I have 3 phase electric to the house. Each phase feeds one line in the main fuse box to spread the load. I also have a number of 3ph sockets in the cellar.
I get quite a few power cuts as I live near the forest, and when the wind blows the trees come down on the lines somewhere. Usually it's only an hour or two, but it was a good few hours last week, then yesterday it was from 10am till midnight. It's also been off again now. It's ok during daylight hours, but once night time comes it's a bit of a pain. Not least because the water pump doesn't run.
So here's what I did, and it's works well, but not sure if it's ok. I made a lead with a 3ph plug on one end that goes to the 3kw generator I have. The other end also has a plug, and I put this into one of the sockets in the cellar. I turned off the electric at the meter, and any high load stuff like the water heater. So I basically back fed the main fuse box. As a result, everything seemed to work ok in the house. The only problem, of course, is that I can't tell when the leccy is back on as it's off at the mains. So is it ok to do this, or are there problems lurking somewhere?
|
Hugely against regulations on several fronts.
The biggest danger is one of the generator and the mains supply both being live at the same time.
You also presumably have a plug with exposed pins driven by a generator
You may have earth problems
Finally, the wiring may not be properly circuit protected.
You really need to be fitting a proper changeover switch.
As an alternative, could you wire up a simple circuit powered only by the generator - so you have a few 13A sockets around the place only on the generator circuit. Then you could unplug your water pump from the mains 13A socket and plug it into the generator 13A socket instead.
|
>> Hugely against regulations on several fronts.
>>
>> The biggest danger is one of the generator and the mains supply both being live
>> at the same time.
I realise this, but I make sure I switch off the mains first. Out of interest though, what happens with solar units on peoples houses that feed back into the mains?
>>
>> You also presumably have a plug with exposed pins driven by a generator
That's correct. But I'm not stupid enough to either touch the pins, or indeed run the genny before it's plugged in.
>>
>> You may have earth problems
There is an earth point on the generator - maybe a big steel pole stuck in the ground will work.
>>
>> Finally, the wiring may not be properly circuit protected.
Possibly, but the 3ph sockets come from the main input to the house off the back of the fuse box, so I'm putting power back into the fusebox at the same place.
>>
>> You really need to be fitting a proper changeover switch.
I know, but I'm tight and was in a rush.
>>
>> As an alternative, could you wire up a simple circuit powered only by the generator
>> - so you have a few 13A sockets around the place only on the generator
>> circuit. Then you could unplug your water pump from the mains 13A socket and plug
>> it into the generator 13A socket instead.
>>
Good idea, I think I'll do that tomorrow actually. The only problem is the water pump motor is 3ph. As is the cooker, but I don't need to use it as I can light the wood oven.
|
>> Out of interest though, what happens with solar units on peoples houses that feed back into the mains?
They will have a feed of the house supply as a reference, and generate in phase with that.
Here's a quote from a supplier:
The Grid Connect Inverter (Solar Inverter) matches it’s output to the mains power in the house. As a safety feature it will not produce any output if detects no mains power from the grid. This prevents the Solar Inverter reverse feeding your house or the grid during a power cut or if a circuit breaker trips.
|
Are you saying your gennie is three phase? and you are powering all three phases in the house through one three phase socket?
Problem 1 is (as tigger pointed out) your gennie is not earthed
Problem 2 is that your feed circuit is not fused
If it happens that often, as tigger says, get a proper auto crowbar installed in the proper parts of the required circuits.
|
If you forgot to turn off the swtich at the meter, you could kill a worker trying to restore the supply.
You really need to be fitting a proper changeover switch. Something like this
www.briggsandstrattongenerators.co.uk/pages/powertransfer.htm
|
That's an interesting question, and one I had considered a few years ago after similarly suffering repeated power cuts in a rural area.
I asked an electrician what the consequences would be, and he said that aside from the obvious legal and safety issues, which like the OP I would have ignored, there was a fundamental flaw because of the nature of the house supply. (Isolated house, own individual supply from transformer tapping off grid lines)
I don't pretend to understand what he was getting at, but it was I think something to do with the way Earth and Neutral were differentiated, and the fact that there was no separate house Earth, only neutral/earth supplied by the electricity company.
I think he might have been saying that even though I thought I had isolated L and N at the main switch, there remained "Earth". My Earth is not a true earth, it is supplied by the company, so is never truely isolated. A fault in my system could have fed a voltage back along the supply E/N
Like the OP, I couldn't see why it wouldn't work as long as, obviously, I isolated the house from the mains first. Imagine that the house was not on the mains at all. Supposing I constructed a network of ring mains, and then fed power into the system from one of the sockets - why would that be unsafe (leaving aside the bare live plug prongs for the sake of argument) ?
|
Well I've done a proper job of it this morning.
Picked up a 'Byggcentral' (Building central), basically a stand alone fuse box that has a plug for 3ph in, a 3ph socket out, and 3 off 1ph sockets out. It contains circuit breakers and an RCD. They use them on building sites before mains gets plumbed in properly. I also drove a galvanised steel pole in the ground with a lead. I've run a couple of 1ph leads up into the house so I can run a lamps/tv/computer etc. All I need to do now is terminate the water pump with a 3ph plug, and add in a 3ph socket to the existing (hard wired) supply. Then I can unplug the water pump and plug it back in the new fusebox when required. All safe, fused, no live plugs, and seperate from the mains supply.
Fortunately, I have a huge (35kw) wood boiler that doesn't need electric, as the draught is mechanical and the water moves itself around the system by convection.
I'm still interested to know how the houses with solar cells that feed back to the grid handle the situation when there's a power cut. In theory they will still be supplying leccy when someone could be working on the dead supply. Maybe they have a box of gubbings that monitors the supply voltage, and if this fails, they stop feeding back to the grid.
|
AFAIK the solar cells only feed the grid - if the grid is there.
No grid, no output. Don't know how it works, but I've seen mention of phase monitoring driving the switchgear.
Some of the larger TV relays have the socket and switchgear to enable a portable generator to be wheeled in and plugged up.
|
|
I have 'back fed' our house/s numerous times with the socket and socket on a lead. The only prob' has been jealous neighbours whingeing about the Briggs volume. My freezer worked and theirs didn't ha ha......
|
i have a small 2kw genny for emercencys and last winter we lost power a few times and close neighbours were able to run there freezers and a low wattage lamp for several hours.
invaluble
|
>> I have 'back fed' our house/s numerous times ...
Me too but recent building works meant that I had a golden opportunity to have a proper changeover switch installed and a blue socket for the genny wired outside. Don't think it's got earth and neutral linked though.
|
|
Assuming the fault is not on a power line to just your house, then even if the mains switch is left on, as soon as the generator is plugged in it will try and power every house that has also lost power. All those lights, fridges, freezers, water heaters, TV's, chargers, etc. So I guess it will soon be obvious that the switch is still on as the cheapo Clarke generator coughs and splutters with the combined load of a few hundred houses.
|
Electric - is this safe/ok? - Tigger
