Generator dies when "idle control switch" turned on?

[demarpaint]

I posted an under VC pic yesterday about a generator I acquired. It is a Craftsman 15HP B&S Industrial engine with a Generac generator. It runs flawlessly, however I do have a question about the "IDLE CONTROL SWITCH." The switch runs the engine at normal [high] speeds when there is a load present, and at idle [low] speeds when there is no load present. It is supposed to greatly improve fuel economy. With the switch off it runs at a high speed ~ 3.600 rpm all the time. It is supposed to do that.

I ran it today with nothing plugged into it. It starts on the first pull and runs at a high speed. I flipped that switch on, the idle kicks down and it stalls. Flip the switch off it runs fine. After I put it away it dawned on me that the switch might work properly when something is actually plugged in and drawing current? Is that the case, normal with nothing plugged in? Or is there a problem with the switch? Maybe the linkage, or the carburetor needs adjustment? I was going to tweak the carb but decided against it because the machine runs so good. Nothing in the OM troubleshooting section, and not much on the WWW that I could find. TIA

 

[Donald]

That switch is only usable for a construction site where nothing is running, the generator is at idle, you hit the button on you power saw and the generator goes to 3600 RPM. You let go of the button on the saw and the generator goes back to idle.

For a home backup there are always things needing power (at the proper voltage @ 60Hz) even if it's not running. Your refrig takes power even if the compressor is not running. There are transformers in most heating systems. Even an oil boiler.

Bottom line unless the generator is running at full speed, 3600 RPM, you are not getting the proper voltage at 60 Hz. Once at 3600 the engine governor will make sure the engine stays at 3600 regardless of load, up to the generator capacity.

 

[demarpaint]

Originally Posted by Donald
That switch is only usable for a construction site where nothing is running, the generator is at idle, you hit the button on you power saw and the generator goes to 3600 RPM. You let go of the button on the saw and the generator goes back to idle.

For a home backup there are always things needing power even if it's not running. Your refrig takes power even if the compressor is not running. There are transformers in most heating systems. Even an oil boiler.

Bottom line unless the generator is running at full speed, 3600 RPM, you are not getting the proper voltage at 60 Hz. Once at 3600 the engine governor will make sure the engine stays at 3600 regardless of load, up to the generator capacity.

Thanks. So if I understand correctly, leave the switch off and let the machine run at 3,600 rpm when I need to use it?

 

[CrAlt]

Originally Posted by demarpaint

Thanks. So if I understand correctly, leave the switch off and let the machine run at 3,600 rpm when I need to use it?

Yes. Leave that switch off.

If its not a 3600 then it isn't 60Hz. The ramp up wont hurt a table saw but could fry anything with electronics or transformers in it. Running a fridge under-voltage or off frequency is a really good way to burn out the compressor.

 

[spasm3]

While that generator is a great free gift, and will run most of your house, it will EAT fuel. I have a 20 year old powerboss 10k generator with an 18hp vanguard. It will burn a gallon an hour under load. I bought a smaller 240 v/115 v generator from HF to use for longer outages, its only a 3500 watt continuous generator, but it will run 16 hours on 4 gallons.

I keep the larger one, to run if i need to run the oven and clothes dryer during a longer outage, the smaller one to run most of the time for fuel savings, and keeping less fuel on hand.

 

[demarpaint]

Originally Posted by CrAlt
Originally Posted by demarpaint

Thanks. So if I understand correctly, leave the switch off and let the machine run at 3,600 rpm when I need to use it?

Yes. Leave that switch off.

If its not a 3600 then it isn't 60Hz. The ramp up wont hurt a table saw but could fry anything with electronics or transformers in it. Running a fridge under-voltage or off frequency is a really good way to burn out the compressor.

Thanks!

 

[UncleDave]

Originally Posted by Donald

Bottom line unless the generator is running at full speed, 3600 RPM, you are not getting the proper voltage at 60 Hz. Once at 3600 the engine governor will make sure the engine stays at 3600 regardless of load, up to the generator capacity.


