electrics Electrical System

[ajlx]

Hi there, 

first post on here after reading for a few years!

we are currently planning our first fit out of a new boat! 

I have done all calculations necessary and calculated cable diameter however one thing that i feel like i need some advice on is the actual circuitry of the boat. I have put together a quck schematic of what i am currently thinking in terms of the installation however it would be great to get some feedback from you experianced boaters!

any advice is more than welcome and thank you in advance!

 

Alex

Full Electrical Schematic -BS EN ISO 101332017 & BS EN ISO 132972014-.pdf

[WotEver]

Hi and welcome.

A few thoughts if you want to be 100% by the book...

The engine battery isolator should also isolate the engine battery alternator. 

Neither of the batteries (leisure and engine) show a negative bond to the hull. 

The bilge pump should be connected direct to the batteries, not via the isolator.  

The bilge pump fuse should come before the control - as close as possible to the batteries but outside the battery box. 

Your 12V Consumer Unit is unlikely to be up to the job of feeding a 12V fridge. Due to the large start-up current and associated large cables (10mm² is common) it is more usual to feed it direct from the battery via a midi fuse (again, as close as possible to the batteries but outside of the battery box). 

It doesn’t really matter but it is more usual to run the AC mains earth bond to the hull from the consumer unit. 

Otherwise it looks fine to me. Maybe someone else will spot something though. 

Cheers,

Tony

[WotEver]

One more thing... have a read of this:

http://www.smartgauge.co.uk/batt_con.html

[rusty69]

Just now, WotEver said:

One more thing... have a read of this:

http://www.smartgauge.co.uk/batt_con.html

This is also worth consideration:-

http://www.smartgauge.co.uk/nb_ac_sys.html

 

[ajlx]

25 minutes ago, WotEver said:

Hi and welcome.

A few thoughts if you want to be 100% by the book...

The engine battery isolator should also isolate the engine battery alternator. 

Neither of the batteries (leisure and engine) show a negative bond to the hull. 

The bilge pump should be connected direct to the batteries, not via the isolator.  

The bilge pump fuse should come before the control - as close as possible to the batteries but outside the battery box. 

Your 12V Consumer Unit is unlikely to be up to the job of feeding a 12V fridge. Due to the large start-up current and associated large cables (10mm² is common) it is more usual to feed it direct from the battery via a midi fuse (again, as close as possible to the batteries but outside of the battery box). 

It doesn’t really matter but it is more usual to run the AC mains earth bond to the hull from the consumer unit. 

Otherwise it looks fine to me. Maybe someone else will spot something though. 

Cheers,

Tony

all of this is great feedback and exactly what i was hoping for! so thank you for this.

one thing i dont understand and cant seem to find any information on the 'why'  is "Neither of the batteries (leisure and engine) show a negative bond to the hull.". do you happen to know hy bonding the negative to the hull is necessary? 

the post on the batteries was very useful. appologies for what may seem like silly questions, my day job has me dealing with larger 400A 3 phase electrics in entertainment venues so the ELV and more specifically the battery side of things is totally alien to me.

once again thank you for your reply!

 

all the best

 

Alex

[David Mack]

http://www.smartgauge.co.uk/earthing.html covers why AC and DC systems should be earthed to the boat hull.

[ajlx]

19 minutes ago, David Mack said:

http://www.smartgauge.co.uk/earthing.html covers why AC and DC systems should be earthed to the boat hull.

perfect thank you for that! who knew batteries could be so confusing!?

Alex

[Giant]

Your diagram doesn't show any earth-neutral bond for the inverter.

Also do you really need separate 16A/32A hookup and a changeover switch? If you want to support both you could just have a 32A hookup, 32A cable, and an adapter you can plug in at the bollard end when you need to use a 16A supply.

That said, 32A supplies at visitor moorings are pretty rare so unless you have 32A at your home mooring, you're unlikely to ever need a 32A hookup.

[ajlx]

1 minute ago, Giant said:

Your diagram doesn't show any earth-neutral bond for the inverter.

Also do you really need separate 16A/32A hookup and a changeover switch? If you want to support both you could just have a 32A hookup, 32A cable, and an adapter you can plug in at the bollard end when you need to use a 16A supply.

That said, 32A supplies at visitor moorings are pretty rare so unless you have 32A at your home mooring, you're unlikely to ever need a 32A hookup.

just added that after reading the above comments, slowly looking more like a functional electrical system!

the logic behind the 32/16 was that i have a lot of both left over from previous installations so it really isnt going to cost much more to have that additional connection if its needed, the mooring we have applied for is 32a single and most of the other moorings we have been to look at have been 32 or 16 on site... plus a converter is so easy to loose where as a 32a socket afixed to the boat is a little less likely to be lost, saying that, we are in birmingham so anything is possible! ;-)

 

Alex

[WotEver]

2 hours ago, Giant said:

Your diagram doesn't show any earth-neutral bond for the inverter.

Good catch. 

[Chewbacka]

Don't think it was mentioned above, but the inverter also needs an isolator switch to the batteries and of course a fuse.

[WotEver]

Just now, Chewbacka said:

Don't think it was mentioned above, but the inverter also needs an isolator switch to the batteries and of course a fuse.

Actually, you raise a question... 

If it’s an inverter/charger then it doesn’t need an isolator. If it isn’t an inverter/charger then where’s the mains charger?

[Chewbacka]

Just now, WotEver said:

Actually, you raise a question... 

If it’s an inverter/charger then it doesn’t need an isolator. If it isn’t an inverter/charger then where’s the mains charger?

