Generator overheat??

[Chance]

I'm curious -- is the new trend now to place the generator at the very back end of the coach to keep them from overheating? If so it seems odd because my old Class C and also rented Thor-made Class Cs with generator mounted forward of that never overheated.

When we started looking we saw a one-year-old Thor motorhome at Camping World that had a very nice Mega Storage compartment in back, and the generator just behind the driver. The very same new model a year later had the generator moved to rear driver-side corner which completely screwed up the storage compartment.

All Axis/Vegas we've seen have the generator at rear also, effectively eliminating a sizable pass-through compartment. If this is all driven by overheating generators, then they need to come up with a better solution that doesn't limit placement so much.

[EA37TS]

Originally Posted by Chance

I'm curious -- is the new trend now to place the generator at the very back end of the coach to keep them from overheating? If so it seems odd because my old Class C and also rented Thor-made Class Cs with generator mounted forward of that never overheated.

When we started looking we saw a one-year-old Thor motorhome at Camping World that had a very nice Mega Storage compartment in back, and the generator just behind the driver. The very same new model a year later had the generator moved to rear driver-side corner which completely screwed up the storage compartment.

All Axis/Vegas we've seen have the generator at rear also, effectively eliminating a sizable pass-through compartment. If this is all driven by overheating generators, then they need to come up with a better solution that doesn't limit placement so much.

I believe the trend is to move the generator to the rear to reduce the noise level while traveling down the road.

Two of the biggest complaints, of which I am aware, of forward mounted generators were:

1. The noise level immediately behind the driver
2. The recirculation of generator exhaust gases into the drivers compartment or coach area if a window was open during travel.

Some will say that moving the generator now creates a noise situation in the bedroom. I would argue that due to most campground noise restrictions you are not going to be running the generator when you are sleeping so that is a non-issue.

Too be honest, someone would have an extremely hard time convincing me that moving the generator from front to rear has any impact what so ever on the generator overheating as long as the generator is installed per manufacturer's installation instructions.

As a note, the Miramar has had the generator in the rear since Thor introduced that model and I am not aware of any overheating problems on their generators.

[Daveht]

Just curious! Does anyone have any idea why a stator would burn out when it is less then a month old? The only thing on was the 13500 AC.

[EA37TS]

Originally Posted by Daveht

Just curious! Does anyone have any idea why a stator would burn out when it is less then a month old? The only thing on was the 13500 AC.

Defective winding or materials used in the production process of the stator is the most common cause. Also an armature that is out of true or bad armature bearings can cause the stator to short out. The problem is common in automotive alternators.

[Chance]

Originally Posted by dstankov

I believe the trend is to move the generator to the rear to reduce the noise level while traveling down the road.

Two of the biggest complaints, of which I am aware, of forward mounted generators were:

1. The noise level immediately behind the driver
2. The recirculation of generator exhaust gases into the drivers compartment or coach area if a window was open during travel.

Some will say that moving the generator now creates a noise situation in the bedroom. I would argue that due to most campground noise restrictions you are not going to be running the generator when you are sleeping so that is a non-issue.

Too be honest, someone would have an extremely hard time convincing me that moving the generator from front to rear has any impact what so ever on the generator overheating as long as the generator is installed per manufacturer's installation instructions.

As a note, the Miramar has had the generator in the rear since Thor introduced that model and I am not aware of any overheating problems on their generators.

This post made me laugh, because I realized that if I combined your opinions and preferences, based on your experiences, with mine that are almost polar opposites, it would lead to elimination of the generator altogether. A generator running under my bed would drive me nuts.

I have never run a generator to run the AC while driving, relying instead on the vehicle's AC. Granted my RVs have been smaller, and my present van has factory rear AC.

I think that if I was going to run the roof AC on a regular basis while driving I would install a large-enough inverter and upgrade the engine alternator as needed. I just can't see myself going down the road with an Onan generator running.

I have run the generator before while driving but only for a few minutes so my wife could use the microwave or make coffee. And that kind of load can be accomplished efficiently by an inverter.

