[RE-wrenches] Magnum MS 4448 AE issues

Howie Michaelson howie at suncatchervt.com
Sun Dec 23 07:45:33 PST 2012


Hi All,

I am trying to help my brother-in-law figure out if he can continue using
his Magnum MS 4448 AE in his now off-grid home in Nova Scotia which we
installed about 3 years ago as at the time a battery backup inverter.  I
would preface the following with the information that he is a very
knowledgeable/hands on physicist (chair of the Physics department at
Dalhousie U. in Halifax, as well as an intrepid sailor having sailed all
over the world in 2 different sailboats he built himself).  I mention this
to explain that he is very capable and understands the inner workings of
his equipment much better than most wrenches I know (and certainly me).

About a year ago he installed a SkyStream 3.7 to add to the roughly 3 kW
of solar on an FM80, and then a short time later disconnected himself from
the grid.  He immediately started having problems with the Skystream
regularly disconnecting from his system and shutting down, then
reconnecting and cycling off again, were as there hadn't been a problem
while grid-tied.  After much investigation and conversation with SW
WindPower tech support and some software patches from them, things
improved somewhat.  But the regular disconnections continued.

Since then he has spent a great deal of time on the phone with Magnum's
tech support but they have not been able to answer his more technical
questions.  The best they've offered is to have him send the inverter in,
but of course that is now not practical.

The basic problem seems to be the voltage regulation during loading and
unloading of the inverter (even with medium sized loads). He tried to get
an internal wiring diagram and/or service manual from Magnum with no luck.
 He has not been able to get through to any engineers that would be able
to answer his more technical questions.  He is trying to figure out if
there are any internal set points that he can adjust or components that
can use tweaking. He has looked at the wave form with a scope and would
like to see if there are changes that he can make to the electronics to
allow for better regulation.

Here is what he has written me:

"Here is my report on the Magnum MS4448AE observing the AC output with a
Fluke 189, measuring the max and min values in slow mode (not it's fast
mode which would look at spikes for short times):

I have checked several water heater elements running on 240 V (they are
between 2000 and 2500 Watts - immersion heaters). When switching any one
of them on, the voltage drops from around 240V to 197 V on average,
sometimes going as low as 170 V. These are serious drops, the lights dim
drastically and the radio may cut out for .5 s or so! Switching the
thermal heaters off again raise the output voltage to 271 V sometimes
reaching 282 V.

The battery bank during those test were at 53 V at the DC input side of
the inverter, measured at the inverter. The voltage drop for the DC was
around 1 V DC. The battery bank is a 800 AH (Rolls S530) with 2/0 copper
cables 5 - 6 ft inverter cables.

We had great wind yesterday and I had to switch to the hock up the
diversion load to 240 V so it would draw 2.5 kW.  Needless to say it
stalled the windmill each time my outback kicked on the diversion load. I
had to leave  the windmill off during the day. When I run the heating
element on 120 V (and therefore 625 W) it works beautiful if the wind
isn't too strong. Obviously the inverter handles 625 W quite well!"

He is also thinking about replacing the inverter with a newer split phase
inverter (an XW or a Radian).  If anyone has an opinion about which might
work for him, I'd appreciate any feedback.  I am not a fan of Xantrex,
although I know some on the list really like the XW. If anyone has any
ideas of either a fix or someone we can get through to at Magnum, that
would be a great help.

Thanks,
Howie
-- 
Howie Michaelson
NABCEP Certified Solar PV Installer™

Catamount Solar, LLC
Renewable Energy Systems Sales and Service
VT Solar Electric & Hot Water Incentive Partner
http://www.CatamountSolar.com
802-272-0004








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