keif's mate

Well, what an interesting thread. Showers most of the day, so I read all the way through accompanied by several tins of 'bow! Very pleasant as I had nothing spoiling or pressing.

WotEver quotes: "However, even within this section it makes no specific recommendation that any MCB or fuse should be appropriately rated, even for downstream cables. There's nothing that I can see in the regs that states for instance that you can't have a 32A breaker feeding a 0.75mm2 mains cable, let alone that any breaker should be appropriate for the incoming feed". You are right that there is no mention of specific current carrying capacity of cables. However, commonsense would point one down the route of using the tables published in "Wiring Regulations 17th Edition BS 7671:2008 incorporating amendment 3:2015" A precis of which for Flexible cords (Flexible cables are defined as those 4mm2 or over. Pedantic I know!) follows: 0.75mm2 6A 1.0mm2 10A 1.25mm2 13A 1.5mm2 16A 2.5mm2 25A 4.0mm2 32A Thus minimum size for shore power cables (Cords?!!) will be for a 16A Blue 2P+E Plug & Socket system 2.5mm2 for a 32A Blue 2P+E Plug and socket system 4.0mm2 for a 63A blue 2P+E Plug and socket system 16.0mm2 Gin Palaces only need apply!!!! The fact that the supply bollard might have a 6A breaker does not allow you to down size your 16A shore power cable as the next bollard you plug into will probably have a 16A MCB. Using a 32A breaker to supply a .75mm2 cable would be to potentially subject the cable to an overload in the region of 6 times its rated capacity. Plus the terminals would be too large to terminate the conductor correctly, also the cord grip probably wouldn't tighten down properly either. Ho Hum.

Paul C But thats the point - the 25mm2 tails are protected by a 100A fuse. There is no equivalent "master fuse" in the boat examples mentioned, thus the overcurrent protection is the sum of all the individual circuits' breakers - which is more than 100A in your case, and more than 16A (the rating of the socket and wiring) in the boat examples. If a boat had a "master" fuse or MCB of 16A (or 32A, or whatever, if the cables and socket were rated as such) then the individual ratings of each circuit are irrelevant. The master fuse in the case of a shore power system is generally the 16A breaker in the supply pole. Overcurrent protection is NOT the sum of all the individual circuit breakers. Consider our Green friends who tell us a 2 Megawatt wind turbine will power 1600 homes. That is wonderful, but we have to put it into context. 2 Megawatts divided by 1600 homes is 1.25 kilowatts per house. So I fire up my 10 Kilowatt shower and I am using 8 houses worth of Lectrickerty. You CANNOT sum all the Braekers/Fuses and say that is the demand of the system. END of.

Keepingup's BSS examiner would have kittens if he looked at the Consumer unit in a modern house. As Cut Hound said, has he never heard of diversity? 40A Shower 32A Cooker 32A Ring Final Circuit 32A Ring Final Circuit 20A Immersion Heater 16A Garage Supply 6A Lights up 6A Lights down Good Lord, that is 184A. All this with a 100A Leccy Board supply fuse and 25mm2 tails!!!! If memory serves me well, Diversity for domestic lighting circuits is 60% of installed load. The guy that dreamed that figure up obviously didn't have kids. They know how to turn lights on but not off.!! so 100% of the lighting is on 100% of the time!!!

That, Gazza is because Top Management knows much more than the mere minions carrying out the work!!!

In view of PaulG2's post, I suppose I ought not to host handy chimney sweeping tip No 4, tie a brick to a chickens foot and put them down the chimney!

Reading your post 116 Loddon, you were not in the Andrew by any chance!!!

Gazza SSA just issued for the Nene, we will have webbed feet at this rate! Just grow another head and get 6 fingers per hand and you could qualify as a Norfolk person!!!!!!

OHH YES IT IS!! Sorry, forgot the Panto season is over

BMC 1.5 or Perkins 4-108 for me. Not overly impressed with the 4-108 Lowline I have in my present boat. Not very lowline, magnificent packaging exercise, but you cannot get to anything. Preferred my old 1.5, reliable, accessible and you can have 'em rebuilt for less than the price of a new 9.9 outboard!

Athy, maybe a bit far, but how much is red at Thorney Toll?

Up here on the Broads, as probably any other inland waterway system, hydraulic drives are not part of the BSS. The BSS man might look for evidence of leaks from the pollution point of view but there are no pressure tests or certificates of compliance required. I do not know if hydraulic systems are part of the RCD scheme. By Jove dpaws, that is a crafty looking piece of kit. Never sin the loik on it up yer in Narfik!

Generally speaking, hydraulic drive does not remove the stern gland from the equation. It is usual to connect hydraulic motor and prop by means of a shaft. I suppose it could be incorporated into an Azipod. Bad for draught, but good for manoeuvrability! If you had an hydraulic system, perhaps an hydraulic bowthruster could be incorporated as well.

Well, well, a greenie, thank you Sir. "And that's before you start on things like do you want 1000 meters or do you want to travel 1000 metres?" Homonyms, no, not rude or illegal, but who would expect an engineer to know that!!!

Back in the mists of time when I used to witter on to trainee Sparkies in Science classes, the question of measurement and units used to come up. The electrical trade was one of the first to metricate. As with any Engineering trade, metres and millimetres are used. The centimetre is a non preferred unt. Even kitchen cabinents are measured in millimetres not centimetres. In the mid 80's, a fiirm of builders we used to contract to told all their Apprentices to "Forget that metric rubbish you were taught at school, we work in feet and inches" They nearest they got as far as metrification was "Brian, go and get me a 3 metre length of 4x2!" The problem comes with visualisation. Probably not so much of a concern to a modern school leaver who doesn't know any better. However for old dinosaurs I used to use an example of the old London bus (probably a Routemaster!). Said bus weighed about 10 tons. Mild steel had a tensile strength of about 30 tons per square inch. So a mild steel bar with a cross sectional area of 1in2 could lift 3 buses. Trawling through the web gives a tensile strength for EN1A mild steel as 400MPa. What the 'ell are they! Converts to 58015 lbf/in2 or about 25.9 tons. Seems like American mild steel SAE 12L14 is tougher, (it would be!!) at 540 Mpa, 78,300 lbf/in2 or 34.95 tons! 1 Pascal = 1 Newton/metre2 So that would be an apple on a square metre (Coxes Orange Pippin, Granny Smiths, Red Jonaprince, Cooker or ordinary?) Hardly a practical unit! No wonder kilopascals and Megapascals have to be used. Ho hum, I suppose Imperial measurements will be all but forgotten in 50 years. But that doesn't account for the Americans whose idea of metrication is to take a drawing and convert inches to millimetres. So the measurement will be 25.4 mm!