PSW Inverter

[NavisBD]

I have recently purchased a Sunshine/RoHS 2000w inverter. I've never used an inverter before, so:

 

(1) Has anyone on the Board got/used one of this particular model? I can't immediately find any reviews

 

(2) Any useful tips?

 

Although new to inverters, I am reasonably confident on general electrics, and will not overload it! However, any guidance on the topics of earthing/interaction with shorelines/anodes would be extremely helpful.

 

Brian

 

 

 

[Tony Brooks]

Unless this is of the variety that synchronises itself to the mains frequency you must NEVER have both the shoreline and inverter connected together so many people use a changeover switch, relay or sockets and plugs to ensure only one source of 240V AC is connected at one time.

 

All sources of mains supply should be earthed but it is not as simple as that with inverters so you need to find out how this needs to be done with your particular one. An inverter derived mains supply should not cause any galvanic corrosion but a shoreline can so shorelines need an isolation transformer or a galvanic isolator.

 

 

All mains type supplies should feed via an RCD and circuit breakers or an RCBO.

 

[WotEver]

... any guidance on the topics of earthing...

If your inverter contains instructions on bonding Neutral and Earth, follow them. If they don't... then some years ago, Gibbo (late of this parish) wrote the following...

 

Ok.............

 

For this type of inverter only (i.e. high frequency) here's the situation.

 

There are three basic circuits that I am aware of being currently used for manufacture of small inverters of this type.

 

1. Totally isolated output. There is no connection whatsoever between the AC output and the DC input and/or earth. This type is perfectly fine to have neutral and earth bonded.

 

2. Partially isolated. The AC output is isolated from the DC input but the AC output is "sort of" centre tapped round the output ground. This type cannot have the neutral and earth bonded.

 

3. Mickey mouse isolated. There isn't full isolation between the DC side and the AC side. This type cannot have the neutral and earth bonded.

 

 

Now to identify which type you have................

 

Firstly, using a multimeter, ensure that the output ground is bonded to the case. If it isn't, take it back to the shop for a refund. End of.

 

 

ONLY do the following if you know what you are doing with mains electricity. You could kill yourself if you get it wrong. I accept no responsibility for any consequences.

 

Get a 15 to 40 watt 230 volt bulb in a bulbholder. Connect it between output ground and one of the AC outputs. Then connect it between output ground and the other AC output. It should not light up on either of them. If it does not light up then you have type 1. above. It is fine to bond neutral and earth.

 

If it does light up fully on one of them but not the other then it already has neutral/earth bonding. Check it has the correct one bonded. Live should light it up, neutral should not.

 

If it lights up on both of them you either have type 2. or type 3.

 

If it's type 2. then you cannot bond neutral and earth but you don't need to. The centre tapping will allow an RCD to operate properly and protect you in the same way that it usually does.

 

If you have type 3. then it should only ever be used with double insulated equipment. They are not suitable for any other type of equipment. They are dangerous if used with single insulated equipment.

 

 

How to identify between types 2. and 3.?

 

Connect the same lightbulb between each of the outputs and the DC negative input. If it lights up even partially on either of them then it is type 3. - Do not use it for anything that isn't double insulated (i.e. only has a 2 conductor mains lead).

 

Finally, for inverters of type 2, using a multimeter, ensure there is no continuity (it must be greater than 1MOhm) between the output ground wire and either of the DC input wires. If there is continuity between either of them the inverter should only be used with double insulated equipment.

 

 

If you do anything wrong in the above, or do not do exactly what is written above you could conceivably:-

 

Kill yourself.

Kill someone else.

Blow the inverter up.

Identify the wrong type of inverter

 

I repeat. I accept no responsibility for any consequences. You are not paying me for this advice. If you kill yourself, that's your problem

 

 

A little clarification:-

 

A connection between the DC input and the AC ground output is acceptable only if the AC outputs are isolated and thus can have neutral and earth bonded (or are already N/E bonded).

 

If the outputs are not isolated (thus putting the inverter into type 2. or 3.) then an internal connection between the DC inputs and ground (which type 3. will have by default) should only be used with double insulated equipment.

 

Gibbo

Edited May 15, 2016 by Theo
Make the quote more obvious. Hope that's OK, Mr WotEver

[NavisBD]

So which type would I use for an earthed appliance (ie three core flex, not double insulated)? An inverter which can only be used for double-insulated equipment would not seem to be particularly useful. What if there is an rcd between the inverter ac outlet and the earthed appliance plug?

[ditchcrawler]

This complies with some EN standards, would these standards cover earthing http://www.sunshinesolar.co.uk/media/gbu0/html/VM2000.pdf

[dmr]

I got the 1000W version a couple of weeks ago. I have just tested it and it appears that the earth and neutral are totally isolated (not bonded).

