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Jim (Jim_in_california)

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Posted on Wednesday, August 10, 2005 - 11:43 am:   

Folks,

My rig is set up for 30amp, with a good-running 1988-vintage Onan 4kw gasser - but it's the better 1800rpm type at least.

Main living area has a pretty normal 13.5k rooftop A/C, garage will have a very high efficiency 5700w (11.3 EER) window-mount-type. I don't anticipate running both at once but I suspect the Onan (or shore cord) could drive both.

Problem: the Onan will eat around .5gal/hr. Not terrible but if boondocking in the heat it will add up $$$wise.

Yamaha has a pair of gennies based on a 171cc 5.5hp motor. Both are inverter model, variable speed, fuel economy close to triple the Onan. The newest variant is ultra-noise-shielded like a giant Honda EU2000i but at 2400w it will drive most 13.5 A/Cs; the other is still fairly quiet (67db max), has the same inverter but is tuned to 2800w due to less noise shielding causing less heat problems and can definately drive a 13.5 A/C.

(The new 2400 was clearly made as a "Honda killer" and can be parallel-connected into a double setup.)

I'm considering trading in the Onan for one of these. Either Yamaha (and I'd probably get the 2800) is around $1200. I'll be using a genset fairly often (boondocking) and the fuel economy difference seems worth it. And I can probably get a decent price for the Onan.

Like a Honda, these have a low-amp 12v output, probably similar to the Honda's 8amps...do y'all think it's possible I could run a small automotive 12v fan along one side of the genset bay with some vent holes and set up one of these things perma-mounted in a bay for security? The idea being, the fans auto-start from the genny's power? Might eat .5kw or so from the available AC output but, on the 2800 it shouldn't matter.

Specs on the EF2400iSC:

* Supposedly shipping "late July".

* 2400watt max rating with 2000 continuous.

* 53-58dba

* 70lbs

* Can run most 13,500 air conditioners.

* Inverter model.

* 1.6gal tank runs 8.5hrs at half load, which is about what you'd be with most aircons once the startup peak is done with.

* Two can be lashed together into a 3800watt continuous genset. They seem to have a bit of "loss" going on with the dual config but it's not that big a deal.

---------

No word yet on whether or not the 2800 can be paralleled. Probably not.

Specs on the 2800:

http://www.yamaha-motor.com/outdoor/products/modelhome/443/0/home.aspx

http://www.yamaha-motor.com/outdoor/products/modelspecs/443/0/specs.aspx

I suspect the fuel use per hour will be a lot less than the 7kw - 10kw diesel setups. Doesn't mean you'd trade the bigger one in, but having the smaller around too as a low-fuel-rate option might be worth it for some...
James Maxwell (Jmaxwell)

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Posted on Wednesday, August 10, 2005 - 12:06 pm:   

Jim: U can listen to Yamaha if u like, that's you're choice, but a 13,500 a/c compressor will pull between 3000 and 3500 watts for starting and about 1500-1750 running. So, they are not lying when they say it will run one, but what they haven't admitted to is that it may not start it. And it positively won't if u have anything else going.

I have a 1000 Yamaha model (non-inverter model) that I use to use when boondocking (for watching tv in the evening----47db). They are nice to have, but they are no substitute for an adequate sized genset.
Jim (Jim_in_california)

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Posted on Wednesday, August 10, 2005 - 12:32 pm:   

Hrm.

Well the next question is: will an Outback VFX2800 inverter/charger add to the genset power from the battery bank?

I'm wiring such that all loads go from genset/shore to a surge protector, then the Outback, then the house wiring. I know the Outback does "input sensing" - if there's AC coming it, it passes it through, otherwise it's an inverter. But can it do both at once, adding inverter power to the AC input?

If it will, it'll cover the startup load just fine. Esp. from an 845amp/hr battery :-). That would make the Yamaha 2400 model practical...

