MEP802A overload tripping

[Bassfishin114]

I am fairly new to the military genset world but have spent countless hours on this site reading and have found so much valuable information. I have my Mep802a hooked up to my house as a back up generator. Today I did the first load test and it was going good. I turned the oven on and it was pulling around 20amps and showing about 60-70% load ( no other circuit connected). After a minute it tripped the overload. I retried this multiple times and got the same result. Have L1,L3 wired to hot, N to panel ground, and it is unbonded at the generator. I do not have a grounding rod or ground connected. Should that be done and would that cause this issue? When it tripped there was no amp increase or load increase indicated. I let it run for about an hour at 40% load with no issues. Unit is running about 62hz/245v without load and 61hz/242v under 60% load. Can anyone lead me in the right direction? I skimmed through the TS section of the manual but didn’t see anything really related.

 

[Scoobyshep]

You absolutely should have the set grounded. In your case if you aren't switching the neutral, (which is most cases) leave the generator neutral-ground bond open and tie the generator chassis to the ground bar in your panel ( should be 4 wire. L1 L3 L0(neutral) and ground. As for premature tripping, I would check the actual current draw with a separate meter first.

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[Bassfishin114]

You absolutely should have the set grounded. In your case if you aren't switching the neutral, (which is most cases) leave the generator neutral-ground bond open and tie the generator chassis to the ground bar in your panel ( should be 4 wire. L1 L3 L0(neutral) and ground. As for premature tripping, I would check the actual current draw with a separate meter first.

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I had my amp clamp meter around 1 hot wire at the panel which is where I got my amp readings from. I will get the ground added.

 

[Evvy Fesler]

Welcome!

I can help with terminology, if you don't mind?
L1, L3, should each be connected to you panel's L1, L2 respectively, typically black.
N should be connected to your panel's N, typically white
Genset selector, inside the control cube, should be in 240v, 1P mode

Grounded in electrical world means N, or neutral, typically white.
The spelling "ed" vs "ing" is special and actually means distinctive things.
Grounding means earth via the grounding electrode, typically bare copper and sometimes green.
Bonding means to make a solid connection between N, grounded and grounding at the first point of disconnect, i.e., the main panel. It is here that white wires are connected to bare copper (sometimes green) wires and the grounding electrode pair. So is the enclosure.

You probably have it connected this way, but it never hurts to have someone restate it to make sure. Be patient. Others will comment about your posted problem. There are a lot of experienced people willing to help out.

Best,

Evvy-

 

[Digger556]

If you have everything wired up correctly and it trips the overload after a min or so, it is likely the contacts in S6 or S8 are dirty.

Buy a spray can of Deoxit D5 and thoroughly clean out those 2 switches to start with.

 

[Guyfang]

But not when its running.

 

[Bassfishin114]

If you have everything wired up correctly and it trips the overload after a min or so, it is likely the contacts in S6 or S8 are dirty.

Buy a spray can of Deoxit D5 and thoroughly clean out those 2 switches to start with.

I got some contact cleaner (waiting for a can of deoxit to come in) and sprayed everything really good and operated s6 and s8 50+ times each. It is still tripping overload after about 60% load. Do I need to remove and disassemble s6 and s8 to get them cleaned better?

 

[Guyfang]

First look and see if the CT's are wired correctly. How many loops go through them? Should be 8 times for a MEP-802A.

The S6 has nothing to do with your problem. Its for meters only. S8, not you may just wind up taking it apart, of simply loosening it. up. Get more spray into the switch then.

 

[Bassfishin114]

First look and see if the CT's are wired correctly. How many loops go through them? Should be 8 times for a MEP-802A.

The S6 has nothing to do with your problem. Its for meters only. S8, not you may just wind up taking it apart, of simply loosening it. up. Get more spray into the switch then.

can you elaborate on”CT’s” I am not sure what that means.

 

[Scoobyshep]

can you elaborate on”CT’s” I am not sure what that means.

Current transducer (or transformer) it's how the instrumentation measure current. The number of wraps changes the current multiple. Look for a block with wire wrapped through a hole

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[Bassfishin114]

Current transducer (or transformer) it's how the instrumentation measure current. The number of wraps changes the current multiple. Look for a block with wire wrapped through a hole

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There is 16 wires through each loop.

I found another post that mentioned measuring AC voltage across K8 and found that with a small space heater
K8-1 and K8-4 has 1v
K8-2 and K8-4 has 1v
K8-3 and K8-4 had 2v.
I am assuming that the last one having 2v is going to be what is causing the overload to trigger.

 

[kloppk]

It could be that resistor R13 is bad or the contacts 13 14 in S8 aren't making good contact. The purpose is to put R13 in parallel with R12. This cuts the burden resistance from 7.5 ohms to 3.75 ohms.
The CT's generate a current proportional to the load on the respective winding set. The CT's current flows thru the burden resistor and generates a voltage across the resistor. K8 measures that voltage across the burden resistor to determine if there is an overload.
If they aren't in parallel the voltage to K8-3 K8-4 will be twice what it should be. K8 uses that voltage to determine if there is an overload in that winding set. So... at 60% load K8 thinks that winding set is 120% loaded.

 

[Guyfang]

I am assuming that the last one having 2v is going to be what is causing the overload to trigger.

Never assume. Know.

 

[Bassfishin114]

It could be that resistor R13 is bad or the contacts 13 14 in S8 aren't making good contact. The purpose is to put R13 in parallel with R12. This cuts the burden resistance from 7.5 ohms to 3.75 ohms.
The CT's generate a current proportional to the load on the respective winding set. The CT's current flows thru the burden resistor and generates a voltage across the resistor. K8 measures that voltage across the burden resistor to determine if there is an overload.
If they aren't in parallel the voltage to K8-3 K8-4 will be twice what it should be. K8 uses that voltage to determine if there is an overload in that winding set. So... at 60% load K8 thinks that winding set is 120% loaded.
View attachment 904693

Well I started tracing wiring and looking at the R13 resistor and found one of the wires just sitting on lead. Soldered it back in place and it back to working properly. Thanks everyone for all of the help.