Like Roy said.
Use the C40 in diversion mode. It IS a dump load "controller".
Notice it 'controls' a dump load. It does not have a dump load in it.
It needs an external load.
Power resistors are best for a dump load. Especially in that system.
It would not be good to try to save a Loonie by using light bulbs if nobody will be there for 2 weeks. Hate to ruin the batteries over a burned out light bulb.
I recommend using much higher wattage resistors than necessary too.
The system could be in a situation to be dumping 100W for weeks at a time.
Might get a better understanding by reading this story,
http://www.fieldlines.com/story/2009/6/18/14139/1634
I have a few, new, very serious mil-spec power resistors from a canceled project that would be great for this. Email me if you have any interest in them.
G-