MEP-803A Overload

Purchased an 803A after finding this website & all the valuable support you guys provide. Generator is intended to be used as a whole-home backup generator. Unit has new filters & oil. It starts just fine, runs the convenience receptacles as it should. I also verified voltage phase to phase/phase to ground. Quad fuse mods were also installed. The S8 reconnection switch has good/noticable dexterity & rotates as it should. The S6 am/vm switch is another story. Very tough to turn & I actually snapped the knob off the front of it. I'm currently waiting for a replacement I found on ebay.
Issues: before breaking the S6 knob, it was in the 3:00 position. Reconnection switch was on 120/240 & wired correctly on phase terminals. Flipped the contactor switch, then my range/oven breaker, then I slowly turned on electric stove burners. Unit changed in sound slightly, frequency dropped from 60Hz to about 59Hz, Voltage held at 240. No movement on the load %. After adding the 3rd burner, Overload tripped. This happened 3 or 4 times.
From what I've gathered on different posts similar to mine, the S6 & S8 may be contributing to my problem. I'll swap the S6 when it arrives. Should I be looking into anything else on the unit? Should I order an S8 as well?
Thanks in advance

The S6 is only there for measurements. It has no bearing on the overload part. Yes, get it fixed, but more likely, your S8 may need some cleaning. There are a million threads on how to do this and the experts will jump in here.

Guyfang said:

The S6 is only there for measurements. It has no bearing on the overload part. Yes, get it fixed, but more likely, your S8 may need some cleaning. There are a million threads on how to do this and the experts will jump in here.

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Thanks! I'll try to get it cleaned up this evening & crank it back up

You need to use a contact spray, and lots of it. I can not remember what its called, and here in germany it would have another name anyway. @Ray70 and @Light in the Dark @kloppk , among others will know.

Deoxit is the spray to use

Guyfang said:

You need to use a contact spray, and lots of it. I can not remember what its called, and here in germany it would have another name anyway. @Ray70 and @Light in the Dark @kloppk , among others will know.

Click to expand...

Deoxit? I have a few different brands of contact cleaner on hand. I'll try them first & order some Deoxit if it still won't run.

Deoxit is magic in a can. Amazon, lots of places sell it. Its a pretty common 'phantom' condition, caused by corrosion on contacts. The nice thing about Deoxit, is whatever witches brew its made from, actually leaves behind a coating to inhibit future corrosion as well.

e_beauregard said:

Deoxit? I have a few different brands of contact cleaner on hand. I'll try them first & order some Deoxit if it still won't run.

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Even if the other contact cleaners work, I would still order some, and use it on all of the rotary switches.

Deox-it is pretty amazing stuff. I would call it cheap insurance, if it keeps a switch from breaking. FWIW, I haven't used another brand since I first used Deox-it, many moons ago.

All the best,

2Pbfeet

Both S6 and S8 are involved with the Overload detection circuit.
Here is a simplified circuit diagram when running 120/240 and the AM/VM in the 3 o'clock position.
The CT's output a current proportional to the load on each leg ranging from 0 at no load to 1 amp AC at 133% load. That current is applied across the respective burden resistors.
The Overload Relay K8 monitors the AC voltage developed across each of the burden resistors.
The voltages normally range from 0 volts AC at no load, 5.6 volts AC at 100% Load and 7.5 volts AC at 133% Load.
K8's tripping time upon an overload is inversely proportion to the amount of overload. IE With a slight overload it may be minutes before tripping. A large overload and it will trip fast.
A way to track down which leg is causing the Overload can be done by using an DMM and measuring the AC voltage across the respective burden resistors or across the respective terminals on K8.
Frequently false overloads are due to poor contacts in S6 or S8. Poor contact results in increased resistance in the path(s).
Using Deoxit and exercising S6 & S8 with the set ** OFF ** usually resolves the issue.

kloppk said:

Both S6 and S8 are involved with the Overload detection circuit.
Here is a simplified circuit diagram when running 120/240 and the AM/VM in the 3 o'clock position.
The CT's output a current proportional to the load on each leg ranging from 0 at no load to 1 amp AC at 133% load. That current is applied across the respective burden resistors.
The Overload Relay K8 monitors the AC voltage developed across each of the burden resistors.
The voltages normally range from 0 volts AC at no load, 5.6 volts AC at 100% Load and 7.5 volts AC at 133% Load.
K8's tripping time upon an overload is inversely proportion to the amount of overload. IE With a slight overload it may be minutes before tripping. A large overload and it will trip fast.
A way to track down which leg is causing the Overload can be done by using an DMM and measuring the AC voltage across the respective burden resistors or across the respective terminals on K8.

View attachment 921391

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Ahhh, okay thank you! I’ll check that out once I can set it to 3:00 on the dial. Naturally, when I snapped the knob off it was in the wrong position.


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e_beauregard said:

Ahhh, okay thank you! I’ll check that out once I can set it to 3:00 on the dial. Naturally, when I snapped the knob off it was in the wrong position.


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Click to expand...

Pliers are natures answer to many things

Light in the Dark said:

Pliers are natures answer to many things

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Oh trust me, that was my first instinct! LOL the plastic shaft that the switch attached to was broken off flush (and is still stuck inside the switch)

I stand corrected!

kloppk said:

Both S6 and S8 are involved with the Overload detection circuit.
Here is a simplified circuit diagram when running 120/240 and the AM/VM in the 3 o'clock position.
The CT's output a current proportional to the load on each leg ranging from 0 at no load to 1 amp AC at 133% load. That current is applied across the respective burden resistors.
The Overload Relay K8 monitors the AC voltage developed across each of the burden resistors.
The voltages normally range from 0 volts AC at no load, 5.6 volts AC at 100% Load and 7.5 volts AC at 133% Load.
K8's tripping time upon an overload is inversely proportion to the amount of overload. IE With a slight overload it may be minutes before tripping. A large overload and it will trip fast.
A way to track down which leg is causing the Overload can be done by using an DMM and measuring the AC voltage across the respective burden resistors or across the respective terminals on K8.
Frequently false overloads are due to poor contacts in S6 or S8. Poor contact results in increased resistance in the path(s).
Using Deoxit and exercising S6 & S8 with the set ** OFF ** usually resolves the issue.

View attachment 921391

Click to expand...

Amazing for troubleshooting. Trying to find an issue with a like new set & this is very helpful!

Update- used 2 cans of CRC contact cleaner, then a can of Deoxit on the S8 switch. Also swapped the S6 out with a new one I found on eBay. VM is working as it should now.
Will attempt load test tomorrow pics of progress:




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[mention]Guyfang [/mention] [mention]kloppk [/mention] & the others, thank you guys for the assistance!! Was able to give it a test run today and it ran great. No more overload tripped! Ran all my appliances except central ac (I’m waiting for a soft start). As the heating elements in my ovens cycled, the load would fluctuate as expected. I will rig up something to apply a steady load test in the future. Ive learned so much from this site. Thanks everyone!
-Ed



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