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Forum Index : Windmills : dump load suggestions..

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Steve9R

Regular Member

Joined: 24/01/2006
Location: Australia
Posts: 72
Posted: 06:55am 16 Mar 2009
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this is what i need.. good dump loads.. what are these ones ? how do you size them ? i need to dump up to about 10a @ 24v from my system.. problem is the hot water dump im using at the moment is only drawing max of 5A.. anyone got any ideas ?



Steve
 
Janne
Senior Member

Joined: 20/06/2008
Location: Finland
Posts: 121
Posted: 11:40am 16 Mar 2009
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If you don't mind some tinkering, old electrical heaters provide lots good ni-cr heating wire. Just cut suitable lenghts from the wire to your system.
If at first you don't succeed, try again.

My projects
 
CraziestOzzy

Senior Member

Joined: 11/07/2008
Location: Australia
Posts: 135
Posted: 11:51am 16 Mar 2009
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probably not a direct answer to what you need (sorry) but I thought using TEC's (those power hungry thermo electric coolers) that run on 12 -24 volts are great and a sweet alternative for dumping...great for cooling your beers too :)
The dumps you show in the pic seem to be just resistive coils of thick "copper" wire encased in protective ceramic.
If you are capable of only dumping 5A out of the total 10A, then you may need another two units on top of the one you have.
I worked out that for ten amps to be chewed up using 105 degrees centigrade rated wire at 14AWG (about 1.6mm thick) copper wire (typically found in some motors if you can get the wire out) for a meter length of wire, you could at the minimum safely dissipate just over 16amps at 0.01 Ohms resistance without nasty things happening....I could be wrong, so best check or wait for opinions from others
Edited by CraziestOzzy 2009-03-17
http://cr4.globalspec.com/member?u=25757

http://www.instructables.com/member/OzzyRoo/
 
GWatPE

Senior Member

Joined: 01/09/2006
Location: Australia
Posts: 2127
Posted: 12:15pm 16 Mar 2009
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  CraziestOzzy said  you could safely dissipate just over 16amps at 0.01 Ohms resistance without nasty things happening....I could be wrong


You would be wrong!

well 24V and 0.01ohms? This would allow in theory 2400A at 24V, or over 50kW. I doubt the battery or wiring would be up to it.

The current you need to dump is 10A at 24V. Probably 28V in reality.

Power = 280W. resistance = 28 / 10, = 2.8ohms.

You may need to have this made. You could use 10x27ohm 30W resistors in parallel.

The resistors you have look a lot like audio dummy loads. I have many similar. These are ceramic former with nichrome wire wound resistor and terminated, with ceramic insulating coating. The ones I have are greenish in colour, 4ohm 100W and 8ohm 50W. I am sure there are many other values and wattages with a similar construction.

Gordon.
become more energy aware
 
carl1
Regular Member

Joined: 16/04/2007
Location: Australia
Posts: 79
Posted: 01:24pm 16 Mar 2009
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Hi Steve

if you are desperate
I can offer you:
2x 2ohm ca.225watt

dia: 30mm x 270mm mounted on a on a metall angle.

cheers Harald
 
Tinker

Guru

Joined: 07/11/2007
Location: Australia
Posts: 1904
Posted: 01:53pm 16 Mar 2009
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Steve, I just made a dump load exactly to the specs you want.
I used 1mm stainless steel wire which I had on hand.
about 10m of this was wound onto a 10mm rod in my lathe.
The spring thus created slid neatly over a thick wall glass tube I had, the glass tube was supported by an internal 6mm steel rod which was held by brackets on each end to a longish hardwood strip. The brackets also prevent the glass tube sliding about. I fitted some heat resisting material under the spiral element to protect the hardwood.

I trimmed the resistance to two 2.8 ohm elements, these are connected to three brass screw terminal posts and give me the option of 2x 10A or 1x 5A dummy load.
The glass tube is about 400mm long which should be enough to dissipate the heat from the load.
Klaus
 
CraziestOzzy

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Joined: 11/07/2008
Location: Australia
Posts: 135
Posted: 03:18pm 16 Mar 2009
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  GWatPE said  
well 24V and 0.01ohms? This would allow in theory 2400A at 24V, or over 50kW. I doubt the battery or wiring would be up to it.

What's wrong with a bit of minimum overkill...lolEdited by CraziestOzzy 2009-03-18
http://cr4.globalspec.com/member?u=25757

http://www.instructables.com/member/OzzyRoo/
 
Steve9R

Regular Member

Joined: 24/01/2006
Location: Australia
Posts: 72
Posted: 10:11pm 16 Mar 2009
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Thanks all for the advice and Harald I might take you up on that offer..

thanks again everyone
Steve
Edited by Steve9R 2016-01-09
 
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