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From: (no name) (no email)
Date: Sat Jan 06 2001 - 13:09:56 EST
In a message dated 01/04/2001 8:15:50 AM Eastern Standard Time,
writes:
> > Heart or Trace or ?.....
>
> ...Turn your alternator upside down?
>
> Either one is OK, I think. The modified-sine wave units are a fair bit
more
> efficient than the true sine wave types. I have the Heart Universal Combi
> 2500 (no longer made) and it runs the water heater just fine. Be careful
not
>
> to get the tail of a tie-wrap in the fan unless you want to test the
> over-temp shut-dowm. Mine works.
>
>
I have a Trace SW2512: 12 VDC, 2.5 KW, $2000, "sine wave" unit. Aside from
two warts (2 relay auto generator start instead of three, and volatile
parameters requiring reprogramming after a 12 VDC interruption) it is a fine
unit.
Be aware that the manufacturers lie about the wave form of their outputs.
"Modified Sine Wave" is the more blatant lie. The output is in fact a square
wave with some off time between the pulses. Nothing remotely resembling a
sine wave.
The "Sine Wave" output claimed for my Trace is in fact a stepped waveshape
resembling a Mayan pyramid. The number of steps vary with the load.
The square wave output inverters are a bit more efficient than the stepped
wave inverters. However, the biggest effect on efficiency is the relative
size of the load.
For example, according to the graph in the manual my 2,500 watt Trace is the
most efficient (about 92%) at a load of 300 watts. At very low loads the
"overhead", or the power required just to run the machine, is a relatively
large percentage of the power draw so the efficiency approaches zero as the
load decreases. At higher loads "I squared R" losses gradually rise as the
current levels increase until efficiency is about 80% at 2,500 watts, maximum
rated continuous load.
Norm
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