Idea for stopping a fire in the generator box, what do you think?

[Kevin Warnock]

I am finally completing a project I started last year. The idea is to take a Honda EU1000i portable gas generator that has just recoil start, and make it electric start running on propane.

I completed the conversion to propane today. It seems to run great, and the eco throttle seems to also work fine, something I was nervous about. I really want the eco throttle to work so I can really quiet the generator down to almost nothing for light loads.

I also got a prototype of the electric start working. I removed the recoil pull cord and used an battery operated electric drill to turn over the engine. I made a 'drill bit' with prongs on it that mesh with the prongs on the engine shaft that normally are meshed with the prongs on the recoil rope starter mechanism. To start, I just mesh up the drill and pull trigger on the drill. The generator starts right up. I then pull the drill away so the drill isn't spun up to the speed of the generator. I need a more automated way to do this and have some ideas, but would like to hear if anyone here has any ideas.

Now to the point of this post:

Over the years I have seen many busses for sale that were mostly destroyed by fire that started in the generator. That got me thinking about how I could stop a fire before it could destroy the bus. I particularly am interested in this since I am taking a portable generator and modifying it and also making it stationary. I don't think I'm doing anything dangerous, but if something goes wrong, I don't want to lose my bus conversion.

So, what I have in mind is the following: build the generator box out of something fireproof. I am thinking about hardiboard tile underlayment with strip aluminum angle material at the corners drilled and bolted. Then, for lining the box, rockwool type sound insulation, which I understand is essentially a mineral, and won't burn.

Finally, for the entrance and exit to the box, put hinged doors that normally are always open, and have these doors spring loaded such that if the doors were not held open they would snap shut and stay shut.

For regular operation, I would keep the doors open with something that will melt or quickly burn away. For this I need suggestions... I suppose I could use standard household white string. If there were a fire, I presume this would quickly burn and break. The doors would shut and the fire would hopefully go out due to a lack of air. How tight would the seals around the doors need to be to put out the fire?

As a second backup option, I see one can buy heat activated fire extinguishers for less than $200 for a small enclosed space, and I could put one of those in there as well.

I was surprised how easy it was to convert to propane - I just bought a kit online and followed instructions. The goal is to be able to run the generator very infrequently without hurting it, and also to be able to run it for long periods without refueling.

Oh, what about adding an additional muffler to quiet it down even more. Can I just buy any car muffler and hook it up to see what happens? I will extend the exhaust pipe trough the generator box to the back of the bus by the way. Is there a distance limit for exhaust pipes I need to beware of?

Thanks

[Jeremy]

That's a very interesting idea, and an issue which we should probably all take more account of. Regarding the fire-suppression - I would think that an automatic way of cutting off the fuel supply in the event of a fire would also be extremely important, especially as your propane is presumably piped into the generator compartment from a big tank elsewhere in the bus.

I would be worried about the temperature that the generator is likely to run at, surrounded as it is by all that insulation. I think you may need two open doors in the compartment, with cross-ventilation aided by fans.

I don't have any particular expertise on exhausts but would worry that increasing the length would increase / alter the backpressure enough to affect the performance of the generator. I have a petrol generator myself but decided not to try to 'improve' the standard exhaust on the basis that you've got to assume that Honda knew what they were doing when they designed the thing in the first place. (I suspect a noisy, low-revving diesel generator would both tolerant and be much improved by extra silencers though)

Jeremy

[rv_safetyman]

Obviously I have a horse in this race, because of my system. 

I really have a phobia about generator fires.  They could happen while you are not at the bus and that spells disaster.

Concerning propane.  There are two types of propane detectors.  The first is simply a detector that yells at you (if you are there), in the case of a leak.  The second is a detector that had a solenoid valve which shuts off if propane is detected.  The unit I sell with my system is a CCI 7719.  Unfortunately, it appears that CCI is out of business.  I have not found a replacement for this system, but some suppliers vendors still have inventory.

