MEP-802a tripping Overload

[Milhouse]

Running a 17.5A load (clamp on Fluke) for an hour or so trips overload, it also shows 125% on the load meter, were using an electric heat fan rated for 4800W to load test the gen sets, anyone know why this would trip? since the set is rated for 26A it shouldn't trip overload with just a 17A, nothing is overheating and the motor isn't even sweating, engine temp was running a cool 170 degrees, stator was warm but not hot. Load connected to L1 and L3, 120/240V mode, perfect 240V at terminals, perfect 60hz.

 

[dependable]

Is it running 17.5A each on L1 & L3?

 

[Milhouse]

its a 2 wire load, L0 is not connected, so you would always read the same current on L1 as L3. I'm wondering if its tripping because it has no common or ground.

 

[dependable]

In 120/240 mode, you should have L0 connected as neutral. It may work OK with a single 240V test load, but if you hook it to your house or try to run any load where the 120V legs are not balanced, very bad things can happen. (I have some experience in this, though not intentionally)

If I understand what you are saying, you are getting 17.5A from one leg. Then your gen output is close to 35A when it trips. You can't be sure your test load from stated rating on it.

Is 'electric heat fan' all 240V or is there a 120V component in fan?

 

[CDR]

Had the same issue found a broken wire on the top ballistic I don't remember the number I'll figure it out

 

[Milhouse]

The electric heat fan is 240V only, its basically just a big resistor, there is no neutral, 2 pole only. On a true 240V system, if you read 17.5A on one leg, you will have the same on the other, and your total is 17.5A load not 35A, current flows from one pole to another. the gen set is rated for 26A @ 240V, so it should not be tripping at 17.5, we measured it with a clamp on Fluke meter.

 

[dependable]

Guess I'm stuck in split phase mode.

Got a garage kit from your town, came out good.

 

[CDR]

The electric heat fan is 240V only, its basically just a big resistor, there is no neutral, 2 pole only. On a true 240V system, if you read 17.5A on one leg, you will have the same on the other, and your total is 17.5A load not 35A, current flows from one pole to another. the gen set is rated for 26A @ 240V, so it should not be tripping at 17.5, we measured it with a clamp on Fluke meter.

Take a picture of behind the panel and upload it and I'll show u what was wrong with mine

 

[RichardR]

Milhouse,

I've never seen the exact problem you're having with tripping on a load that your 802a should handle with ease, but since apparently no one else has seen it either I'll put in my $.02. It seems to me that the ammeter reading 125% when you are only putting about 85% load on the genset is a very good clue. It appears to me that the ammeter reading and the tripping action are in agreement, but both are wrong. Looking at the schematic and trying to figure out what would cause both problems makes my head hurt. Maybe someone a lot smarter than me can decipher how the current meter is hooked up and pinpoint a likely problem source. The schematic with it's multiple switch tables is just about indecipherable to me but it looks like K8, the Overload/Short Circuit Relay, has something to do with driving the ammeter and setting the trip point.

Since I am reduced to guessing at the source of the problem, my guess is that it is K8 and/or its associated circuitry. There are several resistors (Burden Resistors) that hook up to K8 and I think they must calibrate both the trip point and the ammeter. Take a look in that area. That's my guess and I'm sticking to it. Good luck with an interesting problem, and tell us what you find.

Richard