Good ideas for DIY Generator load bank OR how to feed 25kw back to the grid?

[SpookyGhost]

Hey all,

Long time reader and viewer but not a frequent poster. Wondering if you guys have any smart ideas for me.

At home I have 17kw of Enphase grid tied solar, no batteries, and a 27kw Generac RG027 Generator (Makes 25kw on natural gas)

The generator does its weekly 12 minutes, and I have it set to "full speed" which means it runs at the full 1800RPM. The default is "quiet" which runs even lower. In my opinion, this "test" is not a test at all. So, I have it set to do a 1 hour transfer test each month. During this time the house is powered by the generator, and I try to load it up as much as possible (Crank the AC, cook bacon with the electric range, etc). This is so that the ATS actually gets actuated and I know it works, as well as burning off any water that has built up the oil etc.

Problem is, even with the AC on I usually only get it to 6-7kw at most. I want to load it up to at least 20kw and test it. If I had an EV, this would be easy. I'd let it charge my car up at max speed, but, I don't.

So, I want to either build a DIY load bank to test the 27kw generator and my portable 7kw generator, or find a way to actually make use of the power. Does anyone have any good ideas? Cooking things and cooling/heating the house makes sense, but doesn't use that much power

I'd love to feed it back to the grid, but I assume I'd need some kind of inverter situation to sync up. Is there any products to do this? I already have permission to feed back to the grid because of my solar panels

My thinking for a load bank is to buy a bunch of cheap 1800w space heaters or heat guns, and then just wiring up a bunch of switches so I can add load as needed

[viperidae]

There isn't going to be a "diy" solution to feeding into the grid. I can almost guarantee no matter where in the world you are, any device you connect to feed back power will need to be designed built and tested to conform to what ever the local electrical standards are.
At a minimum you'll need to buy a massive inverter, and probably need to get it installed by a licensed professional.

27kW is over 100A, so most likely the feed into your house will need upgrading too.

[rstofer]

Build a real load bank (every generator contractor has one) and tie it to the generator output through a disconnect switch.  When you want a REAL test, close the disconnect switch.  Open it following the test.

You don't want to use the house as a load during this test.  The load bank should approximate the rated output of the generator.

If you have to buy a load bank, figure on about $8k

https://steadypower.com/product/simplex-polaris-stationary-load-bank-5-150kw/

Any place you can rent one every now and then?

[BradC]

In the old days, I've seen a 100KVA gen set tested using 50 2KW bar radiators. 1000KM in the middle of nowhere, no load bank available but a very resourceful electrical contractor who just wanted to get PC signed off.

Here you can buy 2.4KW fan heaters for $15. $150 worth of heaters and you're sorted.

[pqass]

Just need 6 of these: https://www.canadiantire.ca/en/pdp/eastman-water-heater-element-threaded-4500w-240v-0630137p.0630137.html#store=119, each on a 25A breaker and a steel barrel filled with water.

Also, DON'T back-feed your generator to the grid. It MUST be synchronized otherwise it will become a motor and may become airborne!
https://www.wired.com/story/how-30-lines-of-code-blew-up-27-ton-generator/

[SpookyGhost]

There isn't going to be a "diy" solution to feeding into the grid. I can almost guarantee no matter where in the world you are, any device you connect to feed back power will need to be designed built and tested to conform to what ever the local electrical standards are.
At a minimum you'll need to buy a massive inverter, and probably need to get it installed by a licensed professional.

27kW is over 100A, so most likely the feed into your house will need upgrading too.

Yeah, thats what I was afraid of. Even the GroWatt or SolArk devices don't seem to be able to do this

I should have specified that I'm in the USA, so I have a 200a service with the option to go to 400a. I currently have a 200A ATS, the generator input is 104a, and my solar is a line side tap before the ATS. The generator is already installed and functional. (104a is 25kw, because the generator produces less on NG vs propane)

Build a real load bank (every generator contractor has one) and tie it to the generator output through a disconnect switch.  When you want a REAL test, close the disconnect switch.  Open it following the test.

You don't want to use the house as a load during this test.  The load bank should approximate the rated output of the generator.

