Homemade Load Bank

[csheath]

Finally got around to putting my load bank together and testing it. I used four 5400 watt dryer elements, hooking two of them in series to cut one circuit load in half. This makes the total theoretical load 13.5 KW. I bought a 100A six space panel to create three 240V circuits. I used two 25A breakers for the single elements and a 15A on the two series elements. I had the fan and all the metal laying around so I don't know what the whole thing would cost if you had to buy it all. The four elements cost $71.80 off that auction site. I bought a 36 ft RV cord off the auction site that I am cutting up for the wire. I used about 3' of that with the male plug on the load bank which would cost around $25 to replace. I spent $100 or so at Home Depot on the panel, breakers, and stuff. I actually spent a lot more than that but it included stuff for home hookup. Basically it's a rectangular box with the elements and a fan blowing through it to cool them. I used aluminum angle for the frame and 1" aluminum channel across to mount the elements. I pop riveted everything except the outer panels which I used drill tip screws on.

Here are some photos of the project.





I used the dryer elements without any high temp thermostats. The connectors on those are a 5/16" wide quick disconnect which I was unable to source. Using 10 ga 1/4" quick disconnects worked okay by spreading them a little. I held both sides of the connectors with pliers while pushing the connectors on.




And finally here is a video of it being used.

https://www.youtube.com/watch?v=11AIHi78y98

 

[Triton]

That's cool! I like it, I'm going to do something similar with emergency heat strips.

 

[ageregunner]

What a great idea for a load bank. I also like the weatherproof outlet you mounted to the outside of your generator, to plug in the load. Both great ideas.

 

[lonesouth]

I like your load bank more than mine. Great work!

 

[Guyfang]

Do you have a safety circuit that cuts it off in case the intake airflow is blocked? I burned up a nice A427 load bank in the mid 70's by jumping the interlocks instead of waiting for repair parts. My only excuse was stupidity and youth!

 

[csheath]

Do you have a safety circuit that cuts it off in case the intake airflow is blocked? I burned up a nice A427 load bank in the mid 70's by jumping the interlocks instead of waiting for repair parts. My only excuse was stupidity and youth!

No I don't. These elements came without the over temp thermal fuse kits so I didn't worry about it. I am powering the fan through the convenience outlet and I will make sure it's running before turning on any of the elements. I am switching them with breakers in case of a short. The thermal fuse kit costs almost as much as the elements did so if one gets burned up I will just replace it and repair the cause.

 

[DieselAddict]

You can pick up the thermal fuses really cheap at an appliance repair store (online). I ordered them for like $10/ea. Cheap, cheap insurance.

Edit - A quick search on Amazon revealed a 2-pack for like $10.

 

[csheath]

These elements were $17.95 each shipped. I didn't think I wanted the thermal fuses in play to have them opening the current load if they got weak which they sometimes do. It's not something I'm going to use without close monitoring. The elements only had a dim glow with two of them running so the fan does a good job at keeping them cool. Maybe too good since the current loads didn't match the expected values. With two 10 ohm elements turned on it should have been pulling 44 to 48 amps and it was barely pulling 40.

 

[biz]

I've been looking at dryer elements to create my own load bank. Figured it would be easier than needing water when I test. The trouble I've been having is it seems none of the elements I've been looking at say the amps or wattage in the specifications.

 

[patracy]

Neat setup. I've got only a 10kw load bank. I need something like a 20kw. Might build something like this.

 

[csheath]

I've been looking at dryer elements to create my own load bank. Figured it would be easier than needing water when I test. The trouble I've been having is it seems none of the elements I've been looking at say the amps or wattage in the specifications.

I searched several and the only ones I found that had a specification were 5400 watts. 5400W / 240V = 22.5A. 240V / 22.5A = 10.66 ohms. You can connect two elements in series to cut that in half. I checked one of these and it read 10.? ohms. Didn't pay it a lot of attention. Two of them in series were right at 20 ohms even.

There may be elements out there that have different values but I figured loading my 10KW generator to 13.5KW should be sufficient for testing. It runs with no effort with two of the 5400W elements turned on and reads over 100% on my load meter. My unit's voltage drops as I load it and I am going to study that but I think it's a natural phenomenon on all generators when running near capacity. I'm not sure what effect the cooling of the elements has on the current draw, if any, but it seems it would have to lower it some if you keep them cooler. The ohms law calculations don't seem to match my real world measurements but I am also using an inaccurate HF ammeter. I checked the ammeter against a Fluke and it was about 3.5 amps low on a 480V 3 phase boiler with 30KW in elements. 3 phase has a different formula but amps is amps when you are reading two meters side by side on the same leg. With two 5400W elements turned on I was reading 35.4 amps. Adding the 3.5 amp difference and calculating the voltage drop still does not come up to the calculated load.

