Would a CT meter be an option? It should allow reading of higer currents without occupying a lot more space.
Din mounted KWH meters.
- Thread starter Mrdjc
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Essentially yes. 433.1.1(iii) of the regs says:Thank you very much for clarifying thatSo, if I understand this correctly:
So I can say (Coefficient of fuse) x In <= Iz x 1.45 ?
(I2 being 1.45*In for a Type B MCB etc. - so that's a slightly contorted way of requiring Iz ≥ In)
433.1.100 then goes on to indicate that 433.1.1(iii) (as above) applies in the case of fuses to BS 88-2 and BS - 88-3 or MCBs to BS EN 60898 or BS EN 60947-2 or RCBOs to BS EN 61009-2 - for all of which the 1.45 figure is roughly correct. However, in relation to BS 3036 semi-enclosed fuses, 433.1.101 says that In must not exceed 0.725*Iz, since it's '1 hour factor' is much higher than 1.45.
Does that all make sense?
Kind Regards, John.
Further to RF, the OWL system kit? Display could then be located wherever convenient.
Indeed - and if, as indicated, accuracy is not really an issue, it would probably be fine for the job.
If one wants accuracy, it's a different matter - a CT-based meter only measures current and therefore has to make an assumption about an unchanging voltage (which may not even be user-programmable, hence may be preset to, say, 230V) and a unity power factor.
Kind Regards, John.
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They are ok for monitoring, but they do not measure voltage so are not suitable if accurate metering is required.
I'm sure that CT meters I've installed measured voltage directly and current via a CT, but it has been a while since I last fitted one.
All of the 'consumer' ones I've seen have simply had a split-core CT to measure the current and have been powered either by batteries or a ELV power supply, hence have had no way of knowing about either voltage or power factor.
Kind Regards, John.
Sorry I meant proper CT meters as used by electricity suppliers etc.
The energy monitors like the owl linked to above do not measure voltage.
The energy monitors like the owl linked to above do not measure voltage.
Indeed. I suspect, but do not know, that the 'proper CT meters' may be pretty expensive. In fact, when I was looking around last night, I came across one of those 32A 1-DIN meters for around £25, with an optional extra of an £80 CT which they seemed to be suggesting could be used with it to extend it's current capability!
Kind Regards, John.
It does have to be kind of accurate, as she will be working out how much she needs to pay towards the total bill.
Using the Inductive type CT ones I have no idea how accurate they would be, without measuring Power Factor and all that malarky first.
The idea of a DIN one means its neat and its tidy and fits inside the CU box without any issues, and its all in one place.
The ABB ones refer to their Rating being Imax with no overcurrent mentioned.
The Countis one refer to their rating being:
Permanent overload (Imax) 63 A
Short-time over-current 1890 A max for 10 ms
I wonder if that can be computed backwards...
Say 91.35 (1.45*In) for X time.
What's the worst that could happen.. It overheats and melts the plastic then catches fire?
Using the Inductive type CT ones I have no idea how accurate they would be, without measuring Power Factor and all that malarky first.
The idea of a DIN one means its neat and its tidy and fits inside the CU box without any issues, and its all in one place.
The ABB ones refer to their Rating being Imax with no overcurrent mentioned.
The Countis one refer to their rating being:
Permanent overload (Imax) 63 A
Short-time over-current 1890 A max for 10 ms
I wonder if that can be computed backwards...
Say 91.35 (1.45*In) for X time.
What's the worst that could happen.. It overheats and melts the plastic then catches fire?
Yes, I can understand that. However, if you used a couple of cheapo CT-based consumer 'energy meters', one for House A and a 3-phase one for the whole installation (or maybe just a second 1-phase one for House B, ignoring Phase 3), you ought to get a pretty accurate figure for the proportion of the total that was attributable to her, since inaccuracies do to voltage and power factor will largely cancel out.
Where did you get that 10 ms from? I'm not sure what they mean by a 'permanent overload' of 63A - do you think they will mean 63A on top of the rated 63A - i,e, 126A in total?
That would be assuming an awful lot, much of which may not be true
However, if they do mean that, for the 63A Countis one, 126A is OK continuously, and presumably more than that for 'less than continuous' then one might guess that a 32A one could take around 64A continuously (and more than that non-continuously) - but guessing is obviously never a safe basis on which to proceed!That's about it - followed by the house burning down in the worst case.It What's the worst that could happen.. It overheats and melts the plastic then catches fire?
