Mep-803a Fuel or Electrical problem. Will Not Trip.

Zed254 · Aug 8, 2019

Lucky your unit had the quad fuse installed. I'm guessing a compressor or motor started and tripped your generator. This is why the military de-rates these units to 80%... ~41.6 amps or so...to allow for motors and such to cut on and off without shutting the generator down. Startup amps can be quite high for motors.

Using your home as a load bank can be risky: electronic items can get fried when a generator burps and you've seen how hard it is to control amps. I bought a used electric stove to test with which is a 100% resistive load (no motor starts). A lot of the guys on SS have built their own load banks: they are a lot smaller and easier to handle than my stove. Some have bought electric garage heaters.

I've gotten to the point that I run my generators at around 95% - on a stove - for 2 or 3 hours each quarter. I warm them up with light loads, go into a heavier load, then back off on load as I approach shutdown.

mt4x4 · Aug 8, 2019

Zed254 said:
Lucky your unit had the quad fuse installed. I'm guessing a compressor or motor started and tripped your generator. This is why the military de-rates these units to 80%... ~41.6 amps or so...to allow for motors and such to cut on and off without shutting the generator down. Startup amps can be quite high for motors.

Using your home as a load bank can be risky: electronic items can get fried when a generator burps and you've seen how hard it is to control amps. I bought a used electric stove to test with which is a 100% resistive load (no motor starts). A lot of the guys on SS have built their own load banks: they are a lot smaller and easier to handle than my stove. Some have bought electric garage heaters.

I've gotten to the point that I run my generators at around 95% - on a stove - for 2 or 3 hours each quarter. I warm them up with light loads, go into a heavier load, then back off on load as I approach shutdown.

To be clear, my generator did not trip. I'm starting to feel like you guys don't test your generators to the overload or short circuit fault. Can anyone comment on how many amps for what amount of time should cause a fault?

Guyfang · Aug 8, 2019

Farmitall said:
Maybe its just me, and maybe I just don't get it, but why are some people always trying to push their generators to the breaking point?

I understand that these sets are rugged but why purposely try to break them? I see this same mentality with side by side owners too. They buy a vehicle for $15-$20k then take it out to try and deliberately punish it to the breaking point....and usually break it. Then they weep and complain when they are hit with a $2000 dollar repair bill at the shop.

Sitting here scratching my head.

Thank you!!!! :goodjob:

Zed254 · Aug 8, 2019

mt4x4 said:
To be clear, my generator did not trip. I'm starting to feel like you guys don't test your generators to the overload or short circuit fault. Can anyone comment on how many amps for what amount of time should cause a fault?

Depends on the condition of the generator. Mine tripped out one time as I was cleaning it out shortly after recovery.....probably around 75% (39 amps). And I don't like tripping out my generators. It now runs easily at 103% with no hiccups.

I suspect you will be the man that will find the crash zone for the 803. When you do please report back with amps and any repair bills incurred. Good luck.

Daybreak · Aug 8, 2019

Howdy,
If you are trying to make it trip.

Power the unit up, run it at 125%

After some time.... get ready.... it will trip. It's not like a circuit breaker, the fault light will come on with overload, that is when the unit then drops the power to the circuit interuptor.

After this condition, you need to let the unit run a while to cool down, the fault reset will not reset right away. It is a timing thing. After maybe 5 mintues or more, push the fault reset button, did the overload fault reset yet? No, then wait some more.... it is a timing thing... after a while it should take a reset, and you are back operating.

You just do not need to run it til it bogs down. That is not good for the unit, nor for whatever you have hooked up. All things electrical like to have 120/240 60Hz

Daybreak · Aug 8, 2019

Howdy,
You need to go back and watch some of my you tube video's

67 amps per leg on a MEP-803A humming along....

Did it trip? yes, not right away, it is a timing thing... if I stayed running it there say for maybe 4-6 minutes, it would trip.

