Am looking at getting a 6.2kVA backup generator for our home and having it hard wired. Can you Sparkies (or anyone who has a hard wired one) on here like to comment on any potential issues! Just really for running a large gas fire unit (with fans), gas hot water unit and the freezers, Internet etc. Many thanks
annies3,
Mar 5, 8:14pm
We have thought about this too, it seems it is quite complicated but doable so we would like to know about this as well.
stuffed,
Mar 5, 9:06pm
My now retired sparkie mate (a top guy who had 40 plus staff doing industrial stuff) is about to be told what I need done and just want as much info as possible before he tells me to get lost!
Pretty sure it only gets complicated if you want an instant power change over system.
Basic manual change over emergency power systems are very simple compared to the instant systems.
You either run 1 or the other & your change over switch shouldn't be able to let you run both together
johotech,
Mar 6, 12:35am
You have to check if the generator is a "centre tap" type, which aren't suitable as they stand, to connect to a house supply.
The switching is reasonably simple, as Mr.Fixit said, but there are a few other requirements that have to be checked to make it compliant.
The worst possible thing would be for someone to make up a lead with a plug on both ends, and plug the generator into the house wiring.
trade4us2,
Mar 6, 12:53am
I think you might want to turn off the generator at night and run off a battery and inverter.
sr2,
Mar 6, 2:10am
Bad advice; 6.2 Kva is no where near enough to safely hold up the average home. Unless you install breakers and a load shedding system or a separate "essential power" DB as I suggested in my earlier thread there will be problems. Manual vs automatic change over panel is irrelevant (unless you're away on holiday), the big issue is matching the load to the genset.
tsjcf,
Mar 6, 2:48am
If the Op wants to post loading we could discuss that. For what he wants to do your suggestion was over kill hence why the link to the manual change over switch. I use a 5.5kva for the odd power cut here and that enough to keep what i need running.
wembley1,
Mar 6, 3:19am
^^^^This
Your switchboard contains all your protection. Putting energy into a house downstream of the protection is not good.
sr2,
Mar 6, 5:42am
As I said earlier whether the transfer mechanism is manual or auto is irrelevant; attempting to power up the average domestic DB board with only a 5.2 kva genset is asking for problems.
sr2,
Mar 6, 5:46am
Good advice with the proviso that unless your genset has a kva rating to match the supply (as a rough rule of thumb with 75% power factoring) you'll have a recipe for disaster. Hence my earlier suggestion to set up an essential supply sub DB.
richard112,
Mar 6, 10:53am
Interesting reading. We have no mains. House runs off a 3000kva sine wave inverter w/1000amp/hour battery bank. Battery maintained by a generator on time switch auto start + about 600 watts solar if the sun shines. Our 3000 watt inverter runs 2 freezers, 3 fridges, 1 computer 24/7 + the usual odds & ends. We use an electric jug a couple of times a day, microwave as required, electric blankets in winter. i.e. reasonably normal household. Cooking & heating are lpg. Found we needed a grunty generator to keep put a reasonable charge into the batteries (120amps @ 24V) BUT, the 3000 watt inverter is quite happy with the house load, as was the 2,400 watt Mod sine wave inverter we had before it. Before inverters, we used to run the whole house on generators in the 3 to 5 kva range. Provided there are no serious electric heating devices in the mix it's hard to imagine why a 5kva good quality generator wouldn't do the job for the odd power outage. If you are going to use a double ended lead, don't forget to turn off the main switch at the board :-)
johotech,
Mar 6, 12:36pm
You can't connect a generator to a sub board. A standby supply generator connection is only allowed at a switchboard where the MEN connection is.
Besides that, having "essential" circuits on a sub board would require major rewiring of the switchboard and circuits.
As Richard said, the load on a standard house is not that high, once you remove things like electric stove & hot water. Even using the oven (about 2.4kW) isn't excessive.
Standby generators are required to have overload protection anyway, so it would take care of itself.
As I said above, there are a number of requirements that need to be met to connect a standby generator.
The hardest part will be selecting the correct TYPE of generator. Most cheap generators have a centre tapped winding where the centre tap is connected to the frame of the generator. That type is not suitable without modification, and some generators may not be able to be modified to be compliant.
Generators for connection to installations are required to meet NZS3010. I doubt you will find a cheap generator which complies with that standard.
Simple solution is to have a stand alone generator and just connect the load you require directly to the generator with extension leads, so there is no connection to the installation wiring.
Using extension leads may not sound as safe, but it actually is, because there is no connection to any installation wiring, therefore the wiring is isolated (as much as the generator is isolated anyway).
tsjcf,
Mar 6, 1:27pm
If you only need to run the basics 5/6 KVA will be enough for most people. Plenty of people are using those size generators in rural setups without problem.
I've seen that, its an awesome idea. Especially when the power comes back on and the generator does this kind of jump 4 meters to one side.
And that's not to mention how nice and safe a double ended lead is when its lying around.
t_naki,
Mar 6, 4:43pm
I have done it before in the same SB by just having a the non-essential power MCB' s fed via a contactor that drops out when the power drops off and needs a manual push button to restart after the mains power is restored.
richard112,
Mar 6, 4:48pm
That is why you turn off the main switch on the board.
sr2,
Mar 6, 5:19pm
Yes that would be a good workable solution. Just recently I managed the set up of a similar system with an 85KVA Genset backing up a large distribution centre. We switched the contactors for the load shedding with the Tecom Challenger alarm/access system. My preference for new builds has always been to set up a separate essential power DB fed via a transfer panel but when you're retrofitting an existing building you sometimes just have to be creative!
While not wanting to start a slinging match there is a bit of misinformation (although well intended) on this thread; good to see the OP is consulting a Sparky.
trade4us2,
Mar 6, 5:33pm
Two people have seriously suggested a double ended lead to me. That is something I will never do.
kenw1,
Mar 6, 5:35pm
You have to be very careful around autostart supply systyems.
raven71,
Mar 6, 5:53pm
And don't run your generator in a garage with the door shut. I've heard of people doing that and wondering why they feel a bit light headed.
t_naki,
Mar 6, 6:26pm
Absolutely not.
I have also heard of people using this technique as a cheap way of connecting up solar PV systems.
trade4us2,
Mar 6, 7:28pm
OK, completely hypothetical of course, but let's say the generator is in a well aired garage that has fixed wiring (separate from the mains wiring) up to a house. Of course there has to be a cable with a plug in the garage, to plug into the generator. In the house, let's say there is also an inverter and battery, for short term power cuts so we don't have to go out in the rain. And there's a power cut, so the garage door can't be opened anyway. How can the inverter be connected to the fixed wiring? I imagine there will have to be yet another wire down to the garage. Otherwise there would be the dreaded live plug in the garage, and another in the house, which will not be happening.
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