Electrics. Where to start.

[Tony Brooks]

36 minutes ago, truckcab79 said:

Another one for you and I know the proper answer is probably ‘finish doing your power audit’, but in your collective experience for a 36ft leisure boat what capacity typically would I be looking for in terms of:

 

Batteries.  Quantity and capacity.
Solar

Inverter

 

As Alan says, everybody's figures will be different but on my boat, all 12V with small inverter (150W for charging), 12V fridge, small 12V TV, 1V car adapter for powering & charging a laptop, plus the usual pumps and lights (no nav lights) we had 3 x 100Ah dual purpose (leisure) batteries plus a 100Ah start battery,  70 amp alternator, 100W of solar to MPPT, no shore power, and my last battery bank lasted in excess of six years.

 

I used a decent ammeter and voltmeter to keep a handle on the state of charge and endeavoured to fully charge them whenever possible.

[truckcab79]

6 minutes ago, Tony Brooks said:

 

As Alan says, everybody's figures will be different but on my boat, all 12V with small inverter (150W for charging), 12V fridge, small 12V TV, 1V car adapter for powering & charging a laptop, plus the usual pumps and lights (no nav lights) we had 3 x 100Ah dual purpose (leisure) batteries plus a 100Ah start battery,  70 amp alternator, 100W of solar to MPPT, no shore power, and my last battery bank lasted in excess of six years.

 

I used a decent ammeter and voltmeter to keep a handle on the state of charge and endeavoured to fully charge them whenever possible.

……and that’s way lower than I expected.   😂

 

Funnily enough I was watching a YouTube pro solar installer recently. No idea if he’s any good or not but his approach on solar was  ‘Don’t bother working anything out. Narrowboat 500w. Widebeam 1000w’. 😂

[Tony Brooks]

Just now, truckcab79 said:

……and that’s way lower than I expected.   😂

 

Funnily enough I was watching a YouTube pro solar installer recently. No idea if he’s any good or not but his approach on solar was  ‘Don’t bother working anything out. Narrowboat 500w. Widebeam 1000w’. 😂

 

I think that you may well run into roof space problems. I tend to agree about not working things out because the weather will screw whatever you come up with.  November to March you will get very little solar, but I found with a 40w panel it was enough to complete the battery charging when we went home and kept the batteries more or less fully charged over the winter, and I stayed aboard over a weekend about once a month.

 

I should have told you a single 70A alternator charging both banks via a split charge relay for the first ten years and then a voltage sensitive relay for the second ten years. VSRs go will with solar because they can keep both banks charged.

[StephenA]

For USB charging go for 12 volt based units - we had cig lighter sockets and got twin port USB chargers that were a direct drop in replacement. You can even get Rapid Charge ones for USB C devices.

 

Edited September 6, 2023 by StephenA

[PaulD]

We do weekends and weeks out. 12v only. 4 x 110ah domestic batteries plus starter battery. 3 domestic would do. Fridge, LPG cooker, lights, tv and a couple of 12v sockets. Two solar panels keep the fridge running in summer and can keep the domestics at 100% in winter.

 

Was still a biggish installation with a lot of wiring, isolator switches, bus bars and fuse boxes. 

 

You do need to study the BSS before you start as you will have a 4 year inspection.

 

 

[truckcab79]

11 minutes ago, PaulD said:

We do weekends and weeks out. 12v only. 4 x 110ah domestic batteries plus starter battery. 3 domestic would do. Fridge, LPG cooker, lights, tv and a couple of 12v sockets. Two solar panels keep the fridge running in summer and can keep the domestics at 100% in winter.

 

Was still a biggish installation with a lot of wiring, isolator switches, bus bars and fuse boxes. 

 

You do need to study the BSS before you start as you will have a 4 year inspection.

 

 

Cheers for the info.  Been reading the BSS. All sensible stuff.  

[Ronaldo47]

An observation on fuses. In the electrical and electronics industry, the current rating of a fuse is the current it will carry indefinitely.

