Fuses vs Circuit Breakers, What's in your Distro?

[JD]

Ok, even after 30 years (and roughly 4000 set-ups & shows) I run into situations that leave me scratching my head.

Keep in mind, in the following paragraph we are NOT talking about a disconnect or a company switch, but the distro that breaks up the circuit into smaller circuits such as 20s and 50s.

Had a house electrician give me a hard time because my distro used circuit breakers! His point was that circuit breakers can jam and if that happens there is noting limiting the current going into the smaller circuits. True. But I don't think I have ever seen a fused distro in use! Once again, I am not talking about the company switch (fused) or a disconnect box (fused), but the actual breakout distro for the smaller circuits. Now, this was not a young guy, but a licensed electrician who has been in the biz since 1972. Anybody ever run into this?

His attention turned onto the sound company who had no protection in their distribution, and later a different electrician came on duty who had no problems with breakers.

 

[highschooltech]

No, i've never seen a distro with fuses instead of breakers. All the distros that i have used have been breakered. Besides breakers work with magnets the more current that flows through them the stronger the pull. Even if for what ever reason the jammed the breaker would still trip at a certain point, even if it was to late to save the gear.

 

[zac850]

Never seen a fused distro either. I've only ever seen breakers on the distros and fuses in the switch. Never even heard of a fused distro for that matter.

 

[derekleffew]

...Had a house electrician give me a hard time because my distro used circuit breakers!...

You should have asked him what the distribution panel in his house used. Screw-in fuses are becoming rarer each day, so unless he lived in a house older than fifty years, a very good chance he had breakers in his own home. I think he must have previously read your signature, and therefore didn't trust you.

 

[SteveB]

I'm thinkin' one of the fuses in his head was blown.

You cannot even BUY a fused distro., and haven't been able to in at least 30 years, excepting some 3rd world countries - like Australia or New Zealand or some place like that (grin).

Nut job.

Steve B.

 

[porkchop]

A fused distro would anger me, I'm so happy this is not actually something you see. Even before thinking of testing connections that are misbehaving and having to change the fuse every time it pops, my distro's sit on the grid imagine having to change a little fuse while 35 ft. over head. No thank you, the load (aka the lights) can be in charge of their own fused over current protection I like my distros with breakers

 

[ship]

Hmm, just made a 24way 208v power distro with Emergency stop system currently out on tour with some large rock tour and didn’t get anything other than complements for it. It only had one fuse in it and it was in-line for the LED Little Lights and that was only out of laziness in doing that instead of a breaker. Just change a few things or re-tap a transformer and it would even tour Europe sufficiently. This much less a 15KVA 208v Delta to 240/416V wye transformer also using breakers in the past few weeks without anyone citing the other than well done. (Any wonder that I have been less than active in the last few weeks?)

Hmm, circuit breakers, I would hope one is not to be using plug fuses as they could be non-complaint with a stick finger into larger than 1/4" hole type of way. Given a plug fuse AC distro (not even counting such a thing in finding than screwing in such such a replacement fuse in the dark) or finding the replacements, how would one get around that live center of the opening type question of being zapped in a Darwin type way we try to over protect against?

Hmm, for some reason the photos didn't download even if resized.

Assuming this person was all for other than screw in plug fuses, and instead up for something for individual circuits that are smaller such as using a FRN type, why? As licenced electrician wouldn’t that invalidate the current code concepts of tied especially dual phase breakers? Not aware of dual fuses that will cut off power to more than one leg of power should they blow. Even for single phase circuits, gotta find the spare fuses and get them in quickly, this much less while fuses are simple blow, you can dial in your say thermal magnetic fuses for similar coverage.

