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Forum Index : Electronics : Diversion/ dump load options (re-purpose)
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liqud Newbie  Joined: 11/08/2009 Location: United StatesPosts: 22 |
Hi I am new here but I am not new in the electrical field. Although I am not above saying I do not know everything. (I am certain I do not) I wanted to get a handle on what can be used as a diversion load or load dump. I have had a few ideas and would love to get some insight because a 1000w heating coil should not cost $200+ just for a load dump. I am sure there are cheaper versions. I was thinking of using a store bought 120V or 220v base board heater. I am planning for my 12v 1000w wigen. I have been looking at the xantrex c series. I am still on the fence here with the controller. Input to make this a nice thread about good ideas for dump load solutions. for thought- 1000w @12vdc nominal =83.3amps random baseboard heater- 120V 1000w =8.3 amps Need .14 ohms resistance on said heater to work? Possibly a series ran system and wiring leads upgraded. *I do not want to include any inverter situations just straight tie onto diversion load controller obviously the basic construction of the model would not be suitable I assume, But I am thinking with the proper measures a unit as such can be easily modified to encompass this power. and come in under a $50 dollar price range. please advise. anyone interested in a little re-purposing? I will appreciate any knowledge to be shared and do my best to be prompt. thanks for your time  Shawn C Real power is not given its made... |
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niall1 Senior Member  Joined: 20/11/2008 Location: IrelandPosts: 331 |
Hi shawn i,m not much good with the math but i think the store bought heater has just to high a resistance for 12v ... the v is low so it might take a lot of them in parallel to work so as to evenly spread the load ...a while back i tried making an air heater dump using stainless 8mm steel rope (it can be easily unwoven into individual groups of strands)..it kindof worked out as a big low temp dump heater (there is a risk of creating a home made inductor as a by product...  ..)..
ordinary high tensile steel (or nicrome )in some type of strand form might be safer..... stainless has a lower resistance than nicrome but pretty close compared to buying nicrome or a low voltage immersion element it is a whole lot cheaper one section on a tile...  niall |
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| liqud Newbie Joined: 11/08/2009 Location: United StatesPosts: 22 |
that is interesting i like that idea. cheaper is always better. the stainless steal would be a great idea for anything that would contact water. Has anyone tried to modify an existing heater? id like to get a basis for something that would have a UL stamp. Even though modifying it would void the UL tag Shawn C Real power is not given its made... |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Hope you don't mind but I moved this to the electronics section. I'm working on a dump load for a new article on the main web site. I don't know how well its going to work yet. I'm using 50watt 12v bulbs, which I bought for 25 cents each! Cheap enough. I've mounted 6 in a old PC power supply case, with fan, to give a 300 watt dump load. Light bulbs are not the best form of dump load, they have a high inrush current, but these are so cheap it's worth a try. I fear the bulbs will get dust on them and blow from hot spots, will see how it goes. 
In the past I've used heater elements from electric jugs. I had to unwind the heater element, cut into 4 lengths and re-wind it on the former to get the resistance low enough. 
Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| liqud Newbie Joined: 11/08/2009 Location: United StatesPosts: 22 |
so i would say 25 to 30 - 50 watt bulbs to supply an over current load dump per 1000 watt generator just goin off of the nec rating for electric motor start up breaker sizing. i like that idea halogen bulbs could produce a signifigant amount of heat too. let me know where ur experiments lead you. thanks for the time and pics please keep me updated  Shawn C Real power is not given its made... |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Jug elements need to be significantly derated for use as a dump load. To take a 1000W @240VAC approx 60ohms,jug element and rewire to 1000W at say 24VDC 0.6ohms will quickly burn out the elements. Better to use 4X the amount of wire and make 2 series/parallel strings. Gordon. The same goes for light bulbs. become more energy aware |
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Bryan1 Guru  Joined: 22/02/2006 Location: AustraliaPosts: 1344 |
All I did for my dumpload was trip the nichrome wire off an old 240 volt water heating element and wound it over 2 bussbars to get the ohms down. For the fets I used a pair of 169 amp one from jaycar and its worked a dream ever since i put it in. Cheers Bryan |
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oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Liqud 1000w 110v units are ok but remember.. at 110v your drawing 9A@110v for your 1000W... this makes R=E/I = 110/9=12R If R=12R then at 12v I=E/R = 12/12=1amp... so 12Watts. At 12Watts, you need 1000/12=... yes sir... 80 odd radiators... getting out of hand using mains units. If you rewire them (cut and paste type of thing, keep the A per unit to less than 9A minimum ..to get decent life out of them... ie R=E/I.. so 12/9 = 1.3R per resistance string... and parallel them up (about 9 of them) for your .14R... actual calcs will use 13.7v or whatever dump voltage you choose. Bryan's system using water element wire works for modest power, but if you wish to dissipate 1000W continuously, I have found fencing wire wound around inert substances ( I used a florescent tube (36W)...the wire wrapped around a 1" broom stick then transferred to the tube... which horrifies some people.... poor souls) It runs 20A@50v (1000w) without getting near to glowing,.. but enough to brown the zinc coating off the outside. 1000 watts of heat is the same no matter how you say it, and it is a lot to get rid of. You will need active cooling like Gizmo if you want compact, or lots of surface area if you have room to do it. There are no short cuts.. power is power. One more thing to consider, R increases with heat... so cold R is not hot R ..............oztules Village idiot...or... just another hack out of his depth |
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| liqud Newbie Joined: 11/08/2009 Location: United StatesPosts: 22 |
alright ive heard some pretty good points so far im about to throw the modified house heater idea out the window just to expensive unless i demo out an apartment building and get my hand on tons for free. and as far as the light bulbs go i am going to get my hands on some and see what i can actually dissipate. the fence wire is just basically a wound coil i like the simplicity im getting lots of great ideas but i havent been to my shop in a few days i would love to get you some informed feedback i am dying to get back there and try some ideas out. thanks for all your input i am gonna be back on here asap with some good input Shawn C Real power is not given its made... |
