MEP-002A and -003A main breaker

[sewerzuk]

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?

 

[rosco]

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.

 

[glcaines]

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.

 

[Speddmon]

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.

 

[sewerzuk]

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...

 

[sewerzuk]

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...

 

[rosco]

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.

 

[Speddmon]

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

 

[leedawg]

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.

 

[Isaac-1]

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

 

[Speddmon]

Ike,

You are absolutely correct but you forgot to mention that a lot, if not all, newer AC compressors are using scroll compressors. Which by their very design start under almost no load.

To everybody else, I just hung up the phone with an engineer at Heinemann about the breaker problems. Here is some background.

First off, the breakers are a relay trip breaker as well as magnetic trip. What this means is that the R3 adjustment is pretty critical to the operation of the breaker. The main contacts act as a switch only, and the main 100A rating of the breaker basically means nothing more than that is the switching capacity of the main contacts. The actual trip rating of the breaker comes from the relay inside and that rating is 825mA (0.825 amps).

Now, when you have a large inductive spike such as your heavy motor loads being discussed here. That's when the magnetic trip comes into play. There is a plunger inside the trip relay inside the breaker. If the spike if large enough, it will trip the breaker before the relay even has a chance to. The engineer told me that by increasing the resistance of the variable resistor (R3) you can increase the delay of the magnetic trip also, but then you could be running the breaker out of the specified range for an over current situation (which is where the relay trip comes into play).

So in conclusion, and I said earlier, go through and properly adjust the R3 resistor and see if that doesn't help out your motor starting capacity. And if you still desire a bit more, you can AT YOUR OWN RISK increase the resistance of R3 some and see if that helps. It is a very good possibility that the R3 resistor is bad or going bad. They are nothing more than a small cheap potentiometer, and we replace them all the time here in the steel mill because they go bad quite often on our equipment. They are probably the cheapest thing on the equipment in price and quality both.

 

[Isaac-1]

Speddmon, don't get me started on scroll compressors, they may be to the point of being ok for air conditioners now (and even getting common, I have not looked at how common in the last year or two), but they have a long way to go on the refrigeration end of the business that I regularly have to deal with. (scroll compressors are a lot cheaper than traditional semi-hermetics, but for now have a much shorter life expectancy). Having said that I think they will be the future for many applications.

Ike

 

[sewerzuk]

Ike,

To everybody else, I just hung up the phone with an engineer at Heinemann about the breaker problems.

Thanks for the effort!
I had planned on taking some time this weekend studying the schematic to try to figure this out on my own...

I'll take 1 of my -002's and one of my -003's and check the R-3 setting, adjust if necessary, and see if any of them are out of spec.

If this doesn't solve my starting surge issue, I'll make the necessary adjustments with R3 to make it work.

I'll be sure to post my findings here...

 

[sewerzuk]

Speddmon, I am going to dive into this on Saturday morning and get some data on how R3 affects trip delay and setpoint, but I just wanted to make sure I fully understand how this breaker works before I start making adjustments. So, I just wanted to try to clarify a few things:

1. The magnetic trip is a function of how much current is flowing through the main contacts; a large enough current spike essentially overpowers the holding force of the relay, causing it to trip the breaker. Is this correct?

2. The relay trip is a function of how much current is flowing through the smaller lugs in the field/control circuitry; when it exceeds the breaker's setpoint, it actuates the relay, causing the breaker to trip. Is this also correct?

3. If 1 and 2 are both correct, it would seem to me that adjusting R3 for a greater current flow through the breaker would actually increase the holding power of the relay (making it more resistant to surge trips), but decrease the relay's effective trip setpoint (making the relay trip earlier under steady state loads). This is the effect that I am trying to achieve...do you agree with this assessment?

 

[Speddmon]

Not quite, The relay trip is a function of how much current is flowing through the coil of the relay and nothing more. The main contacts of the breaker act as switching contacts ONLY.