 

I will phone Sunshine next week to see if they know if an external bond is allowed.

 

............Dave

[WotEver]

Edited by Theo, Yesterday, 07:48 AM.

Make the quote more obvious. Hope that's OK, Mr WotEver

 

'tis just fine sir

[NavisBD]

Does all this mean that a type 1 (if such is my model) needs no separate earth (although there is an earth connector on the inverter)? It only came with Live and Neutral cables. Can I now connect it up to the live and neutral terminals of my leisure battery and good to go?

 

The common neutral in my boat is connected to the engine block, which I assume - but haven't verified for continuity - is bonded to the hull.

Edited May 17, 2016 by NavisBD

[Tony Brooks]

Does all this mean that a type 1 (if such is my model) needs no separate earth (although there is an earth connector on the inverter)? It only came with Live and Neutral cables. Can I now connect it up to the live and neutral terminals of my leisure battery and good to go?

 

The common neutral in my boat is connected to the engine block, which I assume - but haven't verified for continuity - is bonded to the hull.

 

Hold hard there.

 

Absolutely NO mains wiring should be connected to the engine.

 

The 12 or 24 volt DC NEGATIVE circuits may be connected to the engine but then the engine shoudl be bonded by a single "earth" connection to the hull. This is for the DC side of things. No other negative connections shoudl go to the hull.

 

The AC neutral should also be bonded to the hull IF THE INVERTER IS SUITABLE. Ideally it shoudl be close to but on a separate stud to the DC negative bond so that in the event of an AC fault and the bonding connection becoming resistive you do not put mains into the 12v circuits.

 

DC circuits use NEGATIVE

 

AC circuits use NEUTRAL to provide a path for fault currents.

[ditchcrawler]

 

Hold hard there.

 

Absolutely NO mains wiring should be connected to the engine.

 

The 12 or 24 volt DC NEGATIVE circuits may be connected to the engine but then the engine shoudl be bonded by a single "earth" connection to the hull. This is for the DC side of things. No other negative connections shoudl go to the hull.

 

The AC neutral should also be bonded to the hull IF THE INVERTER IS SUITABLE. Ideally it shoudl be close to but on a separate stud to the DC negative bond so that in the event of an AC fault and the bonding connection becoming resistive you do not put mains into the 12v circuits.

 

DC circuits use NEGATIVE

 

AC circuits use NEUTRAL to provide a path for fault currents.

I have stopped trying to offer advice on mains wiring on boats unless I think some one is going to do something dangerous then I just suggest they don't, bit like CRT ans how far to move.

[WotEver]

Does all this mean that a type 1 (if such is my model) needs no separate earth (although there is an earth connector on the inverter)?

 

No.

 

If you don't understand the post then I respectfully suggest that you don't do any mains wiring yourself and employ a marine electrician to do it for you.

 

Tony

[Loafer]

 

Hold hard there.

 

Absolutely NO mains wiring should be connected to the engine.

 

The 12 or 24 volt DC NEGATIVE circuits may be connected to the engine but then the engine shoudl be bonded by a single "earth" connection to the hull. This is for the DC side of things. No other negative connections shoudl go to the hull.

 

The AC neutral should also be bonded to the hull IF THE INVERTER IS SUITABLE. Ideally it shoudl be close to but on a separate stud to the DC negative bond so that in the event of an AC fault and the bonding connection becoming resistive you do not put mains into the 12v circuits.

 

DC circuits use NEGATIVE

 

AC circuits use NEUTRAL to provide a path for fault currents.

 

It's a path for all currents EXCEPT fault currents!

[gazza]

Electrics is easy.

 

Red to Red.

Black to Black

Blew to bits.

 

NavisBD, the bit in the destructions about seeking a professional electrician would appear to be for you

 

Listen to what others have posted.

Shaking hands with a dollop of electrickery is no fun.

[Theo]

Good to remember here that although the energy store (batteries) are at 12V and won't give you a shock, once the energy is converted through the inverter to 230V it's just as dangerous as the mains at home.

 

N

[Tony Brooks]

 

It's a path for all currents EXCEPT fault currents!

 

Thanks for clarifying that for me. I was trying to refer to the hull bond arm of the AC system. Obviously cocked my writing up there.

[NavisBD]

Sigh. It's a pity that there is no consistency here other than 'get a man in'. I can't understand why something as basic as this shouldn't be a matter of connect x to y and z, or why there seem to be different inverter mechanics. Still, I shall probably employ a specialist.

 

Thanks for all replies.

