Shore power from a house socket?

[blackrose]

Is it safe to take shore power for a boat with a 16 amp breaker (RCBO), from an ordinary household socket with a plug in RCD?

 

If so, I guess the boat's supply would be restricted to 13 amps?

Edited April 18, 2010 by blackrose

[alan_fincher]

Is it safe to take shore power for a boat with a 16 amp breaker (RCBO), from an ordinary household socket with a plug in RCD?

 

If so, I guess the boat's supply would be restricted to 13 amps?

Can't see why not.

 

If you are connecting through a normal British 13 Amp square pin plug, then it shouldn't have a fuse of greater than 13A rating, so that's the effective limit.

 

Although most 13 amp fuses will actually pass rather more without blowing, of course.

 

You should however make sure the house owner is happy with you doing this!

[blackrose]

Can't see why not.

 

If you are connecting through a normal British 13 Amp square pin plug, then it shouldn't have a fuse of greater than 13A rating, so that's the effective limit.

 

Although most 13 amp fuses will actually pass rather more without blowing, of course.

 

You should however make sure the house owner is happy with you doing this!

 

Thanks Alan.

 

Would the RCD plugged into the socket normally be expected to trip before the 13A fuse blew? Also would my boat's 16 amp RCBO still function properly?

[casper ghost]

Wouldn't it just be the same as using a long extension lead at home, only you run it out into the boat. I've never understood about shorelines as I have no 240 volt on my boat.

[alan_fincher]

Thanks Alan.

 

Would the RCD plugged into the socket normally be expected to trip before the 13A fuse blew? Also would my boat's 16 amp RCBO still function properly?

I'd say an RCD, (Residual Current Device), is about making sure that the supply is cut if there is leakage detected to earth, (possibly through some poor sod hoilding a bit of defective equipment )

 

So, no, it has nothing to do with protecting you against drawing more than 13 amps overall, 16 amps overall, or any other over-current situation. It should (in my view) blow only with an earth leak - nowt to do with total current.

 

If you have an RCD as the 13 amp socket, this seems no different to plugging into a marina 16 amp supply that has a similar device fitted permanently, (well not to me at least, but I await the experts telling me why I am wrong).

 

In my experience deliberately introducing a test earth leakage on my boat would often trip the marina's breaker, before the one in my own distribution unit, but I'd not want to rely on that, in case their's ain't working.

 

My distribution unit, (basic Screwfix job), has two circuit breakers in it, one rated 16 amps, the other rated 6 amps. If I overloaded the stuff on the 6 amp circuit, I'd expect that to trip before a normal plug-top 13 amp fuse blew.

 

If I overloaded the stuff connected to the 16 amp circuit, I think it might be touch and go whether the breaker tripped on the boat, or the 13 amp fuse blew first. A 13 amp fuse needs to be able to pass 13 amps continually, without blowing, so could probably pass 16 amps for short periods without doing so. (In fact, on balance, I suspect the boat breaker would go first).

 

I could in theory pass 22 amps through my breakers (16 amps + 6 amps) - if I did, I'd expect that fuse to quickly be history......

 

I'm not, however, an electrician, so if one of those disagrees with me, I'd be happy to try and understand what I've said that's not correct ?

 

 

Wouldn't it just be the same as using a long extension lead at home, only you run it out into the boat. I've never understood about shorelines as I have no 240 volt on my boat.

Broadly, but you need to be rather more careful if you are putting the mains electricity into a large metal box.

 

If you run an extension cable into your garden, , and manage to wear it through on the edge of your wooden shed, you will not come to too much harm if you touch another part of the shed.

 

If you manage to connect the whole shell your boat to the mains, in a way it doesn't cause the supply to trip out, the consequences could be a lot nastier.

 

I used to use a board on the boat that effectively contained nearly all the bits that are now permanently installed on the boat - including the box with both earth leakage breakers and over current circuit breakers. However such an arrangement lacked any proper bonding of earths to the boat, so even that was, frankly, quite a dodgy compromise.

