Skip to main content ↑ ↓
Topic: Generator fire! (Read 1055 times) previous topic - next topic

Generator fire!

Subject should "generate" some renewed interest in the subject discussed over the last few days.
Did have a fire.
I decided I had two problems that might be unrelated.  1- engine running erratically.  2- Cooling fan CB tripping.
My understanding of diesel engines is that most problems are related with fuel delivery, if it is turning over.  I removed the fuel line on the engine side of the fuel pump and found that I was getting good volume when the pump was energized.
While I was attempting to start it I noticed that the cooling fan circuit breaker had not tripped and I continued trying to restart several times with the best effort being about a minute of run time.  While doing this, I heard a sound from the control box and saw flames.  I quickly shut off power and the flame went out.  The new CB had melted.

I called Power Tech and Jeff Jones told me that could happen if there was high amperage from the fan.  Fan motor is rated at 5.5A and 180% of that would be less than 10A, so the CB should have been sufficient.  Jeff told me that they didn't put in the 10A CB, so it must have been FT.  I called James at FT and he said they did not add it; they only attach the fan to the provided wiring.  This makes sense to me because of warranty issues.  Back to Jeff:  He said that the SOP was to wire the fan to  the main CB (45A) and said it would be OK for me to do so.  Is it safe to wire a 5.5A motor to a 45A CB?
I put in another call to Jeff to discuss it further.
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Generator fire!

Reply #1 –
I'm no expert, but there is a reason that 10A CB was installed in the first place. If the fan motor is rated at 5.5A, a 45A CB would not do its job of protecting the fan if it should pull to much amperage over what the fan was intended for. If that was the case, I should be able to wire everything in my house to the 200A main and not worry about all those pesky little 15 and 20 amp breakers.

Again, I'm not an expert, but it seems like common sense to me.

Larry
Larry Warren
1996  U320 36' SBID "Lola" sold 2020
Build #4970
Motorcade #18318

Re: Generator fire!

Reply #2 –
Fuses/breakers are sized to protect the WIRE as well as blow/trip if amp load gets to well more than normal start up load. 

Have you measured starting and running amps?  Hand spun fan to verify bearings OK?

?Start capacitor?
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Generator fire!

Reply #3 –
There is a thing called LRA  (lock rotor amps)  This condition happens when the motor is at stand still and power is applied.  The LRA can be up to 6 time the running amps.

Now if it is a 10 amp breaker in there now and the fan will start up then I would stay with that. The larger breakers are put in to handle the starting of the fan motor without tripping.

Breakers should not start on fire if the load is higher then what the breaker is rated at. The breaker should just trip if load is too great.

Do you a picture of what the breaker looks like after starting on fire?
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Generator fire!

Reply #4 –
Quote from: wolfe10 –
Fuses/breakers are sized to protect the WIRE as well as blow/trip if amp load gets to well more than normal start up load. 

Have you measured starting and running amps?  Hand spun fan to verify bearings OK?

?Start capacitor?
My reason for getting the engine issue resolved first was so that I could take those readings.  I did hand turn the fan and ran the fan using house current (extension cord).
I may have over heated the circuit by attempting to start the engine 4-5 times in a short period of time, with pre heat coming on each time.  I didn't adequately purge the air from the fuel line before doing so.
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Generator fire!

Reply #5 –
"Do you a picture of what the breaker looks like after starting on fire?"
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Generator fire!

Reply #6 –
Yikes. Glad you contained it.
1993 U300 40ft GV SE
Build # 4344

Re: Generator fire!

Reply #7 –
It usually takes something like this to motivate myself to learn about essential stuff.  Brett asked about the capacitor, presumably motor start capacitor.  We used to call them condensers in old cars.  I came across this website with excellent explanations and a great video. 
Motor starting capacitor ยป Capacitor Guide
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Generator fire!

Reply #8 –
That breaker did not break. 10 amps would not get that hot. That looks more like a dead short to me.
95 U300SE

Re: Generator fire!

