Installing mains electric

[twelveeyedfish]

I am super close to buying a boat. It has a lot going for it but it doesn't have mains electricity. I don't think installing mains is a big issue - 4 sockets and a consumer unit. However, when it comes to things like including a galvanic isolator, which cable is acceptable on a boat, what the legal cable routing is and how to integrate a battery charger I was wondering if there was a handy website or book which would help.

 

The actual work doesn't concern me but I do want to do it within the frame work of the BSS for more than obvious reasons. Now I could read them but I just thought an article might offer some other hints and tips too.

 

Thanks in advance!

[blackrose]

This is a good starter

 

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

[twelveeyedfish]

Thanks, that's just the thing! Ta!

[jonathanA]

might be worth a quick look at Graham booth's 'Narrowboat builders book' there is a chapter on electrical installations and some other info on electrical systems.

[Keith M]

As to which cable to use

 

H07 RNF

 

An fit an isolation transformer not a galvanic isolator there is no way of telling when it has failed without getting a multi-meter out and how many people test there galvanic isolators?

 

Keith

[pelicanafloat]

Am wondering why you would want 2 consumer units in smart gauge info?

Edited October 15, 2013 by pelicanafloat

[Alastair]

As to which cable to use

 

H07 RNF

 

An fit an isolation transformer not a galvanic isolator there is no way of telling when it has failed without getting a multi-meter out and how many people test there galvanic isolators?

 

Keith

Not entirely true, as some galvanic isolators come with a gauge.

[Kae]

Am wondering why you would want 2 consumer units in smart gauge info?

 

The Smartgauge website describes different scenarios and how the boat would be wired for those different scenarios. In reality, most installations only have one consumer unit, but the information is useful so you can see how to make a very versatile system.

 

The best approach is to always abide by the KISS principle - Keep It Simple Stupid. The simpler a system, the less likely something will go wrong, and the easier it will be to fix if it does.

[nicknorman]

Not entirely true, as some galvanic isolators come with a gauge.

Although I am not "anti" GIs in the way that Keith M is, the meters you refer to are not a means of testing a GI. Following a previous major fault, its possible that the GI diodes are burnt out open-circuit. There would be no effect on the meter, but it would mean that the boat was no linger earthed. The meter will only tell you that the diodes are fused short circuit, thus effectively meaning no GI in circuit.

 

The latter condition is bad for the boat's health, the former is bad for your health!

 

Therefore, following a short circuit etc that trips the shore bollard, the GI should be disconnected and tested with a battery / bulb to ensure it still conducts both ways once the isolation voltage is exceeded.

Am wondering why you would want 2 consumer units in smart gauge info?

You might for example want one AC system that only works from shore power, eg immersion heater, electrical heaters, and another system that works from the inverter and/or shore power. This is to prevent the classic mistake of disconnecting the shore power and then rapidly flattening the batteries by leaving the immersion heater on by accident.

 

Personally I just have 1 circuit and I am able to run the immersion heater from the inverter. This is useful when running the engine just to produce hot water as we have a powerful alternator. The extra load on the engine helps it to heat it up more quickly, and the extra 1kw from the immersion heater helps to heat the water up quickly. Its up to me to remember to turn the immersion off when I stop the engine. So far, I haven't forgotten but it's probably only a matter of time...

[jonathanA]

just to add the Gi's with status indicators (LEDs) are very simple to test and at least one supplier provides all you need (except a 9v battery) to test the GI.

 

 

As to which cable to use

 

H07 RNF

 

 

Keith

 

Most people use Artic grade 'blue' cable which is considerably cheaper than the heavy duty H07RNF which is only needed where there is risk of abrasion.

 

The point is that the cable should^* be 'flex' not solid T&E for instance as used in domestic wiring

 

* Should - not must AFAIK the BSS strongly recommend the use of flexible cables (and there is a spec about the number of strands) rather than solid domestic type cables for non hire boats.

[Keeping Up]

just to add the Gi's with status indicators (LEDs) are very simple to test and at least one supplier provides all you need (except a 9v battery) to test the GI.

 

And they have the advantage that they offer you greater protection because they have a higher turn-on voltage

[smileypete]

I am super close to buying a boat. It has a lot going for it but it doesn't have mains electricity. I don't think installing mains is a big issue - 4 sockets and a consumer unit. However, when it comes to things like including a galvanic isolator, which cable is acceptable on a boat, what the legal cable routing is and how to integrate a battery charger I was wondering if there was a handy website or book which would help.

 

The actual work doesn't concern me but I do want to do it within the frame work of the BSS for more than obvious reasons. Now I could read them but I just thought an article might offer some other hints and tips too.

 

Thanks in advance!

 

First of all, if you're not very experienced with mains electrics, DO get any install work you do checked over by a registered spark or someone similarly competent before using it.

 

That said, a common and quite acceptable way of wiring the mains on a narrowboat would use:

 

16A shoreline inlet

Galvanic isolator, with LED status monitor ideally

Garage consumer unit including RCD and 16A MCB

Double and single sockets as required

2.5mm² flexible cable 'flex' for connecting up

2.5mm² Bootlace ferrules and decent ferrule crimper for terminating 'flex'

Ring terminal and decent crimper for connecting earth to hull.

