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#137152 06/02/03 06:07 PM
Joined: May 2003
Posts: 107
J
james S Offline OP
Member
1. when installing a ceiling fan is it a requirement to fuse down the feed of the lighting circuit if not is double pole isolation required?

--------------------------------

2. when installing extractor fans ( the type that run on after the light has been switched off) in toilets/bathrooms, is it a requirement to isolate all three live conductors L , switch L AND NEUTRAL . and does this also need to be fused down from the lighting circuit?

ps i do have a copy of BS 7671 and on site guide, but sometimes find it so hard to come to any kind of conclusion as to what are the correct requirements .


[This message has been edited by james S (edited 06-02-2003).]

#137153 06/03/03 07:00 PM
Joined: Oct 2002
Posts: 134
D
Member
Hi James,
1) I can see no requirement to install any further fuses if your protection is a 5A fuse or 6A mcb. These OCPD's should provide adequate short circuit protection for the fan & wiring. In other countries these fans are installed on 10/16A circuits without further fusing down.
I am not certain about DP switching being a requirement if you do not have a timer circuit.

2) Extract fans with run-on timer are required to have 3 pole fan isolation switches installed for maintenance purposes.
As regards fusing down, if 5/6A mcb, I would not say so.

#137154 06/04/03 05:47 PM
Joined: Jun 2002
Posts: 159
L
Member
David,
Please detail reg nos which requires 3pole switching.
I see no requirement for double pole or 3-pole isolation in such circumstances.


regards

lyle dunn
#137155 06/05/03 03:44 PM
Joined: May 2003
Posts: 107
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james S Offline OP
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The reason i ask is because of the specifications on the manufactures instructions, if i find them i will post them on.

#137156 06/06/03 04:20 PM
Joined: Aug 2001
Posts: 7,520
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One practical advantage of a 3-pole isolator is where the system uses TT earthing. Opening the permanent-live and switched-live feeds makes it safe to work on the fan, but if during maintenance you accidentally short neutral to earth you can still trip out the main RCD.

As for the fusing, I find it somewhat amusing that the instructions for many devices here make a big point about how a "3-amp fuse MUST be fitted" or whatever, yet the exact same device is considered perfectly acceptable on the Continent wired on a 16A circuit with no such warnings.

#137157 06/06/03 06:47 PM
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Posts: 107
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james S Offline OP
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I agree i don't think there is any problem with the fusing arrangement off a lighting circuit, i think the manufactures are just trying to cover themselves.thinking about it the only way to fuse the timer type fan, is to install two fuse spares which is a pain in th arse and will look stupid!


ps thanks all for your views [Linked Image]

#137158 06/08/03 01:38 PM
Joined: Jun 2003
Posts: 112
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i was always taught that the purpose of the fuse was to protect the cable..

#137159 06/09/03 05:41 PM
Joined: Aug 2001
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Quote
thinking about it the only way to fuse the timer type fan, is to install two fuse spares
Not quite. You could use a single fuse which feeds both the fan and its associated light.

#137160 06/12/03 02:10 PM
Joined: May 2003
Posts: 107
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james S Offline OP
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I SEE WHAT YOUR SAYING WHICH IS POSSIBLE IF NEW INSTALLATION BUT I WAS THINKING MORE ALONG THE LINES OF INSTALLING ADDITIONAL FANS TO EXSISTING LIGHTING CIRCUITS.

TAKE YOUR POINT THOUGH [Linked Image]


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