Generator Compartment Maximum Temperature

[Stormcloud]

Hi:
I am installing a single-cylinder 3kw air-cooled Kipor generator in the bay of my MCI7. I have constructed a generator compartment lined with 'bubble-foil' insulation, and have the exhaust plumbed outside the body of the bus.
The fresh air intake and additional cooling is provided by an electric radiator fan that runs off the DC charging circuit for the generator, and I have provided an exit for the heat generated through the floor, opposite end of the fan.
I will be remote mounting the controls in the near future, but for now, I am more interested in the compartments internal temperature when the gen is operating.
At what temperature should I set an over-temp alarm? Should the entire floor of the gen compartment be made of expanded metal to reduce the heat?
I'm sure someone else has done this, and I'm interested in their results/recommendations.
Thanks for your input!

Mark

[JackConrad]

    Our PowerTech generator uses the 3 cylinder Kubota diesel engine.  We have the radiator remoted and the muffler is also out of the generator compartment.  With this set up, PowerTech recommends 400 CFM to keep the compartment from overheating.  We have 3  240 CFM  4" bilge blowers installed in the floor of the compartment. The blowers have tubing extensions to near the top of the compartment to pull the hot air out of the top of the compartment at the engine end. The cool air enters through a couple baffles and enters the compartment near the floor at the generator end.
   We use RV Safety System Fire Detection/Suppression System to monitor ambient temperature in the compartment near the ceiling. Temps usually run about 10 degrees above OAT (outside air temperature).  I recall reading somewhere that generator heads should not exceed 140 degrees to prevent damage to the generator head (can't find where I read that).  We have our generator compartment alarm set at 120 degrees. Only time we have had it go off was when one of the bilge blowers failed and tripped the circuit breaker. We have used it in 103 degrees OAT.
   Making the entire floor of exposed metal probably will not help. Since hot air rises, I don't think you would eliminate that much additional heat and the open floor might interfere with the desired air flow from your fan. It would also allow a lot of road dust, rain, etc. into the generator compartment

[JohnEd]

Mark,

In 1990 I purchased two rad fans I removed from a junked Datsun Pulsar.  Many years old at the time.  They are 12 inches across and at a full 12 volts will howl like a banshee and create a small "hurreycain" in air flow.  I installed "one" over my kitchen stove with a roof vent over the hole.  It is located behind my microwave and out of sight.  I have voltage dropping resistors from a ignition circuit with switches that i use to control the speed.  Even in winter the fan runs at a idle and when I get home in the summer I hit the full speed for a minute and then let it run at half speed (silently) unless I turn on AC.  I rarely need AC as a LOT of air circulates and I control it.  The second fan is still stuck in the back of a cubby hole and I expect to never need it.  I have full timed for many years in that coach since I did the install.  The fan is at least 25 years old and I would use this sort of thing for any air moving need I might have.  $15 for two!!!!  The shrowd is part of the fan.

Have fun,

John

[Nick Badame Refrig/ACC]

Hi Mark,

Disapating heat from the bottom will always cause issues. I would see if there is a way to exhaust the hot air

up high and make up air from down low. You know, heat rises.. Just makes more sence.

Secondly, that hot air under your coach will always billow out on you if you were sitting outside.

Good Luck
Nick-

[cody]

I think your right nick lol, sitting around talking at jacks there was a lot of hot air billowing lol    libby said she thinks it was mainly coming from the area of my chair but I think it was more evenly distributed lol.

[gus]

NICK,

My Honda EV6010 water cooled gen takes in all fresh air at the top front of the gen box and exhausts all heat out the bottom. The exhaust pipe also goes out the bottom and part of the exiting gen cooling air goes around the exh pipe where it exits the gen bottom plate.

This plate is actually the bottom of the gen box onto which the gen is bolted. It is exposed directly to the outside bottom of the gen compartmen which is completely open. It is the original AC engine compartment, which on a 4104 was a Cont flathead 4cy gas engine.

The only thing I see wrong with this setup is that it blows dust when parked on dirt. The good part is that the gen incoming combustion and cooling air is taken from as far from the road as possible.

[Stormcloud]

In this case, the outside air enters at one end, then blows over the engine and alternator (same direction as factory fan installed on engine shaft), then exits out the floor, and coincidentally blows over the exhaust pipe under floor level.

I monitored the temperature inside the box adjacent (2 inches) to the muffler , and the temperature approached 140-150 degrees under load.

Is this too high?

Mark

[cody]

Mark, I have the honda 3K inverter generator and it's probably very simular in not only how it works but also in operating temps, I've had it in 2 locations so far, one was in the center bay on the drivers side, the bay has a large vent in the floor that has an expanded metal covering and another simular vent in the bay door, I mounted a fan blowing out in the bay door that was plugged into the generator so it would work when the generator was working.  The fan was intended to exhaust fumes from the bay and worked nicely, it also reduced any build up of heat.  My carbon monoxide monitors seemed to think it was ok.  Last winter I moved the generator to the A/C compartment back by the motor, this compartment has a very large expanded metal section in the door and is open to the back and sides into the motor compartment, again I mounted the fan on the door blowing out, I've noticed no build up of heat or fumes using this aproach. as far as noise levels are concerned, the generator is extremely quiet, even with it openly exposed on the curb side in the back it is very quiet.

[DrivingMissLazy]

As I recall the maximum operating temperature for an alternator with class F insulation is 140 degrees. There is a class H that is considerably higher but I do not recall exactly what it is. I would suggest you contact the alternator manufacturer and try and determine the class of insulation on your unit.

Richard

[TomC]

My gen compartment is tight with the 10kw Powertech with remote radiator.  To cool the compartment I use an inline bathroom blower rated for moist areas (incase of rain) that produces 250cfm.  It has an 8" outlet that is branched to two 6" hoses that lead into the compartment at the back so that the gen head gets first shot at the cool air.  Never had an overheating issue in the about 700 hours the gen has on it (like 28,000 miles).  Good Luck, TomC

[jjrbus]

I would check the DC amp output of the generator, on the Honda 6010 it is only 4 amps. I belive that most radiator fans draw more amps. Your generator may provide more amps ?
If it is a problem, it would be easy to use an AC fan instead.

[Stormcloud]

The DC amp output is 8.3 Amps so should be enough for the rad fan.

I'm wondering if I should remove the factory mounted muffler from the gen, and install one under the bay floor on the exhaust pipe. Would the gen compartment be cooler without the muffler exchanging sound energy for heat energy?

Thanks for the comments so far!

Mark

[gus]

jjr,

I don't know of any DC output on my Honda EV6010 gen?? It has 30 and 20 amp AC outputs but no DC that I know of??

My old Onan had a one amp DC output from the flywheel to charge the dedicated gen starting battery but my Honda has nothing like this.

[jjrbus]

There is no DC outlet on the Honda.  It is the DC that is supplied for battery chargeing. The reason I brought it up is the Honda is designed to supply 1 amp continuous. I am not a generator expert so do not know what other units are designed for.  Also the fuse for my Windstar radiator fan is 40 amps !!

[gus]

There is no DC output from the Honda EV6010. It gets starting power from the bus starting batteries, it has no separate battery.

I had to rig a separate starting battery to my old Onan because the 1 amp  DC output from its flywheel alt messed up my bus alternator regulator.