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Car Forum / Driving, Maintenance, Tuning / RVs / August 2007Inverter Question
I want to add an inverter for my old Class B so I can run the roof top a/c while the engine is running. It doesn't have a generator. The a/c is a 20 yo Coleman 7600 or something. I'm not sure off the top of my head, but I can find out. Anyway, would a modified sinewave inverter be ok, or do I need a puresine inverter? I might also use it to power a small microwave; are they sensitive to the inverter's output waveform? As for the wattage, I'll probably buy a Killawatt meter so I can see how much current the a/c pulls. I'm sure I'll play with it more anyway. I'd use my DVM but it only goes to 10A. Kent You do realize that however many amps that A/C pulls, you're going to need AT LEAST 10 times that amount on the input side of an inverter? I don't think you'll find an alternator that will mount on your engine that will put out that kind of amperage continously. steve >I want to add an inverter for my old Class B so I can run the roof top a/c >while the engine is running. It doesn't have a generator. The a/c is a 20 [quoted text clipped - 7 lines] > I'll play with it more anyway. I'd use my DVM but it only goes to 10A. > Kent > You do realize that however many amps that A/C pulls, you're going > to > need AT LEAST 10 times that amount on the input side of an inverter? > I don't think you'll find an alternator that will mount on your > engine that will put out that kind of amperage continously. http://www.db-starter-alternator.com/Alternators/High%20Output/?gclid=CLnP5c6b9Y 0CFSFxHgodmS4_MA They are available, but it will cost a fortune for the alternator and wiring to make it all work - unless it's a converted ambulance. :-) Tom J >> I want to add an inverter for my old Class B so I can run the roof >> top a/c while the engine is running. It doesn't have a generator. [quoted text clipped - 8 lines] >> pulls. I'm sure I'll play with it more anyway. I'd use my DVM but >> it only goes to 10A. Kent >You do realize that however many amps that A/C pulls, you're going to need >AT LEAST 10 times that amount on the input side of an inverter? I don't >think you'll find an alternator that will mount on your engine that will put >out that kind of amperage continously. Yes and there is the surge on starting too. Furthermore throw in a 20 year old A/C that is not very efficent (very power hungry for cooling it produces) and you have a the wrong setup to even try this with. If you really want to try this you need to first scrape the old A/C and buy a new one with low power draw. Then add a few batteries and a 3K inverter and a sries after market alternator or better still a dual alternator setup with second one dedicated to inverter power. But again none of this will work unless you first get a high efficency A/C with a lower current draw. (or just get a portable generator) ----------------- TheSnoMan.com Running an air from a battery or even alternator powered inverter is probably not practical. There is just not enough amperage available. Modified sine wave inverters haven't seemed to work for microwaves in my experience. You would need a far more expensive sine wave inverter. >I want to add an inverter for my old Class B so I can run the roof top a/c >while the engine is running. It doesn't have a generator. The a/c is a 20 [quoted text clipped - 7 lines] > I'll play with it more anyway. I'd use my DVM but it only goes to 10A. > Kent If you look up "Earthroamer" on the internet you may be able to learn something from the list of equipment which is supplied with their absolutely fantastic motor homes > Running an air from a battery or even alternator powered inverter is > probably not practical. There is just not enough amperage available. [quoted text clipped - 13 lines] >> I'll play with it more anyway. I'd use my DVM but it only goes to 10A. >> Kent >"Dan Listermann" <dan@listermann.com> wrote: >Modified sine wave inverters haven't seemed to work for microwaves in my >experience. You would need a far more expensive sine wave inverter. Our microwaves cook at about half power from our MSW inverters. They use so much power, though, that it isn't practical for anything more than warming up a cup of coffee. Our current microwave draws 130 amps from the batteries.  