circuit breaker problem (fuse box) advice needed.

[homeopathicremediesunlimited]

I've just had an electrician around who says my lazer printer may be surging in its power usage which trips the overload protector switches (what used to be fuses).

If this is the case, I will find out, but I have a problem with printing now - what do I do to protect the mains ring from tripping if the printer does indeed overload it? The electrician says the fuses on the box are pretty standard (40 watt limit I think he said).

The electrician says he has encountered this before. So the printer overloading is probably the problem (I suppose they use a lot of watts).

[Andrew Gabriel]

I suspect you've got what he said mixed up. My guess is your laser printer is generating excessive earth leakage and tripping an RCD. Does that sound more like what the electrician said?

[A.Lee]

It sounds to me like your electrician doesnt know what he is talking about. I am assuming you have a domestic/small office printer? If so, then there is no way such a device, if in good order, can cause such a surge to trip a 13amp CB, never mind a 32/40 amp ring main CB. Have you got loads of different electrical items running on the same circuit at the same time? If so, then they may be running near to capacity, and plugging the printer in and its consequent extra power consumption may take the circuit breaker above its capacity, but I doubt this will be the case. More likely that there is a fault with the printer or its lead, causing the CB to trip, or the CB is faulty itself. Alan.

[Dave Plowman (News)]

Sure he wasn't talking about an RCD rather than MCB - the latter replaces fuses in a CU. The clue would be if more than the one circuit was tripped by the fault. An RCD would normally protect either the entire CU or a subset of MCBs within it.

If the printer is plugged into a normal ring main and that MCB is tripping there's something very wrong - the plug fuse in the printer should go first.

[John Rumm]

The only way this makes any sense is if your circuit is already loaded upto and probably beyond the maximum. This seems unlikely but is possible - you would need something like 8kW or more of loading on a ring circuit to get into this state. The laser printer may have an "instant on" fuser that draws 10A or so for a short burst to heat the fuser when you start printing.

Supply if from a different circuit.

I expect you misheard that bit...

They can use a significant amount compare to most bits of IT kit, but I have never heard of it being a problem in a domestic environment.

[Andrew Simpson]

As a matter of interest my new Brother laser printer uses nearly 500Watts whilst it is printing the first page. After that the usage drops off somewhat. To reduce the amount of power taken by the printer set the printing media to Card and it slows down the number of pages printed per minute thus reducing the power required.

Andrew.

[Graham]

I have heard a figure of 40A inrush mentioned, Like here

't say how many mS, but MCBs are fast acting.

[John Rumm]

Fast acting yes, but you would need 160A to push a type B 32A MCB into its instantaneous trip response. (or 100A for a 20A MCB on a radial)

(note also that laser printer don't usually blow their plug fuses)

[Lurch]

On Sun, 15 Jul 2007 01:09:13 +0100, John Rumm mused:

I suspect the electrician has read something similar to the above but not really understood it.

[meow2222]

here

Doesn't say how many mS, but MCBs are fast acting.

Lots of appliances have inrush current figures of 40A and higher. It means nothing.

If the printer is popping a trip then the pr is almost certainly faulty.

NT

[The Natural Philosopher]

here

> Doesn't say how many mS, but MCBs are fast acting.

Might be the last straw that breaks the camels back..Although things are better today, the inrush on a roomful of PC and monitior SMPS's was enough to flip a 30A MCB in my day.

Had to be switched on one at a time..

[Dave Plowman (News)]

Rings are designed for domestic use where diversity applies. A roomful of PCs suggests commercial use and the circuits should be designed for that purpose.

[The Natural Philosopher]

However the average house is getting more like a commercial operation every day.

[homeopathicremediesunlimited]

He did mention RCD. It's not my printer though - this was unplugged last night when the power went off.

Now I th> In article ,

[homeopathicremediesunlimited]

thanks

[homeopathicremediesunlimited]

(reply to all)

It goes off at night. I left everything unplugged last night even the fridge. I think now it's the alarm. I'm thinking of snipping the wires from the transformer to the circuit board within the alarm to prove this. Is this wise?

I leave the alarm turned off at night.

[Dave Plowman (News)]

The most likely thing is something with some types of heating element. Like a water heater, cooker, washing machine etc. These can go 'leaky' and cause an RCD to trip - even when appearing to work normally. And if not isolated by a double pole switch can even cause problems when switched off. Isolating that circuit via the CU MCB won't sort the problem either as these are a single pole switch.

The cooker and immersion *should* be isolated fully by their double pole master switches. Washing machines etc by unplugging. You can save yourself a deal of cost by finding out just what is causing the problem.

It could be the burglar alarm, but this would be well down my list to check. It should also have a double pole isolating FCU - but some older ones were single pole.

[Tronic]

By the way the alarm will go off *sometimes* when I turn the power back on from the main trip switch.

[homeopathicremediesunlimited]

By the way the alarm will go off *sometimes* when I turn the power back on from the main trip switch.

[homeopathicremediesunlimited]

I've found the main switch to the heating is on. I have turned that off. The secondary trip switches for the heating were all off though.

I'll see how that goes. Everything else is unplugged.