Dump Loads

[daleh007]

I have been looking at what I could use for dump loads and was wondering if anyone has used or has input on the use of Nichrome resistance wire. It appears that a AWG 22 size wire, for instance, is approx. 1 Ohm/ft and if you were to use about 1.4 ft you should see about 10 amps of current at 14 volts. What I would like to know is:

1. How reliable or what is the life expectancy of this wire as 10 amps is supposed  to heat the wire to around 1700 deg. F?
   
2. Is there a Max. wattage rating for a given wire size?
   
3. Resistance values are given for a straight piece of wire, what happens if you make an coil to conserve space?
   
4. What would be an appropriate size wire to use? There may be mechanical issues with wire size as well.
   
   

Thanks,

Daleh

[windstuffnow]

   I've been using Nichrome wire for dump loads for quite some time now and haven't had any problems.   I believe the stuff I have is .032 but the smaller stuff would work fine also with lower loads.  I have them paralled giving a resistance of .35 dumping up to 50 amps total.  I've never seen them "glow" but they do get extreemly hot.  In the picture, lower right is the nichrome heater.  The wire is wound around some ceramic tubes.  My original controller I simply coiled them between two connectors and it worked fine, as long as there is enough room for them to move around without touching something it shouldn't.

Have Fun

Windstuff Ed

[BruceDownunder]

 Hi,  I wound some stainless steel rigging wire (stuff the marine shops sell by the metre for "mousing" turnbuckles. It's soft and ,what I did was turn three 2 metre engths in a battery drill .  then wound it on a couple of ceremic tubes. after, applied head gasket silicon along a couple of sides to keep the coils apart . can't solder ,so small screws and washers are good for connections.

Just a thought , mine works perfect.

Bruce

[richhagen]

I have used power resistors powered through FET's driven by an op amp comparator circuit.  My charge controller caps the maximum voltage allowed out, so I can do this even though the system can't currently use all of the excess power.  I recently purchased some ni-chrome wire to add to the amount of dumped power I could use.  My strategy was to use more resistance and wire per run and parallel more wires.  While this requires more wire, I think that by limiting the current a little more through the wire, and thereby the heat given off per inch of nichrome.  The longer life I expect to get out of the elements should, I believe, more than offset the initial amount of money for the extra wire, and the time to rig up the extra coils.  I am just waiting for it to arrive and rig it up.  Keep having fun, Rich Hagen

P.S. Ed's setups always look so neat.  It looks like it could be used as an example display model from Trace.

[daleh007]

nice setup and photo. Where did you get the ceramic tubes?

Daleh

[windstuffnow]

   The ceramic tubes came out of a phone company power box arrangement.  They were actually spacers on a very large rectifier set up.  I'd like to know where to get them myself, they worked out very nice.  They are 1/2" in diameter with a 1/4" hole through them and are about 6 inches long.   If you or anyone finds them let me know!

Have Fun

Windstuff Ed

[Victor]

 I have a bunch of ceramic tubes from old nob and tube wiring

 They have a 9/16 OD and a 5/16 hole and are about 3.5" long

Victor