MEP-803A 3kw thru 16kw

Guyfang · Aug 8, 2019

Something you all need to keep in mind. The CB-2 contacts. When you shut CB2 and put the set on max load, and just for laughs and giggles say, 67 amps is flowing, what happens when the CB2 load contacts open with 67 amps flowing through them?

You get a big, fat, arc, at the contacts. Every time you trip CB2, by hand or a safety switch tripping the CB2, a bit of metal is moved from one contact, to the other side. This can lead to a set of contacts welding shut, or not making a good contact. Poor contact, means heat. Heat means the Overload switch can trip faster. Or you can not get the set to assume a full load. For all intents and purposes, there is no difference between a short circuit and overload to the overload switch. It is more or less a thermo switch.

Contacts welded shut? Well, one day long ago, and far away, I got a jolt from a circuit breaker the was "open". Turned off. That lesson taught me to NEVER, EVER touch an electrical circuit, I haven't personally tested.

Never turn off a load by opening CB2. Turn the load off first.

Guyfang · Aug 8, 2019

Daybreak said:
Howdy,
You need to go back and watch some of my you tube video's

67 amps per leg on a MEP-803A humming along....

Did it trip? yes, not right away, it is a timing thing... if I stayed running it there say for maybe 4-6 minutes, it would trip.

The overload switch is designed that way to keep a momentary overload from dropping your full load, when a small, momentary overload occurs. Trust me, it will work, unless someone is running the set with a hot wired overload switch.

MEP-803A 3kw thru 16kw

.

mt4x4 · Aug 8, 2019

Daybreak said:
Howdy,
You need to go back and watch some of my you tube video's

67 amps per leg on a MEP-803A humming along....

Did it trip? yes, not right away, it is a timing thing... if I stayed running it there say for maybe 4-6 minutes, it would trip.

MEP-803A 3kw thru 16kw

I did not see any faults in this video.

mt4x4 · Aug 8, 2019

Guyfang said:
Something you all need to keep in mind. The CB-2 contacts. When you shut CB2 and put the set on max load, and just for laughs and giggles say, 67 amps is flowing, what happens when the CB2 load contacts open with 67 amps flowing through them?

You get a big, fat, arc, at the contacts. Every time you trip CB2, by hand or a safety switch tripping the CB2, a bit of metal is moved from one contact, to the other side. This can lead to a set of contacts welding shut, or not making a good contact. Poor contact, means heat. Heat means the Overload switch can trip faster. Or you can not get the set to assume a full load. For all intents and purposes, there is no difference between a short circuit and overload to the overload switch. It is more or less a thermo switch.

Contacts welded shut? Well, one day long ago, and far away, I got a jolt from a circuit breaker the was "open". Turned off. That lesson taught me to NEVER, EVER touch an electrical circuit, I haven't personally tested.

Never turn off a load by opening CB2. Turn the load off first.

Are you saying i should never test my generator to fault?

Guyfang · Aug 8, 2019

mt4x4 said:
Are you saying i should never test my generator to fault?

Not at all. But too much of a good thing is bad. Load the set up. Go to 133%. But why stress the CB2 any more then needed. I worked on gen sets 20 years in the army. Later, I worked on gen sets 8 years for the army. I never saw the reasoning to do such testing unless there was a good reason. Going to war, giving the set to a customer who was going to war. To me, if it goes to 133%, that's way more then what it needs to be. Be happy. Get a load bank if you just have to push the set to the wall. That way, you can raise the load in a controlled manner. When it pops, you will have your answer. But repeatedly pushing it to the wall is not a good idea. Do not use your house. Sad things can happen.

Its your set. Do as you please. But if something goes wrong, don't be surprised.

mt4x4 · Aug 8, 2019

Daybreak said:
Howdy,
If you are trying to make it trip.

Power the unit up, run it at 125%

After some time.... get ready.... it will trip. It's not like a circuit breaker, the fault light will come on with overload, that is when the unit then drops the power to the circuit interuptor.

