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Installing an inverter


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Hi there,

I have been a long time lurker on this forum and it has helped me with many things on my narrowboat. 

I had a browse through old topics but I could not find an answer to this question so I figured I should make an account and ask..

I'm basically looking to upgrade my inverter from a modified sine wave inverter to a pure sine wave inverter. I'm wondering whether I can attempt this myself (without electrocuting myself) or whether I need to hire an electrician. I would also be swapping my battery bank out at the same time. My inverter is in the engine room but the switch is in the galley. I'd quite like to ensure I can switch the new one off and on from the galley too.

I'd prefer to attempt it myself if it's safe for me to do so, but I would need some guidance first.

Has anybody done this before that could give me a rough guide of the process? If it helps I'm looking at a Victron one that will also charge the battery's (my current one also does this).

Thanks a lot!

James

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I currently have a 2500w inverter and I'll be either staying the same or slightly lowering the inverter output. Battery bank will stay the same (three leisure and 1 starter, all at 110ah I think.. although I'm not on the boat to double check right now). Feel free to tell me it's a stupid idea if it's way beyond the capabilities of somebody without much electrical knowledge. I'm just trying to get a taste for the complexity of the job.

Cheers

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It's not a stupid idea.

If the present system worked and you are just swapping MSW for PSW and bunging out goosed batts for new it should be reasonably straight forward.

Better men than I will be along soon enough to highlight specific do and don't stuff .

Edited by Taslim
Spare words.
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It is quite straightforward in principle, but practically there can be a few annoyances if you want to fit a different model with connectors in different places and/or of a different type. I’m think for example of finding that the wires aren’t quite long enough to reach the location of the new connectors. A few photos of the current installation (inverter, or Combi as they are more commonly known, and remote panel) along with details of which model you intend to fit, will allow us to give more specific advice.

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Make sure any shoreline is disconnected.

Take photos of the connections and tag each lead with what it is like 12V +, 12V -, mains L, mains N.

Make sure the 12V master switches are OFF or disconnect the 12V pos lead from the battery end.

Remove leads from old inverter and insulate (mainly just in case).

Remove old inverter and fit new one.

Fit each lead to their respective terminals.

Double check.

Turn master switch on or reconnect lead.

Turn inverter on to test.

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Hopefully it will be a matter of moving the incoming live/neutral/earth and outgoing live/neutral/earth from the old inverter to the new, and moving the fat 12v dc + and - wires from old to new, being very careful not to touch the + to anything metal. If the new Combi is significantly more powerful than the old, it might be necessary to upgrade the 12v fuse and/or wiring.

Normally there is a battery temperature sensor to install but that is just a matter of attaching it to the battery and plugging the other end into the Combi. The remote might be more problematic if you can’t re-use the existing cable, having to run a wire a long way through a boat - neatly - can be fiddly!

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If you are competent to change a mains socket on the wall and replace a 3 pin plug then with care and instructions you should be ok, but if you are not, then get someone that is competent to watch over you and advise.  As your current system is both an inverter and battery charger then you will have mains coming in and going out of the box.  It is important to ensure the earthing is done correctly as the installation will probably work fine if the earthing is wrong, but it may become unsafe in the event of a fault.

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It's something I'm in the middle of right now, although I'm going the opposite direction to you, i.e. from a Combi (inverter/Charger) to a separate inverter and charger. Many here would advise you to keep the units separate for more economical repair/replacement options if and when you suffer a breakdown.

I have an engineering background so I'm content with my skill level and I'm confident that I know what the job entails and the hazards associated with it.  On the 12V DC side you're dealing with very heavy current and on the 240V AC side you're dealing with a lethal voltage.  These things can bite you badly before you have chance to ask "did I do that right?". If you feel you might need a bit of technical support as you do the job, that's one thing, but if you need to ask whether you can do it safely, you probably don't have sufficient knowledge or experience and that's quite another.

JC, I don't know your skill level but, from the way I read your question, I'd say that you should get someone in.

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With the a.c. side you can turn it off completely 

You cannot fully isolate the battery so be aware that the positive cable will spark if it touches the hull. Even a spanner can cause a short circuit if it touches the hull whilst tightening a positive battery connection.

