My workshop has a radial socket circuit fed from a hager 16a b type MCB. I heat the space with a 3kw fan heater. I normally turn the heater off before using any power tools to avoid overloading the circuit. However today I was cutting some wood with a circular saw with a vacuum cleaner and forgot to turn the heater off. I had all three devices running at once for about a minuite with a total load of about 6200w which works out to be about 27 amps at 230v, way over the 16a rating of the breaker. To my supprise the breaker did not trip, should it have done so in that situation? Is this normal or is the breaker defective? If it is indeed normal, do I need to continue turning the heater off before using high power tools?
Is my 16a MCB defective?
- Thread starter leew2
- Start date
Sponsored Links
No, not if it was for only a minute or two. According to the specification curves, a Type B 16A MCB should take about 400 seconds (6-7 minutes) to trip at 27A. The greater the degree of overload (or 'fault') the more rapidly they trip - to get 'instant' tripping of a 16A Type B MCB, you'd need about 70A.
Kind Regards, John.
5 x 16 A = ?
Very true - but (because of the main part of the question/answer) I was in 'looking at curve' mode rather than 'thinking' mode, and must have miscounted (by 1) the lines on the logarithmic scale - but what's the odd 10A difference 'between friends, anyway
Kind Regards, John.
Sponsored Links
.. but what's the odd 10A difference 'between friends, anyway
.
Quite a lot if your hanging on to a faulty kettle waiting for the mcb to operate.......(No RCD !)
True, but I doubt we're really talking about faults - it would be a very specific, and hence extremely rare, fault that would result in a fault current of 70AQuite a lot if your hanging on to a faulty kettle waiting for the mcb to operate.......(No RCD !).. but what's the odd 10A difference 'between friends, anyway
Kind Regards, John.
If you turned on all 3 devices together, I would expect the MCB to trip, but from what I can gather all 3 weren't turned on at once. when the vacuum cleaner and saw are up and running the current they draw is very small, it is the start up current of motors turned on simultaneously that usually trip an MCB
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
