A couple of weeks ago I posted a message concerning electrical failures in my greenhouse and got some very good information, but I still haven’t isolated the problem. The problem is that sometimes the circuit breaker trips, shutting off my ventilation and causing my greenhouse to overheat. This only happens on sunny, warm days when the exhaust fans are running. Yesterday an engineer from the local power company came out to inspect and analyze my situation to try and help resolve the problem. Unfortunately he didn’t find a problem. He agreed that the wiring and control system design looks sound. The 15 amp breaker has sufficient capacity, though he agreed a 20 amp might sidestep the problem (everything is wired with 12 ga wire). He couldn’t find any evidence of a problem. He suggested that the real problem was likely a sporadic short. This problem has occured several times over about 5 years. During that time I have re-designed and re-wired the control system, yet the failure persists. While the true reason for the failures could be different, I really don’t believe that they are. There is one important common factor throughout my experience that I haven’t investigated – the circuit breaker itself. I have been through about 3 breakers, 2 were GFCI, the last (current) was a standard breaker. Originally I suspected that the problem was a ground fault, but since a standard breaker tripped, I don’t believe that any more. However, they were all purchased from Home Depot and are a brand called ‘Murrey’. Yesterday I learned a bit about how breakers actually work and now I am questioning the quality of the breaker. Can anyone comment on experiences you have had with this brand of circuit breaker, either good or bad? Thank you very much, Chuck Crisler
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hi Chuck, I stayed out of your last discussion, but I did read it ,
first ..I am an electrician .
.second, this is all guessing...
now ,
Murray is an old company, and like everyone, their stuff is probably made outside the U.S. and I have not installed any of their gear in the last 25 yearsor so. but,
breakers are passed through a magnetic field as a final test by some Mfrs. if they don't trip,they are rejected.
so, that may eliminate the.., breaker is sometimes bad ..thought.
your style of breaker is a common one and just about every Mfr will have a compatible breaker that will fit your panel. Even Sq D Homeline will most likely work
I feel your problem is more mechanical than electrical however,
I thought that the mechanism for your louvered ridge could be binding up while other things were trying to "turn" on and increasing the elec load on the circuit.
is there any way to split the circuit into smaller parts with additional breakers ...is there room on your contactor for one more hot?
there are datalogging multimeters that can capture the event, and display the results on your computer, but the price of some of them is quite high for a one time use like yours.
I know how frustrated you are becoming ....especially trying to not lose your orchids..... intermittent problems can cause premature hair loss for some folks..
I don't know if I helped ?
"
Edited 11/10/2005 11:30 am by maddog3
"I feel your problem is more mechanical than electrical however, "I suspect that also.But as I was typing this it could be two types of mechanical. What I was thinging at first was a cut in insulaltion some place in the wiring.But might also be a something in the motors/linkage that binds up from time to time and overloads the motor. But I suspect that the motors have builtin overload protection and are also fairly small.Here are some examples of similar problems. The first I read about years ago, the other two I found.1. This was back in the days of vaccum tube Vortacs (ground based part of aircraft naviagational systmes). Had one site that had a fues that kept blowing on one piece of equipment. They would get the out of service alarm and go out and check it from top to bottom and everything was OK. Replaced the fuse and it worked again.This went on for months. Then one day, as they where in route for routine maintance it happened again. When they got there the fuse hold was HOT. The problem was loose clips on fuse hold allowing it to heat up cause the fues leak to melt.2. Clothes Dry. I was ask to check out a clothes dryer that was not drying, but the motor was running, to see if an appliance service man should be called. Background - I do "handyman" work for this person and one of the problems in the past was with the washer. Aparantely he had pulled out the washer switch to take a phone call or something like that and forgot to push it back in. Then when he got how the washer was full of water and he through that it had broke.Anyway checked the breakers and it was a Zinsco/Sylvania with split breakers with a tie bar and one side had tripped, but did not trip the other. Reset it and the dryer worked. I did not have much in the way of equipment with me at the time so I left it at that.3 weeks later and the same problem. So I go to amp the leads at the breaker. First one was right on the mark. Went to pull some slack in the 2nd one (the side that had been tripping) to make room for the amp probe. And the wire pulled out in my hand.The screw terminal on the breaker was down tight. Best I can tell for 25 years that wire was just pushed against the terminal and it worked for all of that time.3. Dampner control system on newspaper printing press - They use a misting system with a multiple nozzel bar on each unit and a tower can have multiple units and there are multiple towers. There are local controls on each unit and a master controller that you can select any unit and control it.The system work fine when the presses where not running. However, when they where running the locals would work, but not the master.The claimed electrical interference. Had the electricans go over everyting. Likewise the tech's from the dampener system manufacture. Redid some of the power wring and grounding to reduce "interfeernce", but still the same problem.Now I only wrote the software for the controllers for the company that manufactured the electronics and sold them to the company that makes and installs the dampner systems. BUT, I got elected to "solve the problem".Go on site and connect a scope to the communications wiring and see the problem as soon as the pressure run. But it was not "electrical noise".The com wiring was #22 stranded, twisted pair. In one of th4e boxes a couple of strands of the wire did not get in the connector and stuck out the back.When the press was running there was enough viberation that a strand would hit the box and short out.