[gazza]

Sigh. It's a pity that there is no consistency here other than 'get a man in'. I can't understand why something as basic as this shouldn't be a matter of connect x to y and z, or why there seem to be different inverter mechanics. Still, I shall probably employ a specialist.

 

Thanks for all replies.

 

if its any help, buying a slightly dearer inverter is a better way to go, the cheap stuff seams a lottery in terms of quality and fit for the job.

 

i'm looking at one of these, http://sterling-power.com/products/pro-power-pure-sine-wave-inverters-with-rcd?variant=891769219 opinion varies on Mr Sterling on here, but i'd rather take a chance with a UK firm than a bulk shipment of gear from the far east.

Edited May 18, 2016 by gazza

[WotEver]

 

if its any help, buying a slightly dearer inverter is a better way to go, the cheap stuff seams a lottery in terms of quality and fit for the job.

 

i'm looking at one of these, http://sterling-power.com/products/pro-power-pure-sine-wave-inverters-with-rcd?variant=891769219 opinion varies on Mr Sterling on here, but i'd rather take a chance with a UK firm than a bulk shipment of gear from the far east.

 

Excellent advice. With one of those inverters there are no unknowns with regards to earthing arrangements, no tests required and, as long as the options are correctly set (Neutral-Earth bond), they can be treated just the same as a shore supply.

 

Sterling stuff is fine. It's all made in the far east but so what, what isn't?

 

Tony

[gazza]

 

Excellent advice. With one of those inverters there are no unknowns with regards to earthing arrangements, no tests required and, as long as the options are correctly set (Neutral-Earth bond), they can be treated just the same as a shore supply.

 

Sterling stuff is fine. It's all made in the far east but so what, what isn't?

 

Tony

 

 

With regard the Far East comment, i meant that i would rather deal with someone like Sterling than a middle man importing unkown quality kit by the box load. As you say, plenty of kit made in the Far East that is fine, you just have to be choosy what you buy and who from.

 

I've just had a nice touch on Ebay, 1000w Sterling Pro RCD inverter from Midland Chandlers @ £265, ex display just the job!

[NavisBD]

Sorry, didn't mean to return to this but I just spotted the following on a site for a company called Midsummer Energy:

 

"If your inverter has an earthing point [which it has - Navisbd], connect this to a suitable earth with heavy gauge wire, preferably 2.5 square mm. On a steel-hulled boat, a suitable earth is any substantial bolt or stud on the hull/engine [my italics - Navisbd] that is close to but not touching the point where the DC negative meets the hull/engine."

 

My inverter has four connection points (2 red 2 black) and an earthing point. The instructions with the inverter tell me to - logically enough - connect the red leads to the battery positive and the black leads to the battery negative, but no instructions re the earth. The above section from the Midsummer Energy site would suggest that I could earth to the bolt connecting the engine to the hull as long as I have ensured continuity between that bolt and the hull. No?

 

Don't worry, the comments have sufficiently worried me to arrange to get it done professionally. But I shall be a little hurt if it turns out that the professional wires it up thusly. Also is there any Standards Body (ie similar for CORGI for gas fitters) for boating electricians? I have a number of cards which I picked up on a recent trip round a couple of marinas, but none of them quote any trade body initials of any kind.

Edited May 19, 2016 by NavisBD

[nbfiresprite]

Just ask if they are a BMEEA-certified Marine Electrical or Electronics Installer.

 

http://britishmarine.co.uk/Membership/Our-Associations/Group/British-Marine-Electrical-and-Electronics-Association

[WotEver]

The Midsummer quote correctly states that the inverter's earth should connect to a stud adjacent to the -ve stud. BUT it says nothing about earth-neutral bonding.

[NavisBD]

Never realised this subject was so damned complicated! House wiring is a p of p compared to this - get the book, follow the wiring diagram, how to test if the socket is on the ring or on a spur, how to wire up a double pole switch, don't spur from a spur, red flag the live neutral, earth any socket with metal casing etc etc. No ambiguity, no if buts or maybes!

 

Any search on google produces tens of thousands of hits on the subject of inverter bonding and grounding, almost all of which contain some element of 'with the exception of....'

 

Still, some boat electrician somewhere will benefit from my trepidation!

[Keith M]

Before hand any money over to a marine sparks ask them if they have passed the BMET exam and if they have and up to date copy of the BMEEA code of Practice

 

If they yes to both question they should be ok

 

If a no is given to either question carry on looking.

 

 

Keith

[NavisBD]

Before hand any money over to a marine sparks ask them if they have passed the BMET exam and if they have and up to date copy of the BMEEA code of Practice

 

If they yes to both question they should be ok

 

If a no is given to either question carry on looking.

 

 

Keith

 

Thanks Keith.