Breaker tripping?

I have a question that won't tax too many people, but it's got me scratching my head.

Recently, I installed a set of lights on the landing of my home. These use

3x40 watt bulbs as opposed to 1x60 watt bulb. Ever since then, every time a bulb blows, (regardless of what room it's in), the breaker trips. Now am I right in thinking that because of the increased load on the circuit, the breaker trips more easily? If so, do I buy myself a rechargable torch and live with it, or do I replace the existing breaker with one that has an increased rating?

Help, comments and thoughts would be smashing.

Thanks.

Daz.

Reply to
daz
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Breakers are rated for the loads they must carry, but most importantly wire is rated by the amount of amps you send through it. Increasing the the Breaker amperage, depending on the size of the wire going to your lights, will greatly increase your chances of a fire. Which would in fact light up your house, much better than a flashlight. I would either try separating your devices on the circuit, use a more energy efficient bulb, or before changing a breaker, ensure your wire is capable of handling the amperage. Also, you could try replacing the breaker with exactly the same rating first. You might have a faulted breaker? Feel it (the breaker) and see how warm it is, you might be close to exceeding its usefulness.

Jack

Reply to
Jackcsg

I'm assuming you are UK based with an ntlworld.com email, but you should say when asking such questions.

It's unlikely this has anything to do with changing the light, but you should add up the power rating of all the lights on the circuit and make sure you aren't exceeding it.

It would be useful to know the exact rating of the MCB -- it's going to be something like 5A or 6A, and marked Type B or C or Type 1 to 4. One problem when filaments break is that they can start an arc in the bulb, and the arc very quickly shorts out the lead-in wire creating the classic pop and flash which happens sometimes when a lamp dies. This is pretty much a dead short across the mains. Lamps mostly have integral fuses in the lead-in wires in the base, and this failure mode causes the fuse in the lamp base to go. However, UK/European MCB's contain a magnetic fault current trip which trips in half a mains cycle on a short circuit, and this can operate faster than the lamp base fuse. This is why such a lamp failure can trip an MCB. The 'Type' rating of the MCB is a measure of how much fault current it will allow to pass before triggering the magnetic fault current trip part. In most homes, you could go to a 6A Type C MCB on the lighting circuit which will allow 5-10 times the MCB current rating to pass before the magnetic fault current detection will trip, whereas a Type B will only allow 3-5 times. However, a more reliable way to remove the problem is to swap out the lighting MCB for a BS1361 5A cartridge fuse carrier, which is slower acting in the face of fault (short-circuit) currents, and will allow time for the lamp base fuse to blow and remove the fault current.

Reply to
Andrew Gabriel

Not quite. Breakers are selected based on the wire used in the circuit. It's the breaker's's job to protect the wiring, not the load. The wiring is sized to the expected load.

"Better" isn't quite the word I'd use. ;-)

Yes, replace the breaker, do not under *any* circumstance replace it with a breaker with a higher rating! I'd also look around to see what else is on that branch. 120W isn't much for a (at least) 15A breaker.

Reply to
Keith R. Williams

That would be great if people never changed light bulbs! Expected? Are you kidding me? There is always a cenacle person who feels he's always correct, everyone else is wrong. Exceed the load and the breaker trips to save the wire. Is that better? Wire is rated for amperage, not some expected, or unexpected amount of load. The breaker protects the wiring when the load is exceeded. I don't think you would determine your wire size based on having 4, 60 watt bulbs in a circuit, if that were the case you could wire all your lights, separating your devices per breaker with 18 awg wire, as you wouldn't exceed

1.0 amp, based on your formulas. Please feel free to correct me if I'm mistakenly trying to kill someone, not when I was trying to keep it simple. Isn't a "load" measured in amperage? hmm 3 cents back

Jack

Reply to
Jackcsg

You would be well advised to use proper Usenet quoting principles. Your attack means nothing without context.

That said, you're *wrong*. Wiring is sized to the load. The Ciruit breaker is sized to the wire. Break this rule and you have a fire waiting to happen. If that's what you want, stick your tongue into a socket before you over-rate things, so at least your family can survive.

This cenacle (sic) person sez you're an idiot! You can't understand simple electricity nor elementary English. ...and people are going to follow your advice? Please kill yourself, but please don't take anyone else under doing it, with your incredible stupidity.

As opposed to the wire burning the house down, yes, I belive this is a good deal. In fact that's what the CB's job is!

You're a fool. The wiring is sized to the expected load. The over-current devices are sized to the wire. Exceeding the capabilities of the wiring is a bad plan. Is that such a difficult concept to grasp with your feeble mind?

You really are a fool. Circuits that have only a few lighting circuits may be done in 14GA (15A circuits). Code calls for 20A (12GA, normally) circuits for outlets, and several of these where traditionally heavy loads are encountered (kitchens).

The wiring is designed for these expected loads and the over- current devices are designed for the *WIRING*. Is that so hard to understand? The fire department likes to sleep at night, rather than scrape your melted remains out of what was once your bed.

