[RE-wrenches] Diversion load for AC coupled system

[Hugh]

At 18:38 -0800 29/11/11, jay peltz wrote:
>Hi Kent,
>
>You can't parallel them.
>They each must have their own load.

But you can connect two Tristars to the same battery, each with its 
own load and this is normal recommended practice.

The two controllers may not agree exactly about when to move to the 
float stage, but when you think it through that doesn't actually 
matter at all.

At 18:30 -0800 29/11/11, Kent Osterberg wrote:
>The Tristar 60 manual says to keep diversion loads below 45 amps (or 
>somewhere close to that).

Load sizing is very confusing, but no, you can use any resistive load 
that will not exceed 60 amps (at EQ voltage).  The 40 amps is the 
maximum renewables input (source current) if you are going to conform 
to the NEC requirement that the dump load must be sized to 150% of 
the maximum rated current of the solar, wind and hydro sources 
combined.

In short you can use a 40 amps source provided that you have the 
capacity to dump 60 amps, and this depends on finding a suitable 
load.  (In reality a load that dumps 60 amps at 60 volts will only 
dump 54 amps at 54 volts float so you are down to a 36 amp source 
current but this may be built into the safety margin already, who 
knows?.)

I normally choose a big wire-wound resistor.  In this case one ohm 
4kW would be suitable.  In reality this would be built from several 
1kW or whatever I could find.  For example 4 resistors at 1 ohm and 1 
kW, configured in two pairs series/parallel.

More about the subject here. http://scoraigwind.co.uk/?page_id=637

Best wishes,
-- 
Hugh Piggott

Scoraig
http://www.scoraigwind.co.uk