Re: Security Light Surge Trips MCB

["Frank Mc Alinden" <fmcalind@xxxxxxxxxxxxxx>]

Hi Nick

The circuit concerned is fitted with a 3A breaker.  The breaker trips
> out every time the lights switch on.  I can reset it by hand and the
> lights come on and stay on.  I can only assume that the surge current
> at switch on is exceeding 3A by enough and for long enough to trip
> the breaker.

When the filament is cold the resistance is quite low therefore a large
inrush current is present for a short period......I think you will need to
up the rating on your breaker.....Personally with security lights i would
have the cbus relay unit driving another relay(240v coil)  so if the
filament goes pop it doesnt weld the contacts of my CBUS relay....Much
easier to replace a plugin omron relay than to send the CBUS relay unit
back
for repair.....

Frank

----- Original Message -----
From: <nick@xxxxxxx>
To: <ukha_d@xxxxxxx>
Sent: Tuesday, October 19, 2004 6:04 AM
Subject: [ukha_d] Security Light Surge Trips MCB


>
>
> All my C-Bus outputs are protected with quick acting MCBs.  One of
> the circuits controls two outside security lights of 300W each, so a
> total of 600W or around 2.5A.
>
> The circuit concerned is fitted with a 3A breaker.  The breaker trips
> out every time the lights switch on.  I can reset it by hand and the
> lights come on and stay on.  I can only assume that the surge current
> at switch on is exceeding 3A by enough and for long enough to trip
> the breaker.
>
> Is there a rule of thumb to work out the switch on surge current for
> 2 x 300W halogen bulbs?
>
> Cheers,
>
> Nick
>
> http://www.nicklocke.co.uk/Auto
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