So, the main reason for me to have a generator is to run the AC while parked and only if shore power is not available. I mostly did this to leave our dog in the RV while shopping or eating out. Also a couple of times to sleep in rest areas.

After reading this thread I'm starting to question if the cost of a generator wouldn't be better spent on a large inverter and extra batteries.

[EA37TS]

Originally Posted by Chance

This post made me laugh, because I realized that if I combined your opinions and preferences, based on your experiences, with mine that are almost polar opposites, it would lead to elimination of the generator altogether. A generator running under my bed would drive me nuts.

I have never run a generator to run the AC while driving, relying instead on the vehicle's AC. Granted my RVs have been smaller, and my present van has factory rear AC.

I think that if I was going to run the roof AC on a regular basis while driving I would install a large-enough inverter and upgrade the engine alternator as needed. I just can't see myself going down the road with an Onan generator running.

I have run the generator before while driving but only for a few minutes so my wife could use the microwave or make coffee. And that kind of load can be accomplished efficiently by an inverter.

So, the main reason for me to have a generator is to run the AC while parked and only if shore power is not available. I mostly did this to leave our dog in the RV while shopping or eating out. Also a couple of times to sleep in rest areas.

After reading this thread I'm starting to question if the cost of a generator wouldn't be better spent on a large inverter and extra batteries.

Chance,

First, I never stated my preferences on the location of a generator one way or another. I recalled the complaints I have read and heard regarding front mounted generators. In fact, I haven't given much thought to generator location until now.

I did state my opinion concerning generators "supposedly" overheating because they are now mounted in the rear of the coach rather than in the front of the coach. To me that lies somewhere between hogwash and unadulterated BS. If the generator is installed and operated in accordance with the manufacture's installation instructions and operating parameters it shouldn't matter if it is mounted in the front, rear, top or bottom of the coach, it should not overheat. If it does there is a problem with either the equipment or the installation instructions and either way it is the manufacturer's problem not the coach owner's.

In my prior Class C I always ran down the road with the generator running. I preferred using the generator rather than LPG for the refrigerator. On my current coach, due to the manner in which the inverter is wired, there are times when I have to run the generator while rolling down the road. For example, the passenger's work station 110 outlet is not wired through the inverter. If my wife needs power for her laptop I have to run the generator.

To be honest, I haven't checked to see if my AC units are connected through the inverter. I'll need to trip my shore power breaker turn the inverter on and see if my AC units run. I just looked at my Electrical Schematics and the only mention of anything being on the inverter are the televisions. Looks like I need to do some investigating and notating on diagrams.

As to my preference, since I refuse to stay in any park or campground that allows running generators between 11:00 PM and 7:00 Am sleeping over the generator is not an issue; it's not running while I'm sleeping.

Since nobody is allow to be sleeping on the bed while the vehicle is in motion, the generator running under the bed while moving is not an issue.

Since the generator is mounted in the rear of the coach if it is running while travelling I do not have that noise right behind my head.

[EA37TS]

Originally Posted by dstankov

...
To be honest, I haven't checked to see if my AC units are connected through the inverter. I'll need to trip my shore power breaker turn the inverter on and see if my AC units run. I just looked at my Electrical Schematics and the only mention of anything being on the inverter are the televisions. Looks like I need to do some investigating and notating on diagrams.
...

As an update, on my Challenger 37ND the refrigerator and televisions are the only items run off the inverter.

Based on an Amp to Watt calculator I would need to have a 2200 Watt inverter, at a minimum, to run the refrigerator (7.2 amps) and one of my 2 AC units (10.2 amps per unit).

Based on the cost of a larger inverter and additional batteries and the fuel consumption of the Onan 5500 (1.13 gal per hour at full load), that generator better be ready to run wide open going down the road this summer. If it isn't Onan better be ready for one PO'd consumer.

