“Load and behold”

[loosegravel]

I’ve been researching how to make an economical way to accurately load test these awesome MEP generators. I came across a 1975 documentation from Caterpillar. It explains how to use a brine to load test generators. It got my attention enough to put it into practice. I used (3) of the grounding rods that usually come with these units. I drilled .300” holes in them and attached a 4 ga. cable with a soldered on eye terminal to the end of each of them with a 1/4 - 20 bolt. I secured and spaced the grounding rods in a piece of 2x4. I hung them above a 5 gallon bucket filled with tap water and about 45 grams of salt for each gallon of water. Just for safety the bucket was placed on a 6x6 piece of lumber off of the floor. I connected the other end of the cables to the MEP-803A generator in three phase and fired it up. I then began lowering the rods into the brine mixture and the percent rated current gauge began climbing right away. I could increase the load by lowering it more into the brine mixture or decrease the load by raising it. Unless someone has an objection with using this method, it seems like an easy way to do a load test on these generators with minimal time and costs!

 

[Scoobyshep]

Its basically a variable resistor. Just be careful and ground

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[loosegravel]

Its basically a variable resistor. Just be careful and ground

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Thanks for the reply. Yeah, I’m not sure how to ground this set up? I wouldn’t no where to hook a ground cable. To the floor? To the bucket?

 

[Scoobyshep]

Honestly in your setup, all you can really do is ground the set.

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[m32825]

Interesting, link to document?

 

[Bill Nutting]

I think the rods could be much shorter. Maybe a few inches longer than the height of the bucket. I would clean up the connections and coat them with silicone rubber cement to prevent corrosion. Consider adding a plastic spacer at the bottom of the rods. If those rods were bumped and contacted each other it would be a bad thing. I see no reason to ground any part of this “variable resistor”. Please be very careful raising or lowering the rods while they are hot.

 

[loosegravel]

Interesting, link to document?

For some reason I can't copy and past the link here. It starts out as : www.waterstorage.tpub.com/TM-55-1930-209-14P-9-4

 

[loosegravel]

Interesting, link to document?

Try this one. BRINE TANK LOAD TEST (tpub.com)

 

[loosegravel]

I think the rods could be much shorter. Maybe a few inches longer than the height of the bucket. I would clean up the connections and coat them with silicone rubber cement to prevent corrosion. Consider adding a plastic spacer at the bottom of the rods. If those rods were bumped and contacted each other it would be a bad thing. I see no reason to ground any part of this “variable resistor”. Please be very careful raising or lowering the rods while they are hot.

Thanks for the reply Bill! I appreciate your input.

 

[Guyfang]

I used this method in the early 70's. Even used ground rods just like yours. Scared the hell out of me. Way to many things can go wrong. As I have been hooked up to AC voltage a few times in my life, I have a VERY high respect for it. There are ways to make this safe. As suggested above.

Yes, it works. But some "refinement" might be needed.

 

[Jeepadict]

I'm with Guy as big power warrants big respect which generally translates as fear within me. I have much respect and admire the ingenuity and simplicity of the brine setup, tho I'm just not that brave. I really like the Comfort Zone 220v 5KW shop heater that retails for $100 from multiple sources...its not as thrifty as the brine but I'm much more comfortable using them as a load, and $200 is far more reasonable for me than an actual load bank.

Amazon.com: Comfort Zone CZ220 5,000W, Fan-Forced Ceiling Mount Heater with Dual Knob Controls: Home & Kitchen

Amazon.com: Comfort Zone CZ220 5,000W, Fan-Forced Ceiling Mount Heater with Dual Knob Controls: Home & Kitchen

www.amazon.com

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[cuad4u]

I bought several 4500- 5500 watt water heater elements. I fill a 55 gallon plastic drum (with the head removed) with clear tap water. I put how ever many elements in the water and load test the generator. If I want to load test a generator for a long time, I just put a water hose in the bottom of the drum and let cool water trickle in the drum. Clear water DOES NOT conduct any much amount of 240VAC current. To prove this to people who doubt me I have put my hand in the water while load testing a generator. If you are not OK with this method then do not try it. I am an electrical engineer and have been around electrical work all my life.

