Help Me Wire My House

[Crossy]

Crossy Said in Post above :

"Does the knife have any fuses? If so ensure only the live is fused, a fused neutral can be extremely hazardous. "

"Inside that cover is space for two fuses, they invariably have fencing wire installed but on the off chance that one is a fuse make sure it's in the live side."

So you simply mean, Live has rated fuse wife (say 60 Amps) and the N has fence wire or in my case a sexy huge wood nail jammed in there.

Why is it so dangerous, not being silly, just learning?

Me too I'd like to know also.

All the knife fuse boxes I've seen have always had those fuse strip thingies on both the neg and live.

See my Post #51

[haveaniceday]

Thanks, I am not to worried right now, but for 170b each, I will pick up some more 20A CB's next trip to the big green shop.

Next thing, today when I had lots of covers off outlets, seeing what mess is inside, I noticed the I actually have two earths / grounds connected.

The 3 distribution boxes are connected together joining to 1 X 16mm cable to a common earth stake in the ground.

Seperate to this, the water pump is on its own earth stake, the manufactures wire and also a heavier one to a motors bolts connects to the earth stake, I did this to better ensure it is earthed as it plugs into an outlet, to make it easy to change over to the generator when the power dies. This is a temp set up till a full time UPS is installed.

Now the generator is also grounded to the same earth stake, it has a earthed triple wire coming out of it to some red outlets in the house, (the water pump wires run to the same area for ease of changing over). The generator circuit is totally Independent of the house 220V circuits.

Well so I thought, looking at one of the red outlets today , I see it also has a earth from a house 220V circuit going to it as well, the last genset outlet is next to a mains outlet, and the earths are conected.

So this means that, when the generator is plugged in, there is a direct link with the earths. Meaning that there are effecftivly two earth stakes that are some distance apart connected to the house, and the gen set one is only 2.5mm (compared to 16mm) on the main one.

I can and shall easily fix it by isolating the gen set circuit, (remove the connecting earth wire) but curious, would this make a problem if I did nothing?

I read that in Australia you are meant to have only one ground stake. Not sure why.

Edited February 20, 2012 by haveaniceday

[bankruatsteve]

I don't think you need to worry about the earthing and I wouldn't disconnect anything from that. "Earth" is kind of a generic for zero voltage potential - it doesn't matter how many points are connected to it.

[Crossy]

I read that in Australia you are meant to have only one ground stake. Not sure why.

I understand that Aus does not permit multiple ground stakes due to the high lightning incidence. A local ground strike will generate a large potential gradient between the stakes, a (very) large current may then flow in the conductor between the stakes (it being a better path than the ground between them) leading to a possible fire hazard.

[electau]

Thanks, I am not to worried right now, but for 170b each, I will pick up some more 20A CB's next trip to the big green shop.

Next thing, today when I had lots of covers off outlets, seeing what mess is inside, I noticed the I actually have two earths / grounds connected.

The 3 distribution boxes are connected together joining to 1 X 16mm cable to a common earth stake in the ground.

Seperate to this, the water pump is on its own earth stake, the manufactures wire and also a heavier one to a motors bolts connects to the earth stake, I did this to better ensure it is earthed as it plugs into an outlet, to make it easy to change over to the generator when the power dies. This is a temp set up till a full time UPS is installed.

Now the generator is also grounded to the same earth stake, it has a earthed triple wire coming out of it to some red outlets in the house, (the water pump wires run to the same area for ease of changing over). The generator circuit is totally Independent of the house 220V circuits.

Well so I thought, looking at one of the red outlets today , I see it also has a earth from a house 220V circuit going to it as well, the last genset outlet is next to a mains outlet, and the earths are conected.

So this means that, when the generator is plugged in, there is a direct link with the earths. Meaning that there are effecftivly two earth stakes that are some distance apart connected to the house, and the gen set one is only 2.5mm (compared to 16mm) on the main one.

I can and shall easily fix it by isolating the gen set circuit, (remove the connecting earth wire) but curious, would this make a problem if I did nothing?

I read that in Australia you are meant to have only one ground stake. Not sure why.

You can have more than one earth electrode under AS3000 but they must be bonded together. Most electrical installations only require only one electrode 13mm copper clad 1.2/1.8M.

[electau]

I read that in Australia you are meant to have only one ground stake. Not sure why.

I understand that Aus does not permit multiple ground stakes due to the high lightning incidence. A local ground strike will generate a large potential gradient between the stakes, a (very) large current may then flow in the conductor between the stakes (it being a better path than the ground between them) leading to a possible fire hazard.

With the MEN system and electrical installations earthing to AS3000 lightning is not a problem in Australia.

More than on electrode is permitted providing that they are bonded together (equipotential bonding). Most installations have only one electrode 13mm copper clad steel 1.2/1.8M.

SPDs can be installed at the main switchboard in areas where lightning is more prevalent.

　

[electau]

I still have 2 small air cons on 2X2.5mm / 1X1.5mm wire. The longest run is only 15m.

Crossy indicated that a small 13,000BTU air con : "A 13,000 BTU A/C will pull about 6A on run, so no reason why you should not put him on a 20A breaker."

​They are currently on B32A CB's. Is it essential to get B20A Circuit Breakers to protect the 2.5mm wire on the next trip to the big smoke ?

I am assuming the answer is yes, but I remmeber something about putting air cons on a bigger CB for the start up.

Last trip to the big smoke I bought many B16A CB's, do you think they will be fine?

Those MCBs are B curve, you need C curve (standard for most circuits) D curve for equipment with high inrush currents. B curve are for equipment such as generators. B and D curve are generally for special applications.