I may have to ask on the Outback forum...
James Maxwell (Jmaxwell)

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Posted on Wednesday, August 10, 2005 - 1:21 pm:   

I'm not familiar w/the Outback. A Trace SW will do what u are suggesting, called load sharing, at least some models of the SW will. My Trace PS will not supplement the A/C elec. load, it is either a charger or an inverter, and not dual simultaneous mode.
James Maxwell (Jmaxwell)

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Posted on Wednesday, August 10, 2005 - 1:21 pm:   

I'm not familiar w/the Outback. A Trace SW will do what u are suggesting, called load sharing, at least some models of the SW will. My Trace PS will not supplement the A/C elec. load, it is either a charger or an inverter, and not dual simultaneous mode.
Jim Bob

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Posted on Wednesday, August 10, 2005 - 2:06 pm:   

The Outback should do anything the big Trace units can do & more. Outback is the former engineering staff from Trace who left after Trace was bought by Xantrex.
They started with a clean sheet of paper to surpass the Trace models & fix the shortcomings.
Jim (Jim_in_california)

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Posted on Wednesday, August 10, 2005 - 2:16 pm:   

Yeah, I'm aware of the old Trace connection to Outback and have high hopes this combination would do that. I also have the variant that has a 60amp max pass-through limit (versus 30 on some models).

But I want better than "should do".

I posted the question on their forums:

http://www.outbackpower.com/forum/viewtopic.php?t=757

IF it'll pull this stunt, then...gawd, I could almost get by with a Honda EU2000i(!) and the Yamaha 2400 would look GOOD.

In fact...once I hook up the Bogart Trimetric, I could run the 13.5 aircon briefly off battery/inverter only (five minutes tops) which would tell me EXACTLY what the draw is, figuring maybe 15% max losses on wiring and inverter overhead. Once I know what the rooftop AC really sucks down, I can make a final choice between Honda 2000, the Robin/Subaru 2000 which has a wee bit more power than the Honda (100w or so) and the Yamaha 2400/2800 family.
Jim (Jim_in_california)

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Posted on Wednesday, August 10, 2005 - 2:19 pm:   

Hmmm. Let's not forget that in addition to the genset cooking away, I'd also have a 680w solar bank adding to the mix :-). That alone might put the poor little Honda over the top if the Outback can "mix the power", although it'd be balls out :-).

Hmmm. 2400 or 2800 would be better :-).
Brian Brown (Blue_velvet)

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Posted on Wednesday, August 10, 2005 - 3:07 pm:   

If fuel-savings is your motivation, here's a fuel-sipping 5kW diesel genny... 0.24gal/hr @ half-load. http://www.generatorsales.com/order/yanmar_4kw.asp?page=yanmar_4kw

I couldn't remember if your rig is diesel or gas.

At any rate, it seems like requiring an inverter to supplement a genny in starting an A/C compressor might be fraught with issues... technical and otherwise. Plus, on moderate days the compressor will cycle on and off to hit the thermostat set temp, pulling down your batts each time.

The $ and time you spend trying to make up for power can buy you a whole LOT of fuel. So an extra $1k spent on a solution would buy like 1,000 hours of fuel, even on something inefficient. Plus, you don't have to engineer anything... you turn on the genny, start your A/Cs and not have to worry about babysitting a “supplemental solution.”

If it were me, I'd just resign myself to running an adequate "noisemaker" anytime the A/Cs are running. Inside where it's cool, you'll barely hear a genny over a rooftop unit going full-bore anyway.

Keep in mind that your Onan will require more ongoing maintenance (points, plugs, timing, etc.) that a diesel would not, or at least not nearly as often. Those old mechanical governors aren't real good, either. They can swing voltage widely and "hunt" at times. BTDT and glad to be free of it, honestly.

My $0.02,
BB
Stan

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Posted on Wednesday, August 10, 2005 - 3:32 pm:   

Jim: I would be a little suspicious of the Yamaha numbers for long term use. Your old Onan 4 KW uses a 14 HP engine with gives a HP to KW conversion of about 40%. The 5.5 HP producing 2.8 KW is about 70% conversion. This seems to be very high considering all the losses in an internal combustion engine added to the losses in an inverter.

I haven't done any research on the Yamaha units and you have checked them out quite thoroughly but a quick approximation of the numbers makes me wonder how they can achieve that efficiency.

