[RE-wrenches] Magnum MS4448AE Compatibility Question

[John Raynes]

I second Dana's response.  I have observed that the MS4448 waveform 
quality degenerates quite rapidly with imbalanced loading of one or 
the other of the 120 volt output legs.  I can't give a quantitative 
(% distortion/amps) number to it, but I would classify it as 
severe.  I first noticed it when doing some test measurements in the 
shop, and found large discrepancies between various current metering 
devices I was using, as some of the meters were not measuring RMS, 
and the distortion was throwing them way off.  And when using 120 
volt motors, even though their surge may be well within specified 
load limits, count on things not going well.

I'm generally satisfied with the Magnum MS4448, but this is one the 
two key shortcomings that I see with the product.  The other is the 
idle power draw when not in search.

John Raynes
RE Solar
Torrey, UT


At 11:16 AM 2/9/2009, you wrote:

>Wrenches,
>We have an unusual problem, and I need to know if anyone else has 
>had this or a related problem, and what to do about it.
>
>This concerns a new off-grid residential system, very conventional: 
>1,800W PV, Midnite E-Panel with Magnum MS4448-AE inverter, MX60, 16 
>S-460s, installed summer 2008. This existing home is being 
>extensively remodeled, and the home is not yet occupied. A local 
>mechanical contractor installed a new infloor radiant (gypcrete) 
>hydronic heating system using a Netherlands-made (German company) 
>Buderus GB142 high-efficiency boiler. The problem is that the boiler 
>won't start reliably on the inverter. It appears that the 
>hot-surface igniter does not get full AC voltage (it runs on 
>straight 120V AC, but is supplied through the boiler's control 
>circuitry). We tested the igniter by disconnecting it and plugging 
>it straight into inverter AC and it lit right up.
>
>The mechanical contractor has tried a replacement Buderus GB142 
>boiler with the same result. I was told that they brought out a 
>generator and it also failed to ignite on generator AC, but not 
>knowing the generator used or the way it was wired (I believe an 
>extension cord to a portable) I don't put much weight on this data. 
>They also took a Lochinvar Boiler to the site to test the theory 
>that a different manufacturer's boiler might work. The Lochinvar 
>boiler, which uses a different control and a spark ignition rather 
>than a hot surface igniter, worked on site without any problems.
>
>I'm looking for solutions. Magnum tech support had not heard of 
>this. Have you?
>Also, if indeed we have an inverter that is incapable of running 
>this load, how do we make it right to the homeowner and the 
>mechanical contractor? What should be Magnum's obligation? What 
>should be ours? This issue hasn't come up here since the days when 
>the Trace SW mod-sine series was the waveform standard.
>
>Thanks,
>Allan Sindelar
><mailto:allan at positiveenergysolar.com>allan_(at)_positiveenergysolar.com
>NABCEP certified solar PV installer
>Positive Energy, Inc.
>3225A Richards Lane
>Santa Fe NM 87507
>505 424-1112
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