What happens if given fuses and you have two phase gear if one phase blows but the other didn’t? Isn’t that a bit dangerous and specifically to be prevented? Jamming of circuit breakers I would assume he was thinking with dual phase handle tied but not internal trip breakers which can if not properly done jam. More realistically they will jam in the off position - personal experience with that by way of flexibilty of that in not being able to turn it on but still it could jam on as a concept, or for multi-pole breakers a single pole in theory in blowing could not be sufficient to trip the rest. How does the individual circuit breaker work better than persay not a tied breaker but internal/external bridged breaker for controlling two phase circuits? Single breaker trips in exposing an open or even floating return path in concept which could get very dangerous in concept of what he would seek to protect against.

Most distros these days are two or more phase and even if not are normally circuit breakers and UL listed plus engineered gear from very reputable companies that sit on the NEC board. Not aware of any fused breaker distros on the market these days. Would just love to pluck from his mind that while in general fuses are better overall for simplicity, how dependant on what type of breaker you use, they are superior especially given what fuse verses breaker type is used. This much less how he thinks it’s better and what gear he recommends and who is using it. Just love to talk with confused people in plucking out info from them that is often useful to know even if often years out of date.

Nope... even this past week in making a CamLoc to 32A6h 3P+N+G adaptor and using a 32A three pole circuit breaker with the necessitated indicator lights and plywood backer on it, never once thought about using fuses for it. This other things made in the past couple of weeks or other than code compliance for its application.

Believe you just met the “grumpy old man of the theater”. Congrats. Learn what you can from him and take what you can from what you can for where it can be useful, otherwise just often they just need some time to talk in being heard.

Would love to hear his thoughts about the new four pole breakers - one with the 50% neutral breaker that breaks the circuit if it detects an un-balanced load of over 50% on the neutral, this or the various GFCI and other new types of breakers. Just pricing out main breakers for my 48way E-Stop power supplies recently, amazing the trip ratios available much less the options and features available.

 

[TimMiller]

I would never put fuses in a distro. Heck, at work we have shy'd away from installing fuses in control panels and started using breakers. Only thing i use fuses for are for big 3 ph motors used for industrial applications, and then if they were to blow a fuse, they would over load the other two legs and trip the over load protection. One new type of breaker i have seen has built in under voltage protection. I am thinking about using these in our generators, they trip the breaker once the voltage hits around 80V. Which if the generator were to fail for any reason it would shut the breaker off, so the gear does not completely brown out. Once automation directs website is back up i will post a link to the breakers i am talking about. What do you think ship?

 

[Chris15]

Hmmm.. fused distro... sounds rather non code compliant at least on this lil island...

Ship et al please do correct me if I'm wrong but last time I checked, breakers can still disconnect the load even with the handle locked in the on position - an arrangement used sometimes for supplies to fire alarms, security alarms etc.

 

[TimMiller]

Breakers can shut off a load even with the handle locked to the on position. That is why you must turn the breaker to off then back to on to reset it. It will not allow you to just push it back to on. Using fuses is not against the NEC, its just completely not pratical.

 

[ship]

Hmmm.. fused distro... sounds rather non code compliant at least on this lil island...

Ship et al please do correct me if I'm wrong but last time I checked, breakers can still disconnect the load even with the handle locked in the on position - an arrangement used sometimes for supplies to fire alarms, security alarms etc.

Yes but that would disconnect individual phases and not ensure all phases got disconnected in multi-phase circuits. Problem when you only disconnect one phase say on a 208v system is the live circuit not disconnected. Might be only my world where most distro circuits are used in two or three phase mode but individual circuits are mostly tied. Can't even buy them these days without that even for 120/208v switchable power distros. Crew chiefs complain that what if one of my circuits go out,... I'll loose two lights (if in 120v mode) to which I say that's correct, on the other hand you won't if you loose one phase in 208v mode have half the power to a fixture looking for a return path - any return path it can find searching for that return path. After that, they do what they have to do for the tour but had best return the gear to it's specification by the time the show returns. That's with tied circuit breakers as opposed to individual breakers. Not feasible to tie fuses to ensure if one goes out they all do which could be really important.