BTW, I think you have a great idea if you can pair up a small genset with an inverter that will load share on high load and recharge the battery on lower load.
Jim (Jim_in_california)

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Posted on Wednesday, August 10, 2005 - 3:45 pm:   

Brian: remember that the times when the aircon isn't drawing a max load, any "excess" power the gennie has available will be fed back to the battery as charge - the Outback is an inverter-charger. PLUS the battery bank will be fed by the solar panels too...680w ain't chump change, although I won't see quite that much very often.

Now if my battery bank was small, I'd worry about cycling it up and down. But it's anything but, it's bigger than four Trojan L16s, a single 845amp/hr battery. So cycling it a little won't hurt it any if the cycles are less than 10% of capacity as I'd estimate they'd be.

Stan: the Yamaha's performance is right on par on a size/horsepower/wattage basis with the small Honda inverter-based gensets like the EU2000i, which have been heavily document as real. I think we're simply seeing the result of much more modern tech is all...the Onan is seriously "old school".

Oh, and my unit is a gasser, although that doesn't eliminate a diesel genny. I'd be tempted to do very small scale WVO...
Richard Bowyer (Drivingmisslazy)

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Posted on Wednesday, August 10, 2005 - 3:49 pm:   

Stan, I am suspicious of the idea that a 4 kw Onan uses a 14 hp engine. The generally accepted ratio of HP to kw, in this power range, is two to one. Most manufacturers would use an 8 hp or somewhat smaller engine to drive a 4 kw alternator.
Richard
Jim (Jim_in_california)

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Posted on Wednesday, August 10, 2005 - 4:04 pm:   

Richard, if that's the case, Yamaha is claiming to get 2800w out of a 5.5hp engine...fractionally off from your figures and might be accounted for via a more modern genhead.
niles steckbauer (Niles500)

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Posted on Wednesday, August 10, 2005 - 4:10 pm:   

Whooa there Stan - I thought the 14HP models were the 6.5 to 7 KW which would be about 2HP per Kw which would have the same efficiency of about 70% - but I was wrong once back in '02 - please don't make me be wrong again -

Niles
niles steckbauer (Niles500)

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Posted on Wednesday, August 10, 2005 - 4:13 pm:   

Sorry - DML posted before I finished (had a phone call interuption) - wasn't gangin up on you -
niles steckbauer (Niles500)

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Posted on Wednesday, August 10, 2005 - 4:24 pm:   

Jim - I'm anxious to see how the 'real world' plays out with your designed system - but from what I have had related to me, an array of your size matched with a decent bank of batts, considering the inefficiency of all the components in totality, along with the minimal actual time and frequency of 100% conduction - will do little more than maintain a float on your batts - FWIW - Niles
Richard Bowyer (Drivingmisslazy)

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Posted on Wednesday, August 10, 2005 - 6:03 pm:   

Jim, the 2 hp per kw is kinda a talking number and generally is somewhat less than 2-1. The 2-1 ratio also gives you a little extra capability for overloads. In the olden days, engines were generally not available in the fractional hp ranges like 5.5.
Richard
Jim (Jim_in_california)

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Posted on Wednesday, August 10, 2005 - 10:40 pm:   

Well for now, the answer is that Outback is working on it but isn't there yet. They're close enough that they've set up the controller ("Mate") with the command to set it up but they don't do anything with it yet.

They do have a free firmware program though.

One issue seems to be that gensets of different makes/types often run slightly varying frequencies from 60hz. My understanding is that the EU2000i in particular and probably other inverter-type gennies from Honda, Yamaha, Suzuki/Robin are probably as good. I've suggested that they get an EU2000i as a test mule and if necessary only support specific gensets with this "boost feature".

It would still be useful as hell in that form.
Username

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Posted on Thursday, August 11, 2005 - 1:22 am:   

My experience with an EU2000 may be revealing:

According to their literature, running at 25% load (400W) yields 5455 Wh/gal, and at 100% load (1600W) you get 5818 Wh/gal. I found this interesting, because, when graphing Wh/gal as a function of output wattage, the 2000's curve is much flatter than the remainder of their product line, where economies at 25% ranged around 50% to 67% of their full load economies.

