| Author |
Message |
Steve (Steve)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 23, 2004 - 9:23 pm: | |
Hey , I have a 1981 MCI9 and I'm trying to figure the best bay to install the onan 12500 generator. The bus air works great so I,m keeping it. So that stops me from putting it in the 1st bay on drivers side because the cold air inlet is on the left bottom of the generator and the hot air is on the right bottom and would pick up hot air from the coach a/c fan in front of the 1st bay and pull hot air into the generator inlet. So I was thinking about installing it in the 2nd bay with the back of the generator at the rear bulk head wall. This would let the generator inlet air pick up cool air and exhaust out the drivers side along with the bus hot air. And another thing is the weight of the generator is 660lbs. The book says it has to be installed in a place that can hold 3 times its weight. Also the exhaust exits the right side of the generator. Does this idea sound right? Sure could use some input on this.
Thanks, Steve |
TWODOGS (Twodogs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 23, 2004 - 9:45 pm: | |
sounds good to me |
John that newguy
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 23, 2004 - 10:13 pm: | |
I have a few free bays you can put it in.
Let me know.. |
bruce king
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 23, 2004 - 10:59 pm: | |
I have an onan 12.5k too.
I removed the bus air on my mci 9 and put the battery bank into that area. I mounted the generator on the drivers side in the first bay.
Holes cut in the bay:
I cut a 5" round hole in the bulkhead between the condensor compartment and the first bay, and
installed a 110v electric fan that moves air into the bay, powered by a generator-only outlet I installed. I cut two rectangular holes in
the floor of the bay (cut the bay aluminum only, not touching stainless support rails) approximately 3" by 7" each, at the rear of the
bay. So one hole at the front of the bay, two at rear.
Exhaust handling:
For the exaust I used flex tube from the generator to the floor, and then 2" galvanized electrical conduit along the bottom of the bus to the the rear, attached with U bolts. I was concerned intially about clearance, but then reasoned that If it was damaged it'd be easy and cheap to replace. It hasn't hit anything with 8000 miles of use, so I think it's ok.
Intial air flow verification:
So when the bus is moving, there's enough air pressure to provide a good air current from the front of the bay to the rear. I verfied this by having my girlfriend drive the bus around while I was in the first bay.
When the bus is still, the 110v fan provides air flow.
Generator mounting plate material note:
I mounted the generator on a slideout, initially on a marine plywood base, but later removed that and replaced the plywood with a 1/8" steel plate. I did this because my generator seeps a little oil over the course of a year or so, and this was soaking into the plywood. The oil seems to come out of the dip stick fitting. I haven't been able to find any other source.
Modifications to the plate:
A steel plate allows me to clean any oil seeps or spills, or fuel, or whatever, quickly, and will not add fuel in case of a fire. I cut an 8"x8 square hole in the plate under the generators radiator, and two smaller holes where the hot air exits, opposite the control panel end.
Reasons for a slideout:
The slideout allows the generator to come completely out of the bay, and this allows you to move it with a cherry picker if you need to do some sort of major service, or just easier access when you are changing the oil or checking fluids. It also allows you to pressure wash the bay to clean the inevitable road grime that will accumulate in any compartment open to the road. Esp. important if you travel in areas where they salt the road.
Sideout and exhaust:
To make the slidout work without having to disconnect the exhaust, I cut the exhaust hole at the radiator side of the generator--opposite the end that the generator exaust comes out.
When the slide is retracted, the flex tube rests
about an inch from the rear wall of the generator.
When the slide is extended, there is enough length that the generator can emerge completely without being disconnected. I was concerned about the flex tube getting hot enough to mar the finish on the rear of the generator, so took pains to make sure that the hole through the floor and generator were situated so that in its retraced state the flex tub was taut and not contacting the generator casing or the barrier wall.
Road test of this setup:
I ran the generator in this compartment without any venting at all to see if it would do it. the air temps at the top of the compartment were in the 170 to 200 degree range in a few minutes, but the generator was able to run for an hour or so before I shut it off.
