Hey Shaun I am also an electrician. I think you are right that it is the outside breaker it is showing rust. That outside breaker is your main feed being fed from your meter pan. It's live until your power company kills it which unfortunately for you means they have to shut it off for it to be replaced.
If you want to check your amperage use you will need an amp probe. Open up the panel in the house and with the dryer and the other device on put the amp probe on each of the main feed wires. Each one will give you a reading of the amperage in use. If one is a lot higher than the others shut off that 2nd device on the 30amp breaker. See if the amperage goes down if it does move that 30 amp breaker to one of the other 2 feeders(the one with the least amperage) and that should solve your problem.
Again I think it's the outside breaker.

100 Amps is no more dangerous then .5 amps
each WILL kill you just as fast

110v v.s. 277v that is a whole different thing-

Thanks 86, I'll do some testing tomorrow.

here's the dryer. not a home, light industrial. it cures freshly silk screened t-shirts running on the conveyor belt.

http://forums.pelicanparts.com/uploa...1390171029.jpg

Borrow a clamp on ammeter or buy one.

See what the machine is really drawing. My guess is the breaker is not working properly.

I would change it live, but I'm a professional (and an idiot).

I was told by a city inspector that a single-throw switch is required after the utility meter, within a certain distance (3-5ft?), and before any breaker box.
Such would allow safe conditions when working on sub-boxes.
Residential house.
(However your city code might not require this.)

I've been told breakers can get soft and trip easy, but wholly second the advice of testing amp draw first and using an electrician for an hour.
The wiring could be undersized, breaker bad, or machine drawing too much juice.
You don't have time for a house fire.....

Any way to do this with a regular Fluke multimeter? Sears has a clamp on meter for $60 I could get if not.

I would imagine that each of the loads are protected by fusing or a distribution panel for the space. If those are not tripping then the main could be suspect or perhaps something that was once cute and fuzzy was chewing on some wires...
The 100 amp main for the house (the house is a sub panel, main is in the garage) went bad at Christmas a couple of years ago. The main would trip while nothing else would....
They are not a big deal to change out.

Fluke makes a clamp on tool for use with a regular meter, if you can borrow one.

You may have an intermittent ground fault.

No, not directly. You don't want 100A going through your Fluke it will fry it and you. And it would give you the reading you want anyway.

I'm no electrician, but the clamp on attachment for using a Fluke isn't the same thing. Where you going to hook the Sears clamp on meter, you have to put it on an electrical leg inside the box where the 100A juice is open and exposed. Or you can open the box at the dryer and clamp each leg of wire to see the draw. My vote again is aging breakers with corrosion and corroded buss bars.

Shaun - If you're not 100% comfy working on this, hire it out. You've already used up too many of your 9 lives.

Hugh's wisdom still reigns supreme.

Me in your shoes: I pull with a replacement on hand, look it over - if it looks corroded or crushed up, replace it. See what happens. If it still blows trips, call the electrician and get be true load checked out. Could be something stupid pushing it close to load rating and with a fatigued breaker, that would do it. Plugged in a new coffee pot or toaster lately? Sometimes...ya never know.

That dryer should be on its own dedicated circuit.

When the electrician installed the dryer wiring, and exposure unit (5000 watt bulb), he put them on their own circuits. He told me he had to disconnect the HVAC wiring and use it.

I never have the dryer and exposure unit on at the same time. Mostly because you never have to, but the electrician said it would trip the main breaker.

These breakers, inside, never trip. I always have them off when not using the equipment too.

http://forums.pelicanparts.com/uploa...1390221932.jpg

Breakers. I wouldn't hire an electrician, do it live. If you don't there will be five bills to pay. One to shut it down, one to take out the screws, one to pull the breaker, one to install the breaker, and one to watch the others do the work. Unions...

You can get the correct clamp on attacment for your Fluke. They automatically scale down the reading to the 10 amp scale you should have on the Fluke. It's not a direct current to meter configuration...

Having said that and looking at the downstream breakers I've got two suggestions...

One, you should probably be on a 200 amp service or more. Can't believe a licensed electrician would put that kind of load on the secondary panel.

Also, I do suggest measuring your current draw but, like others, I suspect either your main breaker has gotten weak from age or you have a corrosion issue.

Hey Shaun the 100 amp breaker is to the left of your panel? If so shut it off open the metal enclosure check wires coming off breaker make sure they are dead. Remove wires and replace breaker. Go inside run all your devices see if it trips. If all is well it was the breaker. If not it is something else in the house. I don't have that type of a system with the main outside the house in my house you have to pull the meter to kill the power at the main.

Pelican David Goodman sent me an email this morning and left his clamp adapter on his back porch for me. I'm going out now to take some measurements.

here are some pics of the box. 86, this is a light industrial building.

http://forums.pelicanparts.com/uploa...1390242362.jpg

http://forums.pelicanparts.com/uploa...1390242374.jpg

http://forums.pelicanparts.com/uploa...1390242382.jpg

http://forums.pelicanparts.com/uploa...1390242393.jpg

My advice is if you feel comfortable changing that yourself, then save a couple hundred bucks and see if it trips again with new breakers. This will rule out the breaker issue. Somethings are just worth paying for. This maybe one one them.

here are the readings I got.

First set are with only the dryer on. Second set is with the dryer and the flash dryer on.

I wonder if I screwed something up given the first set readings on the 3rd wire over. I took pics of a few of the outputs, it was jumping around. With both on, the 3rd acted like the first two.

Note that with the dryer and flash both on, the breakers were buzzing a little and were hot. It typically takes 20 minutes for this to flip with both on.

Only Dryer On

http://forums.pelicanparts.com/uploa...1390244230.jpg

http://forums.pelicanparts.com/uploa...1390244246.jpg

http://forums.pelicanparts.com/uploa...1390244317.jpg

http://forums.pelicanparts.com/uploa...1390244333.jpg

http://forums.pelicanparts.com/uploa...1390244349.jpg



Dryer and Flash Unit On

http://forums.pelicanparts.com/uploa...1390244379.jpg

http://forums.pelicanparts.com/uploa...1390244396.jpg

http://forums.pelicanparts.com/uploa...1390244410.jpg

I'm definitely comfortable doing it myself. I will ask for advice here on exact step-by-step just so I don't kill myself. Will order the breaker today. That one on Amazon is correct, yes? Will see is someone local has it.