Before starting remove rings, watches and medallions etch.

Use insulating tape to insulate spanners, cable and ends, to minimise the risk of them accidentally touching the hull.

DC burns can be very nasty due to the high currents involved in short circuits.

If you are not confident, then don't do it.

 

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6 hours ago, cuthound said:

 

You cannot fully isolate the battery so be aware that the positive cable will spark if it touches the hull. 

If you are not confident, then don't do it.

 

Spark? SPARK!? You make it sound positively benign!  The results can be catastrophic!  You could weld with such a current and it'll be quite happy to melt your spanner with disastrous results such is the stored energy. There must be a video somewhere on YouTube of someone shorting a 12V battery - and we typically have 4 fully charged ones in parallel, so please don't try it at home!

You can isolate the batteries fully - if the lines from the battery bank aren't connected, how much more isolated can you get?  Just ensure you disconnect the negative lead from the bank first then it won't cause an arc if you have a little slip with your spanner (we all can) and you do 'touch the hull' because they're at the same potential (but don't do that anyway).  That done, you won't have an issue if you have a little slip with your spanner on positive connections either (whether you remove the positive line at the batteries or not) because you're not now creating a circuit. That way you don't need to rely on tape on your spanners for your safety.  Whilst proper insulation is essential for unavoidable work on live systems, it's not clever to rely on insulation tape for safety when isolation is perfectly possible.

I agree with CH's bottom line.  If any the above is not absolutely 'the bleedin' obvious',  "don't do it" is exactly what the OP should do.

  • Greenie 1
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On 10/20/2017 at 10:39, JCheetham said:

My inverter is in the engine room but the switch is in the galley. I'd quite like to ensure I can switch the new one off and on from the galley too.

 

On 10/20/2017 at 12:58, JCheetham said:

I currently have a 2500w inverter and I'll be either staying the same or slightly lowering the inverter output.

Just checking but when you say "the switch is in the galley" are you referring to a 12 volt isolator switch that is carrying the full current required to run the inverter on load, or just to a control unit that in some way allows you to control the switching on and off remotely, (but through wiring not carrying the full inverter current)?

A 2500W inverter can draw well in excess of 200 amps under full load, so will need to be on very heavy duty cabling, and with all wiring runs as short as possible between battery bank and inverter.  I'm hoping you don't mean you have a big load carrying cable from the battery bank to a switch in your galley, and all the way back to the inverter, but if you do, and the distance is more than a few feet, it really needs changing.

I suspect I'm misunderstanding your meaning though, so this post is "just checking"!

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28 minutes ago, ditchcrawler said:

Now this could be a pop corn moment, calling Gibbo

I was going to reply but the phrase ‘flogging a dead horse’ sprang to mind. 

Maybe I’ll simply say that there is a VERY good argument for disconnecting the positive first and leave it at that. 

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1 hour ago, Sea Dog said:

Spark? SPARK!? You make it sound positively benign!  The results can be catastrophic!  You could weld with such a current and it'll be quite happy to melt your spanner with disastrous results such is the stored energy. There must be a video somewhere on YouTube of someone shorting a 12V battery - and we typically have 4 fully charged ones in parallel, so please don't try it at home!

You can isolate batteries fully - if the lines from the battery bank aren't connected, how much more isolated can you get?  Just ensure you disconnect the negative lead from the bank first then it won't cause an arc if you have a little slip with your spanner (we all can) and you do 'touch the hull' because they're at the same potential (but don't do that anyway).  That done, you won't have an issue if you have a little slip with your spanner on positive connections either (whether you remove the positive line at the batteries or not) because you're not now creating a circuit. That way you don't need to rely on tape on your spanners for your safety.  Whilst proper insulation is essential for unavoidable work on live systems, it's not clever to rely on insulation tape for safety when isolation is perfectly possible.

I agree with CH's bottom line.  If any the above is not absolutely 'the bleedin' obvious',  "don't do it" is exactly what the OP should do.

You cannot isolate batteries fully, isolate a battery at the isolator and put a spanner across the terminals of either the battery or a 2 volt cell if you don't belive me.