I sought to verify this (using a $50 Kill-A-Watt power meter, accurate to 0.2%), and was unpleasantly surprised. Actual fuel economy at 25% load was only 3640 Wh/gal, and at 100% it yielded 5141 Wh/gal. This was confirmed via coarse measurement of another unit's performance.

So either Honda is lying through their teeth, or someone just slipped up in generating the ad copy. Given as they were advised of this issue a year ago, they should have corrected their figures by now....

Worse yet, though, was that the unit was unable to sustain a 1600W output when running in the shade in 90 degree F weather; voltage would sag when loads exceeded 1200-1400W in such a fashion so as to limit power output to that produced at the initial point of sag.

Note that this testing was done on 100% incandescent loads, using several dimmable 300W and 500W halogen fixtures. Granted, the dimmer itself distorts the waveform somewhat, so the number, wattage, and voltage (120V vs. 130V bulbs) of lamps was selected to approach the desired loadpoint as closely as possible. Also, note that these tests were run at near to sea level.

Moving on to motor loads: a single roof air of late 80's vintage (I'm guessing 11-13K BTU range) could just barely be started if the variable speed mechanism in the genset was disabled such that the unit always ran at full speed.

I also found that the unit had very little surge capability, which is unsurprising because its energy reservoir is simply some number of capacitors within the unit, vs. e.g. a typically much more capacious battery.

Now, as for a combined genset-inverter setup. In order for the inverter to provide genset support, the inverter must be capable of grid tied operation, with the genset acting as the grid. For Outback, this would be the GFX or GVFX line; I looked for this line on their website several months after I first heard them announced, and saw no reference thereto. Maybe it indeed is shipping and this is an example of poor attention to detail that is unfortunately so endemic within the renewable energy field, or maybe it cannot yet be had...

Some amount of deviance from exactly 60Hz may be acceptable; UL standard 1741 defines the conditions of frequency and voltage variance, expressed as a function of the duration of the deviance, under which a grid tie inverter must disconnect from the grid. As long as the genset can operate within spec, everything would be fine.

However, that spec encompasses both steady state loads and load steps, i.e. transient loads. I noted that the EU2000 could, when presented with a 0 -> 1600W load step, take nearly 1 second to fully ramp up its speed. Likely, a grid tied inverter would be designed to sense the AC passthru current from the input port fed by the pseudo-grid Honda, and only provide boost when the current exceeded a user specified value, e.g. 15A, 20A, 30A, 50A, or etc. If a load step was applied that was sufficiently large to outstrip the genset's ability to ramp up its output, i.e. its output slew rate, then the inverter would sense a voltage sag that may cause it to kick out.

Thus, it may be necessary to run the genset in fixed full speed, vs. variable speed, mode, which defeats a considerable amount of the benefit of an inverter based genset. In effect, you're trying to use one inverter to look like the grid from the point of view of another inverter, but the first inverter is simply not up to the task of duplicating the immense capacity of the grid (in fact, it is likely weaker, i.e. less 'stout', than the other inverter).

So, as far as I am aware, there is still no mass market engine driven device or system that suitably optimizes engine behavior, and thus fuel consumption, to applications where loads are significantly less than the unit's rated load, and/or applications having high load slew rates.
Jim (Jim_in_california)

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Posted on Thursday, August 11, 2005 - 2:16 am:   

OK. Hold on a sec here.

I think I get "Wh" as in "watt/hour" per gallon of gas. But...what do you mean by "load slew rate"?

-----------

Next...the wattage drops under running temperatures...well...I've been browsing the EU2000 yahoo group. A number of people are running 13.5k aircons by cranking the cooling to "max high" (so it doesn't cycle) and then either hoping that particular device will start or pulling some stunt to get over the initial hump. Some people alter the aircon so you can start up the motor separately from everything else; at least one guy was starting it up on an Onan 4kw or above (didn't say) and then somehow "hot switching" fast enough to keep things alive.

And then they're running all day like that.

Now...either those aircons are drawing amazingly low power levels, or you got yourself a lemon specimen of EU2000 (which is possible!).

