Quote: Amps X Volts = watts.
Thats been the rule I have heard/read forever. If these converters draw more amps, then they are consuming more watts..I just don't see any way around it.
The rule is correct. If the converter specs are correct, they give the true power consumption in watts. The problem is that the generators aren't rated in watts. The advertising is in watts, but after you buy the generator and look in the Owner's Manual, the specs (in most cases, but not for Champion) show the power rating in volt-amps. The "watts" rating is conveniently gone. Most converters have a power factor of about 0.7, meaning that they need 43% more volt-amps than watts. So you buy what you think is a 1,600 watt generator that's really a 1,600 VA generator. The converter might be spec'd at 1,200 watts and doesn't state its VA requirement, which is 1,716 VA, and the 1,200 watt converter overloads the 1,600 watt generator. Generators rated in apples, converters rated in oranges, and the non-technical user left wondering why it doesn't work.
Generator and RV accesory mfg would do all of us a big favor and avoid confusion if the word "watts" on generators was replaced with "volt amps" since that accurately describes generator performance and if accesory mfg. specified max current (amps) and max VA in addition to or rather than watts. At a minimum at least listing power factor would allow one to determine max current draw.
and I'll disagree, volts x amps = watts applies ONLY to pure resitive loads. it does not apply to reactive (non resistive) loads on AC circuits such as motors, microwaves, converters, etc.
In these cases watts=volts x amps x power factor is a more accurate formula for actual power consumed. Or amps= watts/(volts x Pf)
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facory wrote: Someone please clarify: How many amps of current will a 2000 watt inverter genny (Yamaha, for example) supply?
Given that, how many watts of power does it support?
Now, how many amps does it take to start and maintain an 11,500 btu AC unit? My Y EF2000iS will not start my 11.5 AC.
Honda 2000 is rated at 13.3A continous. The honda is really a 2000VA peak, 1600VA continous generator.
The problem you may be experiencing is that the 12A or so the ac specifies is ONLY the running current. A coleman Mach III has a 45A locked rotor current. That is the max initial current the AC can draw when trying to start the motor from a stop under worst case conditions. Once the motor starts to turn the current goes down, but the generator needs to supply well over the running current to get the compressor motor started. AC starting current is likely in the 20 to 40A range.
ktmrfs wrote: volts x amps = watts applies ONLY to pure resitive loads. it does not apply to reactive (non resistive) loads on AC circuits such as motors, microwaves, converters, etc.
In these cases watts=volts x amps x power factor is a more accurate formula for actual power consumed. Or amps= watts/(volts x Pf)
I don't by any means want to start a peeing contest, but I think you're inventing a new definition of watts here. What you've described is VA, and it has a different name because it's a different thing. I'm no big expert on it and like most others I get frustrated by the definitions that launch into heavy math and leave you feeling stupid. To me, the big picture is simply a matter of infrastructure requirements. The AC electrical equipment is most efficient (in terms of hardware and materials) when the voltage and current is a perfect sine wave with the voltage and current exactly in phase. This is the situation where the generators, transformers, and wires can handle their maximum useful power, which is measured in watts. If the waveform or phase angles change, the equipment can handle the same maximum volts and amps, but can't handle as much useful power.
For an example, consider a power converter using 1,000 watts and 1,500 VA, and for simplicity, the converter, generator and wiring are 100% efficient. The power converter produces 1,000 watts of DC output. That's the "real" power. The generator and transmission wiring care about volts and amps, not watts, so they must be sized for 1,500 VA (the "apparent" power). The engine turning the generator (based on what I've read) need only supply 1,000 watts of power. So the power in is 1,000 watts, the power out is 1,000 watts, but the generator and transmission system have to be capable of 1,500 VA. Since the 1,500 VA equipment is capable of 1,500 watts under ideal conditions, and most people don't know what a VA is, the manufacturers just fudge the terminology a bit, using the unrealistic best-case situation.
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ktmrfs wrote: Generator and RV accesory mfg would do all of us a big favor and avoid confusion if the word "watts" on generators was replaced with "volt amps" since that accurately describes generator performance
I don't think VA alone describes generator performance. You need to know both VA (or power factor PF, which is the more common listing) and watts. Most larger and older generators, such as the Onans I love, list both. The watts rating tells you how much power the generator engine can produce. The PF rating tells you how much current the windings can handle. You can't exceed either. If you exceed the watts, the engine can't keep up and stalls out. If you exceed VA, the windings heat up and fail prematurely (newer gens will sense this and cut off).
Most smaller generators (less than 10KW) are designed with a PF of 1. They can handle as many VA as watts. Unfortunately, most devices are rated in watts, but converters, in particular often have a low PF. Since watts is VA times PF, they have a high VA, higher than the rating for the small gen.
Larger gens are typically designed with the industry standard 0.8 PF. They are also usually marked with that rating. If your load has a PF greater than 0.8, you are limited by engine horsepower, i.e watts. If your load has a lower PF (some converters have 0.7 PF) you are limited by amperage and the wiring/heating.
Quote: if accesory mfg. specified max current (amps) and max VA in addition to or rather than watts. At a minimum at least listing power factor would allow one to determine max current draw.
I agree - it would help if the load you want to run was marked with PF. Some are, but for others, we have to hunt around.
Quote: and I'll disagree, volts x amps = watts applies ONLY to pure resitive loads. it does not apply to reactive (non resistive) loads on AC circuits such as motors, microwaves, converters, etc.