[Chance]

A roof AC that only pulls 10.2 Amps is excellent. Mine (years ago) was 13,500 BTU/hr and pulled around 13 to 15 Amps, sometimes higher under hot conditions. I'm glad to see they have improved them and made them more efficient like residential ACs. Do you mind posting brand/model? I'd like to note that for future reference.


For what it's worth, one major problem with operating ACs off inverters is that the compressor's instantaneous Lock Rotor Amps can exceed the inverter's capacity and trip it on over current. I've read some success by over-sizing inverter, but others can't get enough juice to get the AC running. A smaller AC or a more efficient model should help with that issue.

[EA37TS]

Originally Posted by Chance

A roof AC that only pulls 10.2 Amps is excellent. Mine (years ago) was 13,500 BTU/hr and pulled around 13 to 15 Amps, sometimes higher under hot conditions. I'm glad to see they have improved them and made them more efficient like residential ACs. Do you mind posting brand/model? I'd like to note that for future reference.


For what it's worth, one major problem with operating ACs off inverters is that the compressor's instantaneous Lock Rotor Amps can exceed the inverter's capacity and trip it on over current. I've read some success by over-sizing inverter, but others can't get enough juice to get the AC running. A smaller AC or a more efficient model should help with that issue.

The units are Airxcel Mach 3 Plus.

Here is the link to the web site

Airxcel | RV Products | Rooftop Air

It would surprise me if that wasn't the same 13.5K unit that Thor uses on most of the coaches.

[Chance]

Specs show 15.3 Amps for cooling under standard test conditions, and 63 LRA for startup. Maybe they haven't improved that much after all.

Compared to residential air conditioners, RV roof-mounted ACs use a lot of power. Must be due to compact size.

[EA37TS]

Originally Posted by Chance

Specs show 15.3 Amps for cooling under standard test conditions, and 63 LRA for startup. Maybe they haven't improved that much after all.

Compared to residential air conditioners, RV roof-mounted ACs use a lot of power. Must be due to compact size.

I got the 10.2 off the Electrical Schematic provided by Thor. There is a section on the schematic titled Appliance and Generator Specs and it lists the amperage draw and voltage requirements for the major items (fridge, AC, microwave etc...). I just looked at the schematic again and although they list the AC as 10.2 amps both units are routed through individual 20 amp breakers.

[JamieGeek]

I doubt RV A/C units have changed much over the years. I also doubt that there is any efficiency laws for them like there are for residential units. They would only make changes to accommodate the new refrigerants required of all A/C units.

[Chance]

Originally Posted by dstankov

I got the 10.2 off the Electrical Schematic provided by Thor. ....cut....

Perhaps the electrical designers based that on a different AC that is more efficient -- although I personally doubt that's likely. Or they could have put an Amp clamp on an operating AC thinking they were getting an actual number, but if temperatures were not typical then the AC could have pulled much less than specified by manufacturer.

The 10.2 Amps corresponds to an Energy Efficiency Rating of around 11, which is very possible. The specs for your unit works out to an EER of 8.2, which is more likely correct.

The best way to know, if it were important, is to measure the actual current. That's what I did because my 4kw generator was struggling with AC and microwave at same time.

[ProsperTrail]

I have a Thor Hurricane 2015 with the same problem, generator runs fine at full load when the RV stationary. Once you hit the road, at 80F+ the generator will stop after 1 o 2 hours ( quicker the hotter it is outside).
lots of suggestions about vents, no door, fans and wireless temperature gauges to monitor problem.
Bottom line Thor and/or Cummins are avoiding issuing a recall.
My proposal, while waiting for a fix to my RV, was to file a complaint with the Federal Highway Administration.
if you are experiencing a similar issues I would suggest your do the same, the more complaints received the more likely they are to get involved.
https://www-odi.nhtsa.dot.gov/VehicleComplaint/
I consider a safety problem for my family and pets to ride in an RV with proper cooling, and a safety problem some of the suggestions by Onan/Cummins I have seen where they recommend removing the door to the generator compartment for proper ventilation.
I hope everyone gets their unit fixed to you an enjoy traveling with A/C running as the vehicle was design for. These vehicles are not cheap, they should work as designed or be returned under lemon law.