 

I'm convinced that proper use of 240 volts in a steel narrow boat must involve doing things in the prescribed manner.

[DHutch]

It will be fine. We have done in the past a lot.

 

 

Typically the socket in the house will be protected by a RCD and a MCB (or a combined RCBO) with a current rating of 32amps to protect the house ring main. Old houses maybe on fuses without without and earth/inballence protection)

 

The plug however will (should) have a 13amp fuse in it, which will protect the plug, and the lead leading from it, to a limit of 13amps (all be we it tollerating peaks above that before blowing) so will the wire.

 

Then you boat will have its RCD/MCN or MCBO's which limit the current to whatever there set at. Although, typically, this in excess of 13amps or even 16.

 

The diffrence between 16amp and 13amp is infact only three amps anyway. And a 13amp plug is fused.

We also have an addapter to take 16amp down to 13amp. Nominally this should have a fuse in it, in practice i do not see it to be necessary.

 

Daniel

[johnjo]

You also need to take into account the cable run [length] from house to boat and ensure it's of the correct type, if only for temporary use 2.5mm 3core arctic cable should be fine but protect it where necessary.

Edited April 18, 2010 by johnjo

[Guest]

I agree it is safe, providing you use RCD protection, and sufficiently sized cable to avoid volt drop. You are of course limited to a 13Amp supply, by nature of the fuse in the plug top.

[blackrose]

I agree it is safe, providing you use RCD protection, and sufficiently sized cable to avoid volt drop. You are of course limited to a 13Amp supply, by nature of the fuse in the plug top.

 

Is there such a thing as a 13A breaker that I could plug into the socket? It just seems easier to have something trip rather than have to replace a fuse everytime I draw too much current.

[DHutch]

Is there such a thing as a 13A breaker that I could plug into the socket? It just seems easier to have something trip rather than have to replace a fuse everytime I draw too much current.

Probably not.

- What are you planning to run, i wouldnt imagine you would find it tripped very much at all.

- You can put 16amp through a 13amp fuse for a good count to ten, if not far longer.

- Hence unless you routinely trip the 16amp breaker it just isnt going to be an issue imo.

 

 

Daniel

[EricMark]

Working and living in a caravan site I have many heated arguments with other electricians who to me were just trying to follow regulations with no thought as to what made sense.

1) With 30ma RCD (that includes RCBO’s) in both house and boat any fault and likely both will trip. If you can’t assess house RCD then maybe fitting a 10ma RCD in the boat would help. However not so easy to get hold of and really they should not trip unless there is a fault. Cure would also be to use a S type 100ma in house but that would not comply with regulations see 709.531.2.

2) While talking about regulations I should point out ESQCR law bans the use of a TN-C-S supply (PME) to boats and if the house has a TN-C-S supply you will need to turn it into a TT supply or with isolation transformer a TN-S supply for the boat see 709.411.4

3) The fuse will normally allow more than any MCB at same rating for overload but not with short circuit fuses act faster than a MCB with short circuit. The RCBO has three methods of tripping. A) Earth leakage Overload [Thermal part of trip] and C) Short circuit [Magnetic Part of trip] the latter is shown with a letter B = 5 x marked current, C = 10 x marked current and D = 20 x marked current so a C16 30ma RCBO would need a 160A short circuit current to trip to do this it must be able to draw 160A which means the earth loop impedance (ELI) needs to be below 230/160 = 1.4375 ohms.

Now I am coming to the point unless the ELI is below 1.4375 ohms the fuse will pop first. Since you are not allowed PME the earth loop impedance is not really an issue but prospective short circuit current is and both are measure with same meter.

Now assuming the house has a B32 MCB supplying ring main the max ELI would be 1.4375 ohms and I hope you can see problem this leaves on ohms for connecting lead between boat and house so to have any discrimination you must use a B type MCB.

