DIY Boat mains circuit

RobBrown

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I currently use one if the Towsure type -3 outlet 10A twin pole RCD mains power supplies to bring power on-board. Is there any problem in using this as the backbone of on onboard mains ring system? Basically take off the shore power plug & 20 of the 25m of lead, install a Hubbel female 16A mains plug socket which I already have & run the shortened cable & the unit from this, sited somewhere suitable on board then run two mains cables possibly with outdoor rated plugs, from the immersion in the calorifier & the battery charger, leaving one socket to run a plug in mains spur from, with say 3 13A sockets sited through the boat, using the remnant of the original cable for this wiring. Is this a safe & workable solution? (I have a separate 20 m shore power lead and a Hubbel male 16A plug which I can add in place of the existing end plug).

The unit is similar, if not identical, to this:

http://www.towsure.com/product/Camping_Site_Mains_Supply_Unit_3_Outlet

I had considered possibilty of a garage unit based set up, but as I already have the constituent items above, thought this may be an easy and low cost solution. If a bad idea, happy to consider other cost effective & safe suggestions.

PS if workable, would appreciate any recommendations for suitable onboard 13A plugs and sockets to source.
 
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RobBrown

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Interested why you say not to use Hubbell. I thought they were highly rated for marine use? The point being I already have the male & female sockets. The unit has an RCD and the attraction was that therefore this element already wired in, making it simpler for me. Equally as I dont intend to have the mains permanently attached to the boat whilst on the berth, is a Galvanic Isolator actually necessary? You will understand from your recommendations that I am already £100+ down and more complex work, meaning likely to get in a Sparks, so additional costs there. I was hoping simple & cheap- ie mainly using items I already had :(.
 

Keith-i

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So long as you get your male and female plugs and sockets the right way around for the sake of safety, I can't see it being a problem. Slightly unconventional but ok. I assume you calorifier element is only 1kw and nothing much greater.
 

VicS

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I currently use one if the Towsure type -3 outlet 10A twin pole RCD mains power supplies to bring power on-board. Is there any problem in using this as the backbone of on onboard mains ring system? Basically take off the shore power plug & 20 of the 25m of lead, install a Hubbel female 16A mains plug socket which I already have & run the shortened cable & the unit from this, sited somewhere suitable on board then run two mains cables possibly with outdoor rated plugs, from the immersion in the calorifier & the battery charger, leaving one socket to run a plug in mains spur from, with say 3 13A sockets sited through the boat, using the remnant of the original cable for this wiring. Is this a safe & workable solution? (I have a separate 20 m shore power lead and a Hubbel male 16A plug which I can add in place of the existing end plug).

The unit is similar, if not identical, to this:

http://www.towsure.com/product/Camping_Site_Mains_Supply_Unit_3_Outlet

I had considered possibilty of a garage unit based set up, but as I already have the constituent items above, thought this may be an easy and low cost solution. If a bad idea, happy to consider other cost effective & safe suggestions.

PS if workable, would appreciate any recommendations for suitable onboard 13A plugs and sockets to source.


The campsite unit may be an attractive solution for a temporary connection of portable appliances but once you progress to built in items such as immersion heaters and battery chargers you should be looking at a proper fixed installation with full earth bonding to the boat's systems including the DC negative, anodes and the hull in the case of a metal hull.

The document which sets out what is required is ISO 13297. You will find an obsolete version on line but you really should follow the requirements of the current (2012) edition.

Once you start bonding the shorepower earth to the boats systems you should also fit a galvanic isolator in the incoming supply.
 
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Interested why you say not to use Hubbell. I thought they were highly rated for marine use? The point being I already have the male & female sockets...

So spend another £10 and get 16A connectors, put the Hubbells on eBay. They were banned when I worked at the BBC, and probably still are; the main problem being the earth pin can bend and short to the live!
 

RobBrown

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Thanks for the further comments. Immersion is 1.2 kw. I have used the unit to run both the immersion and battery charger in the past, though of course not left connected indefinitely.

I had not come across the issue with Hubbells that Nigel flags. They are in fact very expensive fittings, tho I know that does not always translate into assured quality.

