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Thread: MEP-002A and -003A main breaker

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    General sewerzuk's Avatar
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    Default MEP-002A and -003A main breaker

    I have been tinkering these sets for a few years; I currently have three -002A's and two -003A's in my shop.
    I have noticed what I believe is a design problem common to all of the machines, and I'm wondering if anybody has insight or has gone down this path before...

    The main breaker seems to trip far to easily when hit with a starting surge (such as an electric motor). None of my -002's or -003's will start the hydraulic power packs on my car lift, ironworker, tubing bender, air compressor, etc. The main breaker just trips instantly. However, a little 5kW coleman generator that I have kicking around has no problems with these loads. The problem is a little less pronounced (but still exists) with 3 phase loads; the -002A will start my milling machine, but not my lathe. The -003A will start my lathe, but won't start a 10HP motor under no load (same issue...breaker trips before the motor even begins to move). These loads are well within the capacity of the generators...they work fine on smaller civvy units.
    On the flip side, the 50A rating for the -002A and the 100A for the -003 is too high...it is possible to significantly overload the set with a more resistive load (such as a large welder, heater, or lighting). I believe than the main breakers should have a longer overcurrent delay, but a lower trip setpoint (30A breaker for the -002, and a 50A breaker for the -003).

    I pulled the main breaker out of one of my parts sets just to see how it is put together...it has 6 main lugs (protecting the generator output), and 6 smaller lugs (appears to be protecting control circuitry inside of the generator). I couldn't find any other info on this breaker (model number) other than the manufacturer, but though a little web mining I believe that it is the Heinemann series AM-MIL.

    So, on to my questions:

    1. Is it possible that the starting surge is tripping the breaker because of the control circuitry? (Is the load's starting surge causing a corresponding surge in the field control circuit that is causing the breaker to trip?)

    2. If #1 is true, I should be able to place a small resistor across the control circuitry terminals in increase this trip setting. Has anybody tried this? It wouldn't be a permanent solution, as it partially bypasses the breaker...but it may help determine what is causing the trip...

    3. What does the R-3 adjustment procedure do? Is it in any way related to the control circuitry trip setting on the main breaker?

    4. According to the schematic, it looks like the control circuitry trips the breaker through some kind of internal heater; does anybody know if these heaters are swappable (similar to the overloads on a motor controller)?

    5. Can anybody see a disadvantage to separating out the main and control circuitry breakers? For example, if I just got a 3 pole 50 A thermal breaker for the main breaker, and small 1A pushbotton breakers (or fuses) for the control circuit, would there be any issue with this?

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    I too, am interested in answers to your questions - hope somebody kicks in with comments. You don't mention how big the motors are, that are tripping the Sets. Haven't been able to try it yet, but I wonder if a 1 Hp well pump will start with the 003?

    Have you tried to monitor the current that is tripping the Sets? Some Clamp meters will measure a spike at the peak load. Generally, I try to be conservative around this stuff because sometimes when I work on it, the smoke leaks out from the insulation on the wires.

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    I have an MEP-003A genset and I have never had the main breaker trip, even with large loads. I have an air compressor with a 5 hp motor and it starts fine without tripping the breaker.
    Gary
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    Have you gone through and properly done the R3 adjustment? It's quite possible that the R3 adjustment has something to do with the delay of the main trip setting. I'm not 100% positive about that though. I doubt that the control circuitry is seeing any kind of a surge and causing the trip, but a good meter with a hold function (Fluke 87), inline with the control circuit should show you if you are getting any spikes in the control circuit.

    You are correct, the breaker is manufactured by Heinemann, and it is still available for sale. I just bought 2 of them recently for the 003a's. I don't know what the manufacturer part number is right off hand, but Newark Electronics can get them for you. The Newark part # is 23H0163. This part number will not show up on their website, but if you call customer service then can get you a price quote and lead time for them. Mine cost about $179.00 each, so they are not cheap.

    You could try to contact Heinemann and see if they can help you out with the more technical questions that you have, like adjusting that trip setting. If you find anything out, please post the information because I would like to know if the R3 adjustment does change that delay.
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    Quote Originally Posted by rosco View Post
    I too, am interested in answers to your questions - hope somebody kicks in with comments. You don't mention how big the motors are, that are tripping the Sets. Haven't been able to try it yet, but I wonder if a 1 Hp well pump will start with the 003?

