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Salt box load bank questions


Hi and happy new year to all !!

Back in the seventies I worked at a boatyard. We overhauled small boats like the LCM,s and LCU's among others for the Navy, Army and the Corps of Engineers. The electricians there built a salt box load bank. It was a large wooden box lined with metal (maybe 100 gallon capacity) They made a metal grid which could be raised or lowered into the water to control the load with a small winch. Water was pumped through some coils to control the heat.
My questions: Where can I find some info and plans to build one ? Just what type metals are needed ? How much box and grid area are needed for X amount of kw's ? What about building one for three phase ? What amount of salt is used if any ? Is such a thing even legal to build and use ? :eek:
We presently have two load banks, one is 10 kw and the other is 100 kw. Sometimes we need to test larger generators and as you know load banks cost lots of $$$.

Thanks, Mark :wave:
Hi Mark
I have never seen a salt box, heard of them though.
I have seen tham made out of electric furnace elements.
It was a sheet metal duct with a fan installed to cool the coils.
There was several different coils inside selected with a bunch of large switches. 120\240 single and 3 phase was no problem. 480 volts was a problem, burned out every coil that was turned on. I think you would have to put 2 coils in series to use that voltage. I dont think I would use it above 50 KW. Or your salt box also! I know the guys I work with have used as many as 5 100KW loadbanks to do a 500KW unit that was 9 stories up. Packed all up there and hooked everyone of them up at the same time.
If I get back to the furnace coil loadbank I will take a picture of it.
I see loadbanks on Ebay once in a while.
From a post I made on 11/29/05.
I used salt water. I took 1/2 an 55 gallon drum and mounted a post on each side with nails/notches to support a non-conducting crossbar at different heights. Two(or three) copper electrodes made from old pipe were attached to the crossbar, short enough so as not to touch the bottom of the drum. The power is fed to the two(or three) electrodes and the neutral is tied to the drum itself.
Fill the drum about 2/3 full of water, set the electrodes all the way down, turn on the power and add salt until you get the current you want. As the water warms the current will increase. Raise the electrodes to decrease it as necessary. When the water boils it will stabilize. I have had no trouble loading to maximum on a 15kw unit (62.5 A single phase).
As always be careful when working with exposed terminals that are hot both electrically and thermally.

Of course I only needed to dissipate 15 KW so I made a small one , but the principal is the same. Run it boiling, the heat is dissipated as steam and you just need to add makeup water. I had more electrode than I needed using 1 inch copper pipes about a foot long.
Jack Hottel