MOELLER do make a B12 MCB which would likely trip before any 13A fuse but not very common and likely you would need to order from Farnell or one of the other specialist suppliers.

With so little lea way the resistance of the wandering lead is very important. You have likely 1.4375 ohms max to play with. 1.5mm² = 0.027 ohms per meter 2.5mm² = 0.016 ohms per meter and 4mm² = 0.010 ohms per meter giving max of 53, 90, and 144 meters length however getting anything bigger than a 1.5mm² cable in a 13A plug is rather hard.

Combined with ESQCR rules therefore it may be better to have a WMDU (Weatherproof Main distribution unit) outside the house. i.e. a box or shelter with a garage consumer unit inside. At this point you can drive in earth stake and change from TN-C-S to TT and provide a point where you can easy re-set any RCD or MCB that trips. It could it’s self be just plugged in but because it is close to the house it would have very little volt drop and could then have the normal 16A socket so you could use 2.5mm² cable from box to boat. This would also then comply with 709.553.1.8 which says BS EN 60309-2 up to 63A i.e. standard 16A socket.

709.553.1.13 says you need to have instructions if you need the wording I can send you a copy. There are four pages 192 to 196 covering supply to a boat however to copy and print on this forum would be against rules and forum is rather open so both for myself and forum owners it would be foolhardy for me to post whole section.

You must consider to what extent you need to follow regulations. Who will check what you have done? And are they likely to be pedantic? To me having a 13A plug is not really a problem but regulations are designed for marinas and cover tidal and canal so tend to be OTT when considering canals. However earth problems are more of an issue with fresh water as it does not conduct as well as salt water so an earth fault with a canal boat could electrocute someone swimming by but that would not be case with salt water. Not that I think swimming in the canal is really something one would want to do except for Llangollen where there is a good flow of water from Dee.

I have enabled email notification of replies so ask if uncertain.

[nb Innisfree]

It would seem that a RCD detects an earth leakage problem only but if we plug our Victron Multiplus into shorepower and turn the shorepower dial up it will trip the shorepower RCD when the load exceeds the shorepower supply which then requires the Shorepower RCD to be reset.

[EricMark]

Is there such a thing as a 13A breaker that I could plug into the socket? It just seems easier to have something trip rather than have to replace a fuse everytime I draw too much current.

There are unfused 13A plugs but only available in hospitals special where power supply failure could endanger life. So unless you know someone in a hospital no. There are some adaptors from china 13A to 2 pin EU and USA without fuses but when I find one it goes in bin. If you used earth rod then maybe but not really good idea.

 

Yes 13A are available see http://uk.farnell.com/moeller/pls6-c13-dw/...pole/dp/1205337 but rare likely you will need to order.

[EricMark]

It would seem that a RCD detects an earth leakage problem only but if we plug our Victron Multiplus into shorepower and turn the shorepower dial up it will trip the shorepower RCD when the load exceeds the shorepower supply which then requires the Shorepower RCD to be reset.

An RCD measures the power out on line wire and power return on neutral wire and as long as the two are within 30ma of each other it will continue to supply power.

There are different types of RCD a passive RCD will not trip with power failure but an active type will. Because if voltage drops below a threshold RCD's may fail to work where a volt drop is likely we use an active type so it will fail safe. An RCD will not trip with over current only a RCBO will do that. The RCD will have two current ratings one for current it can handle under normal conditions so may be marked as 63A and the other under fault conditions 4700 amps for example which is related to the earth loop impedance. Nearly all current trips will have a B, C, or D in front of number i.e. B16.

 

There is also type A and type AC where an inverter is used it should be type A to ensure it will trip as type AC is for AC only.

[blackrose]

Probably not.

- What are you planning to run, i wouldnt imagine you would find it tripped very much at all.

- You can put 16amp through a 13amp fuse for a good count to ten, if not far longer.