Unless its an inverter generator. Then it can make 60 cycles or Hz out of any RPM.

It doesn't sound right that it just dies when he hits the switch with no load, but constant RPM gensets only work at full RPM as you state - so what this switch about anyway? Guessing its a zero load only deal, but thats going to cause problems with ramp up.

Whats the model # of this genset?


UD

 

[gathermewool]

Originally Posted by UncleDave
Originally Posted by Donald

Bottom line unless the generator is running at full speed, 3600 RPM, you are not getting the proper voltage at 60 Hz. Once at 3600 the engine governor will make sure the engine stays at 3600 regardless of load, up to the generator capacity.


Unless its an inverter generator. Then it can make 60 cycles or Hz out of any RPM.

It doesn't sound right that it just dies when he hits the switch with no load, but constant RPM gensets only work at full RPM as you state - so what this switch about anyway? Guessing its a zero load only deal, but thats going to cause problems with ramp up.

Whats the model # of this genset?


UD


OP, is this an INV gen-set? If not, then I have no idea why it has a low-RPM switch.

I literally makes zero sense for a synchronous generator to allow for lower RPM than is required for 60Hz output...

 

[demarpaint]

Originally Posted by UncleDave
It doesn't sound right that it just dies when he hits the switch with no load, but constant RPM gensets only work at full RPM as you state - so what this switch about anyway? Guessing its a zero load only deal, but thats going to cause problems with ramp up.

Whats the model # of this genset?


UD


It seemed odd that it stalled when I hit the switch, which is why I questioned it. I never owned a generator before so I'm asking and learning.

It's a Craftsman 580.327181

gathermewool- I have no idea if it is an INV gen-set

 

[eljefino]

If it had an output relay it could interrupt that if the power were too low. But then how would it sense demand? Weird. Most generators with "AVR" (automatic voltage regulation) cut out a relay or at least kill spark to the motor when power goes bad, so you don't suffer (as much of) the horrible surging when they run out of gas.

It could be you have an idle jet in the carb that's clogged. It runs full speed fine but won't idle.

 

[CrAlt]

Originally Posted by gathermewool
f not, then I have no idea why it has a low-RPM switch.

I literally makes zero sense for a synchronous generator to allow for lower RPM than is required for 60Hz output...

When there is no load it goes to idle. When you kick on the table saw or drill it cranks up to 3600. This way everyone on the job site doesn't have to listen to an openframe generator screaming at 3600 when its only being used intermittently.

The problem with these big jobsite gensets is if you plug something small like a cell phone charger or other electronics it might not sense the load and ramp up to 3600. Also there is a delay while it goes from idle to 3600 so you get a second of off freq/under voltage. Your circular saw wont care but your LCD tv might. Also these things guzzle fuel.A gallon an hour would be my guess. And they are LOUD as [censored].

I would clean out the carb and get it running 100% then sell it and use the money for something more appropriate.

Here is a video of one very close to that model. You can see around the 4:00 when he plugs in the light it ramps up. And going back to idle when he unplugs it.

 

[Donald]

Originally Posted by eljefino
If it had an output relay it could interrupt that if the power were too low. But then how would it sense demand? Weird. Most generators with "AVR" (automatic voltage regulation) cut out a relay or at least kill spark to the motor when power goes bad, so you don't suffer (as much of) the horrible surging when they run out of gas.

It could be you have an idle jet in the carb that's clogged. It runs full speed fine but won't idle.


My guess it's an idle jet. I rebuilt the carb for my Coleman 5000 watt generator. I have the same situation when I turn on idle switch. The speed dropd and it seems like it will stall. I assume I did not clean the idle jet when I rebuilt it.

 

[Dinoburner]

This may not be completely relevant but my welder/generator drops to idle at no load then kicks up to 3600 when striking an arc or turning on whatever is plugged into the panel. The idle circuit in the carb must be functioning like others have said.