    Have you tried to monitor the current that is tripping the Sets? Some Clamp meters will measure a spike at the peak load. Generally, I try to be conservative around this stuff because sometimes when I work on it, the smoke leaks out from the insulation on the wires.
    I don't have a clamp ammeter...its something that I should add to my toolbox. I do have an older oscilloscope and several good DVOM's (but none are data logging). So, I haven't monitored the current on the loads yet...

    Both sets start smaller motor loads; portable air compressors, my cement mixer, power tools, etc. It even starts a 5HP (peak) electric motor on a cheap compressor that I have. The problem loads are the hydraulic power packs for my tubing bender, ironworker, and car lift and my big shop compressor. Bender and car lift are 1.5HP, and the ironworker is 2 HP. All 3 are single phase 240v. The -003 will sometimes start these loads, but will sometimes trip. Neither machine will start my air compressor with a 5 HP motor; it is also 240v, rated at 22 amps running.

    However, I can crank up my mig welder to nearly full power, and overload the -002's to the point that the engine drops nearly 1/2 of its RPM and my shop browns out...but the breaker never trips. (obviously I don't make a habit out of doing this, it's probably pretty hard on the VR circuit in the generator and can't be good on my welder either). My point is just that the breaker doesn't trip when it should, but does trip under a relatively small surge current.
    A conventional thermal circuit breaker allows a large transient current without tripping...the main breaker in the -002 and -003 doesn't seem to like this. But I am 100% certain that both machines produce more than enough power to run the loads that I spoke of, ESPECIALLY since a cheap coleman set runs them without a problem. The same coleman set can't seem to handle nearly the same amount of resistive load the the -002 can, that what has me convinced that the breaker tripping issue is a design problem.

    I also forgot to mention; I have the same problem with all 5 sets that I currently have in my shop; so I'm certain that it isn't a defective breaker issue...

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    Quote Originally Posted by Speddmon View Post
    Have you gone through and properly done the R3 adjustment? It's quite possible that the R3 adjustment has something to do with the delay of the main trip setting. I'm not 100% positive about that though. I doubt that the control circuitry is seeing any kind of a surge and causing the trip, but a good meter with a hold function (Fluke 87), inline with the control circuit should show you if you are getting any spikes in the control circuit.
    I haven't done the R3 adjustment procedure; I have experienced the same problem on literally over a dozen sets over the last year or two...so I am assuming that it is more of a design issue with the breaker than an adjustment issue. My thought was that if I could fudge up on the setting a little bit, I could make the breaker less sensitive to tripping, but I'm not 100% sure exactly what the R3 setting does just yet...
    Last edited by sewerzuk; 12-06-2010 at 01:16.

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    I was about to say that you need a new main breaker, until you said that all the machines had the same problem. But why is Speddmon buying new breakers? At the same time, that still might be true.

    If you get a Clamp Meter as mentioned, be sure to get one of the newer ones that has the capacity to measure DC current, as well as the AC. Also with the hold feature.

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    Quote Originally Posted by rosco View Post
    But why is Speddmon buying new breakers?

    Speddmon is buying new breakers because I have several spare output boxes, and 4 of them are for the MEP-002a's. The only difference in the two boxes is the main breaker, and the number of times the power wires are wrapped through the CT/CVT assembly. So with getting two breakers from work at a VERY reasonable price, I can convert two of the MEP-002a boxes to MEP-003a boxes
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    I too would like to know the answer to this question. I have an Mep-003a and it runs my entire house in addition to the well pump 3hp motor and the compressor in the barn 5hp motor no problem. However my house has a 12 ton ac unit that trips the breaker out every time. I can get it to stay in if everything else is turned off then slowly add things back on after it is running. It appears to be the spike in load that trips it when the compressor kicks in. I thought perhaps the breaker was weak in my unit I'm glad to know its not just my set that has the problem.

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    There are a couple of things to consider here, air conditioning compressors are always starting against a load unlike most other types of motors. This means they have high inrush currents (this is why the NEC now requires special HVACR rated breakers for air conditioners), if the compressors starting capacitor is going out it can cause the compressor to draw even more amps than normal, this would be the first thing I would check/replace to see if it fixes the problem. They also make "hard start kits" for for air conditionng compressors which are basicly additional capacitors, these are often installed on aging/older compressors if they start tripping breakers due to high current draw at start up. (among other reasons).

    Ike

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