Which fuse rating to use in a plug

[JohnW2]

I'm not sure I agree with that - I fitted one here, as an inexpensive upgrade to what I had .... If one RCD now should trip, it will take out half the house, but that's no biggie for me to resolve.

Have you not shot yourself slightly in the foot in relation that, at least as far as the regs are concerned?

If it had been me doing that, I could honestly have said that that it was my house, in which I had to live, and that I would not regard it as a significant inconvenience to lose the electrical supply to 'half of my house' - hence really not non-complaint with 314.1(i) (at least, so long as I was living there)

However, if you were being equally honest, you would presumably have to acknowledge that you have stated that you could regard it as 'very inconvenient' to lose just one circuit - thereby seemingly admitting that (per your own feelings) what you had done was non-compliant with 314.1(i) ?

 

[JohnW2]

I started as a VP8, then went to GW7, and for a time VR2, so I have to look it up, as the VP8 had a larger 2-meter band, and VR2 no 70 cm band, even when it was the same RAE exam, not Falklands (VP8) that was a personal interview with the post master general.

Most of the bands (in UK) were pretty straightforward back then - 80m, 40m, 20m, 15m and 10m were all harmonically related (3.5, 7, 14, 21 and 28 MHz), so could all be generated by frequency multiplication from a single source and, similarly, the only VHF/UHF bands that were significantly used (and I used them all), namely 2m, 70cm and 23cm were also harmonically related (144, 432 and 1296 MHz), so the same advantage. Even 4m (70 MHz) was, arithmetically, related to the others, but I don't think many people attempted a x5 multiplication! The only (slightly) odd man out was 'top band' - with a lower bound of 1.8 MHz it very slightly failed to be exactly half of 3.5 MHz, but it was where most people started in those days, with a maximum powerof 10 W (in comparison with 150 W on other bands).

 

[Harry Bloomfield]

If it had been me doing that, I could honestly have said that that it was my house, in which I had to live, and that I would not regard it as a significant inconvenience to lose the electrical supply to 'half of my house' - hence really not non-complaint with 314.1(i) (at least, so long as I was living there)

Not really, almost zero likelihood of one tripping, but if one did, there is still half the house working, and someone very capable on site, to investigate, isolate, and get the tripped half, back on. A minor, very unlikely issue, and nowt to prevent me later upgrading to add RCD's should I feel the need.

 

[pete01]

and someone very capable on site, to investigate

Who?

 

[JohnW2]

Not really, almost zero likelihood of one tripping ....

Are you not being a tad inconsistent? What you've just written sounds as if I wrote it, backed up by my experience of about 40 years of living with RCDs with very very few trips (except when I've touched N&E together whilst working with SP isolation ) - it's that 'near zero' probability/'likelihood' of circuit(s) being lost (i.e. 'once in a blue moon') that has led me to my position that I've been describing. However, when I explained that basis of some of my personal views/approaches , you responded with ....

The likelihood, is of little interest to me, the point is that for little extra cost, circuits can gain independence, and minimise the chances of suffering loss.

 

[Harry Bloomfield]

Are you not being a tad inconsistent? What you've just written sounds as if I wrote it, backed up by my experience of about 40 years of living with RCDs with very very few trips (except when I've touched N&E together whilst working with SP isolation ) - it's that 'near zero' probability/'likelihood' of circuit(s) being lost (i.e. 'once in a blue moon') that has led me to my position that I've been describing. However, when I explained that basis of some of my personal views/approaches , you responded with ...

Are you loosing sight of the fact that all the circuits are fed from and are reliant on one single main fuse, and one point of supply? Lose either, and the lot goes off.

Most of the messing about I do, where I might still short neutral to earth, is in my workshop, which has it's own RCD, plus likely as not, would be powered from my isolation transformer. If it should trip, on the very, very rare occaision when I am modifying the internal wiring (I don't evisage needing to do any), so what?

 

[JohnW2]

Are you loosing sight of the fact that all the circuits are fed from and are reliant on one single main fuse, and one point of supply? Lose either, and the lot goes off.

Not really, but you seem to be sounding like me, rather than yourself, again!

Sure, the cutout fuse could blow, or something could go wrong anywhere else between the CU and substation, and one would lose all power. However, quite apart from the fact that I can't do anything about those possibilities, I regard the likelihood/probability as being so low as to not justify losing a moment's sleep over it.

You also agree that the probability of losing a block of circuits due to an RCD tripping is extremely small but, having previously said that you had no interest in probabilities being low, you now seem to accept it as a reason for not having 'concerns' about it, so I'm a bit confused.

Most of the messing about I do, where I might still short neutral to earth, is in my workshop, which has it's own RCD, plus likely as not, would be powered from my isolation transformer. If it should trip, on the very, very rare occaision when I am modifying the internal wiring (I don't evisage needing to do any), so what?

I'm not sure that is all that relevant to our general discussion but .... what is this 'isolation transformer' achieving? You seem to be implying that you would expect a N-E short downstream of the transformer to trip an MCB - is that the case? If so, you must presumably have earthed one side of the secondary of the transformer, in which case it would no longer be 'isolating' anything, would it? - so I'm again a little confused!

 

[ericmark]

Sure, the cutout fuse could blow, or something could go wrong anywhere else between the CU and substation, and one would lose all power.

I am sure something could go wrong, but extremely unlikely to lose all power. I hope to renew the battery on my power pack with did give me 300 watt, my portable inverter can give me 150 watt, and I do have a spare battery, The problem was none of these would run my freezers or central heating. So when the solar panels were fitted I got it, so I have 5 kW available from the inverter to power central heating, and freezers, plus one spare socket in the kitchen.

I did consider including more, but the lights we use are far in excess of what is required in an emergency, and decided some auto light rechargeable touches was a better idea for lighting.

In the previous house we had a caravan parked in the drive, we still have a camping stove, etc. Be it candles or a full-blown generator, I am sure everyone has something in case of power failures, again previous house we had gas, and one gas fire which would keep us warm.

Again last house I was a member of the local RAYNET and had my emergency pack to hand, since moving I have not bothered joining the local group around here, but still have handies one which will open the works' repeater, which would not be strictly legal, but in an emergency I am sure no one would object. Even my PMR466 have first 8 frequencies with the same code squelch as ones at work.

However, what all this has to do with plug fuse size, I don't know? I think freezers have 3 amp fuses, same with central heating, as to if they would blow on a 5 kW inverter supply I don't know, the inverter may close down first?

 

[Harry Bloomfield]

I'm not sure that is all that relevant to our general discussion but .... what is this 'isolation transformer' achieving? You seem to be implying that you would expect a N-E short downstream of the transformer to trip an MCB - is that the case? If so, you must presumably have earthed one side of the secondary of the transformer, in which case it would no longer be 'isolating' anything, would it? - so I'm again a little confused!

My isolation transformer, is a 1Kw proper isolation transformer - there is no connection between the secondary and L, N, or E, which is the whole point of an isolation transformer. It used to make working on live chassis TV's, and radios, much safer.

 

[JohnW2]

My isolation transformer, is a 1Kw proper isolation transformer - there is no connection between the secondary and L, N, or E, which is the whole point of an isolation transformer.

That was my point

It used to make working on live chassis TV's, and radios, much safer.

... and, yes, I've done the same, for the same reason.

However, where is the RCD which you said might conceivable trip? In the absence of any 'referencing' of the output from the secondary of the transformer, no RCD could operate as a result of something which happened with that 'floating' supply.