Jim

[Damn Yankee]

Why on earth do you want to go through so much hassle for so little power Liquid cooled generators run much cooler than air cooled ones that catching fire is of little concern except near the exhaust system. I would go with a honda 4010 or 6010. I think these can be converted to propane. Maybe Gus will chime in here.... I think he's running a 6010 in his coach. As for the 1000w why not install a propane quick disconnect and leave it outside the bus and plug the shore cord into it when you don't require much power but it's nice to have enough capacity to run a A/C when needed.

[Kevin Warnock]

Whoops, I forgot to mention I am installing this small Honda in addition to a larger generator that I will use for the ACs. This small Honda I already owned as a backup, and I never used it except on the bus, so I figured I should make more use of it. The super low fuel consumption is also really nice. One thing I plan to use it for is powering a small 5,000 btu window air conditioner while I sleep. I have a very quiet Panasonic window AC, and when running, it uses 520 watts, per the watt hour meter I checked it with. I will run the Honda output through the Trace SW4024, so I will have no problem starting the AC. But the Honda will also start the AC directly connected to the AC. But for that to happen, the eco switch can't be on, which means more noise. One cool feature of the Trace is you can tell it how many AC amps to draw from the AC source. So I can dial in just the number of amps the AC needs, which in my case makes it run at about the middle of its noise making potential. However, I suspect as a practical matter that I will be able to set the Honda at it's lowest speed via the Trace, which is about 300 watts, and then the AC will almost certainly cycle throughout the night since there is no sun load on the bus. The house batteries will provide 200 watts extra to run the AC while running, and when it's not running, the Honda will use its 300 watts to recharge the just used power. I haven't conducted a real test in hot night time weather running all night, but I really think this is likely to work. I like this idea better than trying to run the AC all night on just battery power.

Finally, to be clear, I was planning an input door and an output door for air for the box. i am confident I can keep it cool for an extended time, as i built a test box out and ran a test with the Honda running a long time. There just isn't a huge amount of heat coming off this small 49cc engine. The way the engine cooling designed is very appropriate for putting the generator in a box. There is a fan in front of the engine, and this fan is turned by the engine itself. The air inlet for this fan is a well defined circular opening about 6 inches in diameter. I plan to seal a duct around this hole, and only let the fresh air in this hole. The generator has a heat shield around the engine, and this heat shield remains cool to the touch when running, since so much air is running between the heat shield and the engine. I actually predict I won't need any additional cooling since that engine driven fan is running at 3000 to 5000 rpm and seems quite powerful. Maybe I will need two computer muffin fans to help force the air around the sound dampening turns in the box, and I have them ready if required.

With regard to my plan to use Hardiboard, I would also use tile mortar and fiberglass mesh tape to seal the corners, as if I were sealing the joints in preparation for tiling. I think this would make the box much more sound proof.

I didn't mention it before, but if it's still not quiet enough, I could put the entire hardiboard box inside another box, made of more conventional material like plywood. But I don't think that will be needed.

Note the Honda really is small once you take it out of that red plastic case. A lot of that case was the gas tank, which I won't be using.

I have seen street vendors use the Honda 1000 all day every day in a full livelihood situation. They just have a five gallon gas can nearby and fill it up when needed. So my guess is that running on Propane, I will be able to for a long long time.

I will look into a heat activated switch that I can wire to a propane tank shutoff solenoid, to stop the flow of fuel in the event of a fire.

Thanks for all the comments.

[JohnEd]

1967,

I would still involve RV_SAFTYMAN in your project.  It is his "profession" and you can't help but benifit from a professional's advice.  I would be concerned with heat build up regardless of how cool your tests show the system.....it has the "potential" to get hot enuf to hurt.  Secondly, you need some sort of propane alarm and shut-off.  Lastly, Jim sells a fire extinguishing system that is rechargable and doesn't destroy anything.  If you have two gen compartments I am sure he can set up a system to cover both gen boxes.  He can design a system that covers the bays and engine compartment so it follows... Even if the fire is electrical in nature/origin....you still haver to put it out, right?

Good luck and please keep us posted on your project.

John

Jim, You owe me!

[Dallas]

Well, here's an idea that's been swimming around in my head since I saw this thread the first time today....

