RCD info?

[BruceS]

I'm copying a post from another forum that Oldtrack123 has posted.
I would like some comments on it please. Right or wrong?
Consider some of us in big vans, motorhomes or even houseboats that DO have only one 15A, 3 pin plug cord bringing in our power supply.

I suspect your RCD /overload breaker is [rcd /olcb] is doing it's job.
It is tripping due to your current draw exceeding 15A
You simply cannot run two heavy current draw devices @ the same time off a 15A power outlet
Check the wattage of the two appliances, if adding the two, exceeds 3600 Watts, the overload part of the rcd /elcb will trip to protect the wiring from overheating,
The extent of overload will determine how soon it trips.
High overload will cause it to trip almost instantly
Minor overloads can take many minutes to trip
An earth fault causes the RCD section to trip. It will do that almost immediately if the leakage current exceeds 40mA.
No, you cannot have a higher rated RCD /ELCB fitted.It must be no higher rated than the cables/ accessories it is protecting
[ENDQUOTE]

[T1 Terry]

He is on the money as far as I understand things. It would be a 16 amp RCD rather than a 15 amp I'd imagine, that is the more common size.

On another note, I have found a number of "slim line" RCD's that look to be double pole (the requirement for a portable premises) but actually only switch the active, the neutral is a direct through feed. 2 wires go into the top and 2 wires come out the bottom so it looks just like a double pole RCD, but only one wire is switched so it is not meeting the requirements of the ADR's regarding transportable premises). Why does it need to be a double pole switch? To protect against power points wired with the active and neutral crossed or the extension lead wired with these 2 crossed. If this crossed wiring was before the single pole RCD, simply cutting the one line could mean only the neutral was switched off, the active would still be connected to the RV system but that is wired to the neutral. If there is an active earth/neutral link on the RV system side, the body of the van would be now connected to active. Now we have a situation if a person was to put one hand on the metal body and another part of the persons body touching the ground, they would become an appliance. The RCD has already tripped so there is nothing to turn it off, anyone touching the electrocuted person would also be electrocuted and so on until enough appliances (people) finally overloaded the supply RCD. If the supply is a generator, there is no RCD in most cases, the chain of appliances (people) would have to wait for the generator to run out of fuel before they could all fall to the ground dead. If the RCD cuts both lines, this wouldn't happen, the first person would yell a rude work but by the time they got the sound out the circuit would already have been cut.

T1 Terry

[BruceS]

Sorry Terry, I should have explained my thoughts that he is a bit wrong.
The pedestal in front of my boat has a 45A circuit breaker & there is only one 3 pin connection.
I had this argument a while ago on the Yachties forum as well.
I have a Honda 6500w generator that has two 15A outlets.
I queried how I could use the 6500w out of one socket if in Oldtracks post, he reckons only 3600 can be used out of one.
I wanted to know if immediately outside of the generator I could join both outlets into my lead.
My electrician/air conditioner installer talked me into having the 15A cable upgraded to black cable that has .6kv/1.0kv stamped on it. He was happy with the normal 15A 3 pin plugs on the ends though.
There are some big boats in the marina & all of them have the standard 15A plug on them. I'm willing to bet many use a lot more than 3600w at a given time without the power going off.

[supersparky]

Bruce, I think your question is 'Is what Oldtrack saying correct?' The answer is yes.
But, you can have 2 x 240 15amp feeds into your transportable premises. Quite a few big M/homes are wired like that. One feed for the airco and one to run the rest of the show.
Or you could have two completely separate circuits running the house if you don't use airco.
You may notice that quite a few C/p pedastals have two 15/16Amp feeds per site now.

What T1 has posted is spot-on. There are reasons why the regulations and standards are written. Sometimes they are a P.I.A. but they are to stop people from being hurt. Not needed in a perfect world, but we all know that doesn't really exist.
In the domestic environment (read: a house )a single pole RCD will work fine because the installation will have been polarity tested prior to supply being energised.

Edit: Bruce, the .6kv/1kv on your lead is only for the cable insulation and maximum voltage. There will be more writing a little further along that will described the current carrying capability. Maybe something like 6m2 or maybe 10m2. The black insulation is usually on flexible cables used in mining or submersible pump applications.

[T1 Terry]

Really, if more than 15 amps is required and the cabling is suitable, it should have a different plug and socket as well. This identifies that this power point can supply a greater output but only a suitable plug and lead can be plugged into it so that the whole set up from RCD onwards can handle the higher current.
I'm not sure if I showed you the melted mess of a 15 amp plug and lead from a "new to the game" caravanning family. Simply way too much current being dragged through the lead and plug melted the plug end, the cable outer sheath, the socket end and the plug in point on the side of the van. They bought an Amphibian to protect against doing the same thing again but complained it kept tripping and was a nuisance. I suggested buying a single 15 amp box set up from Bunnings and adding a 16 amp RCD so they could plug into 15 amp supplies and still be protected from any over current problem.
Because the van was fitted with lithium batteries, a lot of solar and a 3000/9000w inverter as well as a Projecta 2000w inverter, the system had UPS capability (uninterrupted power supply) because the inverters immediately switched in if the mains were lost. They were still in the front yard and we were still living in the bus at the time and we got a frantic call that there were alarm noises and the power kept going off.
Turned out the 16 amp RCD had tripped and they were trying to pull 5000w out of the 3000/9000w inverter, it would do it for a few minutes and then shut down from over heat. What was using so much power? The electric hot water was on, so was the air con and the TV, lights and computers, then the oldest boy switch the 2400w kettle on to wash the dishes ....... They looked bewildered when I said they just couldn't have all that on at the same time, the reply was they had been doing that for months since they had headed off on the road. I asked if they had linked the melted cord and nuisance tripping of the Amphibian with the massive load they were trying to power ..... no, hadn't even thought that might be the cause, we do that at home ........
They are now much more experienced travellers and the problem never comes up now

Another way around the problem is using a 5 pin 3 phase cable and socket. This gives 3 x 10 amps available as long as the RV wiring is done in a way that each phase doesn't see more than 10 amps for more than a few mins. You could move up to a bigger cable plug and socket and increase that 10 amps per phase to what ever, but finding a suitable 3 phase powerpoint gets much harder.

T1 Terry

T1 Terry

[bagmaker]

snippity
I have a Honda 6500w generator that has two 15A outlets.
snip

I wonder if the gensets over 3.6kva are running a phase for each outlet or somehow splitting outlets from a single phase with big output.
If the former, one shouldnt be able to co-habitat the same outlets, they must be on different circuits within the boat/rv/house

[Busman]

With the fires around Stanthorpe and a sub station being taken out we have been existing on a lead from VP to the house.
We have also done a lot of upgrading of pumps and the ability to move water around the tanks (7 0ff, about 120,000 ltrs)
Which is all well and good as long as the power is on.
Hang on if we are here fighting the fires VP is going to be here, so may as well add my spare inverter to the other 2 (Rich Electric) and make VP 3 phase. Changeover switch is on order (sparky fitting next week)
Can't wait to be travelling again and get asked for some power for someones flat battery, ask them if they have a 3 phase charger ?
As the house is 3 phase life should be as normal, as long as we are a little bit careful.

[supersparky]

Busman, Be very careful connecting 3 single phase inverters to a common outlet. Unless they are all synchronised you will have some pretty strange voltages floating about. I hope your sparky knows what he is doing.

[Busman]

All good David thanks, they are all synchronised with a manufacturers magic box so all voltages and hertz are the same.

[Toolman]

And cleaner power than from the pole