dummy load for diesel generator set

[mechanicaldup]

Hi

Where can I get guides on dummy load for gensets
the dummy load have to operate on low load conditions to protect the genset.

what type of dummy load is recommendable, water dissipated or air cooled?

What is low load limit (%) on diesel engines?

Thks

 

[TheBlacksmith]

Low load limits vary, you need to contact the engine manufacturer. There should be no need to provide a load to "protect the genset" per se. The generator should be able to run unloaded continuously and if the engine can't run at the low load, you've got the wrong engine or too big a genset. Applying a dummy load is like riding the brakes in your car, you're burning fuel and creating wear and tear for nothing. If you're just testing, you can rent portable load banks for commisioning, etc.

Blacksmith

 

[GregLocock]

I've used air cooled radiant heater wire, and watercooled immersion heaters. Neither needed any particular control device installed, when the cold resistance was correctly specified for the voltage.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[dave3902]

If you want to build your own you can do what I used to load test a 100KW gen. at full load. This will take some tweaking to get the exact load you need but here is a guide based on what i did.

1. take 3 ea. 55 gal drums with lids cut off.
2. wire drums to neutral and ground them, I used a ground rod just for safety.
3. add about 40 gal of water and about 1/2 lb. of rock salt (too much salt and the resistance will be too low and the gen. will of course stall)
4. center electrodes are 3/4" copper tubing supported by wood. I recall the copper was about 12-18" into the solution for a 30KW load..... ( I tried aluminum and stainless steel but copper provided better results)
5. The load is a 3 phase 208V L-N.
6 Use caution as this set up will create some vapors. I am not sure as to the chemical make up but do not breathe them as ther may be some salt by products in the vapors.

This load can be scaled down for smaller gens. Say 5 gal bucket with a few ounces of salt for a 5 KW gen.

 

[NickE]

The vapors are hydorgen and oxygen.- maybe some chlorine. probalbyh not the best stuff to breathe. But the hydorgen will make a pretty good air bomb.

Here is another link where we talked about dummy loading of big generators.

thread404-125096

go to the sound reinforcement link I added there, they built some big dummy loads for amplifier testing.

 

[MikeHalloran]

I am aware of two circumstances under which dummy loads are required:

1. Testing the genset output to keep everybody honest.

2. To get the exhaust temperature up enough to keep a catalytic exhaust treatment unit from clogging; this typically requires >70 pct full load.

[ I have been involved in installing so-called passive catalytic Diesel treatment units on two megayachts owned by green- thinking billionaires. They _never_ met their original specifications for backpressure, had to be manually cleaned on a daily basis to keep them from clogging up entirely, and were removed and dumped overboard in six months or less, after a lot of tinkering and increasingly angry communications. ]

There is an active system that uses the dummy load to heat the catalyst. It enjoys a better reputation. I have not personally installed one, but I am not aware of any having been buried at sea.



Mike Halloran
Pembroke Pines, FL, USA

 

[UWH]

In general, large diesels do not like to run at less that 50% load as cylinder glazing and slobber can occur.

For a permanent installation a resitive load bank would be your best option. The salt-water drum will work but is not very safe.

May I suggest your genset is oversized if you need to use a load bank to supplement load very often?