Instead of doors that shut, sensors that go off, alarms the scream, extinguishers that go poof...

Just mount the plastic black water tank above the generator. 

If the genny catches fire, the plastic will get hot and melt. PooPf .... no fire!

(sorry, I really tried not to post this!) 

[Lin]

Oh that's such great advice, Dallas.  What about the methane gas exploding?  Now running the generator off the black tank methane!  There's an idea that stinks. 

[Dallas]

Use a blast shield over the top of the tank, so the explosion is forced downward. Kind of the way they put out oil rig fires! 

Oh that's such great advice, Dallas.  What about the methane gas exploding?  Now running the generator off the black tank methane!  There an idea that stinks. 

[buswarrior]

RV Safety Man is the busnut's best fire suppression vendor friend, in my books.

Knows what he knows and not afraid to admit what he doesn't.

Getting to be more and more rare as the days go by...

happy coaching!
buswarrior

[rv_safetyman]

Thanks for the kind words folks.

I really missed the "black water line in the compartment" thought process as I developed my system .  Should have been obvious

I guess it is obvious, but there is no way to contain a fire.  You can design a compartment that will slow the progress, but fire will burn through almost anything we can think of.  The only way that a contained area can suppress a fire is to keep oxygen from getting in the box.  Given the application, that is not possible.

Jim

[Kevin Warnock]

Jim,

Why is it not possible to keep oxygen from getting in the box, my I ask? Is it too difficult to make an air tight trap door that will close during a fire? How about lining the door frame with that rubber magnet material that is used to keep refrigerator doors air tight?

The box I have in mind will be air tight otherwise, since I plan to use Hardiboard sealed at the corners with fiberglass tape and tile mortar.

Thanks

[Tim Strommen]

I don't think he is saying it's impossible to keep out the air, but given the size of the "typical" enclosure, and the amount of opening required to keep such a generator cool and breathing - I think it is more impractical to do so...

That said, if you have a good chunk of space set aside for the enclosure, there are off-the shelf shutters intended to shut off air ducts, but again they are not air tight (and the magnetic seals would probably burn very easily...).

You will want to at least remove two of the three basic links of the fire chain-reaction (air, fuel, heat).  The easiest two to do are fuel and heat assuming that you catch it before the vehicle gets involved.  A propane/CNG shut-off valve is not hard to come by (you can get one that is normally closed, and opened when powered), I found several buy doing a quick Google search.  The heat removal is done by installing a proper extinguisher system, like the one that Jim sells.

Air can be very hard to cut off especially if the vehicle is in motion...  If you have every heard a whistling in your cab while driving, that is probably air ingress that would be like an air spray gun through a tiny hole.  More than enough air would get in to at least keep a fire smoldering.

I'm not discounting the sheetrock/hardiboard solution as something that you shouldn't do - it will help to keep the fire contained until the fire suppression system can kill the fire completely.  You will also need so way to prevent the genny from trying to start again after the fire was put out.

Also, keep in mind that if it does catch fire, it may melt wiring (like the AC output...), which may provide a second source for a fire to start.  A "complete" fire suppression system should shut down the genny, try to put out the fire, and disconnect any services that may act as a second ignition source, and prevent operation until a human has inspected the system and approved it for re-use.

Hope this helps.

-Tim

[JackConrad]

I installed one of Jim Shepherd's system in our coach a s well as a customers coach. The system includes a relay that shuts down the generator when the fire supression system is activated. A LP valve could easily be added to this circuit. Jack

[BG6]

So, what I have in mind is the following: build the generator box out of something fireproof. I am thinking about hardiboard tile underlayment with strip aluminum angle material at the corners drilled and bolted. Then, for lining the box, rockwool type sound insulation, which I understand is essentially a mineral, and won't burn.

As a second backup option, I see one can buy heat activated fire extinguishers for less than $200 for a small enclosed space, and I could put one of those in there as well.

Aluminum burns quite nicely.  Try stainless steel with some insulation behind it, and your automatic extinguishers (as well as a fire alarm inside the coach).