If you have to buy a load bank, figure on about $8k

https://steadypower.com/product/simplex-polaris-stationary-load-bank-5-150kw/

Any place you can rent one every now and then?

Yeah they get pricey, even a used one is at least $3K. If anything, I think I need to DIY one. I'm not really a fan of having to rent anything

In the old days, I've seen a 100KVA gen set tested using 50 2KW bar radiators. 1000KM in the middle of nowhere, no load bank available but a very resourceful electrical contractor who just wanted to get PC signed off.

Here you can buy 2.4KW fan heaters for $15. $150 worth of heaters and you're sorted.

Here in the US our standard space heaters are 1.8kw, which is not too bad. I've been thinking of doing this, wouldn't be too hard to wire up with a bunch of spare light switches

Just need 6 of these: https://www.canadiantire.ca/en/pdp/eastman-water-heater-element-threaded-4500w-240v-0630137p.0630137.html#store=119, each on a 25A breaker and a steel barrel filled with water.

Also, DON'T back-feed your generator to the grid. It MUST be synchronized otherwise it will become a motor and may become airborne!
https://www.wired.com/story/how-30-lines-of-code-blew-up-27-ton-generator/

Thanks for suggesting that heater element, that is something I had not thought of. That might be the best solution yet!

[pqass]

...

Just need 6 of these: https://www.canadiantire.ca/en/pdp/eastman-water-heater-element-threaded-4500w-240v-0630137p.0630137.html#store=119, each on a 25A breaker and a steel barrel filled with water.

Also, DON'T back-feed your generator to the grid. It MUST be synchronized otherwise it will become a motor and may become airborne!
https://www.wired.com/story/how-30-lines-of-code-blew-up-27-ton-generator/

Thanks for suggesting that heater element, that is something I had not thought of. That might be the best solution yet!

You should be good for a 2.75 hour test.   

[Berni]

Yep all you need is a bank of the most powerful mains powered heaters you can find.

One option is getting a bunch of kanthal/nichrome heater wire (People use it to make DIY kilns), string it back and forth between two insulating rods to make a large heating element and use a large fan to push lots of air trough it. Basically a electric space heater but scaled up x10. This is mostly how real load banks work. You can also put multiple strings on a switch for power selection. Once you have enough airflow you can put orders of magnitude more power into that heating element without it melting (as compared to operating it in just open air). A good example is a hair drier that has a heating element smaller than your first yet can suck up a kilowatt no problem.

Heating water is indeed another good way to dump a lot of power. If you have a pool then you can use the pool pump to flow cool water over the heating elements. The more compact option is to boil water instead in a smaller container (Since 1 hour at 20kW is a lot of energy) but you will want to build some sort of chimney to guide all that steam up and away, it could produce quite a lot of steam.

That is quite regular maintenance on that generator tho. I would expect just a monthly few minute test run to be enough for just home use.

[SmallCog]

Is that weekly 11min run recommended by the motor manufacturer or something you’ve come up with?

To my mind it’s potentially a bit short of a run and on the verge of more harm than good.

The majority of engine wear is at startup, so I’d be doing longer runs less often

*my experience is with diesel generators and I presume yours is more-or-less a large petrol engine adapted to run on gas so perhaps things are very different

[themadhippy]

You don't want to use the house as a load during this test. 

Sage advice.It gets a bit embarrassing if you forget the load  is still attached when  commissioning the newly installed ups set up.At least it proved the overload protection worked.

[SeanB]

Simplest load is an old 44 gallon drum, mounted on a nice concrete slab, and then filled with water. 2 electrodes in the water, roughly one third of the diameter spacing, made from steel pipe extending down to about a foot from the base, mounted on a set of insulators. Then add salt till the current is around what you want, and when the water level drops too far add more fresh water.  Do not touch tank, keep away from children in use, and so on the usual safety things, and you will get a test load that will handle 100A for a few hours, just so long as you keep filling it up, or you can use a toilet fill valve, all plastic, and plastic feed pipes, to keep a constant level in it.

Used as a test load at plenty of generator places, where they have to go to high current, and if you need more just add extra barrels in parallel.

[SpookyGhost]

Yep all you need is a bank of the most powerful mains powered heaters you can find.

