5 kva inverter

[ians]

I am trying to figue out how an inverter that has a 22 amp rating requires :

50 amp breaker - 8 awg/ 16mm wire.

Please tell me what I am missing.

Its like a machine which was delivered to site the other day ... the customer asks the machine supplier for cable requirements ... he tells the customer we must install a 16 mm cable with a 60 amp isolator and a 60 amp circuit breaker.

The machine arrives ... max load 13 amps ... in Africa you just smile.

Then the "technician" tells me the earth wire is too small ... I can live with putting in a bigger earth wire ... after doing some research ... it is recommended that you have a decent earth wire for CNC machines ... but it is not a good idea to install an earth spike outside the building for the machine.

[Justloadit]

50A Circuit breaker - Probably to handle the inrush current when switched on.
16mm wire - who knows

[ians]

I am busy making up 2 DB's ( the top one with all the changeover switch/mcbs and e/l unit 230 VAC stuff and the one below it to connect the battery cables 48 VDC stuff to sperate them ... i could fit the 150 a fuse holders in the same DB and fit a partition ... but plastic DB's are cheap) to fit directly below the inverter (its a temp supply for load shedding ... until we get the 3 units in parallel installed)

When using a bypass/changeover switch ... do you take the wires from the inverter output terminals through the earth leakage unit then into the inverter input of the bypass switch or do you take them directly to the bypass terminals ... then out ot the e/l unit ... It makes sense to go through the e/l unit then to the bypass switch ... when in bypass the circuit will be protected by the e/l unit and circuit breaker in the DB it is fed from.

When the changeover/bypass switch is in the inverter position ... and the power is being fed via the inverter or the supply from the DB is interupted ... lets say the circuit breaker trips ... you need the earth leakage protection ... but dont want 2 e/l units in series with each other ... wasnt going to fit another earth leakage unit but decided to rahter not take a chance.

Does it make sense?

[ians]

By the way did I mention the AC/DC changeover switches (SF2P-40 ... 40A ) are really cheap and nasty units ... I am scared operate it too many times in case it breaks

[Frans400]

The input breaker of 50 amp is to allow the pass trough(including inrush current) current and the additional power need for the battery charger. As soon as an installation manual mentions AWG I use the manual only as a guide line because it will be based on the American installation standards on not ours, the next thing you will see is that they mention neutral should be blue. In sans 10142-1(annex P if i am correct) there are a nice circuit diagram showing how to protect the final circuit with e/l both during normal operation and when backup power are required.
Remember to make sure your neutral are earthed during backup power. Easiest way to test this is with your e/l plug tester. Assuming you are working with an axpert TYPE inverter with American specs the neutral and earth wont be bonded.

[ians]

That could explain it ...

5000 watt / 230 VAC = 21.7 amps

5000 watt / 110 VAC = 45.45 amps

So it would be a good practice to fit a 20-25 D curve amp in line with the inverter breaker.

[ians]

Selecting a male and female plug ... do I fit a standard 16 amp socket outlet and plug top or do I do it right and fit a 32 amp plug top and socket outlet (unfortuntely there is no 25 amp plugs/couplers)

If a 5 kva unit is rated at 22 amps ... even if you use a 20 amp breaker ... a standard 16 amp plug would not be suitable.

[Frans400]

If we talking about the inlet i won't use a standard 164-1 plug but on the outlet i don't see any problem. If I'm correct the regs allows a circuit to exceed 1.25 the value of the smallest rated plug. That is why all the regular 16a plug circuit are protected by a 20a cb. You can also consider two separate circuit's protected by 16a cb each.

[ians]

If we talking about the inlet i won't use a standard 164-1 plug but on the outlet i don't see any problem. If I'm correct the regs allows a circuit to exceed 1.25 the value of the smallest rated plug. That is why all the regular 16a plug circuit are protected by a 20a cb. You can also consider two separate circuit's protected by 16a cb each.

I do agree with you if I was only supplying 1 plug circuit ... however dont agree with you if the inverter feeds into a sub DB (essential supply) ... literally every single 5 kva (meccer ... RCT ... axpert etc ) I have seen either feeds into a sub DB or an existing DB split into essential and non essential.

In my case ... rather safe than sorry ... for a little extra I got a 32 amp 3 pin coupler.

What I am doing is making it so that you dont need a changeover switch ... you just unplug the unit and join the coupler and you have a means to bypass the system.