After this condition, you need to let the unit run a while to cool down, the fault reset will not reset right away. It is a timing thing. After maybe 5 mintues or more, push the fault reset button, did the overload fault reset yet? No, then wait some more.... it is a timing thing... after a while it should take a reset, and you are back operating.

You just do not need to run it til it bogs down. That is not good for the unit, nor for whatever you have hooked up. All things electrical like to have 120/240 60Hz

I will start over. The way i think a generator should work is it should fault before the engine bogs down. I'm not talking a few hz, i mean really drop in hz to someting like 35. Also not just a dip. It drops and stays dropped until i disconnect the load. If the mep-803a does not work like this, than this is a really poor design.

Someone call me out as being wrong. The mep-803a or any other generator should fault and drop the load before the engine slows down by significant rpm's. Mine does not. This is a problem i want to fix. It is unsafe to have a safety mechanism in place that does not work or is never tested.

At this point with your guys help i think the problem is with my engine. I will run a test this weekend to try and clean it out.

mt4x4 · Aug 8, 2019

Guyfang said:
Not at all. But too much of a good thing is bad. Load the set up. Go to 133%. But why stress the CB2 any more then needed. I worked on gen sets 20 years in the army. Later, I worked on gen sets 8 years for the army. I never saw the reasoning to do such testing unless there was a good reason. Going to war, giving the set to a customer who was going to war. To me, if it goes to 133%, that's way more then what it needs to be. Be happy. Get a load bank if you just have to push the set to the wall. That way, you can raise the load in a controlled manner. When it pops, you will have your answer. But repeatedly pushing it to the wall is not a good idea. Do not use your house. Sad things can happen.

Its your set. Do as you please. But if something goes wrong, don't be surprised.

The good reasoning to test the faults is this gen is new to me and i don't know if they work. I don't know the history of this set. At this point i have a problem with this set and i don't think its wrong to want to fix it. If it were up to me i would want it to trip at 12k but i'm not sure i can change that. I'm not looking to get more power, i just want to make sure the faults work?

Daybreak · Aug 8, 2019

Howdy,
Go back and read my post.

Before you hurt something or someone. It will trip. run it at 125%, let it stay at 125%, no extra amounts. It will trip. That is by design.

Coug · Aug 9, 2019

mt4x4 said:
I will start over. The way i think a generator should work is it should fault before the engine bogs down. I'm not talking a few hz, i mean really drop in hz to someting like 35. Also not just a dip. It drops and stays dropped until i disconnect the load. If the mep-803a does not work like this, than this is a really poor design.

Someone call me out as being wrong. The mep-803a or any other generator should fault and drop the load before the engine slows down by significant rpm's. Mine does not. This is a problem i want to fix. It is unsafe to have a safety mechanism in place that does not work or is never tested.

At this point with your guys help i think the problem is with my engine. I will run a test this weekend to try and clean it out.

In proper operating condition, yes, these will trip before you get that kind of droop. at 35 hz you're talking serious issues with the load if it isn't purely resistive.

So yes, if your machine is drooping more than a few hz, there is something wrong with the engine that needs fixed. About the only way you'd get that kind of droop normally is massively overloading the unit and having the breaker bypassed. If one or more injectors are plugged up, valves out of time, or airflow is restricted in either the intake or exhaust circuits it can lead to loss of engine power, and the engine to droop before reaching designated load capacity.

As others have said, it's not an instant trip. It takes time to cause a trip unless there is a physical short of some type (or the GFCI gets tripped, which is different)

Typically breakers use a bimetalic trip mechanism. The mechanism is good for a certain amount of heat build up before it causes the breaker to trip, then has to cool down and reset before it will allow the breaker to be reset (think a dual circuit like a relay engaging a larger circuit, only in this case both circuits in the relay are on until the smaller circuit overheats and takes out the larger one)

I'm still new to military gensets, but in many civilian ones, if the engine slows down and frequency drops, it's not going to cause the breaker to trip. Only excessive loading of the breaker causing the heat buildup will cause the trip. Civilian generators that have a low frequency shutdown will kill the entire unit, not just trip a breaker. It's a completely different system in the control panel.

