Generator load

[MF294-4]

Want to make a load for generators. Commercial units I have seen are in the thousands. Want something up to 45 kw. Would like something rather compact. I was thinking of mobile home electric furnaces. Good bad idea? Anything any better? I cant remember how many kw they are.

 

[Janicholson]

I would build a water heater element based system. A used 50 gallon electric water heater with insulation stripped off, (Bare tank). put fittings in the tank at intervals staggered so they are arranged upward and around the tank. Cut the top with a 10 inch circle so no pressure can build up. 10 elements like the link connected so a switch system could add parallel connections to increase load in stages. 10 low watt toggles and 10 relays to turn on each element will make 45Kw total load. Boiling water is the only hazard, and keeping it filled would be easy with a copper float valve and a garden hose. It might be a bit messy unless places where it could not make a mess. The water can not get above boiling temp no matter how much heat is put in unless the level is allowed to drop below the highest element. Jim
Rheem 4500 watt

 

[RCP]

At my old job, we had load banks that used electrodes that were lowered into water tanks. It sounds scary, but it was not. The farther you lowered the electrodes into the water the more energy they would absorb and turn into steam. They reminded me of old fashion humidifiers we used to use when the kids had colds and congestion.

 

[Tony in SD]

I have a heat pump with a standby 20kw heating element. 2 of those elements in parallel, with a cooling fan, would get you 40kw of load. Might check with a HVAC company to see if the have any wrecked out elements.

 

[Geo-TH,In]

I scrapped out an electric furnace from a rental house.
If I recall, keep in mind I did this 19 years ago,
the electric furnace had 4 banks of 5 kw heating elements = 20 kw = 68240 BTUs. I'm sure someone will tell me I'm wrong. It always happens.
Yes, it would work as a test load as long as the blower is working.

 

[John T]

Here's the deal when it comes to generator ratings/capacity (continuous versus short term initial surge) and load testing:

THERES A HUGEEEEEEEEE DIFFERENCE IN A PURE RESISTIVE LOAD (resistive heat strips) VERSUS AN INDUCTIVE LOAD (compressor motors and start up)

The thing is when a compressor motor starts up it may draw 3 to 6 times its normal full load current AND THATS WHEN A GENERATOR NEEDS ADEQUATE SURGE CAPACITY above and beyond ONLY its normal load capacity.

Soooooooo even if a genset has adequate capacity to supply a resistive load (furnace heat strips) that does NOT necessarily mean it has adequate initial surge capacity to start a compressor motor !!!!!!!!!!! Thats when they stumble grrrrrrrrrr and cant start a compressor even if once up n running they work fine..

That being said, sure a resistive furnace heat strip is a good load for testing a genset but in order to be able to start a compressor motor MORE than that capacity is typically required........

Bottom line an elec furnace resistive heat strip is fine for a pure resistive load BUT JUST BE AWARE the surge capacity to start a compressor needs to be MORE.......

Im sure I missed something so hopefully the other fine sparky gents can add to this

John T

 

[Red Dave]

Electric furnaces would work fine. They should have their wattage rating marked on them somewhere. It will take several to get 45 Kw. The one I removed from this house was a 15 Kw.

Professional generator technicians use what they call Load Banks, which are nothing more than strip heaters. We installed a pair of 300Kw backup generators where I worked and when they did the acceptance tests they used multiple 1Kw strip heaters that were switched. Just kept switching on more strip heaters until they got to the load they wanted.

It's not nearly as complicated as some people try to make it.

 

[miangus]

It's amazing how true your comments are. I think the inductive load of the motor may cause the voltage to lag behind the current reducing the available power. A number of years back I was using a 120-volt 2500-watt generator to run the block heater in my 4020, 2000 watt. I wanted to have a small air compressor at the barn just to pump up low tires. I put the smallest drive pully that would work on the motor of a small compressor and still no dice. One would think a 2500-watt generator, which provides about the same wattage as a 20 circuit could easily start a small compressor. But I never got it to work.

 

[John T]

Thanks for the kind words, hey I try my best to help and enjoy doing so.......

You state:
One would think a 2500-watt generator, which provides about the same wattage as a 20 circuit could easily start a small compressor. But I never got it to work.

NO SURPRISE, Thats EXACTLY what I was talking about. Still a resistive furnace heat strip provides a cheap n easy RESISTIVE load.

John T

 

[JMOR]

(quoted from post at 09:24:44 03/22/23) Thanks for the kind words, hey I try my best to help and enjoy doing so.......

You state:
One would think a 2500-watt generator, which provides about the same wattage as a 20 circuit could easily start a small compressor. But I never got it to work.

NO SURPRISE, Thats EXACTLY what I was talking about. Still a resistive furnace heat strip provides a cheap n easy RESISTIVE load.

John T

ust use the whole furnace...already has blower and add more elements before or after blower, in space where the evaporator was located.

 

[Geo-TH,In]

Larry could boil a lot of turnips in a 45kw cooker real fast.
Cut down on canning time..

 

[buickanddeere]

(quoted from post at 08:54:25 03/22/23) It's amazing how true your comments are. I think the inductive load of the motor may cause the voltage to lag behind the current reducing the available power. A number of years back I was using a 120-volt 2500-watt generator to run the block heater in my 4020, 2000 watt. I wanted to have a small air compressor at the barn just to pump up low tires. I put the smallest drive pully that would work on the motor of a small compressor and still no dice. One would think a 2500-watt generator, which provides about the same wattage as a 20 circuit could easily start a small compressor. But I never got it to work.

Generator needed to be 3X larger .

 

[MarkB_MI]

45 kW or 4.5 kW? Those commercial loads are expensive for good reason. 45 kW at 240 volts is almost 190 amps.