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Topic Title: Replacing Switchgear and
Topic Summary: falling foul of disconnection times
Created On: 27 December 2017 06:02 PM
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 02 January 2018 08:33 PM
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mapj1

Posts: 10414
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not sure if you meant "psychic" rather than "holistic". Agree, more info needed.

-------------------------
regards Mike
 03 January 2018 08:05 PM
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nad

Posts: 410
Joined: 14 January 2005

WB2 - the switchfuse, overload and starter are all in the MCC panel.
All apologies for vagueness but was interested in the bigger issue - the 17th ed. reduction in disconnection times to all circuits under 40A, and the subsequent impact on alterations to installations where the existing cabling does not meet the new disconnection times.

-------------------------
Nad

*Regularly edited due to spell cheque misdiagnosis
 03 January 2018 08:12 PM
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paulskyrme

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Nad,
Could this be considered part of a machine as would be covered by the machinery Directive / Supply of Machinery Safety Regulations?
 03 January 2018 08:32 PM
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nad

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Hi Paul, My initial thoughts are no, as this is the fixed wiring in a factory and the MCC is acting as the Distribution Equipment. But I'd be happy to be corrected here?

-------------------------
Nad

*Regularly edited due to spell cheque misdiagnosis
 03 January 2018 08:57 PM
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paulskyrme

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Is it an MCC, or is it a machinery control panel, complete with PLC etc?
To me an MCC is a panel of circuit protection and motor starters in discrete cubicles.
This depends on what the motor is part of and the layout etc.

It's very difficult without seeing it I suspect.
 03 January 2018 09:42 PM
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nad

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Hi Paul, as you can guess panel building is not my sphere of work, I've become involved as I've been asked to look at the site cabling. It is a Motor Control Panel, with cubicles as you describe. At the risk of me being shot-down by others I'd have to check with the panel designers where the PLCs sit but this could well be within the panel. The motors are not part of the panel, these are part of the controlled field equipment, the conveyors, pumps, valves, etc.

-------------------------
Nad

*Regularly edited due to spell cheque misdiagnosis
 03 January 2018 10:19 PM
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paulskyrme

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Single incoming supply for all of the equipment?
Or, equipment interlinked to perform a specific sequence of operations?
Manufacturing plant?
Common control system?
If you don't want to put the plant lacation.name in open forum, PM it, but, it may well be that it is not covered by BSS7671 in which case the 5s rule still applies, and there are a few other idiosyncrasies.
 04 January 2018 07:30 AM
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Nedryerson

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Nad,

Been to site yet ? We are on the edge of our collective seats here awaiting the test results !

This pales the maternity hospital into insignificance,

Ned
 04 January 2018 05:52 PM
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nad

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Ned, not yet but if it fails we'll just through some more copper at it.

Paul, its a large factory, with automated goods-in, processing and packaging lines. Its a complicated site, which has been added to and modified over the years so its likely a mix of those things. But generally an area will have one or more MCCs with a single incoming power supply and multiple outgoing power supplies and controls cabling to various pieces of remote equipment. There is an overall SCADA tying it all together. There are other items such as packaging lines which are clearly a single piece of equipment but this is not the case with the MCC I have been referring to.

I'd be very interested hear why certain systems fall under BS7671 and why others don't. What regs cover those that don't and what those 5rules are?

-------------------------
Nad

*Regularly edited due to spell cheque misdiagnosis
 04 January 2018 07:11 PM
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Weirdbeard2

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Originally posted by: nad



I'd be very interested hear why certain systems fall under BS7671 and why others don't. What regs cover those that don't and what those 5rules are?


BS 7671 applies to all fixed cabling from a surface clipped bell wire between a doorbell push switch and a self contained battery operated chime, to the fixed cabling between an expensive motor control centre and motor, but not all sections apply to everything.
 04 January 2018 08:08 PM
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iie63674

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Originally posted by: Weirdbeard2

Originally posted by: nad







I'd be very interested hear why certain systems fall under BS7671 and why others don't. What regs cover those that don't and what those 5rules are?




BS 7671 applies to all fixed cabling from a surface clipped bell wire between a doorbell push switch and a self contained battery operated chime, to the fixed cabling between an expensive motor control centre and motor, but not all sections apply to everything.

BS7671 does not deal with the internal wiring and devices of an assembly, which are covered by BS EN 61439 series.
 04 January 2018 08:37 PM
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Weirdbeard2

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Originally posted by: iie63674

Originally posted by: Weirdbeard2



Originally posted by: nad


I'd be very interested hear why certain systems fall under BS7671 and why others don't. What regs cover those that don't and what those 5rules are?



BS 7671 applies to all fixed cabling from a surface clipped bell wire between a doorbell push switch and a self contained battery operated chime, to the fixed cabling between an expensive motor control centre and motor, but not all sections apply to everything.


BS7671 does not deal with the internal wiring and devices of an assembly, which are covered by BS EN 61439 series.