I do feel it is a good idea to be able to disconnect an inverter or combi for a couple of reasons.  Mainly having had a cheap inverter that started to release it's magic smoke, you want to be able to disconnect it quickly.  The other reason is if ever working on the 230V ac distribution system you want to be very confident that the inverter can not start up, so a 'soft off' switch is not good enough for me, and disconnecting batteries is a bit of a faff considering a switch is not that expensive.  But agree that if it's a combi it is not mandatory.

[WotEver]

My concern always with a 3kVA inverter is that you’ll need a really good quality isolator. I know they’re available but the uninitiated may not appreciate the difference. 

[smileypete]

Might be nice to have some background on the boat itself, otherwise I'd assume a typical narrowboat say 55' or so.

With a 32A supply it'd be possible to feed the boat with two 16A radials, maybe one for the kitchen and one for everything else. Or even a single 32A ring main, provided the loads can be distributed fairly evenly on each side of the ring - not always easy in practice.

Then just add the normal 2 pole RCD, all of it will fit in a standard 4 module 'garage consumer unit' that's typically used.

Unless the boat is serious money I'd fit a decent galvanic isolator with remote LED status monitor like the safeshore ones, instead of an isolation transformer, but that's personal preference.

You could then have just a single selector switch between 16A, 32A, inverter. Maybe use an extra pole on the selector to isolate the calorifier and charger when the inverter is selected. 

On the DC side the better quality DIN sockets can be used for heavier loads alongside some car 12V sockets for small chargers etc. Maybe them fused centrally but protected by lower current DC breakers next to the sockets.

If the boat IS serious money, it may be worth paying a good marine electrical specialist for an hour or two to review the design and give some tips.

Edited February 11, 2018 by smileypete

[1st ade]

11 minutes ago, smileypete said:

Maybe use an extra pole on the selector to isolate the calorifier and charger when the inverter is selected

I was about to comment on this but you beat me to it.

As per the drawing, nothing except common sense to stop you leaving the charger on when disconnecting from the hookup and moving to inverter...

[smileypete]

One other thing, this topic mentions the use of stranded instead of solid cable, together with 'bootlace ferrules' necessary on fine stranded wire.

 

Edited February 11, 2018 by smileypete

[Tony Brooks]

Things I noticed:

Bilge pump fuse seems to be in both the pos & neg line, it should just be in the positive. Ditto the isolator switches.

Pos & neg takeoffs from both ends of the battery bank. This si generally considered less than ideal.

[reg]

Please would the more experienced correct me if I am wrong about this but I was told that I had to use 4.0mm ac cable and not 2.5mm cable between my victron multiplus inverter and the rcbo. This was because theoretically the multiplus could merge multiple inputs I. E mains, generator and battery. 

Only reason I mention it is because I was told this after I had wired up and boxed in the units so modifying it was a pain in the... Best to install it correctly in the first place. 

[nicknorman]

38 minutes ago, reg said:

Please would the more experienced correct me if I am wrong about this but I was told that I had to use 4.0mm ac cable and not 2.5mm cable between my victron multiplus inverter and the rcbo. This was because theoretically the multiplus could merge multiple inputs I. E mains, generator and battery. 

Only reason I mention it is because I was told this after I had wired up and boxed in the units so modifying it was a pain in the... Best to install it correctly in the first place. 

Depends on the rating of the RCBO! Certainly a Combi can output more than 16A in power assist mode, but if the RCBO is sized to protect the 2.5mm cable (as it should be), the RCBO will trip before the cable overheats.

And just to mention that a Combi cannot merge generator with mains. I can merely supplement either generator or mains, with inverted power from the batteries. Well unless the generator is putting DC into the batteries I suppose.

oh and also, the max current of 2.5mm cable depends on a lot of factors - single conductor or as part of a 2 conductor and earth flex, temperature rating of the insulation, way in which is installed (eg buried, in trunking, clipped to a surface with air circulation etc). Generally, 2.5mm cable not buried in a wall can take significantly more than 16A.

Edited February 13, 2018 by nicknorman

[reg]

2 minutes ago, nicknorman said:

Depends on the rating of the RCBO! Certainly a Combi can output more than 16A in power assist mode, but if the RCBO is sized to protect the 2.5mm cable (as it should be), the RCBO will trip before the cable overheats.

That was my layman's thought but as it was the very last job required to get my rcd certificate I didn't argue. Was only about 18ins long and was a pain to retrofit. 

If it is required to meet the letter of the law then it's preferable to install it a fit out stage rather than find out later. My surveyor was very strict about everything for which I thank him now 13 years later. 

[nicknorman]

Just now, reg said:

That was my layman's thought but as it was the very last job required to get my rcd certificate I didn't argue. Was only about 18ins long and was a pain to retrofit. 

If it is required to meet the letter of the law then it's preferable to install it a fit out stage rather than find out later. My surveyor was very strict about everything for which I thank him now 13 years later. 

Clearly it is better to install the equipment so it can be used to its maximum capability, but from a safety point of view your 2.5mm cable with a 16A RCBO would have been safe and in compliance with the RCD.

[Detling]

On 2/11/2018 at 12:37, Tony Brooks said:

Pos & neg takeoffs from both ends of the battery bank. This si generally considered less than ideal.

Note that one diagonal pair is for the inverter and the other diagonal pair is the domestic, thus spreading both loads evenly across all batteries, and the inter-connecting links. Both loads on the same diagonal puts more current through the final battery inter-connecting link (2/3rds total) so causing greater voltage drop (OK 1 or 2 mV maybe with good inter-connects)

 

The schematic looks as though it is for a live aboard on a mooring, no Solar installation and only 3 domestic batteries so there could be problems with prolonged cruising. I would suggest a good battery monitoring system that measures amp hours in/out will help when cruising.