One option is getting a bunch of kanthal/nichrome heater wire (People use it to make DIY kilns), string it back and forth between two insulating rods to make a large heating element and use a large fan to push lots of air trough it. Basically a electric space heater but scaled up x10. This is mostly how real load banks work. You can also put multiple strings on a switch for power selection. Once you have enough airflow you can put orders of magnitude more power into that heating element without it melting (as compared to operating it in just open air). A good example is a hair drier that has a heating element smaller than your first yet can suck up a kilowatt no problem.

Heating water is indeed another good way to dump a lot of power. If you have a pool then you can use the pool pump to flow cool water over the heating elements. The more compact option is to boil water instead in a smaller container (Since 1 hour at 20kW is a lot of energy) but you will want to build some sort of chimney to guide all that steam up and away, it could produce quite a lot of steam.

That is quite regular maintenance on that generator tho. I would expect just a monthly few minute test run to be enough for just home use.

I have a lot of loud, fast, server fans kicking around. So my thinking would be to mount a bunch of those up, and have them blow the air. a 15K RPM 80mm fan moves quite a lot of air. I think I could build something cool with them

I do have a pool actually, how would you suggest I get the water through? Divert pipes or just dump something in the pool?

After speaking to a lot of really knowledgeable people (SmallEngineMechanic on YouTube for example) it seems the general consensus is that if you want the generator to last, a good 30-60 min run a month under load is a good idea. I'd also much rather find a problem during a test than 4 days into a hurricane outage

Is that weekly 11min run recommended by the motor manufacturer or something you’ve come up with?

To my mind it’s potentially a bit short of a run and on the verge of more harm than good.

The majority of engine wear is at startup, so I’d be doing longer runs less often

*my experience is with diesel generators and I presume yours is more-or-less a large petrol engine adapted to run on gas so perhaps things are very different

That weekly run is recommended by the manufacturer. I can set it to less frequent runs, but I can't set it to more than 12 mins. I agree it seems too short, but it does seem to get up to temp in that time

Yeah, this is a 2.4l Mitsubishi 4 Cylinder, usually runs on petrol/gasoline

Simplest load is an old 44 gallon drum, mounted on a nice concrete slab, and then filled with water. 2 electrodes in the water, roughly one third of the diameter spacing, made from steel pipe extending down to about a foot from the base, mounted on a set of insulators. Then add salt till the current is around what you want, and when the water level drops too far add more fresh water.  Do not touch tank, keep away from children in use, and so on the usual safety things, and you will get a test load that will handle 100A for a few hours, just so long as you keep filling it up, or you can use a toilet fill valve, all plastic, and plastic feed pipes, to keep a constant level in it.

Used as a test load at plenty of generator places, where they have to go to high current, and if you need more just add extra barrels in parallel.

Very interesting! I might look into this. Thanks for the suggestion

You don't want to use the house as a load during this test. 

Sage advice.It gets a bit embarrassing if you forget the load  is still attached when  commissioning the newly installed ups set up.At least it proved the overload protection worked.

I've made that mistake before! I've also had horrible CyberPower UPS's drop the load when doing a self test, and then reporting all green. Fun.

[katzohki]

I have used these with success:
https://www.landmsupply.com/comfort-zone-industrial-5-000-watt-fan-forced-utility-heater-cz220
You can hook up several of them to get the power you need

[fcb]

I built a big AC load-bank with a bunch of 2kW £10 hot-air paint stripper guns. Noisy, but small and cheap.

[Gyro]

That weekly run is recommended by the manufacturer. I can set it to less frequent runs, but I can't set it to more than 12 mins. I agree it seems too short, but it does seem to get up to temp in that time

Yeah, this is a 2.4l Mitsubishi 4 Cylinder, usually runs on petrol/gasoline

Is that weekly run specifically for the natural gas converted model? I would have thought that you would be able to extend the interval significantly compared to one running on petrol. There ought to be a lot less moisture and less chance of fuel gumming up in the pipework / jets / injectors (depending on type).