Edited by cuthound
Spillung
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21 minutes ago, cuthound said:

You cannot isolate batteries fully, isolate a battery at the isolator and put a spanner across the terminals of either the battery or a 2 volt cell if you don't belive me.

and disconnecting both terms and covering the posts with multi-coloured insulating tape?

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25 minutes ago, system 4-50 said:

and disconnecting both terms and covering the posts with multi-coloured insulating tape?

You cannot insulate the terminal posts until you have disconnected the cables. It is whilst disconnecting the cables that there is a risk of shorting the posts with a spanner.

The colour of the tape has no bearing on its insulating properties.  :P

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30 minutes ago, cuthound said:

You cannot insulate the terminal posts until you have disconnected the cables. It is whilst disconnecting the cables that there is a risk of shorting the posts with a spanner.

The colour of the tape has no bearing on its insulating properties.  :P

  • ok:
  • turn off isolator
  • Cover the pos terms with insul tape - no risk
  • Disconnect the negs - no risk
  • Cover the negs with insul tape - no risk
  • Uncover the pos terms and disconnect - no risk
  • Cover the pos terms with insul tape - no risk
  • and rest

How did I do? (I like blue tape best.)

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9 minutes ago, system 4-50 said:
  • ok:
  • turn off isolator
  • Cover the pos terms with insul tape - no risk
  • Disconnect the negs - no risk
  • Cover the negs with insul tape - no risk
  • Uncover the pos terms and disconnect - no risk
  • Cover the pos terms with insul tape - no risk
  • and rest

How did I do? (I like blue tape best.)

Yup that's a safe way to do it, you don't have to use tape,  cut off finger from rubber gloves work well. Might upset the missus though.  :D

When I first started work,  I identified my tools by putting blue tape on them. 

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7 minutes ago, cuthound said:

Yup that's a safe way to do it, you don't have to use tape,  cut off finger from rubber gloves work well. Might upset the missus though.  :D

When I first started work,  I identified my tools by putting blue tape on them. 

Good-o! I've got to rewire my interbat connections with heavier stuff in a different order to connect my new BM2 next week so we'll see how we go. Maybe yellow tape? No, keep that for gas. No, we'll stick with the blue tape though that doesn't make the batts yours!

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53 minutes ago, cuthound said:

Yup that's a safe way to do it, you don't have to use tape,  cut off finger from rubber gloves work well. Might upset the missus though.  :D

When I first started work,  I identified my tools by putting blue tape on them. 

You forgot to say, making sure that there are no finger(s) in the glove.:rolleyes:

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1 hour ago, cuthound said:

When I first started work,  I identified my tools by putting blue tape on them. 

Well that wouldn’t work ‘cos so did I. So how would we know yours from mine?

1 hour ago, system 4-50 said:
  • ok:
  • turn off isolator
  • Cover the pos terms with insul tape - no risk
  • Disconnect the negs - no risk
  • Cover the negs with insul tape - no risk
  • Uncover the pos terms and disconnect - no risk
  • Cover the pos terms with insul tape - no risk
  • and rest

How did I do? (I like blue tape best.)

See the bit in bold? It’s wrong. There’s a HUGE risk on some boats. Always disconnect pos first (carefully, with an insulated spanner). 

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14 hours ago, WotEver said:

I was going to reply but the phrase ‘flogging a dead horse’ sprang to mind. 

Maybe I’ll simply say that there is a VERY good argument for disconnecting the positive first and leave it at that. 

This'll be about equipment damage if something not isolated by the battery isolator switches itself on after you disconnect the negative, will it?  If so, whilst that (contentious? unresolved?) argument goes on without me, I'm simply trying to dissuade the OP from welding himself to the hull. Sometimes these technicalities blurr the issue for the non-technical - and by his own admission the OP is certainly in that grouping. My advice to him is to get someone in to do the job (how the professional deals with his disconnetions is up to him).

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13 hours ago, cuthound said:

You cannot insulate the terminal posts until you have disconnected the cables. It is whilst disconnecting the cables that there is a risk of shorting the posts with a spanner.

The colour of the tape has no bearing on its insulating properties.  :P

Not with a insulating spanner tho.

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