All that said I am trying not to over think it. I suspect if my voltage drops to 230V and 58 hertz my house will survive or I will learn another expensive lesson in life.

 

[DieselAddict]

NiChrome wire will gain about 15% in resistance going from room temperature to 500C. So under normal conditions your two elements in parallel would drop from 10,800w to about 9100w. Add the voltage drop of your loaded set (230v vs 240v) and you'll drop a little more power. Down to ~8747w.

If we take your actual measurements of 35.4a + 3.5a error times 230v and calculate power it comes out to 8947w. Within 2% of expected values (assuming 500C on the wire).

I think your measurements are totally plausible.

 

[Chainbreaker]

So what happened to yesterday's posting of a Garage Heater that was started as an alternative to building a Homemade Load Bank? It appears that his post was deleted without any explanation. Perhaps the commercially available item on sale was no longer available?

Regardless, I thought the poster had a good idea in using a commercially available 220V off the shelf Garage Heater as a load bank; it seemed like a "very economical & safe" alternative to a DIY build as not everyone has the time/tools to build one. No intent meant here to discourage building a homemade load bank vs buying an off the shelf solution. Both are excellent load test solutions!

 

[DieselAddict]

The issue with that one is it was a locally available item. For sure a good idea and maybe even at regular prices a more viable one if someone doesn't want to DIY a water heater or dryer element setup.

I took a look and many are in the 5kw load range. Most had 2 settings. No real information in regards to what the "low" setting was. I would assume it would be half of the full blast setting.

Based on what I was seeing you would need to buy 3 heaters to full load a 803. That would put you in the $400 range for most of the offerings I see there. Simple, yes but more costly.

 

[kloppk]

So what happened to yesterday's posting of a Garage Heater that was started as an alternative to building a Homemade Load Bank? It appears that his post was deleted without any explanation. Perhaps the commercially available item on sale was no longer available?

Correct. That item was no longer available and the OP asked for a moderator to delete the post.

 

[Chainbreaker]

One advantage to using generic Garage Heaters is that if later on you no longer needed a load bank, you could use them as intended (as just heaters) or put them on Craigslist and easily sell them locally recovering much of your investment vs trying to sell a DIY special purpose load bank.

BTW, the Northern Tool Garage Heater unit that was a 220V 5kw unit, Model#*PH-950, did indicate that the 2nd setting was 2.5kw. So for me with 5kw MEP-002a's that just might be the ticket! When not in use as a load bank I can plug in to 220V receptacle and heat my shop when working there!

 

[csheath]

My homemade load bank would produce 36,850 BTU with the two 5400W elements running. I could stick it in the window and plug it directly into the generator if all I needed was heat.

 

[Chainbreaker]

My homemade load bank would produce 36,850 BTU with the two 5400W elements running. I could stick it in the window and plug it directly into the generator if all I needed was heat.

True, but I thought Floridians only needed to get rid of heat! Well...having lived there long ago in Lakeland there were a few times it did get below freezing so your "if" makes sense. However, an added benefit when using a commercial heater as a either a load test or heater would be they have a thermostat and thermal safety cutoff. If a DIY device were not closely watched (which you obviously would) and somehow set something on fire your HO Insurance may be hesitant to cover damages to property.

Regardless, I'm envious of your rig! Nice job!

 

[csheath]

I will kick this to the top with an image of my digital meter conversion. Not the prettiest conversion but it's functional. The voltage reading on the green meter on the right is a little low but the hertz was dead on with my Fluke meter so that is what I needed there. The line voltage/current meters are accurate on both counts so the overall voltage is the product of those two added together. I set the unit to 246-248v unloaded.

This is running all three circuits on the load bank.

 

[Light in the Dark]

I am going to be lifting this idea for my own build, but doing it slightly differently.

For those interested, you can source 5/16" female terminal connectors (to match the male prongs on the heating elements) here: http://www.newark.com/te-connectivity-amp/63820-1/terminal-female-disconnect-0-312in/dp/01C2514