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MEP-803A Overload

e_beauregard

New member
16
19
3
Location
Louisiana, USA
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
 

Light in the Dark

Well-known member
Steel Soldiers Supporter
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MA
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.
 

2Pbfeet

Well-known member
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728
93
Location
Mt. Hamilton, CA
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.
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
 

kloppk

Well-known member
Steel Soldiers Supporter
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Location
Pepperell, Massachusetts
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.

1713358123028.png
 

e_beauregard

New member
16
19
3
Location
Louisiana, USA
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
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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CallMeColt

Well-known member
Supporting Vendor
1,009
1,461
113
Location
Wilson County, Texas
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
Amazing for troubleshooting. Trying to find an issue with a like new set & this is very helpful!
 

e_beauregard

New member
16
19
3
Location
Louisiana, USA
[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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