 

However, the automotive industry still follows the older practice of marking fuses with the current at which they will blow, which is around twice the carrying current. So if using blade-type fuses to protect something drawing 10A, you will need a 20A fuse.

 

I still have a few old glass fuses that bear both current ratings.

[jonathanA]

I would tend to disagree with Jen on using fuses, why would you want to have to fumble about possibly in the dark trying to find the blown fuse, then find what colour it is to find a replacement that you knew you had if only you could remember where....  makes n'sense to me.   

 

use a switch panel with resettable trips - much better to deal with, see the popped breaker press and off you go (assuming fault is fixed)* , less chance of some numpty shoving a 30A fuse in a 5A circuit and no need to keep a box of spares....

 

*and if the fault isn't fixed you are not using up your valuable stock of spares trying to find the problem and won't be tempted to just 'shove a bigger fuse in' 

 

if I was the op I would go for something like the GS controls 6 or 8 way panel, (keep it simple) if you speak to them they will put whatever size trips you want in or there are plenty of far eastern cheapo equivalents of varying quality on your local auction site.  or very nice ones from the likes of blue sea of much better quality of course (at a price.).

[David Mack]

38 minutes ago, jonathanA said:

if I was the op I would go for something like the GS controls 6 or 8 way panel, (keep it simple) if you speak to them they will put whatever size trips you want in or there are plenty of far eastern cheapo equivalents of varying quality on your local auction site.  or very nice ones from the likes of blue sea of much better quality of course (at a price.).

These trips were recommended in an earlier forum thread on a similar subject. Available in various ratings and you can make up a panel to suit your requirements.

https://cpc.farnell.com/potter-brumfield-te-connectivity/w54-xb1a4a10-15/circuit-breaker-15a/dp/FF01647

[jonathanA]

32 minutes ago, David Mack said:

These trips were recommended in an earlier forum thread on a similar subject. Available in various ratings and you can make up a panel to suit your requirements.

https://cpc.farnell.com/potter-brumfield-te-connectivity/w54-xb1a4a10-15/circuit-breaker-15a/dp/FF01647

yes I've used them in non boat applications and they are fine.  the little rubber boots can be handy.  I think for the OP with a very simple requirement its probably easier to buy a ready made panel. 

[truckcab79]

10 hours ago, jonathanA said:

yes I've used them in non boat applications and they are fine.  the little rubber boots can be handy.  I think for the OP with a very simple requirement it’s probably easier to buy a ready made panel. 

I’m inclined to agree. And they look neat too. 
 

Going back to my earlier question. Given that the answers have ranged from you don’t need any to 40w to 1800w. Is there a reason other than I might not need it, that the original ‘kit’ I posted might not be a good start?  Ignore the battery. They don’t deliver batteries and I’m not collecting from Lewes any time soon. 
 

Many thanks. 
 

https://www.bimblesolar.com/offgrid/complete-packages/250-500w-kits/300W-complete

 

 

and…..shore power?   Again mostly not needed I suspect but makes sense in my mind for me to install. Any thoughts?   

[MtB]

21 hours ago, Ronaldo47 said:

An observation on fuses. In the electrical and electronics industry, the current rating of a fuse is the current it will carry indefinitely.

 

However, the automotive industry still follows the older practice of marking fuses with the current at which they will blow, which is around twice the carrying current. So if using blade-type fuses to protect something drawing 10A, you will need a 20A fuse.

 

I still have a few old glass fuses that bear both current ratings.

 

Fuses can be even more complicated than that actually. My own stock of internal fuses for boilers comprises fast blow, slow blow and 'normal' (whatever that is!) in each current rating.

 

More than you ever wanted to know about fuse specifications here, for example:

https://www.littelfuse.com/~/media/electronics/product_catalogs/littelfuse_fuseology_selection_guide.pdf.pdf

 

 

 

[Chewbacka]

On 07/09/2023 at 23:07, MtB said:

 

Fuses can be even more complicated than that actually. My own stock of internal fuses for boilers comprises fast blow, slow blow and 'normal' (whatever that is!) in each current rating.

