any idea pls

[L Plate]

Why it is important to consider the method of installation for current capacity?

thanks guys and have a nice day

 

[SPECIAL LOCATION]

Why it is important to consider the method of installation for current capacity?thanks guys and have a nice day

Basic ground rules:-

1. Electricity ALWAYS generates heat as it passes along a cable.

2. A physical cable can only withstand a certain amount of continual heat before the insulation starts melting.

3. More current = more heat

4. The cable must be able to dissipate any heat generated.

5. A cable suspended in open air can release more heat than a cable squashing in a confined space or buried under insulation.

6. If several cables are bunched together (e.g. trunking) they will all be generating heat and make it harder for adjoining cables to dissipate their heat.

Reading:-

Appendix 4 page 259 onward BRB

Page 52/53 On site guide tables with specific reference to flat T&E PVC cables. etc...

SO the same physical cable size can carry MORE current if installation method does NOT restrict the air flow around it.

 

[Brian 157]

Mainly the effects of temperature, if a cable is run in insulation (for example) heat cannot dissipate so easily so it cannot take the same current (which causes heat) as if it was surface clipped. Cables run together will all generate heat so this will have to be taken into consideration also. Appendix 4 of BS7671:2008 covers current-carrying capacity & goes into much more detail than I can here & contains the correction factors & tables showing current carrying capacities for different cabkes & installation methods.

 

[L Plate]

Basic ground rules:-1. Electricity ALWAYS generates heat as it passes along a cable.

2. A physical cable can only withstand a certain amount of continual heat before the insulation starts melting.

3. More current = more heat

4. The cable must be able to dissipate any heat generated.

5. A cable suspended in open air can release more heat than a cable squashing in a confined space or buried under insulation.

6. If several cables are bunched together (e.g. trunking) they will all be generating heat and make it harder for adjoining cables to dissipate their heat.

Reading:-

Appendix 4 page 259 onward BRB

Page 52/53 On site guide tables with specific reference to flat T&E PVC cables. etc...

SO the same physical cable size can carry MORE current if installation method does NOT restrict the air flow around it.

Thanks a lot SL , this would be a big help for me .. I know i cant offer you this Guiness Drink since its too early , I have this for you instead

http://topnews.in/healthcare/sites/default/files/Starbucks-Coffee1.jpg

 

[L Plate]

Mainly the effects of temperature, if a cable is run in insulation (for example) heat cannot dissipate so easily so it cannot take the same current (which causes heat) as if it was surface clipped. Cables run together will all generate heat so this will have to be taken into consideration also. Appendix 4 of BS7671:2008 covers current-carrying capacity & goes into much more detail than I can here & contains the correction factors & tables showing current carrying capacities for different cabkes & installation methods.

thank you

 

[SPECIAL LOCATION]

Thanks a lot SL , this would be a big help for me .. I know i cant offer you this Guiness Drink since its too early , I have this for you instead http://topnews.in/healthcare/sites/default/files/Starbucks-Coffee1.jpg

cheers...... :x

But...

wheres the bloomin biscuit for me to dunk? ]

ROTFWL :coat

 

[L Plate]

cheers...... :x But...

wheres the bloomin biscuit for me to dunk? ]

ROTFWL :coat

Oh i thought you are in a hurry so i did not bother the biscuits