- Hence unless you routinely trip the 16amp breaker it just isnt going to be an issue imo.

 

 

Daniel

 

I'm planning to run my whole boat off it. When you live aboard it's not actually that difficult to trip even a 16 amp supply, although I've only done it a few times. If I have the washing machine on, the battery charger, and then the immersion heater timer happens to switch it on then I think that might come pretty close to tripping a 13 amp supply. If I used the microwave on top of any of that then it would trip for sure.

 

There are unfused 13A plugs but only available in hospitals special where power supply failure could endanger life. So unless you know someone in a hospital no. There are some adaptors from china 13A to 2 pin EU and USA without fuses but when I find one it goes in bin. If you used earth rod then maybe but not really good idea.

 

Yes 13A are available see http://uk.farnell.com/moeller/pls6-c13-dw/...pole/dp/1205337 but rare likely you will need to order.

 

Thanks for that.

 

No I don't want to use an unfused plug, I just want something that will trip before the fuse blows.

[EricMark]

My son is trying to live on 4A supply. Method is battery charger and 3KVA inverter. I think likely he will need to run engine from time to time or get a larger battery charger but with careful planning it can be done. I had a caravan on 6A supply and I also did some odd things like the room heater was connected to thermostat which diverted power from room heater to hot water boiler and I changed the element in hot water boiler to 1Kw instead of standard 3Kw and it worked.

 

As I see it your biggest problem is likely to be earthing and ensuring that you don't have any electrolysis problems. If a steel boat then use a steel earth rod not copper coated and you should be OK.

 

I would be very surprised if house is not on a TN-C-S supply and I think you will need to sink an earth rod and I have grave reservations as to getting a non marine electrician to understand your special needs.

 

The whole idea of sticking diodes in the earth would get most electricians sucking through teeth and coming out with jobs worth statements and the meters needed to test the earth rod mean DIY is really out.

[blackrose]

My son is trying to live on 4A supply. Method is battery charger and 3KVA inverter. I think likely he will need to run engine from time to time or get a larger battery charger but with careful planning it can be done. I had a caravan on 6A supply and I also did some odd things like the room heater was connected to thermostat which diverted power from room heater to hot water boiler and I changed the element in hot water boiler to 1Kw instead of standard 3Kw and it worked.

 

As I see it your biggest problem is likely to be earthing and ensuring that you don't have any electrolysis problems. If a steel boat then use a steel earth rod not copper coated and you should be OK.

 

I would be very surprised if house is not on a TN-C-S supply and I think you will need to sink an earth rod and I have grave reservations as to getting a non marine electrician to understand your special needs.

 

The whole idea of sticking diodes in the earth would get most electricians sucking through teeth and coming out with jobs worth statements and the meters needed to test the earth rod mean DIY is really out.

 

Is earthing from a 13A household supply any different from a 16A marina supply? I would have thought that a marina posed greater potential problems in terms of potential galvanic corrosion. There are many more steel boats and pilings in the marina.

 

Why would you need an earth rod if your hull is properly earth bonded? Anyway, with respect I've been reading up on the earthing debate for a few years and to be honest I've really had enough of it now. I'm satisfied with my setup.

Edited April 18, 2010 by blackrose

[DHutch]

...although I've only done it a few times...

Well thats it. And as i say, 9 times out 10 ten in these cases, the 16amp mcb on the boat will go well before the 13amp fuse.

- Because its going to be something like that washing machine heater coming on with a bang, that adds 2.4kw, taking it from 8amps to 18. MCB trips, fuse is fine.

 

 

As said, if this i going to be a long term solution, rather than a one weeked job, do you have a GI...!

 

 

 

Daniel

[blackrose]

Well thats it. And as i say, 9 times out 10 ten in these cases, the 16amp mcb on the boat will go well before the 13amp fuse.

