I want to use multicore cabel for domestic instalation ,but i dont have 2,5 mm cable. But I have only 4 core by 1.5 mm. Can I join the cores 2 by 2 to reach a beter ampacity? And what MCB for this combination? The cable marker is - H05 V V - F
Not viable.
This would invoke the "conductors in parallel" part of the regs, and it just isn't viable in the scenario you describe as an alternative to buying the correct 2.5mm cable in the first place.
But 1.5 mm by two is a 3mm. Isn"t this combination supposed to carry a better load than a 2.5mm.
Thank you!
Yes, but if you're determined to breach the wiring regulations why bother asking in the first place ?
Andy
I'm asking because I dont have experience in that kind of work. I juist want to know if it is possible to use it and how much load it is carryng. And whot ampacity of MCB to use for this. I juist want to ack someone with better experience than me.
"" I want to use multicore cabel for domestic instalation ,but i dont have 2,5 mm cable. But I have only 4 core by 1.5 mm. Can I join the cores 2 by 2 to reach a beter ampacity? And what MCB for this combination? The cable marker is - H05 V V - F ""
Thank you!
This reminds me of my impoverished days 20 years ago when I'd just bought my house and the interest rate was about 15 percent.
I had been given a second hand shower - so I bought some bright orange 3 core 13 amp FLEX from J Bull Electrical - I was going to double it up ;-)
A bit later I found some 10mm in a skip and hoarded that for "several" years.
Fortunately I never actually got round to using either ......
I'm asking because I dont have experience in that kind of work. I juist
want to know if it is possible to use it and how much load it is carryng. And whot ampacity of MCB to use for this. I juist want to ack someone with better experience than me.
"" I want to use multicore cabel for domestic instalation ,but i dont have 2,5 mm cable. But I have only 4 core by 1.5 mm. Can I join the cores 2 by 2 to reach a beter ampacity? And what MCB for this combination? The cable marker is - H05 V V - F ""
Thank you!
As a matter of interest, what's the rationale for banning this? It presumably would *work* - is it just that it may cause confusion to anyone working on it in future?
I imagine one issue is current sharing between the conductors. Whilst the current share may be close to 50/50 when installed, any slightly loose connection or corrosion of one conductor could cause one conductor to end up carrying most of the current. not good.
In theory yes, but it is probably against regulations.
sponix
Thanks! But anyone can tell me what kind of MCB I must use for this cable? May be 32 Amps or lower rate?
""" I want to use multicore cabel for domestic instalation ,but i dont
have 2,5 mm cable. But I have only 4 core by 1.5 mm. Can I join the cores 2 by 2 to reach a beter ampacity? And what MCB for this combination? The cable marker is - H05 V V - F """
If you're going to insist on using this cable doubled-up, why not just use a nail in the fusebox? Might as well get hanged for a sheep as a lamb..
No. The measurement is the diameter of the core, but the current carrying capacity is related to the cross-sectional area.
Two by 1.5mm has an area of 3.53 mm2
One by 2.5 has an area of 4.91 mm2.
No. You would need three 1.5mm cores to carry more than a 2.5mm core - and that assumes you can get all three cores to carry their fair share of current. That is a pretty poor assumption in the long run (which is almost certainly why parallel conductors are essentially banned in the regs).
I think you're wrong. The measurement _is_ the cross-sectional area i.e
1.5mm^2If doubling a cable diameter in this fashion is not Kosha then how come a Ring Main is legal ?
chris.
That is correct. A 2.5mm cable actually means a cross-section of 2.5
*square* mm - *not* a diameter of 2.5mm - so 2 x 1.5 *does* equal 3! [One might be forgiven for believing that a 2.5(sq)mm cable was 2.5mm in diameter because it's relatively close to that - at about 1.8mm. However, the difference is very obvious with larger cables. For example, a 10 (sq)mm cable has a diameter of only about 3.6mm.]On 16 Nov 2005 02:14:49 -0800 someone who may be "p" wrote this:-
At least you are honest about that.
It is possible to do most things, but not always advisable. Others have given reasons from the wiring regulations why your course of action is not advisable. I will give you another reason, you could set the building on fire.
How much load a cable carries depends on the load attached to it. So far you have not said what the load is, or the type of circuit you are interested in.
The rating of an MCB depends on the load and type of cable it is protecting (plus a few other things).
Here is some advice. Don't try doing things with electricity, unless you thoroughly know what you are doing. You may well kill yourself, or someone else.
The way you keep on posting, we've switched from "could tell you" to "won't tell you".
You are doing something that is forbidden, that is forbidden for good reason, and that is only "useful" as a sheer cheapskate measure. A major cause of electrical problems is people trying to save a little money like this. This is not a good thing and I doubt if anyone wants to encourage you in doing it.
You're clearly going to do this anyway, but don't ask us to assist you.
30A/32A ring circuit in 2.5mm^2 cable (or 1.5mm^2 MICC) is explicitly excluded from Conductors in Parallel regs.
Yes, that's one issue. I don't have the regs on me, but IIRC, the conductors are required to be the same length, and without any branches. You must show by calculation that the overload and fault current protection will operate correctly for each conductor. For the fault current protection, you have to consider additional types of fault, such as one conductor shorting to ground, passing current directly from the supply, plus that backfed from the other end via the other conductors. Also the case where one conductor breaks and only the backfed path is grounded, so you have a higher earth fault loop impedance than you might otherwise expect. For overload protection, you have to consider what happens if one conductor breaks (without shorting). There are probably more issues I don't recall too.
You would probably end up having to use separate but ganged breakers for each conductor (and in the case of more than two conductors in parallel, possibly ganged breakers at both ends of the cable). There is simply no excuse for doing any of this in domestic installation -- it is far cheaper to buy the correct cable in the first place. Also, H05VV-F is flex anyway, IIRC.
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