 

[loosegravel]

I used this method in the early 70's. Even used ground rods just like yours. Scared the hell out of me. Way to many things can go wrong. As I have been hooked up to AC voltage a few times in my life, I have a VERY high respect for it. There are ways to make this safe. As suggested above.

Yes, it works. But some "refinement" might be needed.

Yes, for sure. There are healthy fears and there are unhealthy fears. I have been riding street bike motorcycles for 43 years. Some feel that I'm crazy and that I'm putting myself in danger whenever I'm on one. I don't know, I just like to ride so I will continue as long as I can. Having a healthy respect for power and it's potential is a good thing. The document did say that the current draw will fluctuate if the brine mixture comes to a boil. My test did start to boil the 5 gallon brine mixture after about 10 minutes. And the splashing brine did cause a 3-5 amp fluctuation on each of the three legs. So like "cuad4u" replied a 55 gallon plastic drum would dissipate more heat. And, of course I would never want to leave something like this unattended. As in it would be much safer to use a portable heater to keep my generator in the 75% power range while operating it at night in low power situations to keep it from wet-stacking. I must admit though, it was kind of interesting to perform this test. Thank you for your input sir!

 

[Zed254]

Too many inches of exposed hot conductors for me. I can imagine a bunch of guys, sipping on beers, testing generators when someone heads to the cooler for their last beer and brushes up against 2 of those swinging rods. I've only got to worry about 10Kw so a used electric stove is perfect for me.

If you are going to stay with the salt water bucket resistor I would figure out a way to cover all of those conductors with some kind of insulator. PVC pipes? Wooden cabinet? 55 gallon plastic drum with the bottom cut out?

 

[loosegravel]

Too many inches of exposed hot conductors for me. I can imagine a bunch of guys, sipping on beers, testing generators when someone heads to the cooler for their last beer and brushes up against 2 of those swinging rods. I've only got to worry about 10Kw so a used electric stove is perfect for me.

If you are going to stay with the salt water bucket resistor I would figure out a way to cover all of those conductors with some kind of insulator. PVC pipes? Wooden cabinet? 55 gallon plastic drum with the bottom cut out?

Yes sir. Thank you for your reply. I’m also using a 10kw unit. This was only a test. If I choose to use this method of load testing on a regular basis I will refine it.

 

[Guyfang]

We used a 55 gal drum. We tested a 45 KW gen set. I could bring the gen set to its knees, (like kill the gen set) with less then 1/4 of a ground rod length.

It just needs refinement.

A friend of mine laid his hand on a badly grounded A427 load bank with a electrical problem. We were testing a D424A Turbine gen set. Rated at 150 KW, was good up to 300 KW, maybe more. At any rate, we had 5 load panks hooked up. That brought an end to his future as a TROSCOM Ground Power Tech Rep. So it can happen whenever things go wrong.

 

[loosegravel]

We used a 55 gal drum. We tested a 45 KW gen set. I could bring the gen set to its knees, (like kill the gen set) with less then 1/4 of a ground rod length.

It just needs refinement.

A friend of mine laid his hand on a badly grounded A427 load bank with a electrical problem. We were testing a D424A Turbine gen set. Rated at 150 KW, was good up to 300 KW, maybe more. At any rate, we had 5 load panks hooked up. That brought an end to his future as a TROSCOM Ground Power Tech Rep. So it can happen whenever things go wrong.

That was my experience last night too Guy. I could load this 10kw unit to 125% of it’s rated load on three phase with no problem. I used my amp clamp on all three legs. They were all within a couple of amps. I agree with much of the feedback that I’ve received on this topic. The grounding rods are too long. (I just didn’t want to cut them down and ruin them) A 5 gallon bucket is too small for an extended load test. The 2x4 seemed to keep them steady and equally spaced with no problem, even with a little turbulence when the brine began to boil after 10 minutes at 100% rated load. At any rate, it was a successful test for this kid and I appreciate having a place to share my experiences! Thanks again.