If you look at the schematics for the 003a you'll see that the current going through R3 is produced by a current transformer (CT) located in the CT/CVT assembly. The CT puts out current directly proportional to the current in the main line, only reduced due to the transformer action taking place in the CT. As you place more load on the generator, the current produced by the CT increases as well. That's why you are to run the set in 120 volt mode at rated load and adjust R3 until you see .75 amps on your meter. I don't know what the turns ration of the CT is but obviously .75 amps equates to about 104 amps on the main line since that's the rated load of the generator.

When the current across R3 is set to .75 amps, and the breaker doesn't trip until that current reaches .825 amps, you basically have a 110% capability much like fuses and normal breakers. Meaning the breaker will not trip under normal loading until you are at 110% of the rated load...or 110% of 104 amps...114.4 amps. You can make the breaker trip sooner too, if you are only running the generator at 50% load and you adjust R3 to get .75 amps, then you are basically setting the trip setting of the breaker at 110% of 52 amps or...57.2 amps. That's why it is critical to have the R3 adjustment done properly, because if you set R3 too low...lets say .4125 amps (1/2 of .825 for simplicity sake) when you are running the set at rated load, then you are basically setting the breaker to trip at 200% of the rated load...or 208 amps...THAT"S BAD!!!!!!

Back to the operation of the breaker. I kind of summed up what happens and how the breaker works during normal loading and operation. When you start a heavy inductive load, such as your large compressor, that's where the magnetic (actually Hydraulic-Magnetic) trip comes into play. When you start a large inductive load, there is a large magnetic field produced called Magnetic Flux. When you start the motor, flux is induced into the relay coil and starts to move the plunger. If the surge is not too great, the flux will very soon dissipate and the current produced in the CT will start to act on the relay coil and the breaker will act normally and not trip. If the flux is very large, the plunger will move far enough on it's own to trip the breaker. This action basically acts as a time delay that is proportional to the overload setting...the higher the surge the faster the breaker trips. So if your R3 setting is set too low like given in the 50% example above, the surge that it takes to trip the breaker instantaneously will be decreased as well.

Attached is a snippet of a document made by Eaton (Heinemann) explaining the process somewhat.

I hope I didn't confuse you too much, but it is pretty important to have that R3 set to the proper value. If you want to bump up you capacity just a little, it's not going to take much at all to do it.

 

[sewerzuk]

I hope I didn't confuse you too much

Not at all! I'm an ex-Navy Nuclear Electronics Technician; I have a good solid understanding of electronics.
I appreciate the help and the time you took to ask the engineer at Heinemann about this issue. I was going to try to figure most of this out on my own...you've probably saved at least a few hours of my weekend.
I'll spend some time with one of my -002's on Saturday and let you know what I learn...

 

[atankersdad]

Speddmon I want to publically thank you for taking the time to explain things so us dummies out there can understand. In fact, I was having problems with one of my 003a's and i read old posts that you did that helped me troubleshoot the problem. The TM is good, but you are great. Once again sir, thank you for taking the time, to break down the items you do that helps all of us non-electricians on this site. We are lucky to have you here as a member.

 

[Speddmon]

 

[Speddmon]

Sewerzuk,

Have you had a chance to play around with your generators yet? I am curious to know if the R3 was out of adjustment, and if so, did adjusting it fix your problems???????

 

[sewerzuk]

Sewerzuk,

Have you had a chance to play around with your generators yet? I am curious to know if the R3 was out of adjustment, and if so, did adjusting it fix your problems???????

I decided to wait until I could get my hands on a good clamp ammeter; I wanted as much info as I could get before I started playing with R3.

I just picked up a used Fluke 337 off of Ebay; got it in the mail a few days ago. It has the ability mt record min, max, and peak inrush currents. I'm going to hit my 003's and 002's with some starting surges and find out exactly what current is causing them to trip, then I'll begin toying with the R3 setting...

I'll be sure to post my findings here.