- Because its going to be something like that washing machine heater coming on with a bang, that adds 2.4kw, taking it from 8amps to 18. MCB trips, fuse is fine.

 

 

As said, if this i going to be a long term solution, rather than a one weeked job, do you have a GI...!

 

 

 

Daniel

 

I see, ok thanks.

 

Yes, I have a GI

[DHutch]

My son is trying to live on 4A supply. Method is battery charger and 3KVA inverter.

What you want is a supply mixing victron inverter charger....

 

 

I see, ok thanks.

Yeah, im not saying it will always be th case.

- Clearly if you suddenly get it bob on 15amps and hold there for a while, the fuse will go, and the mcb not.

- But fuses take a compartively long time to blow compaired to a mcb an are hence actaully fairly roubust.

 

Last years house had two fridge freezers, a washing machine, and a dish washer in the outhouse on a 13amp spur.

And also a toaster, microwave, and fast boil kettle all on the same four way addapter with 13amp fuse.

 

Both, if all on, would add up to well in excess of 13amp, but despight a year of busy mornings when often kettle/toaster/mw over lapped we didnt manage to blow the fuse once. But did take the 32amp mcb out (that fed the whole houses ring main, including these two strings) once. Bar the lights, which all shared one 6amp breaker. It did look odd, with a full sized domestic fuse box with just one rcd, an two mcb's in it, for a whole four bed house!

 

 

Daniel

[Guest]

What you want is a supply mixing victron inverter charger....

 

 

Yeah, im not saying it will always be th case.

- Clearly if you suddenly get it bob on 15amps and hold there for a while, the fuse will go, and the mcb not.

- But fuses take a compartively long time to blow compaired to a mcb an are hence actaully fairly roubust.

 

Last years house had two fridge freezers, a washing machine, and a dish washer in the outhouse on a 13amp spur.

And also a toaster, microwave, and fast boil kettle all on the same four way addapter with 13amp fuse.

 

Both, if all on, would add up to well in excess of 13amp, but despight a year of busy mornings when often kettle/toaster/mw over lapped we didnt manage to blow the fuse once. But did take the 32amp mcb out (that fed the whole houses ring main, including these two strings) once. Bar the lights, which all shared one 6amp breaker. It did look odd, with a full sized domestic fuse box with just one rcd, an two mcb's in it, for a whole four bed house!

 

 

Daniel

 

I am seeing more and more of this. Since the inrtoduction of part P, people are buying those horrible 4 way adaptors from the likes of B&Q (I don't mean the ones with a flex, these plug directly in like some sort of insane plug top.) I believe they will damage the sockets, like those 'orrible two way adaptors.

 

Also we are back to people running extension leads under carpets. Seen a couple lately, they were very popular in the '70's

 

Part P is a step backwards.

[nb Innisfree]

I am seeing more and more of this. Since the inrtoduction of part P, people are buying those horrible 4 way adaptors from the likes of B&Q (I don't mean the ones with a flex, these plug directly in like some sort of insane plug top.) I believe they will damage the sockets, like those 'orrible two way adaptors.

 

Also we are back to people running extension leads under carpets. Seen a couple lately, they were very popular in the '70's

 

Part P is a step backwards.

 

Back in the 50s when I was a lad my mum used to fancy herself as an electrician and we had wires under the carpet running all over the place to various standard lamps etc + things would occasionally liven up with a blue flash as she cut through a live wire with a pair of scissors while 'updating' something. One day a council electrician took a massive jolt while working on the consumer unit, mum found him white as a sheet on the toilet floor and she gave him a rocket for not switching the juice off :lol:

Edited April 19, 2010 by nb Innisfree

[blackrose]

I am seeing more and more of this. Since the inrtoduction of part P, people are buying those horrible 4 way adaptors from the likes of B&Q (I don't mean the ones with a flex, these plug directly in like some sort of insane plug top.) I believe they will damage the sockets, like those 'orrible two way adaptors.