[SpookyGhost]

That weekly run is recommended by the manufacturer. I can set it to less frequent runs, but I can't set it to more than 12 mins. I agree it seems too short, but it does seem to get up to temp in that time

Yeah, this is a 2.4l Mitsubishi 4 Cylinder, usually runs on petrol/gasoline

Is that weekly run specifically for the natural gas converted model? I would have thought that you would be able to extend the interval significantly compared to one running on petrol. There ought to be a lot less moisture and less chance of fuel gumming up in the pipework / jets / injectors (depending on type).

Yes, for both Propane and Natural gas

We do get a LOT of humidity out here, unsure if that could be an issue with less frequent running. I doubt it though, some Cummins models have just an 8 minute exercise up to 6 months apart (Which seems far too infrequent!)

Personally I don't mind the weekly exercise, as long as its not hurting anything (I doubt it) I'm fine with it running

[SpookyGhost]

I have used these with success:
https://www.landmsupply.com/comfort-zone-industrial-5-000-watt-fan-forced-utility-heater-cz220
You can hook up several of them to get the power you need

Thanks for posting this, I think this might be a good solution. Might be more expensive than building it out of smaller ones, but 5kw right on one device sure makes it easier! 4 of them and I'm in business

[BrokenYugo]

No electric dryer? Those are like 6-7kw on high. The stove should pull about that again with everything on (boil water), gives the AC something to fight against too. 

[SpookyGhost]

No electric dryer? Those are like 6-7kw on high. The stove should pull about that again with everything on (boil water), gives the AC something to fight against too.

Only large draw devices I have are the range and the AC. Everything else is Gas. Now its cooler out too, the AC won't really be possible

I can put my mini split heat pumps on heat, but they use so little power

[SmallCog]

Yeah, this is a 2.4l Mitsubishi 4 Cylinder, usually runs on petrol/gasoline

Oooo wonder if it's a 4G5x or a 4G6x

Mitsubishi has been making and using various iterations of these for ever, pretty bullet proof

Fairly sure they showed up in Chrysler vehicles in the states.

I promise to stop nerding out over your generator now

[SpookyGhost]

Oooo wonder if it's a 4G5x or a 4G6x

Mitsubishi has been making and using various iterations of these for ever, pretty bullet proof

Fairly sure they showed up in Chrysler vehicles in the states.

I promise to stop nerding out over your generator now

What's the best way to tell? Rumor has it Generac are moving this model to their own custom engine. Booo. Wouldn't purchase that

[edpalmer42]

Another source for big heaters would be an old electric stove.  The burners would give you a couple of KW and the oven would be a couple of KW for each element.  You should be able to buy the elements alone at a junkyard or appliance recycling store.

They're nice loads because they're physically rugged and they're made to run red hot.  Figure out some supports, maybe threaded rod and some kind of clamp, add some box fans to blow air across them to keep the heat where you want it and you're done.

[bdunham7]

What's the best way to tell? Rumor has it Generac are moving this model to their own custom engine. Booo. Wouldn't purchase that

It is a later-model (2000-ish) 4G64 SOHC 16V.  There was a 115HP LPG version and this is probably pretty much exactly that just slowed down to 1800RPM and derated.

[SpookyGhost]

Another source for big heaters would be an old electric stove.  The burners would give you a couple of KW and the oven would be a couple of KW for each element.  You should be able to buy the elements alone at a junkyard or appliance recycling store.

They're nice loads because they're physically rugged and they're made to run red hot.  Figure out some supports, maybe threaded rod and some kind of clamp, add some box fans to blow air across them to keep the heat where you want it and you're done.

This and those 5kw space heaters I think are my current favorites. The problem with the space heaters is I think they might trip on thermal protection

I plugged in a 120v 1500w space heater into my portable generator when I was doing the initial 5 hour break in, and it was so hot outside the heater kept shutting off

[SpookyGhost]

What's the best way to tell? Rumor has it Generac are moving this model to their own custom engine. Booo. Wouldn't purchase that

It is a later-model (2000-ish) 4G64 SOHC 16V.  There was a 115HP LPG version and this is probably pretty much exactly that just slowed down to 1800RPM and derated.

Fingers crossed it lasts a long time! I really like it, its SO much quieter than the 3600RPM air cooled models