 

[demarpaint]

I discovered the switch late. Weather permitting I'll dig into it again and get the carburetor dialed in. I might even have one laying around. Thanks for the replies.

 

[rubberchicken]

Keep it, do not sell it. On the rare chance you have to use it, then it might burn a bit more gas. Over the course of a year, that might be , what, $10 ?

 

[UncleDave]

Saw the vid - ehhhhhh ok I get it. Never seen this before - mainly because I dont look at open frame work type gensets

Im a spoiled brat with inverters and big diesel gennies.

They turn it down to some lower rpm but its still fairly off idle high like 2600 from 3600 then it ramps under load - and yeah for a bunch of guys at a worksite hitting it with induction motor saws and tools and small air compressors its gonna be fine . Its a noise abatement feature more than fuel savings.

Cralt outlined the downsides of this style unit problem comes when someone will try to use as a home backup or camp genie and partial low loads and or compressor based devices like big AC units dont like voltage sag on startup and you can fry them if you undervolt a bunch.

As long as you are cognizant of whats being plugged in you won't have any problem 0 aside from the roaring and very thirsty nature of this beast she'll likely to drive you broke before you wear it out with basic maintenance.

I agree with the idle circuit /jet clogged theory - happens all the time in gensets that sit.

UD

 

[demarpaint]

Originally Posted by rubberchicken
Keep it, do not sell it. On the rare chance you have to use it, then it might burn a bit more gas. Over the course of a year, that might be , what, $10 ?

I have no plans on selling it.

If the weather cooperates I'll get the carburetor sorted out today. You're right for the one time every couple of years I might need it I'll pay up for the gas.

I got a lot of good info from this thread. I want the machine to run properly. When the time comes to use it I will let it run at 3,600 rpm and not use the switch. I want everything working though, which means the low idle circuit has to be addressed. This will be an easy fix.

Thanks again for all the replies.

 

[Donald]

Originally Posted by gathermewool
Originally Posted by UncleDave
Originally Posted by Donald

Bottom line unless the generator is running at full speed, 3600 RPM, you are not getting the proper voltage at 60 Hz. Once at 3600 the engine governor will make sure the engine stays at 3600 regardless of load, up to the generator capacity.


Unless its an inverter generator. Then it can make 60 cycles or Hz out of any RPM.

It doesn't sound right that it just dies when he hits the switch with no load, but constant RPM gensets only work at full RPM as you state - so what this switch about anyway? Guessing its a zero load only deal, but thats going to cause problems with ramp up.

Whats the model # of this genset?


UD


OP, is this an INV gen-set? If not, then I have no idea why it has a low-RPM switch.

I literally makes zero sense for a synchronous generator to allow for lower RPM than is required for 60Hz output...


Read my post. It's for construction sites where at times no power is needed until you turn on a saw for 30 seconds and then go back to no power needed.

 

[demarpaint]

It was an easy fix. I dose OPE with B-12, I did that the other day with some fresh fuel. I let it run again today, and toggled the switch on and off, then hooked up my sawzall to it with the switch on and triggered the sawzall on and off several times. It works perfectly. I guess the B-12 needed more time to work its magic.

Thanks for all the help!!

 

[CrAlt]

Originally Posted by rubberchicken
Over the course of a year, that might be , what, $10 ?

Its not really the cost that is the problem with those jobsite generators. Its the amount.
2 5 gallon jerry cans gets you 10 hours on that thing. On my honda inverter set 10 gallons gets me 80 hours.
And Honda isn't the only game in town now for inverter style generators. Champion makes an OK machine for less then 600 bux. There are also lots of affordable options now for "duel fuel" propane/gasonline machines so you don't have to deal with storing and rotating the crappy ethanol fuel we are stuck with here in new england.

Yes that jobsite genset is better then nothing but if I needed backup power I would be looking to get the right tool for the job.