Hardwiring inverter to a couple of sockets vs extension cord

[bennetimo]

Hi all,

I have an inverter with a single output socket (and no hardwire outputs), and it has very little information about how it is setup for grounding/bonding. I would like to have a couple of AC outlets run off the inverter so that I don't need to use an extension socket. I've been trying to digest all I can about gfci/rcd/grounding setup for inverters but a couple of things I'm still hoping to get clearer in my mind.

1. If I can plug an extension cord into the single socket of the inverter, is there any difference between that and hardwiring a plug going to a couple of sockets? It seems like it should be the same to me, aside from maybe giving the impression to someone who didn't know the setup that they could plug multiple high load devices in simultaneously. But if you had some hardwired sockets and only used one at a time, is there any problem with that?

2. When is it necessary/recommended to use an RCD (GFCI) or not with hardwired AC circuits? If I plug in directly to the inverter socket there isn't one, but most seem to add one when hardwiring sockets. From what I understand if my inverter doesn't have an NE bond internally, then an RCD wouldn't even work. What do I do if I don't know if my inverter has that bond or not? The inverter I have is this Renogy 1000w one and it doesn't say anything in the manual about the grounding/rcd internals. I'm in the UK and there is slightly more information on the equivalent US one, which mentions it has an in built GFCI. I'm presuming my unit has some internal differences.

Apologies if this has been asked before. This is for a van that has no shore power hookup, so it's the only AC system. I've tried contacted Renogy support multiple times now, and have yet to get a single word back from them!

Thank you!

 

[macheung]

Other than visual appearance and number of plugs, there isn’t any difference between hard wiring a socket to plugging in a power strip.

As for grounding, the purpose of the ground is such that if the equipment you connect is defective and the hot wire comes in contact with the case or exposed metal part, the case is connected to ground which will provide a short back to neutral near the power supply, causing high current to flow and trip the breaker / blow the fuse. Without this, the case will remain with high voltage and shock you should you touch it. You would need to check if the ground is tied to neutral inside the inverter. If not, it may be possible to add a link, but check with the inverter mfg. A GFI socket actively monitors the current and breaks the circuit as soon as there is a little bit of current flowing in the ground (where a normal grounded circuit will need a lot of current before breaker trips), adding additional safety. Typically used in wet conditions.

 

[NwCali]

I'm still installing my system and was using a lamp the other day that had a short in the cable (unknown to me) and it was hooked up to a GFCI. I got a little tingle (mild shock) but the gfci tripped fast.

I'd suggest that a person always use a GFCI in mobile systems and in most cases where they can at home.

I once flew a doctor to a dead person so he could retrieve his eyes for transplant. He was young, wife/kids. They handed him a drill (he was working under their house) and it fried him...

I've also been shocked a lot in life (industrial welder for awhile).

So, regardless, you can wire in a gfci. What I didn't know is aparantly the gfci will work even if you have no ground in the system (not yet hooked up on mine, but coming within a day or two).

 

[bennetimo]

Other than visual appearance and number of plugs, there isn’t any difference between hard wiring a socket to plugging in a power strip.

As for grounding, the purpose of the ground is such that if the equipment you connect is defective and the hot wire comes in contact with the case or exposed metal part, the case is connected to ground which will provide a short back to neutral near the power supply, causing high current to flow and trip the breaker / blow the fuse. Without this, the case will remain with high voltage and shock you should you touch it. You would need to check if the ground is tied to neutral inside the inverter. If not, it may be possible to add a link, but check with the inverter mfg. A GFI socket actively monitors the current and breaks the circuit as soon as there is a little bit of current flowing in the ground (where a normal grounded circuit will need a lot of current before breaker trips), adding additional safety. Typically used in wet conditions.

Thanks, that's what I thought for hardwiring it. I guess some inverters with actual hardwire AC outputs are designed with doing hardwiring in mind whereas a smaller, cheaper inverter that has a single fixed plug on it is probably designed to be used in a simpler system. But if I'm just adding additional sockets for location convenience and being careful to only use one at a time, as if it was the single output on the inverter, it seems like that should be o.k.

