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Hager mcb type MTN and NCN same bus bar.

Discussion in 'Electrics UK' started by aladinsane339, 24 Mar 2018.

  1. aladinsane339

    aladinsane339

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    If you can't work out how, you really shouldn't be doing this.

    It's unlikely that any circuit in a domestic setting could permit use of a type D 32A MCB.
    https://www.electricalsafetyfirst.org.uk/mediafile/100106752/master_EARTHFAULTLOOPtable.pdf[/QUOTE]
    But they do, and the manufacturers of compressors advise it, as for not being able to do this, hmm maybe your right but since my friend passed away I have done all the electrics, and at 68 yrs old I take your point, maybe I will get a spark to do it, just as my friend who was a spark did.
     
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  3. JohnW2

    JohnW2

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    If the inrush current were only for a small number of milliseconds, even a 16A Type B would require at least 48A to trip, and a 16A Type C (or 32A Type B) one would need at least 96A. However, I think you may be underestimating the possible duration of the start-up/inrush current, in which case lower currents than those might result in trips.
    See above.
    That may well be OK, but measurements would be needed to confirm that, which is one of the reasons you need an electrician.

    Kind Regards, John
     
  4. aladinsane339

    aladinsane339

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    I agree entirely, however somewhat conversely how many people who have compressors 3 HP do this, recently I have been looking for a second hand compressor, and the circuitry people try to run them off ,nothing short of amazing. A 13 A domestic supply is just not enough 2.2 KW drawing perhaps just short of 10 A would suggest a 240v 13 A supply would be capable, but, that does not take into account the start surge which would trigger the breaker to trip that is why I think 32 A mcb would manage it a lot better, certainly I think an isolated supply 16 A socket would, with a higher rating breaker be infinitely better than running a 3 HP motor off a 13 A socket, even if it was a dedicated 13A socket used in isolation, and from what I have seen, and I have now seen a few in my travels they are not, so put the kettle on and use the compressor, well I think that explains it all.
    I will probably get new a compressor with a brushless motor, they according to the blurb from manufacturers work from a 13 A supply without difficulty, but knowing me I will probably still still use it in isolation, by running cable direct from CU with the protection previously discussed.
     
  5. JohnW2

    JohnW2

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    Yes, we know that - although you may be underestimating how long it takes for a 13A fuse (in a plug) to blow.

    What I don't know is how long the inrush current/'start surge' is likely to persist (nor what the magnitude would be with your compressor). You spoke of 'milliseconds' and, if that were the case, the current flowing for, say, 10 milliseconds required to blow a 13A plug fuse would be something between 100A and 300A, and the current flowing to trip a 16A Type B MCB would be about 80A (and a 16A Type C about 160A). However, as I said before, I think you may be underestimating the duration of the startup current.

    Kind Regards, John
     
  6. aladinsane339

    aladinsane339

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    I do not know that either, it is what I have read from a manufacturer through a dealer of compressors, where they say 'must have a 16 A dedicated supply as a way of objectively saying, I think, not for a 13 A domestic supply. Brushless motors seem to have no such problem, even at 3 hp many compressors that are seemingly[ please note the word 'seemingly as I do not know] and will not know until I suck it and see so to speak,whether they have start up problems or not, but it may well be the way to go...really I just do not know and I would be guessing.

    I put this post up there as clearly as possible, and whatever short comings that are having the contributors guessing, I cannot help with, but they can help me by giving me their considered opinion in not so many words 16 A 2.5 mm cable a run of less than 3 metres direct from the CU 32A breaker, 16 A commando blue socket or not please, or I may just go and do it. Really as for building regulations how many people keep to these, not quite sure myself but I suspect not that many, judging by what I have seen, builders thwart these themselves, particularly in this 6-7 year old house,it has had more problems than one could throw a stick at. Thanks to everyone who has contributed much appreciated, think maybe it is time to wrap all this up now, as I am getting confused with it, time to maybe suck and see when I get this compressor to replace my Ingersoll Rand, that after 68 yrs the pump finally gave up and I cannot get the parts.Now I must get back to trying to establish why this ncn will not fit his bus bar.
     
  7. JohnW2

    JohnW2

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    Frankly, in terms of what we are talking about, I don't think that the difference between 13A and 16A is either here nor there! For a start, in most situations (particularly very-short lived 'overloads'), a 16A MCB would probably trip before a 13A fuse blew.
    That's easy. 2.5mm² cable protected by a 32A breaker is not acceptable, other than in very particular circumstances, which do not apply in your case. If it had a 32A breaker, then the cable would have to be at least 4mm², or possibly 6mm², depending on how/where it was routed.