 

More than you ever wanted to know about fuse specifications here, for example:

https://www.littelfuse.com/~/media/electronics/product_catalogs/littelfuse_fuseology_selection_guide.pdf.pdf

 

 

 

Easy - A normal fuse is slower than a fast fuse and quicker than a slow fuse.

[blackrose]

On 06/09/2023 at 16:21, LadyG said:

 

A 240v fridge needs carefull matching with the inverter. 

 

Not really. Any inverter with enough output will run a small mains fridge. It doesn't really need to be matched carefully. 

[Jen-in-Wellies]

32 minutes ago, blackrose said:

Not really. Any inverter with enough output will run a small mains fridge. It doesn't really need to be matched carefully. 

And that is more than you'd at first think. Fridges take a huge intake spike of power to start the compressor motor, before settling down to something more sensible. General opinion on CWDF says you need a 1000W inverter or so to be sure of having enough oomph to do this. I can say that a 600W one is too small and errors out when trying to start a mains fridge from personal experience.

 

On 07/09/2023 at 22:28, truckcab79 said:

and…..shore power?   Again mostly not needed I suspect but makes sense in my mind for me to install. Any thoughts?   

If you don't need it, don't install it. You'll need to budget another £150 to £200, or so in materials. Not just the wire, socket and shore lead, but a galvanic isolator to reduce the risk of extra corrosion to the boats hull and fittings.

[truckcab79]

2 hours ago, Jen-in-Wellies said:

And that is more than you'd at first think. Fridges take a huge intake spike of power to start the compressor motor, before settling down to something more sensible. General opinion on CWDF says you need a 1000W inverter or so to be sure of having enough oomph to do this. I can say that a 600W one is too small and errors out when trying to start a mains fridge from personal experience.

 

If you don't need it, don't install it. You'll need to budget another £150 to £200, or so in materials. Not just the wire, socket and shore lead, but a galvanic isolator to reduce the risk of extra corrosion to the boats hull and fittings.

In the grand scheme of things £200 is fine. I’d rather have it installed and never need it to be honest.  We’ll be pretty much stripping the interior so it makes sense to run everything before we re-clad the walls. 

[David Mack]

24 minutes ago, truckcab79 said:

 We’ll be pretty much stripping the interior so it makes sense to run everything before we re-clad the walls. 

Think carefully before installing your wiring behind the hull or cabin lining. It will make subsequent alterations, and fault-finding in the case of problems, much more difficult.

And if you have polystyrene insulation you MUST avoid all contact between the polystyrene and the pvc cable sheath/insulation, which means cable behind the lining has to be fully ducted anyway.

This diagram from Tony Brooks' notes shows the usual locations for wiring.

http://www.tb-training.co.uk/MarineE03.html#RUNNING THE CABLES

My choice would be location B, but with a removable cover fitted to the bottom.

 

Edited September 9, 2023 by David Mack

[truckcab79]

Yep.  Pretty much what I  intended.  A or B.  Existing cladding is coming off anyway but nothing will actually be behind it unless unavoidable.  There will be a removable panel(s)  to allow ongoing access just in case. Worked on too many shopfit, kitchen and bathroom installs where no thought is given to future maintenance.  Including yesterday funnily enough where I went to change a set of taps that had clearly been installed into the granite worktop before they dropped it onto the cabinets giving pretty much zero access behind the under-mounted sink.  ‘Won’t be my problem’ is the general approach unfortunately.  
 

In a similar vein I had assumed I would use A or B for my electrics and C for my water to keep them separate. That works I assume?  

[MtB]

4 hours ago, Jen-in-Wellies said:

I can say that a 600W one is too small and errors out when trying to start a mains fridge from personal experience.

 

 

Seconded. 

 

Specifically, my Sunshine Solar PSW inverter will not start my 240Vac 60W bargain basement Igenix fridge. It tries to boot up several times then goes into fault mode and glowers at me. Even my 2.5kW PSW only just gets it going. Even that faults occasionally so I took the whole lot out, mended the 12Vdc fridge and put that back in again. 

