Generac GP7000E voltage regulator modify?

[larry_g]

I have a Generac GP7000E that is a few years old. During the ice storm here we did 13 days without power. This generator was only delivering 98-100 vac at the generator. It is right on at 60 hertz. It got us through but in checking out the machine I found that the voltage regulating capacitor which is supposed to be 28mfd was only measuring out at 24mfd. I ordered the correct 28mfd and installed it and the voltage now is 109-110 vac. Still a bit low. They also have a 35mfd cap in this package and I'm thinking of using it in this generator.

My thinking is if 4mfd got me an additional 9-10 volts that going to the 35mfd, rather than the factory 28mfd, will get me just over 125 vac. Does any one have any experience with tweaking the cap value on cheap generators that use only a cap for voltage regulation and will it cause any harm?

Attending youtube university I cannot seem to find an answer to my question.

Thank you in advance.

lg
no neat sig line

 

[theoldwizard1]

You should be running at 61 or 62 Hz no load.

Without see the VR circuit it is impossible to know what that cap does.

EDIT : Wild *** guess time ! A true VR is usually a potted piece of circuitry with no replaceable components. Some generators have an extra set of wires coming out of the stator used to "excite" the rotor. Because this is also AC, it must be rectified (using diodes) and filtered (capacitor) to make "clean" DC. A larger cap does a better job filtering so you get a slightly higher DC output which should make a slightly higher AC output.

There is typically no speed adjustment on the engine. You will have to bend a tab somewhere.

 

[larry_g]

View media item 111025
As near as I can get for a schematic. The schematic shows a 47 mfd, lower right hand corner, where mine is a 28 mfd. I cannot get the Generac site to recognize the serial number of the model number. I can only assume that this is some special build for the Home Depot where the generator was purchased.

lg
no neat sig line

 

[theoldwizard1]

WOW ! My SWAG was correct !

Get a 47 mfd capacitor and see what does. Larger will not hurt.

 

[Lightning rod]

you may find this service manual useful
https://www.jackssmallengines.com/Generac-Parts-Lookup/Service-Manuals/GP Series Service Manual.pdf

increase the capacitance to increase voltage. make sure the no load frequency is 62 Hz
as wizard mentioned

 

[theoldwizard1]

Some generators have Automatic Voltage Regulators (AVR) and some do not. If you have one it is the black banana shaped plastic thing with wires/connector under the end cover.

Ones that do not have an AVR (Briggs) rely on the engine governor and the mass of the flywheel and rotor to maintain voltage.

Engine speed should be set by looking at the frequency (Hertz, Hz) and as stated, should be about 61-62 with no load and not drop below 59 with a full load. AVR does NOT affect frequency.

 

[larry_g]

Some generators have Automatic Voltage Regulators (AVR) and some do not. If you have one it is the black banana shaped plastic thing with wires/connector under the end cover.

Ones that do not have an AVR (Briggs) rely on the engine governor and the mass of the flywheel and rotor to maintain voltage.

Engine speed should be set by looking at the frequency (Hertz, Hz) and as stated, should be about 61-62 with no load and not drop below 59 with a full load. AVR does NOT affect frequency.

This machine has the

black banana shaped plastic thing

but it is strictly a cap, two wires, no adjust ability. Frequency is not a problem here, I checked it under load and it is a steady 60hz.

The problem is low voltage output. A factory cap did bring voltage up to 109-110vac. I want to know if there are any known problems to put in a larger cap to raise the voltage a bit more?

lg
no neat sig line

 

[theoldwizard1]

The problem is low voltage output. A factory cap did bring voltage up to 109-110vac. I want to know if there are any known problems to put in a larger cap to raise the voltage a bit more?

The cap has very little to do with the AVR and output voltage. It smooths the "humps" of the AC coming from the excitation winding. Lower peaks means the AVR has more voltage available to send to the rotor which will increase the output voltage.

Not a guaranteed fix. If you can do it SAFELY check the voltage going to the rotor (slip rings) while running and under load.

 

[Fasthotrod]

I looked for a manual for that generator, and got a hit on this:

https://www.manualslib.com/manual/767339/Generac-Power-Systems-Gp1800.html?page=23#manual

It talks about brushless capactitor style as well as brushed excitation... and page 22 of the manual (page 24 on the website) has a troubleshooting guide on how to check the brushless system.

Hope this helps.

Mark

 

[larry_g]

The cap has very little to do with the AVR and output voltage. It smooths the "humps" of the AC coming from the excitation winding. Lower peaks means the AVR has more voltage available to send to the rotor which will increase the output voltage.

Not a guaranteed fix. If you can do it SAFELY check the voltage going to the rotor (slip rings) while running and under load.

This generator has no slip rings. According to the manuals linked the there is an excitation coil that induces a voltage into the rotor for regulation. Page 16 of the manual.

I looked for a manual for that generator, and got a hit on this:

https://www.manualslib.com/manual/767339/Generac-Power-Systems-Gp1800.html?page=23#manual

It talks about brushless capactitor style as well as brushed excitation... and page 22 of the manual (page 24 on the website) has a troubleshooting guide on how to check the brushless system.

Hope this helps.

Mark

Yes it helps. Same manual as linked above.

I didn't see in the manual what the acceptable voltage output is on these small generators. Is 110 volts OK or should I be trying the bigger cap to see if I can get it to what I think is a better 120-125 vac. In one section of adjusting the the slip ring generator it specs 124vac no load, so that is what I'm hoping going to the bigger cap will get me on the capacitive discharge will get me. page 12 of the linked manual.

lg
no neat sig line

 

[theoldwizard1]

Some days the planets DO align !

I just watched this video. It is not your specific model of generator, but it is worth pulling the AVR and checking if the adjustment screw is there ! (Link start in the middle of the video.)

Husky Generator - No power

I have found "generic" replacement AVR that state "works on many different brands" for as low as $15 on Amazon.

 

[larry_g]

Some days the planets DO align !

I just watched this video. It is not your specific model of generator, but it is worth pulling the AVR and checking if the adjustment screw is there ! (Link start in the middle of the video.)

Husky Generator - No power

I have found "generic" replacement AVR that state "works on many different brands" for as low as $15 on Amazon.

That machine is different than mine, if you look at this page of the manual, https://www.manualslib.com/manual/767339/Generac-Power-Systems-Gp1800.html?page=14#manual mine is the one on the left. Capacitive Discharge. No brushes, no slip rings, no adjustment screw.

lg
no neat sig line

 

[larry_g]

SUCCESS

I received the 35uf cap yesterday and installed it. It brought the voltage up to 124vac unloaded and with a 12A load it drops to 122 vac at 59.9 hz. I'm going to call this a win and say that my assumptions in the first post were correct. Now we wait till the next outage to see if it has any ill affects over the long haul.

So to recap;

Generator was putting out ~100 vac with the cap reading 24uf
replaced with factory spec'ed cap, 28 uf, voltage now 110vac
replaced the factory spec cap with a 35uf cap and now reading 124 vac

So the assumption that 1 uf will increase ~2.5 volts is close.

lg
no neat sig line

 

[theoldwizard1]

That machine is different than mine, if you look at this page of the manual,

Your link did not work for me. Try this

GENERAC gP series Portable generators - Diagnostic Repair Manual

 

[AP514]

+1 James Condon...His Videos are AWSOME..been visiting his channel for awhile now.

everything about generators..learned a hell of a lot