RCD and AFDD

[ians]

This is something which is going to need to be addressed soon.

The days of walking into a wholesaler and picking up the cheapest type A RCD is just not going to cut it anymore ... it could also explain why there are so many complaints about random tripping ... due to incorrect selection of the RCD required for the application.

Once you have done a little research into RCD types ... then you going to find there is a device which might suit the application better or create even more problems ... an AFDD

As I am researching alternative supplies ... looking at how people are installing (RCD) or commonly known as a earth leakage device in P.1 - P.4 ... throw in a bonded neutral/earth and relays for bonding neutral and earth ... it makes you wonder if the correct type of RCD has been selected ?

Anyone here have a lot of experience using the different types of RCD's and AFDD's ?

[ians]

Do you have to install an RCD before the inverter or UPS.

Common sense in the past would have me "not" connecting a UPS to an RCD circuit ... the reason ... a UPS was used for dedicated socket outlets for computers and stuff ... however since load shedding started people use any means to try keep the lights on.

Do you have to connect an inverter to an RCB circuit?

I have noticed while going through tons of information ... one inverter distributor indicates the use of a type A RCB is required.

If the manufacturer/supplier recommends you connect the inverter to an RCD ... would it affect the warranty if not installed ... and how do they deal with random tripping issues?

Is a type A RCB best suited for that application ... is it recommended by the RCD supplier ?

[ians]

Then we need to start digging into neutral earth bonding and the effects it has on RCD's and the location of the RCD in the circuit.

Some inverters require an external neutral/earth bridge ... and an RCD at the inverter.

[Dylboy]

Do we even get the type A and AC And F etc RCDs in the country ?

But yes the N and E bond is an issue. We found a solar install the other day where this needs a grounding box.
I then tested my inveter yesterday with simulated mains fail of main switch and then cranked a socket and my ELU did not trip... I have an ELU to feed inverter and output of inveter is another ELU. Waiting for grid to go down to rest again as my main switch is an ELU and kn the complex which is old I have no access to my feed switch.

But in the end I am getting a grounding box soon as I saw my N was floating...

Live and learn everyday and glad found this out now on the inverter.

This inveter stuff and solar is new to many an electrician and not everyone is keen on sharing info or "secrets"

Sent from my SM-N960F using Tapatalk

[ians]

What may seem like a silly question I am sure many people are thinking ... if you have a bi directional system (hybrid inverter) if you power is being fed from the mains to the inverter the way line and load breakers are designed to work ... when you feed the power back from the inverter to the RCD ... is it not the same thing as plugging a generator using the suicide cord system?

I was under the impression ... the reason the suicide cord was so dangerous was because the power is flowing in the wrong direction and therefore creates a dangerous environment because the safety devices in the electrical installation will no longer function correctly ?

[Dylboy]

What may seem like a silly question I am sure many people are thinking ... if you have a bi directional system (hybrid inverter) if you power is being fed from the mains to the inverter the way line and load breakers are designed to work ... when you feed the power back from the inverter to the RCD ... is it not the same thing as plugging a generator using the suicide cord system?

I was under the impression ... the reason the suicide cord was so dangerous was because the power is flowing in the wrong direction and therefore creates a dangerous environment because the safety devices in the electrical installation will no longer function correctly ?

Not thought of it that way before... I feel their would be an overcurrent device along the conductor so that should be fine but then isolation could be an issues as you isolate to bottom of switch but now the electrikery is now coming back side to whack you... I guess when maintenance switch off and isolate everything haha

Sent from my SM-N960F using Tapatalk

[Justloadit]

What may seem like a silly question I am sure many people are thinking ... if you have a bi directional system (hybrid inverter) if you power is being fed from the mains to the inverter the way line and load breakers are designed to work ... when you feed the power back from the inverter to the RCD ... is it not the same thing as plugging a generator using the suicide cord system?

I was under the impression ... the reason the suicide cord was so dangerous was because the power is flowing in the wrong direction and therefore creates a dangerous environment because the safety devices in the electrical installation will no longer function correctly ?

Not quite so.
The inverter only feeds back to the loads connected on the incoming side of the inverter, if it has excess energy to share. Once the mains goes down, then this function desists, as an internal relay in the inverter will disconnect the inverter from the supply.

This is also known as "Anti Islanding"

What is Anti-Islanding? Anti-Islanding is the ability to quickly stop sending power into the grid from your solar system. Here's Why Anti-Islanding is important: Electric utility companies refer to residential grid-tie solar power arrays as distributed generation (DG) generators.

Islanding

[ians]

Thinking out loud ... the suicide cord is dangerous because it feeds back into the grid ... which could result in injury to council works or anyone upstream ... it has nothing to do with the direction of flow?

The fact that the one side of the plug top has live exposed conductors (I have a site where the generator installer has fitted a male plug top to the generator) I have advised the customer of the danger ... however the installer assured the customer that it is fine ... ok.

[Justloadit]

Thinking out loud ... the suicide cord is dangerous because it feeds back into the grid ... which could result in injury to council works or anyone upstream ... it has nothing to do with the direction of flow?

My thinking is if this is in a residential area, and the user has the isolator in the on position, the little generator will be overloaded, as it tries to power up all the loads connected to that line on the municipal side, unless it is a big genny then yes there could be a voltage going back, but I think by that time either the extension has burnt out or the circuit breaker would have tripped.

[Derlyn]

With a suicide cord, the earth leakage does not work and all other plugs on the same circuit as the one you are backfeeding into, have no protection.

Not a healthy situation.

Peace out .. Derek

[Justloadit]

With a suicide cord, the earth leakage does not work and all other plugs on the same circuit as the one you are backfeeding into, have no protection.

Not a healthy situation.

Peace out .. Derek

Agreed, I personally will not recommend or even use this type of connection. Some people who do not understand the implications love to live dangerously

[ians]

Dont get me wrong ... I am not saying that it is a good practise (suicide cord) ...

What makes a suicide cord so dangerous so that we can understand why people shouldnt use it even if it is recommended by generator suppliers as a quick easy fix.

I am trying understand how a hybrid inverter works ... current flow to the inverter and back into the essential supply or grid.

How the current flow affects the operation of the protective devices.

The type of RCD which should be used for a specific application like and inverter.

If AFDD with built in RCD might be a better option or not.

[ians]

By the way I dont need to know that the plug has exposed conductors or if you dont switch off the main breaker its feeds back in the grid ... creating a dangerous environment ...

what I am interested to know is the affect it has on the operation of the safety devices.

[Derlyn]

@Ians

I always see an invertor as a supply, the same as the Supply Authority or a generator.

If the invertor or generator is connected in parallel with the supply from the supply authority, then it has no effect on the safety devices of the installation.

The devices dont know if they are being fed by the Supply Authority, a generator or an invertor. They just see a supply.

Peace out .. Derek

[Justloadit]

Being AC, it does not know the direction of current flow, so if it exceeds the rating, it will trip. DC on the other hand has a polarity not because of the current direction, but the direction does affect which side the spark shroud is on. On the wrong side, it catches fire.

In Hybrid systems, there is a CT which measures the load current, and a CT which measures the supply current. It then subtracts the one from the other, and knows the amount of current the loads are drawing before the inverter. It then starts applying the feed back to the grid side, until the mount becomes zero(if there is sufficient PV power to do so).