 

 

 

 

 

[LadyG]

5 hours ago, blackrose said:

 

Not really. Any inverter with enough output will run a small mains fridge. It doesn't really need to be matched carefully. 

So, are you saying not every invertor  will run every fridge!

[robtheplod]

On 07/09/2023 at 10:17, jonathanA said:

if I was the op I would go for something like the GS controls 6 or 8 way panel, (keep it simple) if you speak to them they will put whatever size trips you want in or there are plenty of far eastern cheapo equivalents of varying quality on your local auction site.  or very nice ones from the likes of blue sea of much better quality of course (at a price.).

Have to second this. I've recently replaced my fuse board with a GS one - the guy could not have been more helpful. Supplied exactly what i wanted, supplied spares and printed it out as well!

[Alan de Enfield]

1 hour ago, LadyG said:

So, are you saying not every invertor  will run every fridge!

 

No it won't.

 

A typical fridge is (probably) rated at around 40w - try using a 100w inverter,(fail) or even a 200w inverter (fail), even a 500w inverter is most likely not to start the fridge.

 

It is not a resistive load - a fridge is an Inductive load.

[MtB]

Just now, robtheplod said:

Have to second this. I've recently replaced my fuse board with a GS one - the guy could not have been more helpful. Supplied exactly what i wanted, supplied spares and printed it out as well!

 

 

There is a drawback to this style of fuseboard, I find.

 

All the connectors on the back are spade tags for you to connect onto with push on crimp connectors. Once you've done this with a 20 or 30  surprisingly fat wires all pushed on to the spade terminals, it requires a fair amount of force to shove it into the exact right place as all the wires get bent into position. Hopefully none will actually fall off or get bent off, but they can. And it you unscrew it to withdraw it to add something, some will almost definitely come off the spades. DAMHIK.

 

I scrapped mine in the end and fitted a proper domestic consumer unit with DC rated breakers, and now I can get at the gizzards of it without disturbing any of the other 12 circuits I'm not working on. 

1 minute ago, Alan de Enfield said:

 

No it won't.

 

A typical fridge is (probably) rated at around 40w - try using a 100w inverter,(fail) or even a 200w inverter (fail), even a 500w inverter is most likely not to start the fridge.

 

It is not a resistive load - a fridge is an Inductive load.

 

It's worse than that. 

 

From time to time I see suggestions on here to wire the fridge thermostat (via a suitable relay) to turn the power on and off to a dedicated inverter running the fridge only. The point of this is so the inverter isn't idling and drawing its quiescent current all the time it is waiting for the fridge to actually need to run. 

 

Doing this means you are asking the inverter to boot up with a high current inductive load connected, and mine inverters don't like it. Even the 2.5kW inverter won't start up with a fridge plugged into it. 

 

 

[Richard10002]

7 hours ago, truckcab79 said:

In the grand scheme of things £200 is fine. I’d rather have it installed and never need it to be honest.  We’ll be pretty much stripping the interior so it makes sense to run everything before we re-clad the walls. 

Even if you are off grid completely, you will need the shore power connection to connect your generator in winter. Money well spent.

 

I spend 3 or 5 nights a week on board a 45ft narrowboat. 400W of solar keeps me topped up for most of March to September- if the sun isn't good for a few days, I run the genny.... perhaps 3 or 4 times over the period. 

 

I think I would have got 600w to possibly avoid running the genny in Spring/Summer. 

 

October to March I run the genny to fill up about every 3 days on board. Solar is pretty much a token.

 

 

 

Edited September 9, 2023 by Richard10002

[MtB]

8 minutes ago, Richard10002 said:

Even if you are off grid completely, you will need the shore power connection to connect your generator in winter. Money well spent.

 

 

Not necessarily. I plug the flylead on my charger directly into the 3-pin socket on the genny. (Bear in mind I ought to be dead according to some as I run the genny on the stern deck with rear doors shut.)

 

But otherwise I agree, this is a good use for one of them blue plug/socket things on the back of the boat, with a mains socket inside the boat. Makes the cable connection safer. My method risks chaffing the cable through the doors. 

 

 

Edited September 9, 2023 by MtB
Clarify.