Homemade loadbank?

[hardworkingstiff]

I need a way to check whether the watt-hour meters on marina power pedestals are working. The way I figure it should be done is to put a load on the receptacle and a jumper on the testing terminals of the meter terminal (this jumper changes the counter by a factor of 100).

Now, the problem is how to put a (controlled) load on the receptacle. I could spend 5-10 thousand dollars on a load bank, but I don't know if there will be enough of a payback. What I was kicking around is mounting water heater elements in a box that will float and placing the box (with elements down) into the waterway. I'm thinking at max I will need 4 elements (4500-watt). I can control how many elements I want on at the same time, thereby controlling the load.

My question to the great thinkers on this forum is: What safety issues do you think I will incur?

 

[brian john]

The payback is there if you have a market for them I use mine all the time. BUT RENT ONE check out the Canon website for small portable rent-ables.

http://www.cannonloadbanks.com/

 

[Pierre C Belarge]

I know of a few people who have built themselves small loadbanks.
One concern you may run into with your "heater" type loadbank placed in the water is other people's concerns of what happen when you heat all of that water. Just a thought.

 

[hardworkingstiff]

One concern you may run into with your "heater" type loadbank placed in the water is other people's concerns of what happen when you heat all of that water. Just a thought.

I see I failed to communicate. When I was talking about putting the heating elements into the waterway, I was talking about the Intra Coastal Water Way. I figure I couldn't heat that much water in a long time. :smile:

 

[cadpoint]

How are you going to completly submerge the terminals of the gear in lapping water ?

 

[Pierre C Belarge]

Hardworkingstiff
Remember that there are people out there who are concerned about the changes some may inflict on the environment, whether or not there should be concern.
I am just thinking out loud of how it would be a shame to build this unit then find out that you may not be able to use it, whether you heat a small portion of the waterway or the whole waterway.

 

[cadpoint]

Have a non condutive float stablizer aka Pole, at the ready, missed the float earlier, no need to fry the dock too...

I'd Bond the float !

What are you going to name her ?

True fact, boats are there own money holes, you just happen to be making a working model.

 

[brian john]

For the cost, liability, time RENT

 

[hardworkingstiff]

How are you going to completly submerge the terminals of the gear in lapping water ?

I was thinking the heating elements would be installed so the wire terminals were inside the box and the element would be outside the box. All connections would be kept dry inside the box. The cover could be made watertight.

My concerns lie more in making sure I don't have any current leakage into the waterway. Maybe put a CT on all of the conductors going into the heating box and shut down on current draw, sort of like a GFI.

I guess I would have to build a cage of some sort around the elements so they cannot be touched, but water can flow around them.

 

[mdshunk]

How much load are you looking for? You can buy a dozen ready made hair dryers at WalMart for pretty cheaply if you don't need a calibrated load bank.

 

[hardworkingstiff]

The payback is there if you have a market for them I use mine all the time. BUT RENT ONE check out the Canon website for small portable rent-ables.

http://www.cannonloadbanks.com/

Thanks for that link Brian. I think I just might buy one of theirs.

 

[ron]

I agree with Marc.
You may just consider a big space heater for a big load or hair dryers for a small load. Test it at home with a calibrated meter then take it out to the job site.

 

[coulter]

I agree with Marc.
You may just consider a big space heater for a big load or hair dryers for a small load. Test it at home with a calibrated meter then take it out to the job site.

I don't think that would work. The job is to test meters. I think one needs a calibrated meter on the load to check the power at the connected voltage. For constant resistance loads, the power changes with the square of the voltage. P = E^2/R

carl

 

[ron]

Carl,
Isn't the recommended load banks from the earlier post, just a fancy toaster oven?
If it was to test/calibrate meters, you probably need a NIST calibrated meter connected to the load and keep the load the same then cjeck the meter under test.

 

[quogueelectric]

55 gal drum

55 gal drum

Just mount h2o heater elements in a 55 gal drum. hook up hose in and out to drain so it will never actually get hot just waste a lot of warm water. open a starbucks tea room with the waste.

 

[brian john]

We use load banks with our hand held calibrated meters for a variety of test. I would not rely on the meters on the load banks.

I have used space heaters for a variety of test over the years, but I fell having load banks on a job were you are verifying meters adds that edge of professionalism.

 

[hardworkingstiff]

I have used space heaters for a variety of test over the years, but I fell having load banks on a job were you are verifying meters adds that edge of professionalism.

I believe being perceived as professional gives the customer a warm and fuzzy feeling, and allows you to earn more money. How much better does it look to show up with a professional load bank instead of space heaters, hair dryers (or water heating elements that get the question "what is that contraption?)?

I think I might follow Brians suggestion here.

 

[coulter]

Ron -
You're right. An electric heater is as good a bank as any.

Mostly I was thinking about the "calibration at home issue". A 2% change in voltage is about a 4% change in power.

carl

 

[BigDon]

Using power resistors or heater elements as a load is fine for just verifying that the circuit works properly, but if you want to test the meters you need a calibrated load bank. The 100 ohm resistor (or what ever value you need) will actually vary as it heats up. Without knowing what the actual resistance of the heating element is at a particular instant, your test is invalid.

 

[LarryFine]

Without knowing what the actual resistance of the heating element is at a particular instant, your test is invalid.

You can always calculate the element resistance by measuring current and voltage at the terminals.

There are low-density water-heater elements that don't burn out when energized while not submerged.