? inverters,transformers, how much power

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  #1  
Old 11-02-07, 07:57 PM
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Question ? inverters,transformers, how much power

i am trying to outfit my 30' 1981 class A Winnebago with an alternative power source.
"as is" i have fully operating shore line and functioning ohan 6.5 rv gen set with house battery supplying 12v lighting, vent fans and a few other lo voltage devices.
i have researched both inverters and transformers but i don't know how much power ill need, there is much to chose from.
i don't know if this rv ever came equipped with any other opinions but it dosent have them now.
i would mostly like to use the lo voltage lighting but the generator doesn't power up any thing like a transformer and i don't want to run down the batteries.
any help thanks
chefsam
 
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  #2  
Old 11-03-07, 10:30 AM
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unless someone removed it, that motorhome should have come from the factory with a converter already installed & running. When you are plugged in, the converter supplies power to all your 12VDC items,(lights,pump,fridge, etc.,) as well as supplying a charge to your auxiliary battery, or batteries. I'm guessing when your using your generator, you need to plug your power cord in to a receptacle inside the compartment right? Depending on all the 12VDC options you have on that unit, I would say a 30amp converter would be more than sufficient, to power all your 12VDC needs & still have room for add-ons if required. Do you plan on camping a lot where no hydro available? Do you expect to use your generator mostly where your planning on going. There is some cautions to remember with that Onan generator too. Give us an idea of how you plan on using that motorhome in the future, and that will make our suggestions more specific.
 
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Old 11-03-07, 10:50 PM
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this motor home has set non-op for aprox 4 years, during which time it was rented out as a cabin; it had under gone a number of changes, mostly creative wiring.
the generator wiring had been spliced into, and a second land line had been used to run 1 of 2 a/c units, all of the 12v lighting had been disconnected and a mangle of 110 wiring had been redirected, was able to sort out the mess and every thing is working directly from power source. other motor homes and trailers i have noticed seam to have power surges and dim with the rhythm of the generator. i have turned the thing inside out and found nothing like an inverter, or converter wear might it have been located. i do plan to do mostly dry camping with no hook ups
 
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Old 11-04-07, 02:18 PM
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Originally Posted by chef sam View Post
this motor home has set non-op for aprox 4 years, during which time it was rented out as a cabin; it had under gone a number of changes, mostly creative wiring.
the generator wiring had been spliced into, and a second land line had been used to run 1 of 2 a/c units, all of the 12v lighting had been disconnected and a mangle of 110 wiring had been redirected, was able to sort out the mess and every thing is working directly from power source. other motor homes and trailers i have noticed seam to have power surges and dim with the rhythm of the generator. i have turned the thing inside out and found nothing like an inverter, or converter wear might it have been located. i do plan to do mostly dry camping with no hook ups
P.S. what about that onan ?
 
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Old 11-07-07, 07:58 PM
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I'll do some digging on winnebago's & see if I can find out where they normally were mounted in 81. Did you not find any hint of a fuse panel (old glass style, or spade style fuse holders?) As for the Onan, be careful not to run it too long with little or no load on it, as it will start to suck gas into the crankcase, and thin the oil, and ruin the engine. Keep a close eye on the oil level. If your going to be running it for a few hours, check it before & after. If it's higher after running, then good chance it's because gas has been drawn in to crankcase. Check it often & change it if level goes up. Smell it (oil on dipstick) for fuel smell from time to time too.
 
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Old 11-08-07, 07:16 PM
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Talking

thanks mike ,i do have the power panel with the glass type 12 v fuse board along side the AC breaker box. its located about center of the rv behind the hot water tank, that area had been gutted and a new hot water tank had been installed
prior to my owning it ,how ever it is evident that some damage had occurred ,possible small fire and water damage ,that's all been repaired, i suspect the converted was never replaced so my question still remains how much power do i need from an inverter.
and thanks for the tip on the gen set
 
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Old 11-08-07, 07:37 PM
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This thread has confused me since the first post. Chef Sam, you're asking about what INverter you need, but keep looking for the location of the CONverter. If you only need to run 12V lights and such you don't need an inverter at all.

If it's a converter you're talking about, and really don't already have one, then MikeB has said 30A should be sufficient.
 
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Old 11-09-07, 01:55 PM
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I think you may be forgetting the battery charging function of the converter. 30A converter is barely adequate to charge 2 or more house batteries. Even most travel trailers have higher capacity converters. for a 30ft motorhome I would go with at least a 55A depending on your electrical load you may want 65A or more. Each 12v bulb can draw an amp or just over. so its not hard to go over or near the limit, and if you do your batteries will begin to supply the needed extra. If you only have 2 group 24 or 27 house batteries I would stay away from an inverter unless you are prepared to be very carefull with your power management. Inverters draw dc amperage just making 120vac available. 200A is not much for an inverter. The conversion is over 10 to 1 (over 10amps dc to make 1 amp ac available) due to inefficencies in the system. So in a real world, 200A worth of dc will supply less than 20a ac. Also Minus your addtional 12v loads. People run inverters on 2 house batteries but have to be very carefull with power management and they dont tend to use the inverter much. The plus side of an inverter is that many of them go both ways so to speak and supply 12v and charge batteries when shore or gen power is available.
 
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Old 11-09-07, 05:43 PM
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I agree with Hapdad, when he says that most motorhomes are running 40-55 amp converters. At the same time I'm taking into consideration that you have nothing in the interior of this unit, that is running on 12VDC currently. Probably a house style fridge, (no 12vdc required) electric heaters, if any,(no 12vdc required) no electronic ignition on your water heater (12vdc) . Is there a 12vdc water pump still on board? Then take into consideration that you will be charging 1 or 2, deep cycle batteries, which require a fairly low amperage charge for optimal life (compared to a regular automotive style battery that will take a quick, high amp charge),and 30 amps would have been sufficient, if all you wanted to do was run some lights & charge your batteries, but if you plan on changing it all back over in the future, then yes, 55 amps or higher will probably be a good idea. If you price them out & there isn't too much difference, might as well go higher and have the reserve for extras later. Be aware also, that if your motorhome is still set-up somewhat like factory, you may still have the battery compartments on the side somewhere, and wiring from an isolator there too. This allows your batteries to charge off your alternator as you drive, or any time the engine is running. Let us know how far you plan on going with the inside of this motorhome as far as appliances, lights, furnace etc, that operate off of 12vdc current, and we can help you make your decision. As far as "Inverters" go, what you want to power up with it, will determine the best way to go for that too. TV,DVD, computer, etc, and how many of each. Keep in mind, the more you invert, the more amps you'll want from your converter. (do I have you totally mixed up yet?)
Relax, we'll help.
 
  #10  
Old 11-11-07, 06:54 PM
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hi everyone mike b, hap dad, and core, thanks for all of the info. oh one thing i forgot to mention i am an "rv newbie" so i don't know a lot about how things work when it comes to motor home electronics ,i didn't really understand the difference between inverters and converters but thanks to your help i have a much better understanding now ,so as it stands i need a converter and really have no need for an inverter i am not quite ready to take on power management but i am ready to go camping .thanks again everyone
 
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