With the grounding/earthing I'm a little more unsure what to do as I've been trying to ask Renogy for over a month now about whether there is a neutral-earth bond in the inverter or not and some other questions around it, and they have so far not even responded to any message (terrible customer service!).

If you had an inverter that you didn't know if it had an N-E bond internal or not, how would you deal with it? Is there a way to safely and easily test it? As from what I understood if it's already got an internal bond then adding an additional link is not a good idea.

Ideally I want to have this setup:

Inverter -> RCD/MCB breaker box -> outlets

But as there is so little information about the Renogy inverter I can't figure out whether adding an RCD would actually do anything. I don't want to have a false safety blanket adding an RCD if it wouldn't actually trip.

 

[bennetimo]

I'm still installing my system and was using a lamp the other day that had a short in the cable (unknown to me) and it was hooked up to a GFCI. I got a little tingle (mild shock) but the gfci tripped fast.

I'd suggest that a person always use a GFCI in mobile systems and in most cases where they can at home.

I once flew a doctor to a dead person so he could retrieve his eyes for transplant. He was young, wife/kids. They handed him a drill (he was working under their house) and it fried him...

I've also been shocked a lot in life (industrial welder for awhile).

So, regardless, you can wire in a gfci. What I didn't know is aparantly the gfci will work even if you have no ground in the system (not yet hooked up on mine, but coming within a day or two).

Thanks for the response and yeah it's definitely something I'm taking seriously, I don't want to wire in the inverter until I can be comfortable in my mind that it's safe. I'm starting to kick myself that I didn't buy a more expensive Victron unit, as their documentation and customer support is so far ahead of Renogy that it's not even a competition ?

On your last point, that's what I've been thinking about. I want to add an RCD (GFCI - I'm in the UK), but want to be sure it will actually trip. If there is no N-E bond inside the inverter (which is unknown to me/nothing in the manual), then I can't see how an RCD would work unless I manually add the N-E bond myself.

The only thing I have to go on is the features of my inverter list these two:

• Electronic overload protection with automatic shutdown.
• Output short circuit protection

But, I'm not sure whether to interpret that as it having an in built RCD/GFCI as it doesn't explicitly state those terms

 

[12VoltInstalls]

Your local home bits purveyor I mean hardware store should have a $5-$10 gizmo that is a GFCI tester.

In the USA /120V I would:
-Wire a three-wire 12ga extension cord into a GFCI and box with the male end to be plugged into the inverter
- plug the tester into the GFCI and hit the test button

if it (the GFCI) trips great. The inverter is internally bonded.
if it does not trip it’s not.

(I can’t say what renogy would recommend)

 

[bennetimo]

Your local home bits purveyor I mean hardware store should have a $5-$10 gizmo that is a GFCI tester.

In the USA /120V I would:
-Wire a three-wire 12ga extension cord into a GFCI and box with the male end to be plugged into the inverter
- plug the tester into the GFCI and hit the test button

if it (the GFCI) trips great. The inverter is internally bonded.
if it does not trip it’s not.

(I can’t say what renogy would recommend)

Thanks, that's a good point, I've seen there are some modestly priced RCD testers out there.

I think I've decided that the Renogy inverter I have is not designed for the use case I have in mind (i.e. running more than a single appliance) and I don't feel comfortable installing it with the abysmal support and information they have on it. Considering it's a potentially lethal appliance if used incorrectly, it's pretty poor.

What I think I'll do is swap it out for a Victron Phoenix that I can actually be sure will have provisions for creating the N/E bond internally and then wire it:

Inverter -> RCD -> MCBs -> sockets

And then I'm definitely going to invest in one of the RCD testers you mention. Great idea, it makes perfect sense now (but wasn't initially) that the test button on the RCD only tests the mechanical functioning of the device and not whether it will actually trip under current leaking conditions. So seems like a key device to have on hand to get peace of mind it's all working correctly.