The (relatively) poor fuel economy at lower load levels isn't a big shock. It's basically a moped engine, or very small motorcycle engine and from tuning those for many a year, I can tell you that adjusting what RPM you get max power out of it is a normal thing...the smaller and more "high strung" the motor the narrower the powerband. So if it's tuned for an optimum wattage of...call it 1400w - 1500w, no shock there. And not really a problem in my book, the only things I want it for is air conditioning and battery charging, both of which would need to involve "balls out" running or close to it.

I suspect the Yamaha 2400 or 2800 inverter models are better options though.
Stan

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Posted on Thursday, August 11, 2005 - 8:34 am:   

Re Onan gensets: I used to buy them by the dozen and I had all the dealer data on them. I have long since thrown most of that out but I have looked up a couple of dealer manuals and here is what I see:

Briggs and Stratton engine 8 HP - 19.44 ci displacement - 3600 RPM - 3750 watts. I only tried a couple of these lightweights that had to be carried by men through the swamp. They were a POS that woudn't carry a load and were just a throwaway.

Onan engine 14 HP - 49.8 ci displacement - 1800 RPM - 4000 watt (also available with 5000 watt gen head on same engine). This was an RV model that was a work horse that could go from no load to full load and maintain its 5% tolerance on voltage and frequency.

One further comment on Onan. Since bought by Cummins, I would never buy another one because of the poor support from Cummins.
WEC4104

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Posted on Thursday, August 11, 2005 - 9:08 am:   

Looking at it from an economic standpoint:

Onan uses .5 gal/hr (@ est $2.50/gal) it costs $1.25/hr to run.

IF the smaller unit truely does use 1/3 the gas, you save $0.83 for each hour you run the smaller one instead of the Onan.

Using a $1200 purchase price, you achieve payback after running the smaller unit for 1445 hours, or roughly 24 hours a day for two straight months.

The above figures do not take into account the residual value of the Onan or the purchase of a second Yamaha unit to use in tandem. Personally, I would think you would need to either keep the Onan for high demand times or buy the second unit. Selling the Onan and buying the Yamaha might be a "wash", but if not, adjust accordingly.

Just playing with some figures ...

WEC4104
Richard Bowyer (Drivingmisslazy)

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Posted on Thursday, August 11, 2005 - 9:11 am:   

In my experience, many times the engine for a particular rating was selected because it was one of the models available off the shelf. I suspect that a 6 kw genset, if available, would also have used the same engine.

The engine was almost always at least twice as big but sometimes three times as big because that was a stock size engine.

Many games were played (and probably still are) in this business. The HP rating is usually measured without any accessories on the engine. No exhaust, no radiator fan and no alternator.
Richard
niles steckbauer (Niles500)

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Posted on Thursday, August 11, 2005 - 10:36 am:   

Stan - I believe you - that Onan had a model 14 HP and 4 or 5 KW head - but that is not the norm - here is a link to onan's current 7 KW - 12.3 HP - but things have changed and efficiencies have improved

http://www.onan.com/pdf/rv/a-1431.pdf

Niles
Stan

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Posted on Thursday, August 11, 2005 - 1:19 pm:   

Niles: Spec writer did quite a job on the generator in your link. 7 KW from a generator hooked to an engine with max output of 9.2 KW. Assuming that anyone (other than the factory on a test bench) will ever get 9.2 KW out of the engine, it doesn't leave much margin for a changing load. Note the spec on voltage and frequency regulation - 0% no load to full load!

I have yet to see any engine that could go from no load to full load without losing any RPM with a resulting frequency change. This model appears to be a belt coupled unit to get from 2800 to 3600. There is no indication that it is an electronic output (inverter) or am I missing something?

My experience with gensets is that to get stable power, with varying load, you need lots of rotating mass backed up with HP.
Jim (Jim_in_california)

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Posted on Thursday, August 11, 2005 - 1:21 pm:   

WEC4104: you've got the economics sorted out well.

Change it to "eight hours a day in hot weather" and I've still paid off the Yamaha 2800 in six months. And I still have the Onan with a value of "X" (dunno what it's worth used, unfortunately there's no hour-meter).

I'm now working to pin down what the "real world" fuel use looks like versus "on paper" - the EU2000i yahoo group looks to be a good start.

