Two inverters?

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grizzzman
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Re: Two inverters?

Post by grizzzman »

Ok I get it. Called Ground Fault Circuit Interrupter here. Either at the circuit breaker or at the receptacle. Ok got it
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Re: Two inverters?

Post by Barboots »

BruceS wrote:RCD = residual current device
RVD = residual voltage device

RCD's are compulsory on all houses and other electrical installations.
https://www.electricalsafetyfirst.org.u ... explained/
RVD's are more like snake oil. (just my opinion)
https://www.rvdsafe.com.au/product/resi ... evice-rvd/

Not many people got electrocuted even before BOTH of these devices were invented.
Snake oil is a term used in connection with things that don't work as claimed. An RVD can easily be proven to do what it claims.

There is a big difference between a home installation with Earth protection and a standalone RV installation without any. If you live in a world where appliances and wiring can never go faulty, an RVD is not required for safety in standalone powered RVs.
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Re: Two inverters?

Post by BruceS »

Yep.
It was just my opinion.
I've also never had any car, bus, MH, caravan or house insurance for 45 years. My bank balance is my insurance company.
It's as simple as cost verses risk (assessment).
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Re: Two inverters?

Post by T1 Terry »

A inverter produces a floating supply, line 1 and line 2 and across these two wires is either 120vac or 240vac depending on the country they are designed to be used. By connecting one line to the earth pin the system changes to neutral and active, if an RCD is fitted after this connection point and connection made to the neutral and earth or active and earth will create an imbalance between the current seen on the active circuit compared to the neutral circuit. Sounds like this system would be ideal for an RV eh, but as soon as you plug into the mains supply the RCD in that circuit sees the earth/neutral connection in the RV as a fault and trips, so all Rv's are wired as a floating system..... the mandatory RCD installed in the RV is just one of those truly dumb ideas that lead people into a false sense of security.
The risk with multiple type 1 appliances on a float system is if there are 2 separate faults to the earth circuit, one to each line of the floating supply, if one is the body of the Rv itself you wouldn't feel a thing, but if the class 1 appliance has a short to the other line from the floating system and you touch the body of the RV you become an appliance. The RCD will not trip because nether circuit is tied to line 1 or line 2 before the RCD so it can't see an imbalance after the RCD, just a load, you, connected to the line 1 and line 2 supply. The same problem with 2 class 1 appliances, each with a fault to opposing circuits, neither user fells anything but if the touch each other they both become an appliance.
An RVD looks for any voltage on the earth wire, not current but voltage, if it sees voltage from line 1 or line 2 it cuts the circuit to both line 1 and line 2 until the fault is rectified, it will not reset no matter how hard you try until the fault is cleared.
Which is safer, an RVD by a country mile, but you can't have your cake and eat it too, they cost something like $280 Aust compared to around $20 for an RCD, but the newer design units can also detect a reverse polarity connection on the caravan park supply and instantly disconnect the circuit rather than letting the smoke out of the rather expensive electronic equipment often found in modern rvs

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Re: Two inverters?

Post by T1 Terry »

I have no idea what happened to the last bit I added to last nights post, maybe it is still flying around in the ether some where.
We really need David (Supersparkie) and any other licenced sparkies to read through all my post and correct anything I got wrong cause my interpretation of how it all works could be completely off on the wrong track.

As far as the standards and how they relate to an RV compared to a house still on the grid, it's a bloody mine field. An RV as far as this part of the standards are concerned appears to still be considered a plug in appliance. This means you can have a 3 way switch that cuts both the active and neutral from the mains supply and line 1 and line 2 from a floating supply such as an inverter or generator..... but not on a hard wired grid connected system cause you can't cut the neutral as that effects the earth/neutral link. This means the floating inverter or generator supply must be converted to an MEN (main earth neutral system) as the 3 way switch isn't allowed to cut the neutral, but this supply must be fed in before the house RCD...... so how do you protect the cabling between the inverter to the house power box....... there wasn't an answer to that one from the local sparkie and the whole thing has me scratching the head as to whether it is a better or worse system than leaving the inverter floating and protected by an RVD.... maybe our sparkies on the forum can shed some light on this conundrum.

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Re: Two inverters?

Post by T1 Terry »

bagmaker wrote: Sat Nov 18, 2017 4:47 pm I am a bit of an electrical nufnuff but would it be possible to run a little PSW AND then a grid-tie inverter like is typical in household solar setups?
These are usually 24 or 48VDC but often cheaper than the equal output in watts for a mobile inverter.
I am thinking the larger inverter would sense the smaller signal and match the sinewave
Or am I missing something as usual :D
This one is an interesting hypothetical and in certain equipment combinations could/should work. It can't work with a grid tie inverter because they are an uncontrolled current output device, the solar input limits the output and the grid acts as a huge capacity to soak up the current produced that wasn't used by the house load.......... but what about a Victron Multiplus or Quatro that has the ability to supplement the incoming supply if it isn't enough to supply the load? Say a 500w pure sine wave inverter fed into the input side of the Victron inverter and the max input current set to 2 amps would have the 500w inverter supplying the smaller loads and the Victron kicking in to make up the short fall when a heavy load was applied.... the Victron battery charger function would need to be turned off some how but I can't see why it wouldn't work.... any ideas?

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Re: Two inverters?

Post by Barboots »

I got a laugh out of the irony of the ad following your post Terry [emoji23]
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Re: Two inverters?

Post by T1 Terry »

Hmmmm........ do you think the gods are trying to tell me something :lol:
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Re: Two inverters?

Post by Newcastle George »

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Re: Two inverters?

Post by bagmaker »

I reckon it would be worth a try, at least
Probably only a 300w PSW as the "pilot", anyone buying Victron gear should have a decent fridge. That minimises the idle current a little bit more.

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