Don’t forget that conductor sizes are cross sectional area, so you’ll get your diameter and then throw some pies at it to get the mm²
Extension of Ring Main & Readings
- Thread starter loopy66
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In most cases, meter installers are just that - people who install meters. Nothing else.
I certainly didn't, but I would really have expected myself to - since I generally have no reason to think/know about the max Zs figures for fuses these days!Nobody noticed my Zs value of 1.04 (30A BS3036) already accounts for the 95% Cmin.
Possibly. I must say that I hadn't thought of that possibility.
Kind Regards, John
Were you not aware that leaving things on when you don't need them on is a waste of money? Do you need a smart meter to tell you that?
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The B type should trip between 3 and 5 times rating on the magnetic part of unit, so at 5 times that gives the well known 1.44Ω for a 32A type B however with volt drop this figure may not be enough so the regs said give an extra 5% so 1.38Ω is now used.
However with an incomer of 0.35Ω to comply with volt drop the line - neutral 0.94Ω or 245 amp prospective fault current. Since the earth wire is often smaller than neutral it could be 1.38Ω earth loop is exceeded before the 0.94Ω line - neutral, however it needs two decimal places and one should use at least 250 mA to measure which means a normal multi meter is not good enough.
I have questioned the 0.35Ω figure, for 230 volt that means at 65A it would still be within the 207 volt permitted, however it may be less than 0.35Ω and works on the supply could mean the figures alter over time, so if measured at 0.25Ω should the limit be 1.28Ω to allow for the loop impedance to change? No one has really given me an answer.
With a fuse it did not really matter if one exceeded to loop impedance in the tables a little as it only resulted in a few milliseconds more to trip, but with a MCB once one exceeds the loop impedance needed to trip the magnetic part, there is a big jump to the time taken to trip on the thermal part of the trip.
However with an incomer of 0.35Ω to comply with volt drop the line - neutral 0.94Ω or 245 amp prospective fault current. Since the earth wire is often smaller than neutral it could be 1.38Ω earth loop is exceeded before the 0.94Ω line - neutral, however it needs two decimal places and one should use at least 250 mA to measure which means a normal multi meter is not good enough.
I have questioned the 0.35Ω figure, for 230 volt that means at 65A it would still be within the 207 volt permitted, however it may be less than 0.35Ω and works on the supply could mean the figures alter over time, so if measured at 0.25Ω should the limit be 1.28Ω to allow for the loop impedance to change? No one has really given me an answer.
With a fuse it did not really matter if one exceeded to loop impedance in the tables a little as it only resulted in a few milliseconds more to trip, but with a MCB once one exceeds the loop impedance needed to trip the magnetic part, there is a big jump to the time taken to trip on the thermal part of the trip.
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A standard multimeter is unlikely to have the accuracy to measure low impedance in any meaningful way. You may be able to draw some vague conclusions, but I wouldn't rely on the readings to estimate cable length etc. your measurement technique is likely to affect the readings enough that the error will dwarf your measurements
You can see the electricity being used on an ordinary meter. Either a wheel going round or a flashing red light.
Reading a meter once a month is not exactly a chore is it?
Every smart meter installed costs everyone else with increases to their bills. It does not save you money as the unit rates don't alter. In fact it costs you money as you have to buy batteries for the remote unit. Smart meters are pushed on lies.
I'm not a fan of smart meters, however we will all pay anyway. Because the government will fine companies if they don't fit them. And we will end up paying the fine!
SSE have already been fined.
So if people are stupid enough to have them, let them! They can at least test them for us.
SSE have already been fined.
So if people are stupid enough to have them, let them! They can at least test them for us.
Quick update on this. On page 01 I advised later on that the new ring extension was giving me about 5ohms on the live and neutral hence being extra cautious about cutting it in to the main ring, I have tested the sockets point to point and it looks like there is one leg of the cable which is giving me the high reading, all the others are giving me 0.1ohms. Kinda luckily it's the shortest leg going to the first socket so i'll get that part of the cable replaced.
The smart meter is being installed next week (I know they seem very unpopular) and i'm gutted the person fitting it won't be a proper electrician, I would have loved to have offered him a few quid cash to do me a new consumer unit whilst here, we both get a good deal but, that's the way it goes I suppose.
There has been a bit which has been playing on my mind which is the advice given saying "...external Line and Earth impedance (Earth Fault Loop Impedance) (Ze) to see if it is within the limit which will blow your 30A fuse instantly in the event of a fault." and also the bit advising underfloor cables need to be protected by an RCD. For these reasons, I will make the ring extension perfectly ready to cut in but will get a real electrician in to put me in a new consumer unit with RCD protection, doing away with the old fuse box and hopefully a decent quote to get the kitchen put on it's own circuit at the same time, I think these two items from a real electrician will give me that peace of mind... if it was just me in the house i'd probably take punt but, wife and kids to consider, some things are just worth knowing my limits and paying. There is a guy round the corner where I live who people say is a decent chap so i'll give him a tap and cut in the extension together at the same time as the above work.
I appreciate the help and info on this thread, honestly it has been fantastic. I'll report back when it's all complete.
The smart meter is being installed next week (I know they seem very unpopular) and i'm gutted the person fitting it won't be a proper electrician, I would have loved to have offered him a few quid cash to do me a new consumer unit whilst here, we both get a good deal but, that's the way it goes I suppose.
There has been a bit which has been playing on my mind which is the advice given saying "...external Line and Earth impedance (Earth Fault Loop Impedance) (Ze) to see if it is within the limit which will blow your 30A fuse instantly in the event of a fault." and also the bit advising underfloor cables need to be protected by an RCD. For these reasons, I will make the ring extension perfectly ready to cut in but will get a real electrician in to put me in a new consumer unit with RCD protection, doing away with the old fuse box and hopefully a decent quote to get the kitchen put on it's own circuit at the same time, I think these two items from a real electrician will give me that peace of mind... if it was just me in the house i'd probably take punt but, wife and kids to consider, some things are just worth knowing my limits and paying. There is a guy round the corner where I live who people say is a decent chap so i'll give him a tap and cut in the extension together at the same time as the above work.
I appreciate the help and info on this thread, honestly it has been fantastic. I'll report back when it's all complete.
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High reading is better than a low reading.
Based on my experience, I'd have to question the competence of some of them to even swap a meter
Not a chance even if he was a proper sparky. He'd not have the time, they are given an impossible number of jobs to do in one day so no chance of taking an extra few hours at your place.
And then there's the legal issues. Consumer unit change is a notifiable job - the meter fitter wouldn't be able to do it through any scheme since he'd be doing it as "a foreigner", so you'd have to pay for a Building Control notice in advance - and that can be ridiculously expensive depending on where you live. Oh yes, and he'd not be insured - so if he did something wrong and your house burned down - you could be in trouble.
That does indeed sound like a good idea.
I'm intrigued, Loopy. How long do you think it takes to change a consumer unit?
It is called corruption. There is no place for it in a civilised society.
Probably a full day at least to be fair. In my mind I was just thinking for a few hundred quid cash, i'd call the company and say "this job has got problems, it's going to take me all day to fit this meter", get paid by the company and by the the house owner or, he could come back on a day more suitable. Days like these are probably long gone though, it's all been screwed down
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