 

An electrician I spoke to told me I should check the plug and socket of the house regularly for signs of overheating. I guess when you think about it, drawing the power for a liveaboard from one 13 amp plug is like attaching a giant extension lead to the socket. The round 16amp sockets and plug found at many marinas are more up to the job.

[alan_fincher]

I am seeing more and more of this. Since the inrtoduction of part P, people are buying those horrible 4 way adaptors from the likes of B&Q (I don't mean the ones with a flex, these plug directly in like some sort of insane plug top.) I believe they will damage the sockets, like those 'orrible two way adaptors.

Do you mean because of their mechanical leverage and/or weight, or because you think they can cause an electrical overload ?

 

If the former, I think I agree with you, but in terms of electrical loading, they surely all have a 13 amp cartridge fuse as part of the set-up, so I can't see they are any worse than a "traditional" 4-way extension using a normal, (or moulded), plug, and a length of heavy duty flex.

 

IIRC, old style 2-way adaptors were not always fused, and you could draw 26 amps from one outlet, if you put your mind to it. For some years, I think even 2-way ones have had a fuse incorportated, and those that split 3-ways or more definitely have.

 

Of course I guess you can possibly might find something that breaks the rules, either on a market stall or in a "pound" shop.

[EricMark]

Is earthing from a 13A household supply any different from a 16A marina supply? I would have thought that a marina posed greater potential problems in terms of potential galvanic corrosion. There are many more steel boats and pilings in the marina.

 

Why would you need an earth rod if your hull is properly earth bonded? Anyway, with respect I've been reading up on the earthing debate for a few years and to be honest I've really had enough of it now. I'm satisfied with my setup.

Sorry but yes very different. As long as the marina has steel earth rods and no aluminium hulls the galvanic corrosion will be low and not too much of a problem.

 

But there are three basic types of supply to domestic premises.

TN-C-S most common also know as PME.

TN-S unusual and hard to verify.

TT used mainly in country where overhead supplies are used.

If the house is supplied with TN-C-S which is the most common supply method then it is against the law to supply a boat from that supply. It is also very dangerous which is why it is against the law.

 

There is no reason why a TN-C-S supply can't be changed to a TT supply for the boat but first you need to find out what the supply is.

 

The DNO has a legal responsibility when asked to tell the house holder what type of supply they have. This is used by many electricians to force the DNO to supply a TN-C-S supply and therefore remove the need for the electrician to sink earth rods but in your case you need a TN-S or TT supply.

 

The TN-S supply can look exactly the same as TN-C-S the main difference is to house holder is the earth loop impedance where only 0.8 ohms is required for a TN-S but 0.35 ohms is required for a TN-C-S supply. Because they look very often the same you would have to get the DNO to confirm it was a TN-S supply. And it would be very rare to find a TN-S supply.

 

If it is a TT supply the whole house will be protected by a RCD. Although this could be a 100 or 300ma version not the 30ma version required for a boat. So unless the whole house is protected by a RCD likely you will need to sink an earth rod.

 

When sinking an earth rod there are two ways to test them. Method one required a very special meter with three leads and two test earth spikes and it needs at least three test readings to work out resistance of earth rod. However where a supply exists one can use an earth loop impedance tester instead. The tests can produce dangerous voltages need to earth spike and one has to be very careful but the meter is much cheaper only costs around £250 against the £1000 for proper earth rod tester.

 

The area around the earth rod needs protecting as under fault conditions it can produce dangerous voltages normally a special cover is used.

 

I would agree with other poster that Part P is a pain but any outside supplies from a domestic premises will need a completion certificate.

 

Yes if from a non domestic premises like shop or factory including the office used in a marina then Part P does not apply and any electrician with insurance could connect and test supplies to a boat.

 

But from a house either you need to pay local council building control £100+ or use a registered electrician.

 

Don't shout at me tell the government. You have the chance election coming up.