Go RVing!

[charlie2380]

Originally Posted by ProsperTrail

I have a Thor Hurricane 2015 with the same problem, generator runs fine at full load when the RV stationary. Once you hit the road, at 80F+ the generator will stop after 1 o 2 hours ( quicker the hotter it is outside).
lots of suggestions about vents, no door, fans and wireless temperature gauges to monitor problem.
Bottom line Thor and/or Cummins are avoiding issuing a recall.
My proposal, while waiting for a fix to my RV, was to file a complaint with the Federal Highway Administration.
if you are experiencing a similar issues I would suggest your do the same, the more complaints received the more likely they are to get involved.
https://www-odi.nhtsa.dot.gov/VehicleComplaint/
I consider a safety problem for my family and pets to ride in an RV with proper cooling, and a safety problem some of the suggestions by Onan/Cummins I have seen where they recommend removing the door to the generator compartment for proper ventilation.
I hope everyone gets their unit fixed to you an enjoy traveling with A/C running as the vehicle was design for. These vehicles are not cheap, they should work as designed or be returned under lemon law.

Go RVing!

I got tired of mine overheating while on the road.
This summer trip from FL to OH it did it twice. Once in Atlanta traffic and again in Kentucky hwy. In my Kentucky stop I drilled holes on the door for better air intake on my Onan 3000. Worked the rest of the trip to OH.

When I get home I will cut a square to either install a grille like on the water heater or found a few options for hood air scoops on Amazon.

Thor told me its an overheating problem and to either take off door or modify for an air scoop.

[Bob Denman]

More airflow is the key to keeping your generators cool in traffic.
Adding some "hood-scoops" would make your setup even look racy!

[The Gritz Carlton]

Never has these issues as chassis A/C keeps entire coach nice and cool while traveling...but...I would look into installing an electric cooling fan somewhere in the body of the generator before poking holes in the camper. Chance can probably give some good suggestions for this method...he seems"electrically charged" in a lot of his solutions.

[Miramar Owner]

I agree with dstankov's comments. My Onan 5500 Generator states right on the panel "DO NOT OPERATE WITH PANEL REMOVED". The air intake is on the bottom and it may not operate properly with the door vented or removed.

I had problems with mine overheating and shutting down and it turned out to be mice packing bedding in and around the generator which would not let it vent properly. I now place bags of moth balls around the inside area of the compartment when in storage.

[ProsperTrail]

After many conversation with Onan and Thor, and Onan sending some parts that were not even close to fit or address the issue I took matter into my own hands.

I monitored the temperature with a set of 3 wireless thermostats and found that temperature was rising faster behind the generator (towards back of RV).

once I saw these readings I took a look under the couch and noticed that the next compartment behind the generator was the waste water connections box. Which happened to be about 8 inches lower that the generator cooling vent exit. (not exhaust pipe)

I assumed the hot air was being pushed back towards the generator and causing it to take in the heated air into the cooling air intake.

I purchased an aluminum sheet (extra thick with diamonds shapes for reinforcement) at home depot and cut it into a deflector to push the hot air lower and way from the cooling air intake under the generator.

This worked great for a whole summer.

The following summer I had issues with the gas pump shutting down after 10 minutes in any condition, so I changed it and haven't had any problem since.

I don't think the pump was an issue before, but I do know it is also sensitive to heat, so both the generator and the gas pump will shut down around 120 degree F.


Hope this helps anyone still having issues with Generators.

Happy RV'ing!

[oleflier]

I helped a camper once that had an onan that quit frequently. He serviced the pump,carb ,plug and wire. It still would cut out often. In my manual we found the spark arrester it was clogged with exhaust by -products. I found mine dirty but not plugged at 100 hr service. In the manual it really recommends a thicker oil in hi-temp use.I was going to use synthetic but they don't discuss it.