# PowerMate Gen on freq but high volt



## Soya (Jan 24, 2020)

I have a 1997 Coleman Powermate generator PM04777023. It does not have many hours since it is only used for occasional power outages and when it is exercised every couple of weeks.


I checked the volts and freqs with a meter and found the volts at 140/280. I got a kill a watt meter and checked the volts and freqs and found that if I set the volts, by adjusting rpm, at 120v the freq was at 57hz no load. I set the freq at 62.25 and the volts come in at 131 no load. I set the freq on advice of the local small engine tech who said that they set the gens they work on at 62.0-62.5 hz no load so they have some wiggle room when the load is applied because circuit boards and electronics are most sensitive to out of limit freqs.


When I put a 1800w load on the gen the freq goes to 61.x and the volts is about 126. That's 5% of 120v. Is that something to be concerned with in terms of damaging electronic circuits, motors and equipment?


Secondly is there a way to adjust the voltage output of this gen without changing the rpm of the engine which will change the freq also?


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## tabora (Sep 6, 2018)

Soya said:


> When I put a 1800w load on the gen the freq goes to 61.x and the volts is about 126. That's 5% of 120v. Is that something to be concerned with in terms of damaging electronic circuits, motors and equipment?
> 
> Secondly is there a way to adjust the voltage output of this gen without changing the rpm of the engine which will change the freq also?


Adjust the RPM so that the no-load voltage is just about 130 and then check the loaded voltage & frequency. The allowable voltage is typically +/- 10%, so from 108 to 132.


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## Soya (Jan 24, 2020)

Just saw this today as I did not get an email notifying me of the answer. I'll try what you advise and report back if I have a problem. Thanks for your answer.


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## Melson (Dec 8, 2019)

You could also investigate if the throttle governor can be adjusted for sensitivity to loads. If so you may be able to adjust for less speed droop, holding the frequency closer to 60 under loads.
I have had reasonable success doing this with a variety of small engines that have mechanical governors.


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## iowagold (Jan 22, 2020)

I guess this is the main reason I use an honda inverter generator!!
yea most new sensitive electronics will not stand for the wide band power...
and the fq is a big thing!!
it is all about the rpm on a standard gen set...
I like the voltage range to be at max 114 vac to 126 vac @ 60 hz and the hz range of 59-61hz at max!!
most of our utility grid voltage in my area is at 125 vac... and right at 60hz.

on the lower cost gens, test and set up at rated output.
so if the gen is rated at 5000 rated or 7500 peak
use a close to 5000 watt load...
the oil heaters work well if you do not have a good load bench setup.
and use fans on the oil heaters to keep them on.

most of the time you are only doing a load after the gen is fully up to temperature for a few min.
and then I always look at the output with 200 watts load.

and yes always look up the instructions in the service manual for the gen set you are working on!!!
*THEY ARE ALL DIFFERANT SETTINGS*
sorry for the caps but I had to shout that!! LOL!!

always read the manual!!
I have setup charts I use for testing where I can bench mark record the settings..
good to do on new gens for a record of the factory settings as new.
and when a gen is first in the shop and when it leaves!!

I always set up or check the idle on all new inverter gens!!
the last (2) 2000i units I purchased were from India production and were not set!!
they relied on the servo for the idle!!
and that is not the factory spec for the setup!!
so when you hit them with a load they would not keep up!!
there was a TSB on this for a short run glitch.
late production

so always have your generator tech load test all gens before use!!
it is part of the setup!!
and why you go to a dealer that is a service center!!

over the years I have seen some horrible gen sets....
108 volts...
150 volts (no kidding)
and these were name brand gens of years past most were from the 1970's to 1990's
back when portable gens were just a fad...
not like now where they are a serious biz!!
most folks have seen the light!!
and 911 sealed the deal for most folks to have some sort of plan...
even if it is a small plan for just spare food and a few lights and some water!
better than no plan at all!!

so make a plan, look to see what others are using... and how it is working out for them!!
talk with a few rv folks!!
most of them now days have gens...
and the pro travel folks can share some good info as well to what works!!

the Iowa state fair is the super bowl here for camping...
hot days and hot nights!!
and they have quiet time up there....
so after like 11pm till 7 am the noise needs to be under 60db!!
here is where the Hondas shine!!
folks have made quiet boxes that are power vented... but will take the 55-65 db honda gens down to 
maybe 45db!! no kidding!!
the last one we did for a eu6500 was bumper mounted and was 48 db!!
and did well on those hot 110 deg days in the camp ground!!

