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#208125 - 12/28/12 08:05 PM 60 Hertz issue with portable generator  
falcondfb  Offline
Member
Joined: Sep 2002
Posts: 37
Jersey, USA
Not sure if this has been kicked around yet. I have several customers with portable generators that can't run their furnaces. Nearest thing I can figure is that they are not putting out 60 hertz. I also tested several that had an open ground at the GFCI receptacle and L14/30 receptacle.
So 2 questions:
Is there a simple way to get the output hertz up to 60 if the generator is only putting out 57 or 58.

And separate from the above question
Why is there no ground on the L14/30 receptacle of certain generators.


Work Gear for Electricians and the Trades

#208128 - 12/28/12 09:44 PM Re: 60 Hertz issue with portable generator [Re: falcondfb]  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
What size generators are these?

The output frequency is a function of the speed of the alternator and it sounds like they might be being overloaded.

Just a thought.


Let's face it, these days if you're not young, you're old - Red Green grin

#208130 - 12/28/12 10:04 PM Re: 60 Hertz issue with portable generator [Re: falcondfb]  
renosteinke  Offline
Cat Servant
Member
Joined: Jan 2005
Posts: 5,316
Blue Collar Country
There's no 'easy' answer.

There are $99 generators, and there are $1300 generators - even at the same modest "20 amp / 120v" output range. Ever wonder why the price range?

One of the big areas where they 'save' expense in in the power regulation. The cheap ones are not putting out a very good waveform. This is just fine for lights and motors, but can be pure nightmare for anything electronic - like modern furnace controls.

Other drawbacks to the cheap genny's are high fuel consumption and high noise levels.

And, as Trumnpy has mentioned, overloading the genny will result in the voltage gropping before the machine simply stalls.


#208133 - 12/28/12 11:05 PM Re: 60 Hertz issue with portable generator [Re: Trumpy]  
falcondfb  Offline
Member
Joined: Sep 2002
Posts: 37
Jersey, USA
Trumpy,

1 generator was 7500 watts under half load
1 generator was 3500 Honda with no load
1 generator was 2000 Expensive Honda no load
1 generator was 3500 cheapo maybe 1000 watt load

4 different jobs and none would run the furnaces with consistency.

Also in regards to the grounding or lack there of
the honda 3500 had no ground
1 of the honda 2000 did and 1 did not have a ground


#208134 - 12/28/12 11:09 PM Re: 60 Hertz issue with portable generator [Re: renosteinke]  
falcondfb  Offline
Member
Joined: Sep 2002
Posts: 37
Jersey, USA
renosteinke

That is what i always tell my customers. We always recommend Honda's and typically between 3500 and 7500 with idle/throttle control.

We really did not have a voltage issue but a frequency issue.

Any thoughts to the lack of ground issue too?


#208135 - 12/28/12 11:42 PM Re: 60 Hertz issue with portable generator [Re: falcondfb]  
Trumpy  Offline


Member
Joined: Jul 2002
Posts: 8,211
SI,New Zealand
How are these generators being connected to the furnaces?

Forgive me if I'm wrong, but I was under the impression that you aren't allowed to supply permanently isntalled equipment from a portable generator.
At least, that would not fly over here.



Let's face it, these days if you're not young, you're old - Red Green grin

#208136 - 12/29/12 03:18 AM Re: 60 Hertz issue with portable generator [Re: falcondfb]  
gfretwell  Offline


Member
Joined: Jul 2004
Posts: 9,060
Estero,Fl,usa
Hondas do not bond the neutral in the generator as a general rule. I suppose some do but the ones I have seen, don't.

I am still not sure why either of them would not run a furnace. Did you get power to the thermostat?


Greg Fretwell

#208137 - 12/29/12 05:12 AM Re: 60 Hertz issue with portable generator [Re: renosteinke]  
sparkyinak  Offline
Member
Joined: Jul 2007
Posts: 1,313
Alaska
Crack up the throttle screw ought to boost the freq. I had a portable gen set hooked to an inverter once and the range of the frequency was tight while the generator was all over the place


"Live Awesome!" - Kevin Carosa

#208162 - 12/30/12 10:57 AM Re: 60 Hertz issue with portable generator [Re: falcondfb]  
Alan Belson  Offline
Member
Joined: Mar 2005
Posts: 1,803
Mayenne N. France
A furnace should only have about 300-500W running the fans/oil pump at 120v - and with an induction motor, frequency should not be a problem, unless it's so low it causes motor overheating, [which is not immediate anyway]. It may be under or over voltage rather than frequency - many modern electronic burner controllers have voltage protection both sides of the norm and may also baulk at square waves or spikes. Her's the Danfoss spec -
http://heating.danfoss.com/PCMPDF/OBC_82-10_X009114_VDACY202.pdf


Wood work but can't!

#208163 - 12/30/12 02:35 PM Re: 60 Hertz issue with portable generator [Re: falcondfb]  
WESTUPLACE  Offline
Member
Joined: Mar 2004
Posts: 251
Kingwood, TX USA
First, do not assume all are caused by the same problem. Many cheaper generators have poor regulation. I have seen many that will show 120v but low hz when you raise the rpm to get 60hz the peak to peak wave form will exceed what the equipment will handle. Second issue is grounding. Newer furnaces use flame detectors (Flame Rods) that much rely on grounding. Power with a floating ground will cause the CPU to detect no flame and shut down. I have a Honda EU200 inverter generator, it will not operate my furnace unless I ground the neutral side (It has no internal ground) and make sure all including the furnace and gas line is all bonded together.


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