SignatureDD > >"Dan Listermann" <dan@listermann.com> wrote: > [quoted text clipped - 5 lines] > warming up a cup of coffee. Our current microwave draws 130 amps from > the batteries. I have to wonder where the excess power is going. It can't be good. >I want to add an inverter for my old Class B so I can run the roof top a/c >while the engine is running. It doesn't have a generator. The a/c is a 20 [quoted text clipped - 7 lines] > I'll play with it more anyway. I'd use my DVM but it only goes to 10A. > Kent I run a 5,200 btuh AC unit on my sailboat with a 1,000 watt invertor. I have 2 Optima batteries which will run my AC for about 8 hours when fully charged (Battery Model: D31M Description: High power, dual purpose engine start and deep cycle, sealed lead acid battery). You're gonna need to really beef up your batteries. Someone else here suggested a 3,000 watt invertor as well as a new hi-eff ac unit. This sounds like good advice. >>I want to add an inverter for my old Class B so I can run the roof top a/c >>while the engine is running. It doesn't have a generator. The a/c is a [quoted text clipped - 15 lines] > Someone else here suggested a 3,000 watt invertor as well as a new hi-eff > ac unit. This sounds like good advice. Check out these solid state air conditioners. Some models run straight on 12 VDC. You can mount them where you need them. http://www.melcor.com/ssair.html Amen! Pastor William Rennick >>>I want to add an inverter for my old Class B so I can run the roof >>>top a/c while the engine is running. It doesn't have a generator. [quoted text clipped - 25 lines] > > Pastor William Rennick Thanks, very interesting and so simple. Would the 50 BTU model MAA050T-12 make it comfortable to sleep in an enclosed bed if you mounted it on the ceiling and blew the hot air out the top? Or would it take a bigger one? Shad O'Shay > Check out these solid state air conditioners. Some models run straight on > 12 VDC. You can mount them where you need them. > > http://www.melcor.com/ssair.html The 1200 BTU per hour unit draws 7.3 amps at 110 volts. This would suck down most battery banks very quickly. >> Check out these solid state air conditioners. Some models run >> straight on 12 VDC. You can mount them where you need them. [quoted text clipped - 3 lines] > The 1200 BTU per hour unit draws 7.3 amps at 110 volts. This would > suck down most battery banks very quickly. Indeed it would but unless you have a huge RV you don't need 12000 btus. I think you could manage with far less than that if you had a sensible 15-25 foot RV parked in the shade and just needed to knock the inside air down 20 degrees or so from the outside air if the outside air was around 90 degrees. One of the 12-volt systems would probably be adequate. There's one that draws about six amps at 12VDC which might work for dry camping. You could always have a conventional window air conditioner when you could plug into the grid. Thank God nobody's tried to invent a propane air conditioner yet. Harry Harris SignaturePosted via a free Usenet account from http://www.teranews.com I think you slipped a decimal point. >>> Check out these solid state air conditioners. Some models run straight >>> on 12 VDC. You can mount them where you need them. [quoted text clipped - 16 lines] > > Harry Harris Here's a better solid state: http://www.eicsolutionsinc.com/2500btu_thermoelectric_air_conditioner.htm Amen! Perhaps this would do the trick for your air conditioning needs. Intriguing... http://www.arcticaircooler.com/ Seems like it could easily be built by one as unskilled as I. mdh >>> Check out these solid state air conditioners. Some models run straight >>> on 12 VDC. You can mount them where you need them. [quoted text clipped - 16 lines] > > Harry Harris Guys, check out the specs again. The biggest Melco unit is a 1,200 btu/hour (1/10 ton) not a 12,000 btu/hour (1 ton) unit. My boat unit is 5,200 btu/h, or about 4.3 times bigger than Melcor's biggest unit, and it runs nicely on a 1,000 watt inverter. The Melcor unit draws about 840 watts, almost as much as my 5,200 btu/h unit! Not very efficient. The Melcor's are air conditioners, but they are designed for cabinets... I don't know how much good they would do in an RV. Just my 2 cents. Scout >>>> Check out these solid state air conditioners. Some models run >>>> straight on 12 VDC. You can mount them where you need them. [quoted text clipped - 29 lines] > Just my 2 cents. > Scout You're right! It IS 1200 btu; not 12000, my mistake. But take a look at the 12volt units, this one in particular - MAA070T-12. It draws 4.9 amps at 12volts and produces 70 btu. This could be run directly off a 4 x 85 amp/hr battery bank all night long easily. When you're sleeping is it really necessary to cool the entire RV? You could rig it to only cool the sleeping area. Does anybody know how many btu a sleeping person produces? Harry Harris SignaturePosted via a free Usenet account from http://www.teranews.com > Does anybody know how many btu a sleeping person produces? > > Harry Harris That is a good question Harris. It is about 160 BTU/HR for a seated person not sleeping. Don't forget that there may be other heat sources. If the humidity is low an evaporative cooler may work. Praise! Pastor William Rennick Of interest: http://www.bertaut.com/aquatherm2000.html Glory! Pastor William Rennick > <snip>As for the wattage, I'll probably buy a > Killawatt meter so I can see how much current the a/c pulls. Any idea how many amps it takes to killawatt?:-) kh Ken Harrison wrote: Any idea how many amps it takes to killawatt?:-) It depends on where you hit it. Just to the right hand side of the watt, when you are looking at it, is the best spot for a clean kill. SignatureJerryD(upstateNY) |
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