Cable clips if needed to properly support cable.

 

Then the install would involve the following among other things:

 

The earth inside the consumer unit is connected securely to the hull using a bolt and ring terminal, very important.

The bootlace ferrules terminate the bare ends of the flex where they go into screw terminals, very important.

The galvanic isolator goes in the earth wire between shoreline inlet and consumer unit.

The sockets are all fed by a single 16A MCB, any extra MCB(s) are left disconnected.

The sockets don't have to be wired as 'ring main' with 2.5mm² cable on a 16A MCB, a radial (like a tree) can be used.

Sometimes people use a reel of 'blue arctic' cable for both shoreline lead and fixed wiring inside boat.

The galvanic isolator isn't really mandatory if you only plug into a shoreline very occasionally.

 

If are going to do it yourself and are unsure in any way as to exactly how to wire things up please do ask!

 

cheers, Pete.

~smpt~

Edited October 15, 2013 by smileypete

[Alastair]

Although I am not "anti" GIs in the way that Keith M is, the meters you refer to are not a means of testing a GI. Following a previous major fault, its possible that the GI diodes are burnt out open-circuit. There would be no effect on the meter, but it would mean that the boat was no linger earthed. The meter will only tell you that the diodes are fused short circuit, thus effectively meaning no GI in circuit.

 

The latter condition is bad for the boat's health, the former is bad for your health!

The GI I installed on the barge had a gauge that showed the voltage across the diodes - in either direction. Failed open or short circuit would show up. It does rely on a visual check now and then.

[nicknorman]

The GI I installed on the barge had a gauge that showed the voltage across the diodes - in either direction. Failed open or short circuit would show up. It does rely on a visual check now and then.

No, if it was failed open circuit the meter would be unaffected - there would still be a small voltage showing when plugged into shore power. The meter can't tell the difference between a small voltage across diodes that is insufficient to make them conduct, versus a small voltage across diodes that are open circuit. This is an important safety point!

[smileypete]

You could put a certain number of diodes across the meter, then a small value fuse inline with the meter.

 

If the meter then stopped working and the fuse had blown, that'd tell you something!

 

cheers, Pete.

~smpt~

[twelveeyedfish]

Smileypete, thanks.

 

I have made systems to be installed on gas and oil rigs and ferrules are a requirement in these places. Is it required on a narrow boat or just desirable?

 

Nicknorman: Surely a shorted diode has no voltage across it as it's a short? It's when they fail open circuit which is the problem.

Varistors tend to fail OC which is why TVS diodes are preferred these days.

[nicknorman]

Is it required on a narrow boat or just desirable?

 

Not required, but certainly good practice.

 

Nicknorman: Surely a shorted diode has no voltage across it as it's a short? It's when they fail open circuit which is the problem.

 

Isn't that what I said?

 

Shorted - no protection from corrosion but electrics remain safely earthed

 

Open circuit - no problem with corrosion but electrics are not earthed.

Edited October 15, 2013 by nicknorman

[twelveeyedfish]

Well if that's what you summarised, yes!

 

I was meaning with regarding detecting a blown diode. That should be fairly easy though I am going to look at a circuit diagram for one before I commit to that!

[NorthwichTrader]

Sorry to pirate, but we're going to be using one of these 350809953384 from eBay ( sorry, can't link from the phone), do we need to be concerned about galvanic isolators for this set-up? We mean to use this system for our fridge etc for the entire winter, probably for the best part of a year to be honest!

[smileypete]

I have made systems to be installed on gas and oil rigs and ferrules are a requirement in these places. Is it required on a narrow boat or just desirable?

 

It's not required by BSS but is very much desireable, as the screw terminals in standard electrical bits aren't designed for used with fine stranded wire like flex. If a connection loosens later on it can cause overheating or strange RCD behaviour.

 

cheers, Pete.

~smpt~

[twelveeyedfish]

I was just looking at Screwfix - when you say arctic cable 2.5mm is that literally the first result it throws up? I am just surprised it's so cheap. It's probably so cheap because you don't put the word "marine" in the name!

[jonathanA]

I was just looking at Screwfix - when you say arctic cable 2.5mm is that literally the first result it throws up? I am just surprised it's so cheap. It's probably so cheap because you don't put the word "marine" in the name!

 

Yes but thats for a 50M drum. probably worth shoping around you might get a better price - guess it depends how much you need !

 

you can always go to a chandlers and pay for the "marine" version - exactly the same but double the price... :-)

[twelveeyedfish]

Hehe. I was just looking around for availability. I expect one or two of my electronics suppliers will have it for less but sometimes it's not worth the effort of shopping around for 5 quid savings. My time is worth more to me!

 

It's nice to know there are no surprises so far. The hardest bit will be installing the panel on which I'll mount the consumer unit and charger!

[twelveeyedfish]

So, where do you get an isolation transformer from? I have only seen one model for sale, it's doubly overrated and therefore silly expensive. You don't really seem to get them for sale!

[Kae]

These are good: http://www.airlinktransformers.com/boating_transformers/