[haveaniceday]

In Thailand you can not but C10, C16, C20 etc, they are all B.

Just another screwed up place eh.

Edited February 22, 2012 by haveaniceday

[canuckamuck]

I thought I would check back in to this thread, I have redone quite a lot of the wiring in the old house, and We are all still alive. Thanks Crossy for your advice so far.

The biggest hazard in my place is my father in law. recently he came home with a new welder. he used to have a 200 amp 5kw unit which seemed to work well enough on a 20amp breaker and 6mm wire. But now he has come home with a 300 amp 13kw unit which blew up the meter and burned the wires off at the pole when he hooked it up. It is very possible he hooked it up wrong, but also it might just be that it is too much for the setup. We haven't got the 15(45) meter yet, but we will pick one up on Monday. They say three weeks for them to come and hook it up though. In the meantime we got the old meter fixed and I am hoping he doesn't try to hook up the welder again before that.

Question. what size of breaker and wire does he need for the new welder, and was size of wire should we have from the new meter to the knife switch (approx 30 meters). I think aluminum is cheaper, so I guess I would be interested in that for the main.

[Crossy]

Question. what size of breaker and wire does he need for the new welder, and was size of wire should we have from the new meter to the knife switch (approx 30 meters). I think aluminum is cheaper, so I guess I would be interested in that for the main.

If it's really a 13kW welder that's 68 Amps!!! No surprises the 5/15 went in to orbit, your shiny new 15/45 will already be at 50% overload.

OK, so a welder is an intermittent load, but it's still scary.

A 63A breaker and 16mm2 Al would be the minimum I would install.

What do the instructions say about power supply requirements? Any chance of a 30/100 supply??

[canuckamuck]

Question. what size of breaker and wire does he need for the new welder, and was size of wire should we have from the new meter to the knife switch (approx 30 meters). I think aluminum is cheaper, so I guess I would be interested in that for the main.

If it's really a 13kW welder that's 68 Amps!!! No surprises the 5/15 went in to orbit, your shiny new 15/45 will already be at 50% overload.

OK, so a welder is an intermittent load, but it's still scary.

A 63A breaker and 16mm2 Al would be the minimum I would install.

What do the instructions say about power supply requirements? Any chance of a 30/100 supply??

Things are moving pretty slow on this project, but we are going to go get the new meter this week (probably). What size of wire do I need from the 15/45 meter to the house (knife switch)? It is about 30 meters and currently we have 16mm Al.

[Crossy]

I would use 16mm Cu or 25mm Al on a 15/45.

Many Thai installers would be one size down from that on a pure current-rating basis but volt drop may become an issue if your load is near the maximum allowable (it is).

[electau]

Most welders have a duty cycle eg 10%. They are not run at continuous full load. Most run at a low power factor. You will have to take into consideration the input load current to the welder.

An MCB can be run at 1.13n ( n =rated current of MCB) continuously without tripping, but overloads exceeding the rating of the MCB should not be on a continuous basis, only intermittent. An MCB must trip at 1.45n ( 1 hour).

Volage drop may have to be taken into consideration, along with the effects on other consumers supplied from the transformer.

Note that there is no protective device that has been installed on the consumers mains or metering.

A 63A MCB will protect the installation from continuous overload, with 16sqmm Cu mains.

[canuckamuck]

Most welders have a duty cycle eg 10%. They are not run at continuous full load. Most run at a low power factor. You will have to take into consideration the input load current to the welder.

An MCB can be run at 1.13n ( n =rated current of MCB) continuously without tripping, but overloads exceeding the rating of the MCB should not be on a continuous basis, only intermittent. An MCB must trip at 1.45n ( 1 hour).

Volage drop may have to be taken into consideration, along with the effects on other consumers supplied from the transformer.

Note that there is no protective device that has been installed on the consumers mains or metering.

A 63A MCB will protect the installation from continuous overload, with 16sqmm Cu mains.

MCB is master circuit board? same as Consumer unit, right?

Right now I think I will run 25mm Al from the new meter to the knife switch, from that point I will run 16mm Al to the shed which will have its own consumer unit and will be the new home of the welder. I guess I will get a 63A RCB for that.

But also from the knife switch I will run some 16mm Cu (I have 6M of it handy) to my house Consumer unit which is 50A I believe

Question: can a welder run on an RCBO? or will it constantly trip because welding equals leakage.

[electau]

The 63A MCB is the circuit breaker on the main switch board (ie consumer unit) where the incoming consumers mains terminate.

The welder circuit should be protected by a suitable size circuit breaker.Its current rating will be dependant on the input current in amps to the welder ( from the nameplate).

The welder may be protected by an RCD of 30mA rating or an RCBO ( MCB/RCD).

The RCD protects the primary winding of the welder (and the circuit) in the event of an earth fault.

The secondary winding is electrically isolated from the primary.

The knife switch should be replaced by an MCB.

The welder should have a protective earth installed.

[Crossy]

MCB - Miniature Circuit Breaker

[haveaniceday]

I never did actually put some earth stakes down earthing the roof. For the event of a lighting strike.

The air spikes where never installed, (sad story), it is a metal roof and I have 16mm copper connected to two opposite corners, & they run down the out side of the wall in conduit.

The wire then does a 90' turn and is under a 1.5m wide concrete walkway around the house, then goes about 6 m down a slope to where I was going to hammer in a 3m long earth stake that would go well into moist soil in dry season. The house is on a built up mound.

Is that 90' turn a real issue?