Since there is no such term as "amperage", who knows what he hell you're selling. The "ampacity" of the wire is given by it's size (and code) and chosen for the application. The circuit breaker is sized for that *WIRE*, not the load. The over-current protection device is designed to save the wire (thus the structure), not the widget plugged into the outlet. It's up to the device plugged into the circuit to protect itself (again, not the CB's problem).

I suggest that you stay far away from electricity. You will hurt someone, unfortunately not likely yourself.

...and a nickel short.

Reply to
Keith R. Williams

OK dickhead, I'm sure I'll loose sleep worrying about the fact that I have offended you. Fuck YOU! Stick that nickel up your FAT ASS, if you can find it. You are an "expected load" of shit.

Reply to
Jackcsg

No, he's absolutely correct. As he stated, breakers are there to protect the wiring. Think about it - when a house is built there is no way in hell to size a wire to a load that does not exist! Therefore it must be sized to an expected load, with whatever safety factor mandated by code added in. When the expected load is countertop kitchen appliances, the circuit must be sized for 20 amps.

You are talking "wire" which refers to the conductor(s) itself and is a completely different thing than the term "wiring" which refers to branch circuits installed in a house. You also use the term "amperage" - but branch circuit conductors are sized in terms of "ampacity" which is a different thing. Here's the definition from the National Electrical Code: "Ampacity The current, in amperes, that a conductor can carry continuously under the conditions of use without exceeding its temperature rating." When you look up "amperage" in Webster, you will find that it refers only to the strength of the electrical current.

In addition wiring is sized based on voltage drop, of which there is no mention in your post. You appear to think that "amperage" is all one needs to know in addition to the load. And as already mentioned, one cannot know what the load will be at a receptacle that has not yet been installed.

You do not understand what sizing means. First, all branch circuits in the US must be sized at a minimum of 15 amperes. #18 wire is never allowed to be used in branch circuit wiring. If the expected load is a lighting circuit, you size it for at least 15 amps. If it is countertop kitchen appliances, you size it for 20 amps. Same is true for bathrooms - hairdryers are an expected load, so circuits to bathroom receptacles must be 20 amps.

It has nothing to do with measured!!!!!!! You can't measure the load when you are installing the circuit. Hell, you don't even know who's going to buy the house, let alone what they are going to plug in.

Reply to
ehsjr

If the *only* change was from 60 watts to 120 watts, and now the breaker trips as you describe due to that extra

60 watts, that circuit was already overloaded.

I would suspect something other than an overload caused

*only* by the additional 60 watts. Check out the wiring to the new lights very carefully. You may have a resistive short circuit - a frayed wire or loose connection are likely culprits. And since your breaker has tripped numerous times, replace it with one of the same rating.
Reply to
ehsjr

Seems strange that changing the fitting produces this effect, unless the 'breaker' is in fact an RCD which means there may be some earth leakage in the new fitting.

Reply to
Jb

Wiring for specific loads, such as industrial settings or a dedicated circuit for a furnace or baseboard heater, *is* sized based on the 'expected load'.

But residential branch circuit wiring, it is not so 'cut and dried'. The total number of circuits is determined by the VA per square foot. One isn't allowed to use smaller wire just because the outlet is in a location where the only 'expected load' is one 40W lamp. There is a minimum wire size allowed (14AWG IIRC). Given the ampacity of 14AWG, the circuit-breaker rating rewquired is 15A.

When you get down to this 'lower' end of circuit wiring (as opposed to dedicated circuits), the 'minimums' start to come into play more than the total current draw. In an 'average' room, you might not 'expect' more than two, 100W bulbs and a 150W TV. This 350W/120V load *could* be supplied by wiring smaller than 14AWG and a 15A breaker. But anything less than 14AWG and 15A isn't allowed. After all, what you 'expect' for the typical load, and what another one 'expects', is not the same thing.

Homeowners aren't required to get a PE to evaluate every change in appliance usage/arrangement because the NEC sets these minimums.

On the other side of the coin, if the *minimum* circuit breaker rating

*available* is 15A, then all components in the circuit must be rated for 15A. The NEC requires that if any component in a circuit is rated for a lower current than the other components, the circuit breaker must be rated for this lowest current device. But a sort of a backward result of this is that you can't use wiring rated for an expected load of only 1/2A when the circuit breaker is rated for 15A Even if you are only feeding a 1/2A load (one single 60W bulb), all the components in the circuit (other than the plug-in appliance itself or the lighting fixture) must be rated for the 15A because the minimum breaker size you can find for a service panel is 15A. IIRC, there *is* an exception for this rule (gotta love the NEC), in that multiple 15A outlets can be used on a 20A branch circuit (with 12AWG wire of course).

And of course, voltage drop is another consideration. But that is another story...

daestrom

Reply to
daestrom

Reading back to the OP's original problem, it appears that the breaker trips when any lightbulb bursn out. Bulbs often go short before opening. My suggestion to replace the breaker was based on a breaker sensitive to an intermittent surge. Replacing a breaker with a new one (same rating) seems to be the easy way to move on here. If the breaker still trips, it's time to get serious.

Reply to
Keith R. Williams

In the u.k. the lights are taken as 100w even if they are actually lower. Check BS7671 or your on site guide Gav

Reply to
Gavin Parsons

Try a type C MCB

Reply to
Arthur Simpson

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