simple - but being safe in a variety of corner cases is not trivial. That's why the IET Wiring regs are half an inch thick.

Heh. Fixed that now I think.

Which is in fact the case. The main reason for wanting the emergency supply was to be able to carry on working in my office (with it's 3 UPSs) in case of power cut (we have many such things here as all the lines are above ground).

Anyhoo, thank you for a well thought out and comprehensive reply. The thread has been interesting for me and educative.

However, the conclusion I have to come to is that this genny is fit for what I bought it for (site) but not for an emergency house supply.

Thanks to all for your input.

I shall now consider either a proper genny (now that I've forked out the 90 euros for a changeover switch) or a solar solution (we see a lot of sunshine here).

I think it was the comment.

"I was going to connect a plug to the house side and plug that into the genny,

which would include an earth connection. But I don't know how to wire the plug if I don't know which wire will be "neutral". I suppose I could connect the genny earth terminal to a nearby earth spike, fire it up and see what happens."

That brought these warnings about.

I'm no expert, but have wired a 7.5KVA genny to my house, via a transfer switch, and research showed the many ways it is easy to do it wrong!

One terminal lights it up and the other doesn't. But the wiring here is pretty phase-insensitive - in fact I recently found that the lighting in my house had some switches on the neutral side which was playing tricks with the modern bulbs. I've since changed this around.

Thank you. All interesting stuff. I've decided, however, that the genny isn't up to the job and I will have to bin the idea and try something else.

Cheers.

No.