# Load bank testing



## micromind (Aug 11, 2007)

I don't know how anyone could spend 3 days teaching/learnig how to load bank a gen. Just about any journeyman with industrial experience can do it. 

A 500 KW load bank will be mounted on a trailer. Just hook it up to the gen, either at the gen or at the transfer switch, whichever looks easier. Often there are spare lug holes in the gen breaker or transfer switch. 

If camlocks are already existing, it's much easier. 

You'll most likely be using DLO cable or something similar that's flexible. You can shove way more current down this cable that the code says. Keep the cables separated, don't coil them up and keep crossings to a minimum. 

The load bank will very likely have multiple load settings, I usually make the gen produce 80% of its KW (not KVA) rating for whatever time is specified. I'll also usually make it produce 100% for at least a few minuted. 

A note of caution......if the gen has been run at less than 30% load for any length of time, it's most likely wet-stacked. This is where unburned fuel collects in the muffler and when heated up enough, it'll explode......rather loudly........and occasionally, it'll split the muffler open. If you suspect wet stacking, start with about 20 - 30% load and bring it up slowly. It still might pop off a bit but not like if the load was brought up quickly. 

The hardest part by far is figuring out where to connect the load bank to the gen.


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## SWDweller (Dec 9, 2020)

Load banking is a lot of grunt work we used 500 mcm welding cable as the conductors from the genset to the load bank. Once the two pieces of equipment were over 200 feet apart. Not fun dragging welding cable out and then back on the reels by yourself. Can't leave the conductors on the reels.

Micromind brought up several items that are very relevant. I always assume wet stacked. Most gensets are run monthly with no load for maybe 30 minutes. Which is a waste as far as I am concerned. If you do not transfer into a load then you have not proven the system works. 

No one today is going to spend the money for testing with out a detailed report. Usually the insurance company says 3rd part test. They want it to work. 
Our report was made on Excel with cells big enough to write in. We record all the values every step change. We do a 2 hour test but most are 4-8 hour. 
Saw a load test in Pearl Harbor for submarines that was full tilt boogie for 5 days. 

We offer a refueling adder after the test. We contacted a couple of vendors and as long we give them a couple of days notice they will be on call for us. I usually call once I start the cool down cycle, 20-30 minutes. It would be lot easier if we had the wire reels set up for on and off. The wire has been used for other things so I sort of understand. The service pays the bills but it is not a high profit prospect. Mostly because we report and oil leaks and document filter numbers and dates. We do not do engine or gen work We test the radiator fluid for acidity. 
Most of the ones I have done the radiator fluid is close to being shot.


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## Southeast Power (Jan 18, 2009)

It isn't that difficult with smaller units like that but be very careful to develop a comprehensive checklist that covers pre and post-test checklists.
Be sure to check the line side cables or bus on the breaker in the generator.


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## Cow (Jan 16, 2008)

The Cat dealer does it over here. Our customers have it done directly with Cat, so I'm not sure if they're given written reports or what.


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## brian john (Mar 11, 2007)

The hardest part of the job is laying cables. We often use laborers to lay cables for large long runs of cable for load bank testing. 

Pay me I'll train you.

Bidding a job for testing a 7-meg system, 13.2kv


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## paulengr (Oct 8, 2017)

We have a small load bank but realistically don't buy these things. It's not worth it. Unless you are doing the testing constantly like a generator installation company, everyone just rents them. Other than hooking up the load bank the only other complication is what you record on the paperwork. Usually water temperature, volts, amps, say every 5 minutes for the hour or two it runs.

Monthly exercising is all about the bearings and verification that it WILL start. Ideally you should have a closed transfer switch and actually transfer to load then back again or the monthly exercising is pretty much pointless. But a paralleling generator is vastly more expensive and complicated to install than a simple open transition system and most facilities aren't going to be very happy with a monthly open transition.


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## gpop (May 14, 2018)

paulengr said:


> We have a small load bank but realistically don't buy these things. It's not worth it. Unless you are doing the testing constantly like a generator installation company, everyone just rents them. Other than hooking up the load bank the only other complication is what you record on the paperwork. Usually water temperature, volts, amps, say every 5 minutes for the hour or two it runs.
> 
> Monthly exercising is all about the bearings and verification that it WILL start. Ideally you should have a closed transfer switch and actually transfer to load then back again or the monthly exercising is pretty much pointless. But a paralleling generator is vastly more expensive and complicated to install than a simple open transition system and most facilities aren't going to be very happy with a monthly open transition.



Company hates to rent anything they can buy.

We transfer the larger plant generators online for a hour each week and run the fire pump at the same time as this saves on the electric bill and gives the generators a load. 
The mobiles which are there to back up the back ups have to be plugged in if we want to put them on load. First place i have ever worked where shutting down the plant for a hour is no big deal so plugging in every month would not be a huge deal but it may not be enough load as the mobiles are seriously over-sized.


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## paulengr (Oct 8, 2017)

In general I agree with the whole philosophy of buying rather than renting. You own it. You know the condition of it and you don't have to worry about whether or not one is available for access. And you are paying a profit to someone else. Believe me when I buy cars and trucks for my personal use, I pay cash. I buy them new or almost new and I run them until they are destined for the scrap yard, 12+ years. I have never leased a vehicle except for rental cars for air travel trips.

But here's the thing. Say a load bank costs $5,000 to rent a year and $50,000 to buy. It's pretty simple math here...10 years to pay it off. Most companies are looking for a 25% return on their money and you're only looking at 10%. If you can't pay it off in 4 years or less, it doesn't make sense to buy one. And that assumes that you won't have to pay to have it sent out or fly a tech out to do any service, calibration, or repair to it. All those are going to stretch that 10 years out even more.

We're a motor repair service center, one of the largest in the area. Our field service group probably does more load bank testing than any industrial site will do. And the generator installers do even more load bank tests than we do. But that being said they own a couple load banks and we own one too in the more popular, smaller sizes. Once it gets "big" (over about 250 kW) everyone rents, even the big guys. Even the local Cat dealer rents. It's just that they are renting from either other Cat dealers or from Cat themselves.


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## gpop (May 14, 2018)

paulengr said:


> In general I agree with the whole philosophy of buying rather than renting. You own it. You know the condition of it and you don't have to worry about whether or not one is available for access. And you are paying a profit to someone else. Believe me when I buy cars and trucks for my personal use, I pay cash. I buy them new or almost new and I run them until they are destined for the scrap yard, 12+ years. I have never leased a vehicle except for rental cars for air travel trips.
> 
> But here's the thing. Say a load bank costs $5,000 to rent a year and $50,000 to buy. It's pretty simple math here...10 years to pay it off. Most companies are looking for a 25% return on their money and you're only looking at 10%. If you can't pay it off in 4 years or less, it doesn't make sense to buy one. And that assumes that you won't have to pay to have it sent out or fly a tech out to do any service, calibration, or repair to it. All those are going to stretch that 10 years out even more.
> 
> We're a motor repair service center, one of the largest in the area. Our field service group probably does more load bank testing than any industrial site will do. And the generator installers do even more load bank tests than we do. But that being said they own a couple load banks and we own one too in the more popular, smaller sizes. Once it gets "big" (over about 250 kW) everyone rents, even the big guys. Even the local Cat dealer rents. It's just that they are renting from either other Cat dealers or from Cat themselves.



I agree 100% but its government work which is why we have a back up to the back up to the back up.


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