    2.5mm² cable on a 16A MCB almost certainly would be acceptable, and would very probably be adequate for your purposes (maybe a Type C MCB if measurements indicated that the circuit could support it).

    Kind Regards, John
     
  8. ban-all-sheds

    ban-all-sheds

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    The question about Building Regulations was because the advice you need is affected by whether you plan to comply, not because we are a vigilate BR enforcement group.

    But as for manufacturers advising breaker ratings, if the loop impedance you need for a C32 or D32 is already less than your external supply impedance, then no matter how short your circuit cable you can't have it.
     
    Last edited: 25 Mar 2018
  9. JohnW2

    JohnW2

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    If the running current really is under 10A, then a C10 or even D10 might be adequate, and much more likely to be possible in terms of loop impedances (max Zs for D10 is 1.09Ω). ... or, as I have suggested, maybe a C16.
     
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  11. aladinsane339

    aladinsane339

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  12. JohnW2

    JohnW2

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    I think you have been given fairly clear advice, which should not really be confusing - the important parts of which I repeat below.
    You have told us all that before and we have responded appropriately. To summarise ....

    Whilst you might well get away with a 13A fuse in a plug, that would clearly be a bit iffy. However, as I told you, if the startup current is only "45A for a few milliseconds" then a B16 MCB would probably be OK but, to be 'extra sure', you could use a C16 one.

    With the currents (start-up and running) indicated, there is not really any need to move to a 32A MCB (a B32 one would take up to 160A before tripping, and a C32 would need up to 320A to trip) - but if you nevertheless decided you wanted a 32A MCB (a B32 would surely be sufficient, if the figures we're being told are even remotely correct), you would need to wire the circuit in at least 4mm² cable (but 2.5mm² cable would be fine for a 16A MCB).

    Particularly given the short cable length you are talking about, your installation would almost certainly be OK with a C16 or B32 MCB, but if (despite what I've said) you wanted a C32, you would need to get an electrician to check (by taking measurements) that your electrical installation was suitable for it.

    Kind Regards, John
     
  13. ban-all-sheds

    ban-all-sheds

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    Complying, or not, with the Building Regulations is a decision for you, not an electrician, and it has absolutely nothing to do with what breaker rating you have.
     
  14. aladinsane339

    aladinsane339

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    ,if the figures we're being told are even remotely correct), you would need to wire the circuit in at least 4mm² cable (but 2.5mm² cable would be fine for a 16A MCB).
    Kind Regards, John[/QUOTE]

    No offence but I am not quite sure what your suggesting here, but if your indicating I have somehow conjured these up, indeed to heat up this debate, perhaps you would like the link to this sale of this compressor site, or maybe I am interpreting your speak wrongly, only you know. I take on board what your saying and what other contributors have said to, and will follow this advice, if it works all well and good, but remember it is not me who is saying this, it seems to be a condition of sale warranty and it is the manufacturer through the dealer asserting these statistics,and condition of sale, that is why I cut and pasted the said specifications and words from the horses mouth and for no other ulterior reason. Firstly I will get a sparks advice and go from there, sadly my best friend passed away quite recently[ he was a spark] so I no longer have him in which to ask and confide, more is the pity.

    Thanks one and all for your kind contribution, kind advice and information, much appreciated.
     
  15. JohnW2

    JohnW2

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    Also with no offence intended, particular for someone who has been a member of this forum for only two or three days, I think you are being far too sensitive and suspicious of the advice you have been given.

    Anyway .... I meant/intended nothing other than exactly what I wrote - that, if the information on that website about the compressor's start-up current and its duration is correct, then a C16 or B32 MCB would be adequate - BUT that (as a matter of pure fact), if you wanted to go with the 32A one, 2.5mm² cable would not be acceptable and you would have to use at least 4mm².

    Only those (presumably the manufacturers) who put the information on the website could you tell you why they suggested a C32 MCB (which is rather odd, given that they also say that a lot of their customers manage with a 13A-fused supply)- but, as I have also told you, if you did want to follow their advice and go with a C32 MCB, you would then need to get an electricians to take measurements to confirm that a C32 would be safe (and compliant with regulations) in your installation.

    Kind Regards, John
     
  16. 333rocky333

    333rocky333

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    As for the mcbs MTN is a 6000A breaking capacity and NCN a 10000A breaking capacity, i always thought the profiles were the same
     
  17. Iggifer

    Iggifer

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    They are, save for some superficial notches around the terminals

    B58991F5-EC51-40A0-98BB-7A75A21E295B.jpeg 306E7D46-08E2-4B94-9154-B80615BC689A.jpeg
     
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