One issue with the EU2000i is that it's 12v circuit is dirty as hell and says "battery charging only" for a REASON! Which means I couldn't run a small fan with it to ventilate a bay well enough to enclose it - the fan might burst into flames! (Yes, the DC waveform is that ugly - be warned.) If the Yamaha 2400 or 2800 have cleaner DC that could drive, say, an electric radiator fan off of a small economy car, that would be a major point in their favor.

Another major update on the Outback inverters:

While the generator boost function isn't yet working, what DOES work well is to start the aircon off the inverter power alone and then start the genset. Outbacks change from "inverter" to "passthrough" seamlessly enough to prevent the aircon from noticing - and the Outback 2800w model has burst available to 4000w or so for a respectable time period, easily long enough for a genset to warm up.

Thread on the Outback forum:

http://www.outbackpower.com/forum/viewtopic.php?t=757

---------

As to the Onan's efficiency and horsepower rating: remember that it has a big advantage, the rated ability to operate in an enclosed RV bay with no external venting. To do that it has to have a hell of a lot of "overheat capacity" hence the "14 horsepower" thing I suspect. The Hondas and Yamaha's are NOT so rated. I think they could be adapted to a bay meant for a bigger gennie like the Onan by fan venting but no, nobody needs to send me a fan to let me test :-).

In my case the back wall of the cargo bays face the middle driveshaft and exhaust pipe tunnel. The Onan vents to there as is...and yeah, that means I need a carbon monoxide alarm BAD but if the floor is sealed as well as the designers thought, it should be OK to mount the small car fan against the back wall of the genset bay, mount the fan there, put the gennie in front of it. Might even be able to noise-insulate the door of the genset bay, drop the noise level of the Yamaha 2800 considerably (it's a 67db model, roughly the same as the Onan).

Anyways. I'm leaning towards the Yamaha 2800 overall. Same fuel curve as the 2400 but noisier - due to less sound insulation, which means cooling inside a genset bay should be possible.
WEC4104

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Posted on Thursday, August 11, 2005 - 10:03 pm:   

Thanks Jim. Here's another thought for you. Don't sell the Onan as a complete unit, PART IT OUT! I currently "have issues" with my Onan 5KW gas unit and have looked at a few replacement parts (expletive deleted!) There is a small switch that shuts the unit down for low oil level/pressure. (Onan#309-0307) that is only $293!
Jim (Jim_in_california)

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Posted on Thursday, August 11, 2005 - 10:34 pm:   

Huh.

Well that's a thought.

<scratches>

What I was planning on doing was selling it on Craigslist to a local buyer, show it to them operating both 13,500 and 5,600btu aircons at once, then we pull it together right there at their place. They'd also get the original wall switch control (on/kill with light indicating operation) and we'd trace the five wires so they'd know how to wire the switch.

But...hmmm.

I could take a video of it running both aircons, have a document to that effect notarized then pull the sucker completely apart. Pistons and barrels would go as a matched set of course...ditto the bottom end...yeah, that might be...worth considering.

The control board is probably worth a small fortune, ditto the genhead...carb which would be properly drained and inspected for gasket issues...

The only thing that may be "iffy" is the exhaust plumbing, I haven't taken a close enough look to confirm rust issues or not and was going to do that before selling it outright.

Huh.

Well if I can unload it locally at $700 it would be faster and easier (and that's with the local inspection, they get the switch and wiring diagram, etc. number). I'll try that first. If it's obvious I can only get $500 or less, then parting it looks good.
niles steckbauer (Niles500)

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Posted on Friday, August 12, 2005 - 2:07 pm:   

Stan - I'm with you - hard to believe 76% efficiency and maintain a stable output with varying loads - maybe its the V-TWIN (the Harley Davidson model)-but it does say it will start 2 13.5 ac's - Niles
Richard Bowyer (Drivingmisslazy)

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Posted on Friday, August 12, 2005 - 8:56 pm:   

Absolutely impossible to have 0% voltage and frequency regulation from no load to full load. That is a downright lie!!
Ricard
WEC4104

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Posted on Friday, August 12, 2005 - 11:53 pm:   

Jim:

My "part it out" comment was just a bit of a jab at Onan's parts pricing. This weekend I have to do some troubleshooting to figure out why my 5KW unit runs great for 15 seconds, then quits (repeatedly).