now days with extended run conversions for the new eu7000is where you can run them off a large fuel tank.
they only turn them off to check the oil!!
we run synthetic castrol or mobile one. and use magnetic drain plugs as well as magnetic dip sticks!!
that holds down the trash in the oil!!
I have pix of that on the honda forum.

yea think of upgrading the older 23 year old gen when you get a chance!!
the new honda inverter gen units are worth the extra bucks!!
and just like all electronics gear... the newer stuff is better!!


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## Melson (Dec 8, 2019)

I share your enthusiasm for the honda eu-is series of small generator.
I have mine in a forced-air enclosure which allows the unit to be sensed, but not heard ;-]


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## Soya (Jan 24, 2020)

First of all thanks for the answers. I can only find the owner's manual for the generator. No adjustment info there. I can't find a service manual.


Iowagold, what kind of oil heaters are you talking about for load testing? The oil filled space heaters?


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## tabora (Sep 6, 2018)

Soya said:


> I have a 1997 Coleman Powermate generator PM04777023...manual...


 I think you have too many 7s in your model number... Maybe PM0477023? Does it have a 14HP Vanguard twin engine? If so, see pages 20-21 of this manual:
https://www.mudbuddy.com/manuals/vanguard/vanguard-repair-manual.pdf


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## Soya (Jan 24, 2020)

tabora said:


> I think you have too many 7s in your model number... Maybe PM0477023? Does it have a 14HP Vanguard twin engine? If so, see pages 20-21 of this manual:
> https://www.mudbuddy.com/manuals/vanguard/vanguard-repair-manual.pdf



Yes, I put one too many 7s in there. That's the model (14hp Vanguard) and the manual. Thanks.


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## iowagold (Jan 22, 2020)

yup they work well for a home owners load bank
and they are low cost..
lol
and most yard sales have a few of them!!
the neat thing is you can use them in other ways as well.
they work well for heat during an outage..
you can cycle them and they put out 100% of what is used...
so run the heater for 15 min till it is warm then switch over to another heater during an outage 
if you have a small gen..
that way you can heat a larger set of rooms...
unless you have a gas furnace.
then just run that with the blower locked to on.


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## Soya (Jan 24, 2020)

iowagold said:


> yup they work well for a home owners load bank
> and they are low cost..
> lol
> and most yard sales have a few of them!!
> ...



Got a gas furnace. I have fried the circuit board before when using the gen:tango_face_sad:


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## iowagold (Jan 22, 2020)

what is the current draw on the furnace??
sounds like you have a late model furnace...
yea sounds like you are a good candidate for an honda eu7000is generator... 
or depending on your total current you need during an power outage event...

you maybe able to use an ups on the furnace for buck boost to save the furnace...
but if it is that bad... think of the tv's and all the other electronics items!!
yea all the items to correct bad power..
you could buy a good gen!!


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## drmerdp (Apr 10, 2018)

Soya said:


> I have a 1997 Coleman Powermate generator PM04777023. It does not have many hours since it is only used for occasional power outages and when it is exercised every couple of weeks.
> 
> 
> I checked the volts and freqs with a meter and found the volts at 140/280. I got a kill a watt meter and checked the volts and freqs and found that if I set the volts, by adjusting rpm, at 120v the freq was at 57hz no load. I set the freq at 62.25 and the volts come in at 131 no load. I set the freq on advice of the local small engine tech who said that they set the gens they work on at 62.0-62.5 hz no load so they have some wiggle room when the load is applied because circuit boards and electronics are most sensitive to out of limit freqs.
> ...



What you have is an older generator with a non-avr alternator. Voltage with be bucked or boosted based on the capacitors smoothening. These alternators can take a beating but are notoriously dirty. Power output has a significant amount of harmonic distortion. Frequency and voltage only tell a part of the story, the waveform gives a complete visual. 

Here are some reading from my oscilloscope. This is a Colman powermate 5000watt unit with the same type of alternator. 

No load 











3/4 Load 











Here’s grid power as a comparison.


