Intro and question

[loonie]

Hi to everyone. I have been reading this board for over a year and have learned a lot about re. I hope to some day build my own windmill. I currently have 12 bp 90 watt panels,solar boost 50 charger, 16 t105's, and a dr 2424 inverter. I just bought a used bergey xl1 with 100ft tower I will be adding to the system. My question is would this "http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=230168587801&ssPageName=STRK:MEW



A:IT&ih=013 " 1500w 180ohm resistor work as a dump load? Thanks for reading this post and any help you may give me.

       Loonie

You didn't say, but from the 2424 inverter comment, I assume 24 volts.

24 volts into 180 ohms will be pretty useless as a dump load. Rough calc in my head is about .13 amps draw in that setup.

I will let the users explain in detail and maybe suggest some options.

[ghurd]

I'll give it a shot.

At 24V, the solar is 32A nominal or 41A boosted.  The solar boost 50 is fine.

Ohms Law, V=IR.

With 29V as the dump voltage, it would dump 0.16A.

Watt's Law, amps x volts = watts.  0.16 x 29 = 4.6W.

Deriving Watts = I^2 R, or 1500W = I^2 180, Imax=2.89 amps.

Surplus houses often have a compatible resistor, for the given conditions (5W), selling at about dollar a dozen.

Personally, I am not convinced MPPT will `play well' with a dump controller.

G-

[loonie]

Thanks for the comment the calculations will help me figure this out. I should of given more info. the solar part is already exsisting i will be adding the bergey xl 1 turbine. It has its own controler with its own dump controler separate of the solarboost 50. the manual said a dump load is optional the turbine would go into slow mode when full but instead of the turbine short itself to slow i thought a dump load would be beter. My hot water system is tankless so i thought air diversion would be better for my needs. The unit call for no more than 1600 watts and no more than 60 amps for a dump load. the unit in the ebay link said 1500w at 180 ohms (ohms is something i havent grasped yet) It also said it had to be greater than .5 ohms. another item i saw was 5 resistors rated at 700 watts 5.4 ohms each but i thought that would be to much load. here is a link to those " http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=290158349344&ssPageName=STRK:MEW
A:IT&ih=019 "

bergy makes one for about 300 that can be seen here at the botom of the page" http://www.nwpwr.com/products/wind/XL1.htm " but i was hopeing i could make my own.Thanks for any and all your help

Loonie

[Boondocker]

This may help.   I obtained these two 1 ohm 1000 watt resistors from a gentleman who use to have them on a bergy xl.1. He sold the turbine and kept the controller for solar panels.

Wired parallel, comes out at 60 amps at 30 volts

You can find them new here in the Digi-Key Catalog

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=FSE1000-1.0-ND

[loonie]

Great help! Thanks alot this is just what i was looking for. With this info and an online ohms calculator i now know the ones i were looking at didn't even make sense. Thanks again for your help.

Loonie

[ghurd]

Yikes! $51.50 each! Tolerance of +/-10%.

How about #HLC-1.0-ND. 5%, and only $7.15 each, or 10 for $65.

http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=HLC-1.0-ND

Also available in a 3 ohm, #HLC-3.0-ND, same price. A decent replacement for car head light dump loads in 12V systems? About the same cost and won't fail as fast.

G-

[loonie]

The 1ohm 1000watt calculates to 31 volts and 31 amps so two in parallel would be 31 volts @ 62 amps.For a total of $103. The 1ohm 100w for 7.15 ech come out to 10 volt @ 10 amps so to get what i need, wouldn't i have to parallel 6 of 3 in series to get the same results? That would be 18 @ 7.15 for a total of 128.70 I am sure i am missing something here. I also thought i could use a 300w 3ohm resistor but i would need six in parallel and they are $24 each. Maybe I should go back to carpentry lol.

[ghurd]

My bad.  I thought it said 100W instead of 1000W.

[finnsawyer]

Since you now know what would work, I suggest you check surplus outfits and radio amateur swap meets in your area.  A lot of this stuff reaches the surplus market, or at least used to.

[loonie]

Thanks, that is exactly what I plan to do.

Loonie

[TomW]

loonie;

If you know any potters [folks who make pottery] you might ask them if they have any "bad" kiln element wire. They often have a length that does not fit or burned open. It is basically bulk nichrome wire and you could make custom lengths and parallel connect to match any resistance / load you want. Even a full, new element would probably cost much less than those resistors. It would take a bit of effort to rig it as a load but for the cost difference it may be worthwhile.

Just another option. Older "glowing coil" type electric space heaters can often be salvaged for the element wire, too. All depends on your hands on abilities whether they are useful for you to customize for the task.

Cheers.

TomW.

[gotwind2]

Good idea Tom.

My brothers a potter by profession and has two electric kilns - not very 'green'

whatsoever, here he is:

http://www.ralphjandrell.co.uk/index.php

and I'm sure would have said wire for my dump load applications for free.

[DamonHD]

That looks very like a stealth VAWT rotating on the right of his homepage!  B^>

Rgds

Damon

[Tritium]

Johnstone Supply (in USA) used to sell furnace element re-stringing kits for under 20 bucks that had 2 coils. Might be worth a look. I used them for my small electric aluminum melting furnace.

Thurmond

[Tritium]

Johnstone doesn't carry these parts anymore but here is someone who does.

http://www.apwapplianceparts.com/Store_Part.aspx?Id=1087624

Thurmond