Kind Regards, John.
That's quite a smart observation there actually, if monitoring everything using CT stuff, it would give a percentage, then take that percentage from the REAL (Supplied by Electricity board) meter.
But still, that involves calculating stuff, and having to buy multiple meters
I got the 10ms from here:
http://www.socomec.com/webdav/site/Socomec/shared/SCP/pdf_catalogue/GB/cat_CountisE10-gb.PDF
It gives Imax as 63A, as the maximum load which the device can permanently handle for infinity time.
Their wording is a bit iffy but I think that's the way they imply it.
The "reference" current is 10A, and minimum is 0.5A
I think its more legal cover than anything that data-sheet
I just graphed an exponential function for 0.01s 1890A to 3600s (1 hour) and 63A... I don't think I'll be relying on it any time soon...!
It would be nice if they gave a graph that you could see what kind of overload is permissible for what period of time.
Another alternative is to separate the CU into two different sections with 32A each, but since they are around £30,- and the extra wiring that would be required, not to mention the extra space in the CU it would add up to almost the same as a 63 or 65A one.
Still, somewhere between Iz Ib and I2 You'd hope that the rating of the meter would be included in that without it going into melt-down mode.
Re the Fire risk
Current "fusebox" is made out of wood, with 1950's aluminium wiring that has not been tightened or inspected for at least 40 years, and most the Bakelite covers are either missing or damaged.
Scary.. but it works.. !
I could add a whole heap of images to this forum that would scare people..
But still, that involves calculating stuff, and having to buy multiple meters
I got the 10ms from here:
http://www.socomec.com/webdav/site/Socomec/shared/SCP/pdf_catalogue/GB/cat_CountisE10-gb.PDF
It gives Imax as 63A, as the maximum load which the device can permanently handle for infinity time.
Their wording is a bit iffy but I think that's the way they imply it.
The "reference" current is 10A, and minimum is 0.5A
I think its more legal cover than anything that data-sheet
I just graphed an exponential function for 0.01s 1890A to 3600s (1 hour) and 63A... I don't think I'll be relying on it any time soon...!
It would be nice if they gave a graph that you could see what kind of overload is permissible for what period of time.
Another alternative is to separate the CU into two different sections with 32A each, but since they are around £30,- and the extra wiring that would be required, not to mention the extra space in the CU it would add up to almost the same as a 63 or 65A one.
Still, somewhere between Iz Ib and I2 You'd hope that the rating of the meter would be included in that without it going into melt-down mode.
Re the Fire risk
Current "fusebox" is made out of wood, with 1950's aluminium wiring that has not been tightened or inspected for at least 40 years, and most the Bakelite covers are either missing or damaged.
Scary.. but it works.. !
I could add a whole heap of images to this forum that would scare people..
I'd say that the OWL is probably still a good contender for the job, it just has a slight risk of under-reading, but that wouldn't have too much impact if you were to say round up the price reading it gives and set that much aside.
Yes, but the calculation is trivial and if, as I suspect, in relation to the big picture, the garage/workshop (Phase 3) consumption is minimal, then you'd only need two CT meters, and you can pick them up over here for £25 each or less. Even if you wanted to include Phase 3, hence three meters, that's still significantly cheaper than any of the 63/65A meters you've found - and there's no work involved; just clip the meters onto cables, and you're done!That's quite a smart observation there actually, if monitoring everything using CT stuff, it would give a percentage, then take that percentage from the REAL (Supplied by Electricity board) meter. But still, that involves calculating stuff, and having to buy multiple meters
As you say, odd wording - but I guess it has to mean roughly what it says - that, although described as a 63A device, 63A is also the absolute maximum continuous current. If the 32A ones are similarly described, that could mean that their absolute max continuous current is also 32A.It gives Imax as 63A, as the maximum load which the device can permanently handle for infinity time. Their wording is a bit iffy but I think that's the way they imply it. The "reference" current is 10A, and minimum is 0.5A I think its more legal cover than anything that data-sheet
I think you'd be well advised not to!
Nice, perhaps, but it would involve them in a lot of destructive testing (the 30*I for 10 ms figure probably rates to a 'pass/fail' test which they always pass) - and would, of course, tend to encourage people to do iffy things (beyond the continuous rating) with the products.
Kind Regards, John.
Agreed - or, even better (as I've suggested to him) two (or even three) OWLs.
Kind Regards, John.
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