I checked the manual, and checked my MEP802A outside, there is no provision on these to trip the breaker for low frequency. So that means it won't trip unless it's overloaded. Running at a lower frequency isn't going to cause a trip, because it's not heating up the breaker.

mt4x4 · Aug 9, 2019

Coug said:
In proper operating condition, yes, these will trip before you get that kind of droop. at 35 hz you're talking serious issues with the load if it isn't purely resistive.

So yes, if your machine is drooping more than a few hz, there is something wrong with the engine that needs fixed. About the only way you'd get that kind of droop normally is massively overloading the unit and having the breaker bypassed. If one or more injectors are plugged up, valves out of time, or airflow is restricted in either the intake or exhaust circuits it can lead to loss of engine power, and the engine to droop before reaching designated load capacity.

As others have said, it's not an instant trip. It takes time to cause a trip unless there is a physical short of some type (or the GFCI gets tripped, which is different)

Typically breakers use a bimetalic trip mechanism. The mechanism is good for a certain amount of heat build up before it causes the breaker to trip, then has to cool down and reset before it will allow the breaker to be reset (think a dual circuit like a relay engaging a larger circuit, only in this case both circuits in the relay are on until the smaller circuit overheats and takes out the larger one)

I'm still new to military gensets, but in many civilian ones, if the engine slows down and frequency drops, it's not going to cause the breaker to trip. Only excessive loading of the breaker causing the heat buildup will cause the trip. Civilian generators that have a low frequency shutdown will kill the entire unit, not just trip a breaker. It's a completely different system in the control panel.

I checked the manual, and checked my MEP802A outside, there is no provision on these to trip the breaker for low frequency. So that means it won't trip unless it's overloaded. Running at a lower frequency isn't going to cause a trip, because it's not heating up the breaker.

On the gfci right below the fault lights. Is this a gfci for the load. If i push the test button on the gfci should it drop the contactor? I thought i read it was only for the convenience outlet.

kloppk · Aug 9, 2019

mt4x4 said:
On the gfci right below the fault lights. Is this a gfci for the load. If i push the test button on the gfci should it drop the contactor? I thought i read it was only for the convenience outlet.

Pushing the GFCI Test button will only drop the load to, if any, that's plugged into the convenience outlet.
The main contactor powering the output lugs will remain closed (if previously closed).

Coug · Aug 9, 2019

A GFCI also has nothing to do with frequency. Simplified, it's just checking to see if there is a voltage showing up on the ground wire that isn't supposed to be there, then trips the circuit if it measures any (something like 100mv is enough)
From my past experience with these generators (getting shocked by improperly grounded ones in the Army) the GFCI doesn't have anything to do with the main output terminals.

Circuit breakers are there to protect the generator from excessive load, and doesn't care what the electricity does as long as there isn't too much amperage.
GFCI is there to protect people from getting electrocuted by quickly tripping when voltage is going places it isn't supposed to.

mt4x4 · Aug 10, 2019

OK today I ran at 45 amps for 4 hours. I had seafoam in the tank. It had a little smoke for the first hour then it cleared up. After the 4 hours I took it up to 125% for 10 minutes. It did not trip. I then went to 133% it did not trip. I pushed it a little more and the rpm went south. Tomorrow I'm going to start testing the over load relay. Should 125% for 10 minutes cause a fault?

Daybreak · Aug 10, 2019

Howdy,
Double check everything before doing. Make sure all it 100% working correctly.

Stay at 125%, it will trip. time frame? undetermined due to wire connections, fuse, fuse age, fuse has been hurt prior etc...

It will trip.

Mep-803a Fuel or Electrical problem. Will Not Trip.

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