In the meantime I've started looking at pricing on some of the potentially faulty components. Oil pressure switch $239, Control Board $304, Fuel pump $255, etc., etc. Even if your used stuff has half the street value of new, it adds up quick.

Not sure I'm serious about you actually selling it this way, just playing with more numbers.
niles steckbauer (Niles500)

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Posted on Saturday, August 13, 2005 - 12:38 am:   

WEC4104 - before you do all that - check the breaker at the genset - Niles
WEC4104

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Posted on Saturday, August 13, 2005 - 7:50 am:   

Niles:

A good thought, but I checked. I can also plug a multimeter into one of the AC outlets and I get 120 volts for the 15 seconds the generator is running.

I'm thinking either fuel starvation (from any of several causes) or a control circuit problem (oil pressure switch) I welcome input from others, but don't want to hijack this thread either.
Jim (Jim_in_california)

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Posted on Saturday, August 13, 2005 - 8:24 am:   

WEC: it's not uncommon for something to be worth more as parts than as whole. Much more of a pain of course...

Whether you were kidding or not, there's merit to the part it out concept.
Tom Caffrey (Pvcces)

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Posted on Saturday, September 03, 2005 - 1:21 am:   

"Jim:

My "part it out" comment was just a bit of a jab at Onan's parts pricing. This weekend I have to do some troubleshooting to figure out why my 5KW unit runs great for 15 seconds, then quits (repeatedly)."

WEC4104, I'm not sure if your running time is exactly 15 seconds, but we had similar behavior in ours that we finally solved.

When we used to park our coach and leave the fuel system turned on for the Onan, after a couple of months, it would start right up, run a little bit, then die.

It did this repeatedly until I had enough. Then, I opened up the carburetor. What I found was that the gum that formed on the needle and seat was sufficiently sticky to hold the needle in place against fuel pump pressure.

I cleaned the needle and seat and it worked fine. Until the next time the coach was parked and it did the same thing again. I gave it the same cure. It worked.

After thinking about this for some time, I decided to make a point of turning the fuel valve off while the engine was running and run the carburetor completely out of fuel before letting it set for a couple of months.

This worked like a charm, and I have not had any more trouble. The trouble with not turning the fuel system off was that as the gas evaporated, the pressure buildup in the tank from gas vapors was sufficient to keep the carburetor full.

More and more gum formed as a result.

For what it's worth.

Tom Caffrey PD4106-2576
Suncatcher
FAST FRED

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Posted on Saturday, September 03, 2005 - 6:31 am:   

"After thinking about this for some time, I decided to make a point of turning the fuel valve off while the engine was running and run the carburetor completely out of fuel before letting it set for a couple of months.'

On our boat we use a 6 gal outboard tank , lashed to the rail (so no gas is aboard) and simply unplug the tank at the fitting .
The Onan simply runs out of gas , which DOES save lots of tinkering if the set is only occasionally used.

A cheaop inverter has worked better than the genset (NO MAINT)as a usefull tool power supply,batts being refreshed by solar.

For folks travelong where genset use is rare , the Propane option would probably be the easiest to only operate a few hours/days a year , as the fuel evaporates after shutdown.

It will be interesting to learn the service life /repair frequency of a tiny really really hard working noisemaker , to compare it with the semi loafing that the OHNO, is doing.

The OHNO's have an adjustably carb that might accept a much leaner than normal fairly rich setting.
Access to a exhaust gage , and a lean setting might reduce the fuel use at the limited load, enough to make the unit acceptable.

Then too it might eat the exhaust valves.

FAST FRED
pat young

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Posted on Saturday, November 19, 2005 - 3:12 am:   

If anyone is still reading this post after 30 replies, you are probably crazier than I am, or up at two oclock in the morning.

But anyway, I have some 4 cylinder Herucles disesel engines that led easy lives in fire trucks. Less than 1000 hours in 30 years, very well maintained.

Speaking of wells, they have pumps attached to the back, but I guess you could swap a generator head on there. they are self contained with their own radiator, skid, etc.

Have a good one

patrick Young
playing with large
dirty metal objects in
Fresno CALIF

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