Hi iie, just to be clear are you agreeing or disagreeing?
 04 January 2018 09:10 PM
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leckie

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Now I am really confused about this entire post, and the point of it.

The OP asked (I think) of the options if the max Zs allowed for an OPD is exceeded. So we have various options; additional protection by supplementary bonding; fault protection by an RCD; or rewire/ alter wiring to allow compliance by lowering the Zs. Originally the poster didn't seem to want to take on any of these options due to the difficulty of powering down (even though this would have to happen in order to connect the new motor control assembly).

Now the answer is to throw some copper at it! Why ask?
 04 January 2018 09:28 PM
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Alcomax

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A solution of sorts is in the first post. Stick a 32 amp switch fuse in, then down stream fit 40 amp OPD to make manufacturer happy.


Edit [ again ] above is wrong way round ! 40 switch fuse and 32 opd down stream

Edited: 04 January 2018 at 09:40 PM by Alcomax
 04 January 2018 09:46 PM
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paulskyrme

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Several errors in some of the last few posts.

The EN 61439 series only applies to power switchgear and the like, NOT any kind of machinery under the machinery directive as it is NOT harmonised to the machinery directive, therefore cannot be used to prove that the electrical systems of the machinery comply with the machinery directive.

The machinery directive and the low voltage directive are also mutually exclusive, it's one OR the other, NEVER both.

BS7671 clause 110.2(xi) excludes machinery as covered by the machinery directive, these are covered by EN 60204-1 in general, with lifting equipment covered by -32 and a couple of others.

So, the first thing to establish is whether BS7671 even applies at all, just because it's power wiring does not automatically mean it is covered by BS7671, factory equipment/machinery is often not included.

Generally if it's CE marked, it is not covered by BS7671, there are exclusions, like everything, but as a generalism, it's not far away.
 05 January 2018 09:02 AM
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Nedryerson

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Paulskyrme has hit the nail on the head.

When I was designing MCCs to BS5486 or whatever its called now we never gave a second thought to BS7671 and why would we, the 0.4 second disconnection times were probably never achievable.

Why, because between the fuses and the load was either a thermal/magnetic overload, VSD or a soft starter and the impedance these devices vary continuously.

Ned
 05 January 2018 09:40 AM
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AJJewsbury

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, the 0.4 second disconnection times were probably never achievable.

Why, because between the fuses and the load was either a thermal/magnetic overload, VSD or a soft starter and the impedance these devices vary continuously.

Our southern European cousins probably find our "Anglo Saxon obsession with controlling loop impedances" quite entertaining - being used to almost all their systems being TT, they'd just chuck in an RCD or two upstream and be done with it.

- Andy.
 05 January 2018 02:59 PM
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Weirdbeard2

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Originally posted by: paulskyrme



BS7671 clause 110.2(xi) excludes machinery as covered by the machinery directive, these are covered by EN 60204-1 in general, with lifting equipment covered by -32 and a couple of others.


So, the first thing to establish is whether BS7671 even applies at all, just because it's power wiring does not automatically mean it is covered by BS7671, factory equipment/machinery is often not included.

Generally if it's CE marked, it is not covered by BS7671, there are exclusions, like everything, but as a generalism, it's not far away


Hi Paul, I found this quote from a related past post :

Originally posted by: gkenyon

The machine includes the interconnections.

BUT

EN60204-1 requires inspection and testing after installation with the national "Wiring Regs" - in the UK, that's BS7671.



http://www.theiet.org/forums/f...tid=205&threadid=22955
 05 January 2018 05:00 PM
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Weirdbeard2

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Further questions for Paul, does bs 7671 not apply to the wiring between a heating system after a FCU which goes on to supply the controls, valves , pumps and heater?

How about a machine that happens to have cables run in escape routes would these cables be exempt from the requirements of bs7671 and its ok if they are able to drape down when there is a fire?
 05 January 2018 07:32 PM
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paulskyrme

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Originally posted by: Weirdbeard2

Originally posted by: paulskyrme







BS7671 clause 110.2(xi) excludes machinery as covered by the machinery directive, these are covered by EN 60204-1 in general, with lifting equipment covered by -32 and a couple of others.





So, the first thing to establish is whether BS7671 even applies at all, just because it's power wiring does not automatically mean it is covered by BS7671, factory equipment/machinery is often not included.



Generally if it's CE marked, it is not covered by BS7671, there are exclusions, like everything, but as a generalism, it's not far away




Hi Paul, I found this quote from a related past post :



Originally posted by: gkenyon



The machine includes the interconnections.



BUT



EN60204-1 requires inspection and testing after installation with the national "Wiring Regs" - in the UK, that's BS7671.







http://www.theiet.org/forums/f...tid=205&threadid=22955



Well I would have to disagree totally with Graham there, because the copy of EN 60204-1 that I have here, which is the current version harmonised to the Machinery Directive does not state that.
EN 60204-1 does have a requirement for testing, and that is detailed in clause 18.
IET » Wiring and the regulations » Replacing Switchgear and

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