With the two holes drilled, and stationary, the generator has run continuously for 3 days (72 hours) straight, w/o problem. I plumbed in a remote radiator, but after playing with it for a while and since it ran fine in its current location, removed that experiement and went back to factory stock cooling.
Sound and fire additions:
I put sound insulation material in between the roof ribs in that bay area, and then put in a ceiling of 16 gauge galvinized steel. In case of fire, I want it to take a while to burn through the floor. I secured the steel directly to the ribs supporting the floor using self-tapping sheet metal screws.
Finally, I put in a vertical divider constructed of marine plywood faced with 16 gauge sheet metal to seperate the drivers side generator from the inverter/electrical passenger side. I did this to keep the other side clean and dry, and to provide some protection in case of fire.
I chose marine plywood and metal for weight reasons and bi-metal reasons. the sheet steel ends a half-inch above the floor, and the bulkhead is sealed with fire retardant foam on all edges.
The vertical seperater had the unintended consequence of focusing the air flow. I believe that the air flow was improved by it, due to a larger throughput.
Things I haven't done:
One consideration that I haven't checked out is the load on the front axle. With the battery bank and generator both on the front drivers side, my concern is that I am overloading either the axle or the drivers side tire. I haven't gotten down to a truck stop to weigh it yet, but that is on my list.
Remote switches pretty handy:
Installed, with the bay door closed, the unit is not audible. I ended up buying two remote start units from onan for it. I purchased the start kit with instruments (generator start battery voltage, generator water temp and generator hour meter) and have installed that up in the drivers area. This allows me to look at the generators state without exiting the coach, or start or stop the unit. I mounted the cheaper single switch on the passengers side, next to the inverter, which I found handy when I was configuring the inverter to run the generator. Both remote switches have an activity light to tell you when the generator is running. Since it's inaudible, and started/stopped by the inverter, the hour meter in the drivers area is how I measure fuel consumption and activity. I can't say how many times i've used the switch next to the inverter, but it has saved me a run around the bus at least 70 times.
Having to rework my electrical:
Another problem I had when wiring this bus is that this generator is hard to use all of with a small circuit box. 12500 watts is 100 amps at 125 volts. When I purchased an electrical box I didn't consider that in order to make use of all of the generators capacity I'd need enough real estate in the box to run all of the following circuits:
roof ac 1 20 amp
roof ac 2 20 amp
roof ac 3 20 amp
refer 20 amp
bay outlets 1 20 amp
bay outlets 2 20 amp
inverter one ac in 30 amp
inverter two ac in 30 amp
coach lighting circuit 15 amp
kitchen gfci 15 amp
bathroom gfci 15 amp
living room outlets 15 amp
bedroom outlets 15 amp
electric water heater 20 amp
yes, this is more than 100 amps, but you never
use all of these circuits at full capacity, and you can put in a master 100amp breaker at the top of the box is you are concerned about overloading the generator.
I am gonna take out my smaller box and replace
it with a larger box so I can fit all of the circuits in.
Part of what I do with the bus:
The reason that I have 2 20 amps into the bays is that I use the bus as a construction shack from time to time -- drive it to the site and run all of your power tools, saws, compressors, etc. A medium size (6cfm) air compressor draws 20 amps all by itself, so ran two circuits so tht I could run both the compressor and a table saw or chop saw at the same time. The air compressor has the side benefit that I can use it to air up the bus or to maintain air if I wish to.
Saving some $ on generator fuel:
Finally, in these days of expensive fuel, home heating diesel is usually 30% to 50% cheaper than road fuel. So I installed a 2nd tank in the rear bay, plumbed only to the webasto and generator (non-road uses) and fill that tank with the cheaper fuel from any home heating supply area. Given diesel prices in the $2.40/gallon in wa state, this saves me approximately $70 per tank, and in an emergency I can use a small fuel pump I have to move fuel from one tank to another. This also allows me to fuel non-road diesel equipment on site with the cheaper fuel.