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## Soya (Jan 24, 2020)

drmerdp said:


> What you have is an older generator with a non-avr alternator. Voltage with be bucked or boosted based on the capacitors smoothening. These alternators can take a beating but are notoriously dirty. Power output has a significant amount of harmonic distortion. Frequency and voltage only tell a part of the story, the waveform gives a complete visual.
> 
> Here are some reading from my oscilloscope. This is a Colman powermate 5000watt unit with the same type of alternator.
> 
> ...



Wow, that first trace is nasty looking! Do you happen to have any of a newer inverter powered generator?

Is that a purpose made scope or a smart phone and app?


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## drmerdp (Apr 10, 2018)

Soya said:


> Wow, that first trace is nasty looking! Do you happen to have any of a newer inverter powered generator?
> 
> Is that a purpose made scope or a smart phone and app?


I’ll take picture of my eu7000s waveform tomorrow and post it. 

The phone looking thing Is a cheapy eBay pocket oscilloscope, but it won’t Read 120v. So I run it through a simple 120vac to 12vac transformer. 

I’ve compared it to the modis and it’s dead on. (I don’t own the modis) Not bad for a cheap little thing. When I have a power outage I keep it running in my kitchen to keep an eye on my big generator. Handy. 

Anyone interested in a dedicated thread with Oscilloscope readings from different generators? I have a few.


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## Soya (Jan 24, 2020)

iowagold said:


> what is the current draw on the furnace??
> sounds like you have a late model furnace...
> yea sounds like you are a good candidate for an honda eu7000is generator...
> or depending on your total current you need during an power outage event...
> ...



Not sure of the current draw. It is of 1995 vintage. It's on a 20 amp circuit breaker with 12ga wire. Has blower motor to evacuate fumes, circuit board for safety interlocks and firing up, and of course the duct circulation fan, which is probably the highest starting load.
I'd love to wire in a ups but the furnace is hard wired from the cb panel. I suppose I could wire a ups in line some how but most ups are plug in, plug out. I guess what I really need is a power line conditioner.


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## Soya (Jan 24, 2020)

drmerdp said:


> So I run it through a simple 120vac to 12vac transformer.


Do you mean 120vac to 12vdc?


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## drmerdp (Apr 10, 2018)

Soya said:


> Do you mean 120vac to 12vdc?


Nope, not a rectifier. Just a step down transformer, like what’s used on door bell low voltage wiring.


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## Soya (Jan 24, 2020)

What is the model of oscilloscope?


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## iowagold (Jan 22, 2020)

wow that is some lumpy looking saw tooth! lol!
or "#new new baby shark tooth wave form" sing it gang! insert baby shark song here
lol
that made my day for sure.

yea looking at wave form is tricky..
it all depends on resolution of the scope.
most wave forms look bad on an high resolution digital scope.

and the one thing to remember is some items will stand for a lumpy waveform...
other electronics items that do not have the filtering in the ac to dc supply like they should...
well it just burns them up!

this is the same on the dc to dc converters like for car chargers for our items like apple
even on the ac to dc on the apple units the power supply needs to be real good.

these days they are not using much in the way of large smoothing caps in like furnace boards..
just a couple of cheap diodes (not the good ones) and maybe not even a full wave rectifier setup...

I am not sure if the furnace dc supply will stand for a good cap...
some will not stand for a 500,000 mf at 100 volts rated for heat. like used in a computer power supply.
some engineers use a resistor inline to charge the cap.

yea if you had that scope meter you could probe the furnace and see how nasty it is in there on the dc control stuff.

I am lucky on my little furnace it is all old school 24volt ac controls.
no computer for the sensors and no fan electronics controls.
just relay and stack temp switching.
7 amp inrush on the blower and 1.2 amps run. so when on gen I lock in the blower to fan on.

you get in to the advanced electronics switching on the 90% and better furnace units.

we had a couple of amana units back in 1995 in the old shop they both ate boards like candy!!
and that was on grid!
but we had a lot of lightning, and power surges in that location.
the location was over a coal strip mine that was reclaimed.
a real hot spot for lightning.

so if you are shopping for a prepper furnace before you buy,
pull the covers on the rats nest.. if it looks just like a rats nest with a board under..
I would avoid that for your back up furnace or off grid furnace.
it will be just one good emp away from not working.


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## drmerdp (Apr 10, 2018)

Soya said:


> What is the model of oscilloscope?


It’s a DSO212. Got it on amazon.


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