Advice Needed to Wire in the Generator

[RV Mech Tech]

ibdilbert01 - thanks  for your reply - the reason I mentioned this is because  we have had  several new  RV's over the years that  we  have had to modify before they could even be up for sale and update to a 20 amp circuit for the convection microwave ovens -not a lot of fun to do on a new RV! -  plugging a 15 amp appliance into a 20 amp circuit is not a problem so long as whatever you are plugging into the receptacle  is in good condition and you will still have overcurrent protection if the device is faulty and has a short to ground - but a situation can exist  (14/2 wiring 15 amp circuit on a 20 amp breaker)  where a device is faulty such as an electric motor  (rated for 15 amps)  and can actually start to increase the current draw over 15 amps but not over 20 and then you have a situation where the ampacity of the 15 amp circuit is exceeded and the  conductors start to melt - so allowing  a 20 amp breaker on a 15 amp circuit defeats the purpose of an overcurrent device altogether -  I have seen  this many times in homes and sometimes in RV's where someone who works on electrical systems does this without knowing what the result can be -  many of the RV manufactures are now putting in 12/2  20 amp circuits anywhere its needed in the RV  and as you mentioned about the contractors, they  are doing the same here as well - so if anyone is doing any wiring in their Classic Winnie or Vintage RV please keep this in mind- thanks again!   

[4winds]

Got hold of Onan rep on Phone today.  Guess what?  My genset is a 6.5kva gen set!!! Sometime in the past a PO rewired for 30amp service,now I need to change back to 50Amp.  I mean house wiring not gen,if I can get to inside wiring should not be much of a problem.  I HOPE!!!Anyone have or can tell me where in message search I can find 50amp service wiring diagrams?  Ed

[DaveVA78Chieftain]

Changing house wiring from 50 to 30 would have been real dumb.  Not to mention real difficult.  My vote is they changed out the generator.  I am not even sure 50 amp service was available in the campgrounds in 1981.   Anyway, one reason to have 50 amp service is give the ability to have a 2nd air conditioner.

For reference,
here is what a typical 6.5 NH - 3CR generator looks like:



Here is the wiring diagram arrangements for the 6.5 generator:
Note: Be aware that you can only have one 54.2 amp circuit or two 27.1 amp circuits.







Here is a typical 4.0CCK-3CR generator:



Here are the wiring configurations:





Here is a look inside the box where you cahnge the wires on the top of a 4.0CCK generator.  You can see the wiring labels (M1, M2, M3, M4) for what has to be changed.



There were portable contractor versions of the generators.  They had boxes with recepticles already installed.  They also had different fan shrouds.
Here is what a 4.0CCK portable contractor version looked like:


Dave

[4winds]

Ok,When I find a picture of "dummy"that's me.  My coach had originally been wired for 50Amp service!!! Some PO changed it to 30Amp.  I will change it back when I can get a new power cord.  Thanks for all the help and sugestions, would not have thought to  check my circuit breaker panel without your help.. Ed(the dummy)

[ibdilbert01]

Any suggestions on the size of the starter wire I should run from my chassis battery to the generator?  I've got a 1976 4k BF Onan and the battery box is about 15ft away.

[LJ-TJ]

Man this is good stuff. Real glad we can post pictures with the notes. Makes life so much easier for dumbies like me. Thanks guys.

[JDxeper]

Tim
Here is a web site I use.
http://www.rbeelectronics.com/wtable.htm

[Froggy1936]

Mine has a regular 12 V cable from Genny to Chassis batterys then from solinoid to starter + terminal Then to engine battery All are the same size  Frank

[ibdilbert01]

First, thanks for all your help and I ended up ordering 2 gauge wire for the starter wire.       Secondly, here she is, hooked up to electrical panel and it seems to be running ok.  I let it run for a good hour or so with the AC, Fridge and battery charger hooked up and it seemed to run fine.  I also ran the microwave a few times just to test it out, and no issues.
   Did a little research on three-way transfer switches I found they are kinda hard to find and are costly, so I made my own using two Iota transfer switches.   The old transfer switch was connected to Inverter and Shore power.

Currently the transfer switch will automatically switch to whatever power is available and if it selects the inverter, the battery charger is isolated and it will not try to charge itself off its own power.   Also IOTA has a little delay circuit board so when the generator starts, it takes about 20 seconds before it does the switch, giving the genset time to spin up and smooth out and also preventing the genset from starting when a load is connected. 

Some oddball things to note.  The genset is a smaller Onan 4k BF, era 1976 and was in fairly rough shape.  All of the wiring in the generator bell and in the control panel was old and brittle, I replaced it all.   For fuel line, we used some extra brake line we had and simply used a "T" fitting at the gas tank to tie it in.  Any place wires or hoses go through a wall we wrapped water hose around that area for added protection.

A poor mans tuneup included nothing more than a new set of plugs (Champion H10C), the air cleaner and a DIY cut to fit 2 spark wire set.  The existing points were clean but the ignition relay (not to be confused with the starter solenoid) was faulty and I replaced it with a standard automotive 30 amp relay).  Cleaned the carburetor out, as it was dirty and a previous test run the needle didn't seat and the bowl over ran.  After some external cleaning and the removal of loose rust plus a "Detroit Diesel Green" paint job, it currently runs good.