AC wiring

[churchward]

Looking at the GI Topic reminded me of a questionI was going to ask on AC systems on the boat.

 

In looking at Gibbo's site which among many other things talks about the AC systems and suggestions on how to arrange switching between shore power and inverters, where to put the GI/Isolation transformer etc. I realised the AC set-up on my boat is arranged differently.

 

So here is Gibbo's suggestion. (appologies for reproducing his diagram I hope he doesn't mind)

 

By churchward at 2012-06-21

 

and here is my setup adapting Gibbo's diagram.

 

By churchward at 2012-06-21

 

The question is.... Is my setup OK or should I be looking to get another CSU/RCD/MCB unit and make it more like Gibbo's suggestion. One disadvantage of my setup is that the mains battery charger can (if I am careless) be powered by the inverter whch is not good. I haven't forgotten to switch it off so far but you never know.

 

I assume the boat builder did it that way to just have one CSU rather than two ad so save a bit of money.

[by'eck]

I would stick with Gibbo's suggestion. It solves the charger running on inverter issue.

 

The shore power RCD is really needed after the GI, especially if it fails.

 

You could use RCBO's - combined RCD & overcurrent breaker so save cost/space/wiring.

[Gibbo]

There's nothing wrong with how you have it at present apart from, as you say, your charger can run from the inverter. The one occasion you do this (and you will do it) will not be when you're just nipping out for half an hour, it will be when you leave the boat for a week and come back to completely flat batteries.

 

Further down the page are a couple of other ways of sorting that without using an extra RCD, but they do use a more complex switch. It's one or the other, either 2 RCDs, or a more complicated switching arrangement.

 

If you really are totally convinced that you will never run the charger from the inverter, then I'd leave it as it is.

[churchward]

There's nothing wrong with how you have it at present apart from, as you say, your charger can run from the inverter. The one occasion you do this (and you will do it) will not be when you're just nipping out for half an hour, it will be when you leave the boat for a week and come back to completely flat batteries.

 

Further down the page are a couple of other ways of sorting that without using an extra RCD, but they do use a more complex switch. It's one or the other, either 2 RCDs, or a more complicated switching arrangement.

 

If you really are totally convinced that you will never run the charger from the inverter, then I'd leave it as it is.

 

and there is the rub. I am convinced that some day I will forget.

 

Adding another CSU will be a bit of a pain though (not too expensive these days I guess at around £40 all in) as it will mean a fair bit of rewiring. I would want to keep the inverter/shore power change-over switch as it is a good one being a Blue Sea product.

[by'eck]

and there is the rub. I am convinced that some day I will forget.

 

Adding another CSU will be a bit of a pain though (not too expensive these days I guess at around £40 all in) as it will mean a fair bit of rewiring. I would want to keep the inverter/shore power change-over switch as it is a good one being a Blue Sea product.

 

To keep cost down you could use a single CSU. I bought a small one from CEF. It houses two rail mounted RCBO's & four MCB's which control Combi, additional charger, general distribution sockets, washing machine and immersion.

 

The additional charger is wired outside of the Combi so it cannot possibly be powered by the inverter.

[jonathanA]

if you look at the gibbo/smartgauge pages you'll also see an option with a relay. use a relay in conjunction with your existing setup to only connect the charger when your on landline.

 

I would have thought a suitable 240v coil relay/base and box would cost less than a tenner.

 

Personally I added an extra pole to my change over switch so the charger and immersion heater only get a feed when I'm on landline - making it idiot proof. I was happy to get involved with replacing my changeover switch (CAM switch) but they aren't cheap (£20+) and you need enough room for the bigger switch, but I think its quite an elegant solution.

[Gibbo]

I would have thought a suitable 240v coil relay/base and box would cost less than a tenner.

 

That's the odd part. Due to (again - see another thread) economies of scale, a big 32 amp relay often is cheaper than a 32 amp manual switch.

 

Perhaps I should have a play with those diagrams to reflect this. I'll have a look tomorrow.