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What Should I Use for a Diversion Load?
Several different types of diversion loads are available to the alternative energy market.
These loads are designed to operate with the power output levels common to most
diversion load controllers. The following are several available diversion loads which may
be used successfully for heating water or air.
A 120VAC, 2000 watt water heater element available at most any hardware store, may be
used with a 12, 24, or 48 volt DC system, however do not expect a 2000 watt power
dissipation. The power draw is determined by the heater element’s DC resistance, the
output voltage of the controller, as well as the output current capability of the charging
source(s). These heater elements were designed to operate at 120 Volts AC. A 48 volt 40-
amp charge controller will operate just fine with this type of a system providing about 500
watts of power dissipation. A 12 or 24 volt diversion load controller will work but doesn’t put
out enough power to effectively heat water with only one element. The remedy to this type
of problem is to parallel several of these heater elements to increase the power output. The
chart below shows power dissipation of a 120VAC, 2000 watt heater element operated at
different voltages. Note that the voltages given are roughly the bulk charge stage voltages
for a given system. Remember that if you parallel heater elements the diversion load can
handle more current.
A couple of other excellent diversion loads which may be utilized effectively are available
from Alternative Energy Engineering of Redway California.
1. A 12/24 volt DC or 24/48 volt DC water heater element (AEE Part #20909 or #20919
(24/48V))
2. Open air heater with a fan (AEE Part #2091312 (12V, 720W), #2091324 (24V,720W),
#20 91412 (12V,1440W), #2091524 (24V, 1440W), and #2091648 (48V,1440W)).
For more information calll 1(800) 800-0624,or 1(800) 777-6609, or FAX 1(800) 777-6648.
Regardless of the type of diversion load you decide to utilize, make sure that the diversion
load can handle all the power the charging system is capable of putting out. Paralleling
heater elements (whether open air or water heater) will allow more power dissipation. A
good rule of thumb is to not have a combined charging source greater than 80% of the
diversion load controller’s current handling ability. For example, if a Trace C40, 40 amp
diversion load controller is being used, do not place a combination of charging sources
which are capable of putting out more than 32 amps (80% of 40 amps) on the load
controller’s circuit. Sizing a diversion system this way allows a safety margin for unusual
conditions (High winds, high water flow, etc.). It is not recommended that light bulbs be
used as diversion loads for a couple of reasons.
1) An incandescent light bulb has a substantially lower cold filament resistance than when
it is on. This means it draws more power (up to five times) to start the light when it is cold
than once the filament has warmed up. Even a forty watt lightbulb may have an inrush
amperage at turn-on of 200 amps. This would cause the load controller to shut down.
2) In the event a light bulb load burns out, a smaller-than-necessary load will be present
and the excess energy will have no where to go. When the controller switches to diversion
mode, the other bulbs will probably burn out in succession since they can’t handle the
excess current, and very quickly you will have a no load situation.
Copyright Trace Engineering Co. Inc. Tel (360) 435-8826 Part Number 2680 Rev. C
5916 195 Street, NE Fax (360) 435-2229 November 4, 1998
Arlington, WA 98223 USA www.traceengineering.com Page
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System Voltage Power AmperageSystem Voltage Power Amperage
60 Vdc (48 Vdc system) 500W 8.6 Amps
30 Vdc (24 Vdc system) 25W 4.3 Amps
15 Vdc (12 Vdc system) 30W 2.1 Amps
120 VAC 2000W 16.7 Amps
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