If I were to do it again:
if I have not overloaded the front axle (tbd), I'd consider mounting the onan on the drivers side front bay, and the batteries on the passenger side front bay. In my application, they weigh about the same, and it'd be a good balance.
Battery maintenance note 1:
I have found that having at least 24" of vertical clearance is important for doing battery maintenance -- you need to be able to see down into the battery fill caps when refilling them, and you will need to be able to lift a battery straight up and then out when replacing them.
Battery maintenance note 2:
I had some polypro left over from my holding tank fabrication, and I made a batter base tray out of it, with a 1" lip and a rubber spill tube that directs any spill or overflow out of the bus.
why? take a look at the alumimum under your batteries. Even the smallest spill of battery acid (and it happens when you overfill, for instance, or overcharge) just eats the heck out of aluminum. Last thing I want is to have my batteries fall through the floor onto the road in 4 years.
Good luck.
Bruce |
H3 (Ace)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 23, 2004 - 11:32 pm: | |
Brucew very good description of your work. It sounds very similar to how I did mine. My 12.5 is on the left side mid but my battery bank will be opposite of that on curb side. The air inlet and exhaust sounds VERY similar to mine and when both fans (mine are both 120v) are on, you can really see and feel the air moving. I haven't had a chance to test the temperatue yet as we just today installed some sound material to entire generator bay with the exception of the ceiling (so far). I might do as you mentioned and fabricate a metal celing before sound deading it. I opted to mount my generator on a slide for the same reasons and I also put down a sheet of stainless steel on the floor for easy cleanups.
Thanks again for a very informative post!
Ace |
bruce king
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, October 23, 2004 - 11:57 pm: | |
hey, my pleasure. There's a gap between the ribs holding up the plywood floor on the mci 9 that I put the sound insulation in. It was kinda overkill though; the onan is so quiet to begin with that you don't really have to do much to make it darned close to silent. I didn't put the soundproofing on the generator side to limit possible fire fuel.
so your gen is in the center bay drawing air from the front bay? or do your fans bring it in from the road and then back out to the road?
Theres a soundproofing product that is basically a rubber sheet that you can glue to a single side of sheet metal that stops it from acting as a sound board.
I used some of these guys stuff, but it's pretty pricey.
http://www.hamiltonjet.com/noise/noiseinfo.html |
H3 (Ace)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, October 24, 2004 - 7:34 am: | |
Actually my gen is on the road side about mid way and draws air in from the same bay, but from curb side. That bay is divided by a bulkhead, and the air is ducted thru it to the gen. The air then is dtawn OUT by means of a bladed fan mounted on the radiator that sits off to the side of the gen and the air is ducted thru the front bulkhead of that same bay into the bay that houses the bus a/c fans. I mfgr'd an air box to direct the air DOWN thru the floor and out! With these two fans on, it really does move some air. I only noticed a "little" more noise after I cut the last hole in the floor for exhausting air. The INlet air holes are round that match the side holes of the squirrel cage fan, and screen covered with SS mesh to keep bugs and debris out. The same is about to go on the exhaust hole. Maybe that will cut down on someof the noise as well!
I used the egg carton foam on most all of the gen part of the bay with exception to the celing. I may install a sheet of metal before sound deadening that. The foam made a little difference but not as much as I had thought. Really not worth the expense if you ask me!
Ace |
Henry R. Bergman, Jr. (Henryofcj)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, October 25, 2004 - 6:46 pm: | |
Since I do not know, I am asking. (please) Why would the 'book' suggest/recomend mounting the gen set in a location that can "handle 3 times the gen set weight"?
Is it a structual concern, weight and balance considerations or a fudge factor for bo boes? Or did I miss-read the post that stated such. I need to learn more here. Thanks. |
Kyle Brandt (Kyle4501)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, October 26, 2004 - 12:50 pm: | |
As a mechanical engineer, I would want that fudge factor to cover the dynamic loads from rough roads and sudden unintended stops (collisions). You don't want the genset moving around. |
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