Fuses are also not so much quickly or safely changed during a show. Have a few portable fused knife switch disconnects for use on shows but they are more taking the place of company switches or in use for smaller sized company switches more than sufficient for the rated load.

 

[soundman]

Do you have a link to the switchable distros? I have only seen the motion labs that come as wither 120 and 208 that can not be altered without some serous work.

 

[ship]

got some Motion Labs versions in stock, the Amp disconnects at times have problems years later but so do the CAE versions also using them.

Less used is the Motion Labs switchable racks as opposed to the ones that just have both versions of outlets on the same circuits already done.

CAE for us makes a non-switchable other version but just about anyone that makes such racks can. Basic concept is one Soco outlet for 208v that down stream in adding neutrals feeds two 120v Soco outlets. So in other words you get double the 120v Soco outlets to 208v Soco outlets all same circuit and controlled by tied 208v breakers. Simple enough just have to deal with the concept of if you loose one circuit on 120v, you will loose the second circuit. Production people have problems with this, I agree with that as opposed to back feed.

 

[soundman]

I get the concept of a single 208 breaker tripping to take out 2 120V outs I just don't understand the reasoning of doing that. Could you elaborate on 'back feed'? The way I have almost always seen it has been breakers and outs on the same panel (talking mo labs here) it could be that I have not been exposed to any other ways of doing it but it seems to be logical and make sense.

 

[ship]

One big thing I remember doing on the Motion Labs rack in making them more user friendly to service was to seperate the switchable part cover from it's rack. I cut away the corner of the covers so it passed by the rack mount screws of the switching component. Than oversize hole drilled the next rack space hole next to them and added thumb screws with captive washers retaining them. Believe I also added some handles to the cover so one could remove the cover without having that entire linked rack section - all joined together stressing the screw I'm removing. Always hate to access and service the internal parts of a Motion Labs rack - so many screws to remove and an entire panel to support in just looking for something like a bad AMP connector or nut floating about inside. This or a bad Soco output by way of voltage spike with solder terminals meaning the solder used just melted and fused a lot of phases... or stuff like that. Or a stripped key way or arched terminal etc. Entire panel has to come off. This as opposed to the CAE racks that while individual hinged panels only recently switched to steel hinges as opposed to sagging aluminium ones, and or has more Amp quick disconnects in use than with the Motion Labs racks thus constant things to trouble shoot once the racks get older and travel about the country enough that things get loose or badly crimped things go wrong. Went an entire round with CAE about stuff like fish paper isolation and lock washers on breakers as a concept and upgrade. This much less the CAE mini-breakers are constantly getting broken and there is not a bunch of extra wire in them for installing the new one.

No perfect rack out there, good racks abound but nothing even I make is perfect in ever so many ways to do a rack and or problems/benefits in doing them. Just had a round of Indu Electric distros that needed total upgrade of the way they did the distro off the main breaker, much less some Lex panels that needed new covers for plastic that didn't survive strapping well. TMB also makes them as with many other companies. All kinds of ideas out there on how to do them, all have good and bad about them, all have a way of within current NEC standards doing their racks. All will be changing to keep up with concepts of code and technology over the years including as said above, new breaker technologies and ideas.

Limitating factor I know of so far (waiting list for a class in them) is main breakers that can do one thing that's good such as neutral sensing, won't persay GFCI or minimum voltage sense persay. So far that I'm aware of so you have your choice of what's most important. Minimum voltage I would put under un-balanced load protection, but on the other hand believe I read recently a resurance of GFCI protection required popping back up so it might become most important soon. This given a GFCI on a main breaker probably won't be effected by computers much so it's completely different in type. Three phase GFCI could be interesting.

Just did my first amp meters next to the voltage meters recently - really cool. Could potentially do another amp / voltage meter for the neutral to ground sensing in not persay needing a neutral sensing but compliant GFCI main breaker. This given those using the gear didn't consider like 80V on the neutral to be anything to be concerned about I have heard in the past crew chiefs are not.