Reply #9 –
That cooling fan motor should be an GE motor using an "RUN" Capacitor and will have a valve of or about 5uF, very common setup.
The supply breaker is design to be the weakest link in the electrical wiring circuit and sizing should be 80% capacity of the wire size. If you want to protect the load device the rule of thumb is 25% over running load. Anyway there are several types of breaker/fuse devices that are design for (fast or slow blow) inductive devices such as motors.
Steve
2001 U320 40' IF$ Build #5798
2018 Jeep Grand Cherokee Trailhawk Toad
2015 GMC Duramax HD2500 Toad
2014 Polaris RZR 1000
Litchfield Park, AZ- Soon to be Paulden, AZ

Re: Generator fire!

Reply #10 –
This was a brand new breaker that you installed? 

You had all of the connections tight?

Quote from: Sven and Kristi –
  The new CB had melted.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Generator fire!

Reply #11 –
My shorted fan hot line would have started a fire as well but for the 10a breaker.
Regards,
Brett

'99 42' Foretravel Xtreme
'14 Brown Motorsports Stacker
'05 Chevy SSR
'02 BMW R1150R

Re: Generator fire!

Reply #12 –
No electrical expert here but I would check or have a shop see how many amps the fan draws.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: Generator fire!

Reply #13 –
I just read your other thread the breaker you got from eBay was it a 10 amp or 45 amp?
When you hook the fan up to the shore power did you connect it at the motor or at the generator where the breaker is.
On a side note, a number of years ago people were buying GFI plugs off of eBay they were then starting on fire and burning people's house down.
2014 ih45  (4th Foretravel owned)
 1997 36' U295 Sold in 2020, owned for 19 years
  U240 36' Sold to insurance company after melting in garage fire
    33' Foretravel on Dodge Chassis  Sold very long time ago

Re: Generator fire!

Reply #14 –
The new CB was an OEM part (same manufacturer, part # and amperage).  The motor works on 5.5 amps, so the 10A CB was appropriate (180% of appliance requirement).  As I mentioned earlier, I may have over heated the circuit by making numerous starting attempts in a short period of time.
I am reviewing the function of the capacitors and will check that as a possible source of the problem.
To answer another question, all the contacts were tight - this all started when I was cleaning and tightening them.
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8

Re: Generator fire!

Reply #15 –
Youre missing the fact that no matter what you did, the wiring inside a breaker is appropriately sized so it should NEVER melt or catch fire no matter what you do! The breaker should trip long before anything melts, indicating there was a failure of the breaker to break at what had to be a lot more than 10 amps.

Numerous start attempts shouldnt matter to the fan or breaker. The fan runs continuously when the generator is on, so no amount of running or on/off should affect it. And even if it did, the breaker shouldnt melt. You have a breaker problem and I would guess a locked up fan motor or short somewhere that caused that much amperage to burn that breaker.
95 U300SE

Re: Generator fire!

Reply #16 –
Kids have gone home, so I'm back at the generator.  After purging the fuel at the injectors, I was able to get the generator running smoothly.  I am also getting 120+v at the panel inside the coach and the roof air comes on.  My only issue is the fan.

As I wrote earlier, I applied @110v house current directly to the fan from an extension cord using an old appliance cord and it worked smoothly, so I don't suspect the fan motor.  My continuity tester showed that the white wire went to the cooling fan circuit breaker (that melted).  The other CB wire goes to the left side 45A circuit breaker.
Using a long lead, I tried to locate the other end of the black wire in the control box.  The only terminal that showed continuity was the hour meter (?), which suggests a short in the black wire somewhere.  I do not see fan motor or fan CB in the diagram.  To answer Brett's earlier question about voltage at the 45A circuit breakers, I'm getting 121v at each. 

To summarize, the power to the fan originates at the left 45A "main/on" CB, goes "through" the cooling fan CB and to the fan as a white wire.    I have not found where the black wire to the fan comes from, but suspect this may have shorted somewhere.  If I knew where to find it in the control box, I could replace/bypass it with a new wire.

Meanwhile, the entry way door handle came in and it looks great - have to celebrate the small victories.  Back to the wiring diagram.
2000 U320 mid entry  #5688
2006 Jeep Liberty


USMCR retired
SDFD retired
FEMA US&R TF8