As a matter of info, the inlet I have is the SS version shown here:

http://www.aquafax.co.uk/html/product_details.asp?ID=10584. (& commnensurate 16A plug plus boot. Do these models reputably have that potential problem?

Sounds as if my idea is not really a runner, so poss back to the Screwfix garage unit plus a GI then. That will definitely have to wait for funds and the winter season!:ambivalence:
 

tr7v8

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I build data centres across Europe & work for a US HQ Computer company. The preferred connector in Europe is the IEC60309 also known as the 309 & also Commando plug. Only my US colleagues use Hubbells & even the US is starting to use the Commandos.Not sure why you would use a Hubbell in Europe. I would use an IP rated commando & connect it to a board with an RCD in.
 

Jean

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What you are proposing is not much different to what you have been doing, and although not in line with current standards, should work as safe as your current approach. If connection is not permanently attached to boat, and only used occasionally, then I'd not worry too much about GI.
 

David2452

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Could anyone explain in simple language what GI is and when and why you might need it?

OK, without getting into Pros, cons, GI -v- Isolation transformer etc. Galvanic Isolator, it basically interrupts the path for the protective earth at ultra low voltage level to prevent low level current leakage which can cause galvanic erosion, should a fault occur in the low voltage AC system on board it will still allow a path to earth through the shore lead. If you regularly use shore power then it may be beneficial, on a swinging mooring for instance it's just extra weight.
 
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RobBrown

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Well a GI is a Galvanic Isolator and put into the system when the shorepower earth is bonded to the boats electrical wiring system, to help prevent galvanic corrosion, as VicS says above, but I'm sure someone more clued up can give a fuller explanation. I think the units cost £80-90, which with additional wiring into the circuit was why I was hoping it was not necessary in my case.

Ah-I see someone already has whilst I was posting!
 

VicS

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So you only need it if you're regularly in a marina?

You need a GI if you leave the shorepower plugged in for prolonged periods....... plugged in, not necessarily in use.

Also only necessary if the shorepower earth is bonded to the anodes/ other underwater bits and pieces ..... many people in the past have not done this.
 

William_H

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Before considering a GI you need to decide if you need to connect the mains earth coming in to your ships earth. ie the engine prop and water. This connection is made for safety in case of any equipment developing a leak to their metal body from mains active. If the mains earth coming in is reliable and so connected to the sea it is OK. But any failure here including any other user leaking current to the mains earth can potentially make your metal bodied equipment live compared to actual earth (the sea) and your metal boat parts. So for things like plastic fan heater or plastic electric kettle no worries just using a lead from the shore power. When you connect to a metal water tank with an electric element you have potential for leakage to the tank. (hopefully earthed to the mains earth) if there is a fault. Not so safe if the mains earth is bad and you get that common breakdown of insulation in the element. Again your battery charger hopefully has an insulated negative from mains earth. If not or if there is leakage you can connect your incoming mains earth to all your negative connected 12v equipment. Or if there is a fault internally leaking mains active to the metal box or the 12v output it could be dangerous. The assumption is that your body is very likely to be connected electrrically to the sea via metal boat parts. So if you touch any live metal appliance and you are touching any boat metal (ie sink) you will be dead meat unless the RCD saves you.
So in a proper ring main 240v installation the incoming mains earth is connected to the earth wire going to each appliance and to the ships earth . (engine and hence water.)

However this connection mains earth to ships earth can create electrolysis problems both to your metal underwater and to other boats also connected via the mains earth.
The solution is to fit a GI. This makes no connection if voltages are small. ie up to 1.4 volts. However if any larger voltage hence current appears on the mains earth it will be dissipated by the GI becoming conductive. So providing safety protection while ressiting the small galvanic voltages and currents that over 24/7 long term connection can cause problems.
Hence smaller boats temp[orary mains use no GI. Permanent shore power needs a GI. good lcuk olewill
 

Bobobolinsky

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So long as you get your male and female plugs and sockets the right way around for the sake of safety, I can't see it being a problem. Slightly unconventional but ok. I assume you calorifier element is only 1kw and nothing much greater.

If you fit reverse polarity, the earth leakage automatically trips. For anyone who has not spent the money, Screwfix are doing garage units for 21squid.
 
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