HELP! This is doing my head in!

[VoltzElectrical]

Can someone please tell me WHERE in the regulations I can find where it says that cable connected to busbars operating in higher than normal temperatures must have its insulation replaced with heat resistant insulation. I have been scanning for over an hour now and my temple is throbbing.

`cheeers all.

 

[steptoe]

suitable for external influences?????????

 

[Sidewinder]

Voltz,

Try 421.1, 421.2, 421.3, 421.4, 522.1 group, table 52.1, 523 group, 526.1, 526.2 and see if these help?

 

[VoltzElectrical]

Sidewinder, I respect you, and you're a local brethren. When i say that i have been scanning for two hours, all these generalized wordings have been digested. What i am really after is practical application of these regs. Here is a hypothetical example. i have a series of circuits to connect into a busbar chamber. How do I know what the normal operating temperature is, or supposed to be? lets suppose that it is above the 'normal' temperature (forgetting that I don't actually know). What is to be done? I have a 40 metre run of cable that is otherwise run in acceptable ambient temperature. what should i do with the 50cm that is inside the chamber? Who thinks of these questions? Where and at what temperature would I find these 'above normal temperatures'??

many thanks, and await your expertise.

Loved your rant earlier!

---------- Post Auto-Merged at 19:40 ---------- Previous post was made at 19:38 ----------

http://www.tlc-direct.co.uk/Book/4.3.1.htm

here is a ink to an example of what I mean

---------- Post Auto-Merged at 19:41 ---------- Previous post was made at 19:40 ----------

http://www.tlc-direct.co.uk/Book/4.3.1.htm

 

[Sidewinder]

Voltz,

Just realised who you were originally!

You changed your user name didn't you!

I'll have another look later, got to finish this report!

Not much left now, conclusions & other recommendations only left to do!!!

 

[VoltzElectrical]

Steptoe.. step up to the plate dude. What's to be done? I give you a bus bar. What are the 'normal' temperatures? what is 'above normal'? How would you know? and what is to be done? easy peasy questions I look forward to your expert advice on. Thanks in advance.

---------- Post Auto-Merged at 19:46 ---------- Previous post was made at 19:45 ----------

Love you man. help me out. one day i'll return the favour. take it easy

 

[Evans Electric]

Voltzy , I've heard of that reg. but never seen anyone bother with it. Unless you think the insulation will turn soft and short against the next bar just lug 'em up and bolt 'em on . Is the chamber in a very hot situation or what ?

 

[VoltzElectrical]

It's just a hypothetical situation, which the exam writers love to set. My problem is that I compare every hypothetical situation against every real life situation that I come across. I have come across many a situation, but none that has given me experience of this type of scenario. I would love to learn about real life solutions to these problems from the likes of you, sidewinder, steptoe etc.. I have a reasonable grasp of the regs. I passed my 17th last friday (59/60) but too often they speak in generalizations which i fully grasp, but I want to know HOW to implement them in a practical sense.

 

[Evans Electric]

OK, thing is , in 50 years of industrial & commercial work, I don't think I,ve ever bothered with doing what you said . I've done it when connecting ordinary SWAs to the busbars of furnaces etc. where the cable itself was OK but the tails were exposed to heat because the busbars were conducting heat .

I don't imgine for a moment that exam setters actually live on this planet , let alone have spent any time out in the "real world" , practicing our trade.

Sidey seems to know you , who were you before and why a name change ,I wonder?

 

[Nicky Tesla]

Above say 70 or 90 degrees depending on what cable you are using i suppose.

I bet in physics you could work out the heat produced in a conductor of a certain resistance and csa and surface area etc to a particular current, but ill let you look for it. :|

 

[steptoe]

there is a table that works out the resistance change from 20 - 70 celsius ,

if you are really that concerned then simply work out the rating required at 20 and up one size,

I cant really see a lot of use for this in a normal situation,

are you going to be running this cable close to its max.?

then you probably need to upsize anyway to allow for fault current, ie, 3/4 rule of thumb, (or is it .8 nowadays, I can never remember if its friday or wednesday)

remember though that different types of insulation are rated different anyways, = PVC - Vs - XLPE

 

[Sidewinder]

Voltz,

I've had a think about this and I can't recall an exact example either.

The bus bars should run at a "suitable" temperature.

If this is 70 deg then you need 70 deg insulation.

If this is 90 deg then you need 90 deg insulation.

This info may well have been lost in the Arc, however, since CDM came in there is a statutory legal duty to record such information in the building log book of large installs IIRC, though my head is a bit fuzzy now its late.

If you don't have the info I would say you can't make the exact call.

If in doubt then you could strip off the insulation and sleeve with high temp stuff?

You could if your overload current was limited to a level that would not mechanically deform the connecting conductors under maximum fault current in your branch circuit leave them bare, after all the bus bars are bare!

Will try to think of something else, but I don't hold much hope, sorry.

Perhaps a bit too abstract a Q!

 

[Chr!s]

Busbar temps are limited to those in BS 159 and BS EN 60439-1, 526.4 terminations to the busbar

BS 159 and BS EN 60439-1, these standards give recommendations on how 526.4 is to be met