Applying the 3 meter rule.

[petermouse]

Hi. I am an recently retired industrial electrician, I am worried about an installation in my own home I did about 30 years ago. I supplied my burglar alarm control box. By Spuring off my ring main (unfused) about 4 feet to the alarm box. I may also have down sized the cable to 1.5mm T&E. I did not fit a fused Spur on the supply as the Alarm box is fused internally on the supply as it enters the box. At the time I thought this was O.K. as I understood the 3 meter rule to allow Down sizing and omiting of a fused spur at the point of connection to the ring main. As long as the run was less than 3 meters and the load to be suitably limited by protection at the end or along the supply cable. Since retiring I have had time to ponder these things. Any clarification would be a big help.

 

[westward10]

The 1.5 is probably okay but you should have fitted an unswitched fuse connection unit at the panel.

 

[telectrix]

as he said^^^^^. normal practice is to fit a unswitched FCU (3A) adjacent to the alarm panel. but it's not unsafe. it's worked for 30 years ain't it?

 

[ipf]

As they say^^^^^..... still bad practice 30 years ago, though.

 

[buzzlightyear]

Since retiring I have had time to ponder these things.

must taken a long time to think about it. or was it a light bulb Moment .

 

[Spoon]

must taken a long time to think about it. or was it a light bulb Moment .

He might have only been retired for 1 day..

 

[petermouse]

The 1.5 is probably okay but you should have fitted an unswitched fuse connection unit at the panel.

Thank you.

 

[petermouse]

must taken a long time to think about it. or was it a light bulb Moment .

low wattage. took a long time to warm up.

 

[freddo]

At the time I thought this was O.K. as I understood the 3 meter rule to allow Down sizing and omiting of a fused spur at the point of connection to the ring main. As long as the run was less than 3 meters and the load to be suitably limited by protection at the end or along the supply cable.

I thought you could only apply that rule for connections within 3M of a cutout/meter or busbar chamber, not parts of a final circuit?