[RE-wrenches] Diversion load for AC coupled system

[Larry Crutcher, Starlight Solar Power Systems]

Thanks Kent, Kirpal, Jay, Hugh, Et al,

At 3.8kW, each TS-60 will divert up to 34 amps @ 56 volts, well under 75%. I will have isolated loads for each controller. Kent, what am I overestimating?

One concern about two controllers is that if one has a lower turn on voltage than the other, the total load might be applied to it until voltage rise causes the second controller to to divert power. Without a way to limit controller current, I think this could be a problem. Over-current failure of one controller would cascade to the second then cause battery over-voltage until the Magnum shifted frequency to stop the grid inverter. Has anyone done diversion with two controllers?

Another thought I had is to use a single controller for relay control of a 120 or 240 volt load. I'm thinking this will be easier but I'd sure like some input if you have done this.

Thank you,

Larry Crutcher
Starlight Solar Power Systems



On Nov 29, 2011, at 7:30 PM, Kent Osterberg wrote:

> Larry,
> 
> I think Magnum's recommendation is more about proper battery charging than safety.
> 
> I'll second Kirpal's and Jeremy's recommendations for loads. The Tristar is probably the best choice for this job, but you are overestimating what you can do with it and paralleling two may have some coordination issues. The Tristar 60 manual says to keep diversion loads below 45 amps (or somewhere close to that). I think its a reliability issue so with a secondary shut down method, you might be okay pushing it a bit. I'm not sure how you get two of them to work together.
> 
> Kent Osterberg
> Blue Mountain Solar, Inc.
> www.bluemountainsolar.com
> t: 541-568-4882
> 
> 
> On 11/29/2011 5:35 PM, Larry Crutcher, Starlight Solar Power Systems wrote:
>> Hello Wrenches,
>> 
>> I would like some advice on diversion load control of 3800 watts of PV solar. The battery bank is 48 volts and the battery inverter is the MS4448PAE. This will AC couple with a grid tied inverter during an outage. Magnum Energy recommends the addition of a dump load for safe battery voltage control.  The customer may leave the home unattended for weeks so I am looking for reliability here. Quality, as well.
>> 
>> A pair of Tristar 60's should be suitable for the 3.8kW output but I haven't been able to find a load that is sized for this job. I welcome any advice on this subject.  Thanks in advance.
>> 
>> Larry Crutcher
>> Starlight Solar Power Systems
> 
> 

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