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MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
All the fancy math and terms makes me think there's something more to this that I'm probably missing, but if all you want to do is heat your shop or some other open space, why not use ONE fin-and-tube baseboard heater running oil using a flat-plate solar collector and a circulating pump? I'm into simple. Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Liqud, It was not my intention to put you off your chosen solution, just to crystalise for you what you need to take notice of. If the bar radiator has the old ceramic core with the nichrome wire wrapped around it for it's full length, then just one will do.... we just unwind all the wire which gives us 12 ohms of nichrome. If we then divide it into 9 equal lengths, we will have 12/9R for each... ie we can now wind 9 mini radiators of 1.3R per unit. If we parallel these 9 units, we get 9 little radiators each dissipating 9amps each.. for a total of 81 amps., and each should drop about 9A... giving you about 9 x 9A=81A @ 12v. Total resistance now is 1.3/9=.14R Same wire, different finished resistance..... about .14R instead of 12R The duty of the wire is exactly the same as the original manufacturer envisaged.... 9A. ..........oztules Edit: Macgyver, the intention is not space heating, but rather the bleeding off of excess power, so that the batteries still see 13.7v, and no more, and the mill is still fully loaded so it won't run away. Village idiot...or... just another hack out of his depth |
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AMACK Senior Member Joined: 31/05/2009 Location: AustraliaPosts: 184 |
Gizmo (Glenn ) Have you thought of using quarts down lights, they are not effected by dust spots and are cheap. The only down side is there size. I use them on my dump and they work well. They come in a 55 watt size and bigger I think too. Andy *Note to self 1. Make it thick 2.Make it heavy. 3.Make it stronger than it should be. 4. Don't rush the first job as the second job will cost more and take mor |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
oztules, you lost me after "we unwind all the wire"??? Did some text get inadvertently deleted? Klaus |
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| liqud Newbie Joined: 11/08/2009 Location: United StatesPosts: 22 |
Thanks OZtules Im going to keep all options in mind I am just trying to narrow down my first priority. I actually do believe i have an old space heater that can do the trick with a little care. I will get back to you as soon as i can scavenge it and i will undoubtedly have pictures. I just did the windings on my second coil pack same output but i am setting it up to have a controller to switch between wye and delta actively per windspeed. But that is another thread if i am successful i will upload a schematic even though its not a hard circuit. I am curious what charge controllers does anyone else use I have a 150amp one i am looking at and as always i am thinking of integrity of brand. I found a 160 amp controller for super cheap by a company called 'be a wind hog' one of those to good to be true things I am loving all the input everyone is giving me I am sure this will be a very usefull thread thanks to all of your help Shawn C Real power is not given its made... |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Opps. Tinker there was significantly more there when I posted it, I must have inadvertently deleted some when I did the edit on it.... and didn't look back up higher in the text. I'll go back and re-edit it I guess. ........otzulse...lseutoz...teolzeu.... oztules ( get it right sooner or later) Edit: went back and fleshed it out a Bit Tinker... does it make sense now?? Village idiot...or... just another hack out of his depth |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
"then just 1 will do.... we unwind all the wire, and divide it into 9 lengths (for the old 1000w @ 110v type about 12 ohms), and wind 9 "mini" radiators... each of 1.3R. Each should drop about 9A... giving you about 81A @ 12v" Is that what you were looking for? The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| oztules Guru Joined: 26/07/2007 Location: AustraliaPosts: 1686 |
Yes that looks like the original waffle Gizmo... I must have zapped it somehow when I edited/added info for Macgyver. I'm not second in line for the village idiot title for nothing you know 
.........oztules Village idiot...or... just another hack out of his depth |
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| MacGyver Guru Joined: 12/05/2009 Location: United StatesPosts: 1329 |
Oh! Okay, that makes sense. See, that's proof positive it's never too late to learn. Thanks for the heads up. Sorry, I think I may have messed up oztules post with my lack of knowledge. :O( Nothing difficult is ever easy! Perhaps better stated in the words of Morgan Freeman, "Where there is no struggle, there is no progress!" Copeville, Texas |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Here is a photo of the controller I put together for my new AxFx 48V alternator. This windmill is the mother of a design that fillm has posted pics of. 
The unit just connects to a suitable mosfet. This one stops the windmill when the battery voltage exceeds 60V, and allows normal operation if the voltage has fallen back to 56V and the windmill has been turned OFF for at least 5 seconds. The micro PCB is stuck to the end of a nom 48VDC-reg5VDC converter. The scaling resistors are pretty simple. I have solar connected to these batteries as well and the gridfeed inverter is the nominated proportional loading, so a separate heater bank is not required. Gordon. become more energy aware |
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| AMACK Senior Member Joined: 31/05/2009 Location: AustraliaPosts: 184 |
Gizmo Good to see you went with the idear of down lights. I use them in my set up and they work well. I have seen a mention in a forum topic that said they where going to use them but there were concerned that if one blew the drop in load may damage there battery bank. I think that if one blew then the effect on the batterys would be quite small unless the bank was small and the globe was not detected for some time. Is it possible to find or disign a circuit that would dump to another dump as a fall back system to protect the battery just incase or is this just over the top. Andy *Note to self 1. Make it thick 2.Make it heavy. 3.Make it stronger than it should be. 4. Don't rush the first job as the second job will cost more and take mor |
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