Future rack planning.... love planning and building my own, even have a jig now for punching the Edison / duplex type outlets and a punch for flat panels for the smaller up to 1/2" holes.

 

[ship]

I get the concept of a single 208 breaker tripping to take out 2 120V outs I just don't understand the reasoning of doing that. Could you elaborate on 'back feed'? The way I have almost always seen it has been breakers and outs on the same panel (talking mo labs here) it could be that I have not been exposed to any other ways of doing it but it seems to be logical and make sense.

“Back Feed” has become a bit of a generalized concept similar to recently “Surge” politically speaking. It covers a few concepts and or safety issues in a Darwin like way that could be dangerous and that the NEC prefers made safe.

Back feed as a concept mostly comes involved when a tech person does not un-plug the fixture before servicing it but could potentially become a problem where a AC distro where both 120v/208v circuits are both used on the same circuit or electronically and or with short to ground within it. And also in a short condition above when the fixture is thought to be dead but not unplugged and one phase is still live.

Basically path of least resistance be that by way of filament lamp or what ever. You got in a most basic sense one live leg of power not shut off looking for a return path.

Most 208v gear is not filament in lamp but some are which means all it takes is you to touch a return for a still hot wire and you can complete the path to ground in making that still live circuit active again. Only one phase shut off on a two phase circuit means it’s gear that if not un-plugged - as happens thus the rule about bridged breakers - or if not rule, what most won’t do, in checking the fixture instead of breaker means anything from stray wire touching the frame to you touching it to even down line a 120v outlet on the same channel as the hot one could back feed to neutral or ground in being live. This concept of individual breakers in line before the fixtures, one outlet two phase, another outlet two single phase and grounding conductor. If the 120v outlet on that phase that shut off has a filament it can complete the circuit of the shut down breaker to neutral by way of it in not making a working 208v fixture but instead a 120v fixture in what one thinks dead is instead carrying current to ground potentially. This also electronically one to a shared 120v circuit or even ground short on only 208v can be live. Or live enough given resistance to current flow / leakage and waiting for a path of less resistance.

Lots of ways one can on a two phase one breaker open system get into trouble - mostly in not doing ones job properly but also if it’s a 120/208v system on the same circuits as common, that without bridging it can be dangerous.

Hard to explain properly but I hope I conveyed some ways. Once had a fluorescent light I was working on start up while I was working on it by way of back feed from a neutral wire by way of filament lamp of another phase/circuit and filament lamp - first time it ever worked. This amongst times sensing a zap but not a proper zap - instead a high resistance short.

Years ago when CAE was still making individual breakers for the “but what if one circuit goes out... takes out two circuits” I asked this question to the management about back feed. Now that I’m sort of management in controlling such things, I totally agree with CAE’s decision to no longer sell us racks with other than bridged breakers and field the calls from the crew chiefs concerned about their shows in having two 120v circuits instead of one go out.

For them I listen, explain and if not sufficiently competent in a way I trust say it’s the standard we now follow. For the others and only if it’s 120v and not 208v on the circuits, I send them individual breakers to replace the tied ones with and rely on them to change than change them back to safe after the tour. First time they don’t that will be the end of trusting them to make the rack safe again for the next user of it for them. Management goes with me on this standing and ruling of yes, you might loose two circuits but given idiot proofing of systems for safety, it is something that needs to be done. This as similar to why we don’t use fuses amongst other reasons.

 

[TimMiller]

We have separate 208V and 120V distros to eliminate any possible problems. So i do not have to risk switching neutrals to breakers to feed 208 or anything weird. Its all straight forward. We have also have distros with clearly marked 208 and 120V feeds. The 208 are on 2 pole breakers and the 120 is on single pole breakers.

 

[derekleffew]

...Three phase GFCI could be interesting. ...

Indeed, ship, indeed. See this site. I believe this is the model used to supply power to the 212 moving-nozzle pumps in Lake Bellagio, (picture above the words "Success Stories" on the webpage cited).