If you mean the effect on function of a boat-side RCD (or whatever you prefer to call it), I can't see diodes being of any practical consequence, since they would present a very low impedance at voltages more than a volt or two.
Kind Regards, John
Bad electrical design
- Thread starter Jon c
- Start date
Kind Regards, John
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I tested this when I did the installation on the narrow boat and it all checks out fine. Using diodes is an alternative to isolation transformer for preventing galvanic corrosion.
Indeed, either of those approaches should do the job and, as I said, the diodes should have no noticeable effect on RCD function.
Kind Regards, John
Fitting a 10mA RCD in the garage won't provide any discrimination with the 30mA one in the house - UNLESS it's a mild bit of leakage causing nuisance trips of a 10mA RCD. Any contact for which RCDs are intended to provide protection against would trip both as the current would be higher than the 30mA trip level.
I can vouch for the fact that it's 'kin annoying to have an RCD for the garage in the house. When my brother had a new garage built, the sparky had previously (at my brother's request) used all RCBOs in the house CU so at least only the garage circuit goes off. Unfortunately there's part of the run in the house that needs RCD protection or I'd suggest to my brother that he moved the RCD protection to the garage.
I went in the garage a while ago and found "no lights". Checked in the house and the RCBO had tripped and wouldn't reset. I tried turning off all the MCBs in the garage so I could reset the RCBO - but unless you are lucky to get a working light before hitting on the faulty circuit*, you simply don't get any indication whether the supply has tripped again. It was 'kin annoying to say the least
I'd say that's p*ss poor design.* Yes, I know it's possible for a fault to trip the RCD even with the MCB to the faulty circuit off.
The problem is that most of the users do NOT know the rules - to them a cable is a cable and if the plug fits the socket then that's all that they need to know. So not so much people breaking the rules, but people ignorant of what the rules are that they could be ignoring. There is a balancing act between over-regulation, and under-regulation exposing people (not necessarily the same people as those ignoring the rules) to reasonably foreseeable and easily mitigated risk.
Put another way, if "Mr BIY expert" wires his own van with no RCD and has a fault - then other maybe not even associated with Mr BIY Expert could get a shock from the metal skin of the van. Similarly if he uses a non-RCD protected supply for a properly wired van (many people plug them in at home) and (for example) the cable gets pulled and the live conductor contacts some metalwork through cut insulation - bearing in mind that the metalwork (eg skin panel) might not be bonded sufficiently to ensure operation of overcurrent protection.
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In an ideal world you would be correct. Meanwhile, back on planet earth you need to consider those who don't know what they don't know.
I assume you are familiar with this old one ?
And when out as a pedestrian, do you a) look before you cross the road even at a crossing, or b) assume every driver will do the right thing and walk out without looking if the green man is lit ?
Or put another way, there can be a big difference between what should happen and what does happen. Hence why regulations are written to cope with an imperfect world. In a perfect world every driver will drive safely and carefully, in the real world we have rules for how to deal with those that don't. In the perfect world everyone would be fully qualified and not need BS7671 to be able to design a safe electrical system, in the imperfect world there's a lot of rules there to guide those who can only "wire by numbers".
I assume you are familiar with this old one ?
And when out as a pedestrian, do you a) look before you cross the road even at a crossing, or b) assume every driver will do the right thing and walk out without looking if the green man is lit ?
Or put another way, there can be a big difference between what should happen and what does happen. Hence why regulations are written to cope with an imperfect world. In a perfect world every driver will drive safely and carefully, in the real world we have rules for how to deal with those that don't. In the perfect world everyone would be fully qualified and not need BS7671 to be able to design a safe electrical system, in the imperfect world there's a lot of rules there to guide those who can only "wire by numbers".
I don't walk out until I am sure that the car is going to stop even when the green man is lit.
When driving I do not cross a junction on green without looking to see if there are cars approaching which don't look like stopping.
When on roundabouts I do not assume that those approaching it will give way.
And I am trying very hard to wean myself off the habit of assuming that a driver who flashes his headlights at me when I am joining a road means he is letting me join in front of him or cross his path, no matter how much it ends up pi**ing him off.
When driving I do not cross a junction on green without looking to see if there are cars approaching which don't look like stopping.
When on roundabouts I do not assume that those approaching it will give way.
And I am trying very hard to wean myself off the habit of assuming that a driver who flashes his headlights at me when I am joining a road means he is letting me join in front of him or cross his path, no matter how much it ends up pi**ing him off.
Not at all.
I was pointing out that no allowances should be made to people who don't follow the "rules" for whatever reason.
I was pointing out that no allowances should be made to people who don't follow the "rules" for whatever reason.
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