DKD 6.5 genset output circuit breakers

[j.m.jackson]

I was just servicing my Onan DKD 6.5 genset in my 1993 33ft fleetwood southwind DP, and have experienced a couple of breaker trips while going down the road. I have two roof air units (Old coleman MACH units). I opened the genset breaker box, which has a large 30A breaker, and a physically smaller, maybe half the size, 20 amp HACR breaker.



I noticed that the feeder line coming from the genset is going into one side of the 30A breaker, and is then double tapped on the output. One output goes to romex to the motorhome, and the OTHER output goes to the INPUT of the 20 amp breaker. The output of the 20A breaker goes to a seperate romex into the motorhome firewall.


That doesn't seem right at all. The DKD should be able to deliver 54 amps @ 120v, so why is the 20A breaker input tied to the output of the 30A breaker. I know someone has been in the box and did this (screws missing on faceplate), but i'd like to confirm before I reconfigure the breakers.

[twinboat]

I would say that someone screwed up replacing the 30 amp breaker .

I would move the jumper on the 30 amp breaker.

[Persistent]

If you disconnect anything, you may be unpleasantly surprised.

Your description indicates you have a 30 amp generator. The 30 amp breaker is the "main" breaker. The 20 amp breaker is a branch breaker.

The 20 amp breaker probably protects a 12 gauge branch circuit. What ever appliance is connected to the 20 amp breaker will stop working if you disconnect it. The appliance may be a battery charger or cooling fan depending on model specifics.

If you don't want the 20 amp circuit to be active, just switch it "off".

The second output from the 30 amp main breaker goes to your main transfer switch for powering house appliances. I expect it is 10 gauge wire.

[j.m.jackson]

I think Twinboat is right, someone replaced a breaker and miswired it because this is a 30a shore power coach. Other house breakers have also been replaced during the units lifetime.

This coach has the switch up front in a cabinet that lets you select if you want to run the front OR rear air while on shore power. But while on generator power, you are supposed to be able to run BOTH units at the same time. Confirmed by the coach operators manual.

The 30a breaker feeds the 30A generator input of the house power transfer switch, and the 20a breaker feeds the rear aircon unit. I verified this last night.

Additionally, I put an amp-clamp on the lines when running both aircon units. Each one pulls ~11 amps 2-3 minutes after starting, and I saw 22 amps from the line coming from the genset. Starting current on the rear AC was in excess of 32 amps by itself on a single unit. I saw this by flipping off the 20A breaker, waiting 2 minutes to allow head pressure to drop, and flipping the breaker back on. Saw 44 amps on the genset line for just a moment, then settled back down to 22.

This was in the cool of the night, so was pretty much best case.

Add in the 120v refrigerator compressor start loads and the 12v converter loads, and things can get dicy going down the road.


-----
Mike Jackson
1993 Southwind 33 DP / Oshkosh chassis / 5.9 cummins / 542 allison
2008 hhr toad

[twinboat]

Originally Posted by Persistent

If you disconnect anything, you may be unpleasantly surprised.

Your description indicates you have a 30 amp generator. The 30 amp breaker is the "main" breaker. The 20 amp breaker is a branch breaker.

The 20 amp breaker probably protects a 12 gauge branch circuit. What ever appliance is connected to the 20 amp breaker will stop working if you disconnect it. The appliance may be a battery charger or cooling fan depending on model specifics.

If you don't want the 20 amp circuit to be active, just switch it "off".

The second output from the 30 amp main breaker goes to your main transfer switch for powering house appliances. I expect it is 10 gauge wire.

He states its a 6.5 KW ( 6500 watts ) generator.

30 amps is 3.6 KWs.

[Persistent]

Originally Posted by twinboat

He states its a 6.5 KW ( 6500 watts ) generator.

30 amps is 3.6 KWs.

It is a little hard to tell from the picture. Unless there is a second output junction box and or circuit breaker box, he can only get 30 amps 120 volts out. The 20 amp breaker does not appear to be in parallel with the 30 amp breaker.

The wire gauge does not look like 8 or 6 AWG that would be required for higher current.

[johnhicks]

Just to get freaky...

I have an Onan 6500 NMH. It has two outputs, 30A and 20A. The 30A runs to the transfer switch and powers the house. The 20A _bypasses the transfer switch_ and powers the rear a/c directly via the 20A breaker. The two breakers are in the original Onan case, and four wires go to a junction box, two whites and one black and one black/yellow.

I think yours may be similar with the 20A going directly to the rear a/c. I can independently switch either on or off.

I suspect it's miswired with everything hanging off the 30A breaker and that's why it trips. The operators manual just mentions the breakers but nothing about them.