I'm with you on vibration and poor connections,
I had a problem once on a press in a corrugator plant, the Sta-kon was crimped onto solid #14 (the press was Swiss) , it had broken in half just below the screw head, ...they could Jog the press , but not run it at speed
I spent a very long morning trying to find the problem, I checked everything I finally sat down on top of the ladder and stared at the panel while the press came up to speed....Bingo I saw the small arc and fixed the problem...six hours with a plant mgr . breathing down my neck...."
A 20 amp breaker of a better quality brand bought at a local electrical supply store (not HD) might solve your problem for a few dollars, if you have 12 gauge wire it is worth a shot.
IIRC the 20A breaker is not an option....he was opposed to that suggestion in hs last postbut now you got me thinking that a dual element fuse, would at least give him an indication of the type of fault ...in place of the CB
Edited 11/10/2005 12:23 pm by maddog3
that's probably the safer course -
I still wonder if it's just a cheap breaker
that's my thinking now too, as far as that breaker
and the fuse will split the problem for him"
Chuck,
You need to isolate the problem. If possible, can you disconnect the service and run a long 10 gauge extension temporarily to it and see what happens off a different breaker? If that fixes it, well, lay in a new line, if no, it's in the greenhouse.
WSJ
"Originally I suspected that the problem was a ground fault, but since a standard breaker tripped, I don't believe that any more."
A ground fault is a connection between the ungrounded (hot) conductor and the grounding system, which will definitely trip a standard breaker if the impedance is low enough. A "short" between the hot and the grounded conduit, or grounded motor frame, or whatever, is a ground-fault. I would not dismiss this as a possibility.
Be seeing you...
A couple of times when I've needed to shoot this sort of problem I've broken the circuit into parts and put each on a smaller breaker/fuse (or just moved one breaker/fuse around). This helps to narrow in on an intermittent short or overload.
Another option would be to ask the power co guys if they have some sort of recording monitor for the line that they can lend you. If the recording shows the current rising slowly then you know it's a "simple" overload, while a sudden jump (or a trip too fast for the monitor to catch) suggests a short.
No electrons were harmed in the making of this post.
I didn't know that Murrey was still made. Seriously. I thought Cutler-Hammer bought them out. Murrey is old technology. Probably five to fifteen years old. Quality? I don't know.
I like the fuse idea.There are no electrons! It is all made up. Don't believe it.
Electricity is made by GREENIES.
everybody has been bought up by everybody else...LMAOI was looking for a schematic to an old Furnas drum switch, and Hubbel owns them now...."edit for:Hey talk about old technology, did you know the Fed Pacific is STILL being sold in Canada? they call it Federal Pioneer , but that stuff is the same stuff that is always was
Edited 11/10/2005 6:09 pm by maddog3
Tere's a company in NJ that sells Federal Pacific stuff down here, two, I had to pick one up for our old box pre-upgrade.
A gfci breaker is like $120. Even I wasn't stupid enough to buy that.
I forgot about the NJ outfit.....$120 !!!"
after all of the discussing, have you given any thought to the fuse idea?
A simple pigtail lamp socket with dual element fuse wired in as a substitute for the CB will tell you if the problem is overload or short...
A couple of questions:
1. What loads are on this circuit? Number of motors, full load amps for motors, etc.
2. Are you using separate contactors or motor starters to control the motors? If so, do the motor starters have overload protection?
Another question. If several motors, is there any scenario where they might all start at once?
--------------
No electrons were harmed in the making of this post.
U got it Dan, that was one of the main themes on the first set of posts on the subject - a 20 A breaker will take care of the problem, but someow 15A on 12 AWG is a feel good thing?
Don't have an old Murray breakers to test, but a 30 A sqD QO eil tirp in about 300 ms for a short circuit at the end of a 30 ft 10 AWG wire run, whereas have seen a 20 A GE breaker take 3-4 seconds to trip for a dead short at the end of 20 ft of 12 AWG.
Know some people <G> who for certain tools put a 30 A sqD on 12 AWG lines that are in conduit.
Title seemed interesting, but quickly gave up immediately after I saw the MEGA big paragraph.
Gotta keep reminding folks about breaking up their text into bits and pieces for some of us tired eyes.
Sounds like a problem I had on my well pump system. I live out in the desert and the pumphouse gets very hot occasionally. What happened was that the starting capacitor for the well motor died. This caused the well motor to come on and draw a lot of current without pumping anything, resulting in a popped breaker. Took a while to troubleshoot that one
Erich
If a stalled motor is causing the problem, one can intentionally stall each motor in turn and see if that pops the CB. Small motors are usually slef-limiting so i doubt this is the problem.
This sounds like a car I have: every once in a while, the fuel pump fuse would blow, causing the car to die. If I replaced the fuse right away, it would blow again. if I let it sit for an hour, the new fuse would be OK. I finally resigned myself to dropping the fuel tank to replace the pump: that's when I found a pinched wire that the dealer had left from a previous repair. Every once in a while, it would short to the chassis. If one waited enough, the wire would oxidize enough for it to insulate the short, until enough vibration occurred for the short to happen again.