I'll be picky and say that volts x amps = watts is true for all loads when you look at instantaneous numbers. What you are saying is that average volts x average amps is not average watts, which is absolutely correct. When you start averaging, then you have to worry about phase angles and harmonics. Something like a capacitor or a coil consumes almost no power (watts), but has lots of average volts and lots of average amps flowing in/out. The net power is zero, but you still need wires that are large enough to carry the current without overheating.
Quote: In these cases watts=volts x amps x power factor is a more accurate formula for actual power consumed. Or amps= watts/(volts x Pf)
Agreed - for averages, as in
average volts x average amps x power factor is average watts.
In fact, that's the definition of PF. You compare the actual power consumed/supplied (average watts) to the number you get by multiplying average volts times average amps. The ratio is PF. When the PF is less than one, the gen needs to be able to handle more current.
I have a gen (4 KW Onan CCK) that has the same engine as a 5KW unit. The only difference is the windings. Mine has smaller wires. I can overload it for starting AC, and as long as I don't do it for too long, the wires and breakers will handle it. I'm never watt limited, but I am amperage limited, which means my PF is a matter of concern for some loads.
ktmrfs wrote: volts x amps = watts applies ONLY to pure resitive loads. it does not apply to reactive (non resistive) loads on AC circuits such as motors, microwaves, converters, etc.
In these cases watts=volts x amps x power factor is a more accurate formula for actual power consumed. Or amps= watts/(volts x Pf)
I don't by any means want to start a peeing contest, but I think you're inventing a new definition of watts here. What you've described is VA, and it has a different name because it's a different thing.
I think he put it correctly, except that he was talking about averages. You're both right.
Quote: For an example, consider a power converter using 1,000 watts and 1,500 VA, and for simplicity, the converter, generator and wiring are 100% efficient. The power converter produces 1,000 watts of DC output. That's the "real" power.
This is exactly right, and well put.
Quote: The generator and transmission wiring care about volts and amps, not watts, so they must be sized for 1,500 VA (the "apparent" power).
They care about both. The power (watts)controls the size of the engine needed to supply that power. That's the real power.
Quote: The engine turning the generator (based on what I've read) need only supply 1,000 watts of power. So the power in is 1,000 watts, the power out is 1,000 watts,
Exactly.
Quote: but the generator and transmission system have to be capable of 1,500 VA. Since the 1,500 VA equipment is capable of 1,500 watts under ideal conditions, and most people don't know what a VA is, the manufacturers just fudge the terminology a bit, using the unrealistic best-case situation.
The 1,500 VA equipment doesn't need to be "capable of 1,500 watts" under any conditions. It will work fine with a generator that can only produce 1,000 watts - even under ideal conditions. However, the wires need to carry more than the minimum current you would expect for 1,000 watts. If you hold voltage the same in both cases, you need 50% more current carrying capacity.
The local power company surcharges industry for VA significantly below 1 because their lines are limited in the current they will carry. If a customer makes them carry more current (low PF) they still only get paid for the KW-hours consumed. That's why there's a big business selling industry PF correction devices. They can reduce their power bills by getting PF closer to one.
Is everyone missing the point here? The CPE 2000 will struggle, and often not run typical RV loads, such as a plain jane converter, while other "2000 watt" super fantastic happy generators don't have any issues whatsoever.
As for running an AC unit, well a pair should do it, but apparently 2 CPE's can't always do the work of one Japanese built generator.
I was all for the underdog, or the so called "better value" and not 'overpaying" for a brand name. I got burnt, others have as well. Just look at how many folks on the CPE 2000 thread arintimatelyly familiar with the workings of champions warranty department. Too bad, as it seems to be 90% a programming issue with the modules.
I have been reading the Champion 2000 thread. At over 200 pages it will take awhile. So far I have seen that the consensus of many different peoples tests is that the Champion puts out slightly more than 1700 watts..(Which should be enough to run the WFCO in question.)The Champion doesn't go beyond that to 2000 very easy or for long.
The Hondas seem to be a little better in the 1700-2000 range..But even they struggle.
So far I have read of two cases where the Champion failed. One was where the operater had the fridge on electric..He didn't know it had that capability.
And Hybridhunter.
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Huntindog wrote: I have been reading the Champion 2000 thread. At over 200 pages it will take awhile. So far I have seen that the consensus of many different peoples tests is that the Champion puts out slightly more than 1700 watts..(Which should be enough to run the WFCO in question.)
Holy jimeny christmas man. Have you even read the last 2 pages? It's a VoltAmps issue. It has nothing to do with watts
Huntindog wrote:
The Champion doesn't go beyond that to 2000 very easy or for long Honda's seem to be a little better in the 1700-2000 range..But even they struggle.
The champion doesn't go past 1750 period, end of discussion. The Honda will sustain 2000 watts for 1/2 an hour. Struggling? At over 115 volts, engine full throttle? Sure it's working, but thats the point, it works, it doesn't just pack it in and overload.
Huntindog wrote: So far I have read of two cases where the Champion failed. One was where the operater had the fridge on electric..He didn't know it had that capability.
And Hybridhunter.
Failed? I can find at least 4 that were defective right out of the box, and many many have replaced the module to deal with the overloading. As for not delivering over 1400VA, and not being able to run a WFCO under high load? Until CPE changes the design, it won't do it. Anyone with doubt, just check out youtube. There is even a video of 1 honda starting 2 fans and a saw, and twinned CPE's failing. This isn't made up stuff, and I'm not bashing. Better still, run you battery low and find out for yourself.
The CPE is a cheapish and risky bet. They will work for some, not others. The point I'm making, is there will be many people the CPE does not work for, that the Japanese generators will. My dad thought even though I had problems, he would keep one. He ended up fighting with it when he accidentily drew his battery down too low.
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