Generator Voltage/Current Problems

Johnny Rotten

Member
Join Date
Dec 2004
Location
Ontario, Canada
Posts
194
Yes, this is way off topic, however hopefully someone has heard of this.

We use a propane stove at my hunting camp. It uses the old style 'glow bar' to ignite the stove. Once the 'bar' is hot enough, a thermostat switch closes to 'fire' the 120VAC Gas valve. Gas comes in, ignites, good to go.

This stove used to be natural gas and has been converted properely to propane.

The issue is that it works fine plugged into household 120VAC, but will not work off of the Generator Voltage. The Glow Bar (which is electrical) just 'glows' so to speak, nothing else happens.

The local Propane Technicians said that this system will never work from a Generator, as the voltage is not regulated enough. They have come accross this problem many times.

Any suggestions? Filters? Caps? Chokes?

Johnny

p.s. I need to get away from computers for a weekend.
 
I'm just guessing here, but I'd check the voltage and frequency output of the generator. Low voltage and/or high frequency might not get the glow bar hot enough, or allow the coil to properly actuate.
 
Its a very consitent 120VAC. I think I read 122VAC. I forget what I read for Ampacity, but that glow bar draws allot of current. It was around 11 Amps or something. I did not take a Frequency check, should I?

Anyhow, lets assume the frequency fluctuates. Why would that be? The motor has no issues, as it is a 5000 Watt Gen. Ah yes, 'light bulb', thanks again ElevMike.

I'm obviously thinking as I write, do you think the coil (120VAC) has issues with the fluctuating frequency? The stove's 60HZ Gas Valve has issues with 50HZ Gen Voltage(or whatever that value is)? Damn AC inductive reactance.

That must be it, will do a frequency check on that Gen. I will check the frequency under 'no load', 'full load' and 'user load'.

Will let you know.

Lets say I read 83 Hz, or it just jumps all around, what do I do to that 60Hz coil, to make it work?

Mike, could I just make it a DC Valve? Rectify the AC? What other ides do you have? Throw in a discharge diode/resistor?

I know this is off topic and all, but this must be an issue for others as well with Generators.

Mike, I am happy, there is hope. Will my 74 Yamaha GTX 433 snowmachine get to the camp on Saturday? It is -24 Celcius now.

Johnny
 
I would check to make sure the thermostat is closing before checking anything else. I'm assuming the 120 VAC you read was under load when the stove was trying to start. If not be sure to check it then. Since your glow bar is a straight resistive load it wouldn't take much of a voltage drop to make a big difference in total heat.

I have not come across any valve solenoids that are very touchy with frequency. I've worked on numerous machines that were shipped to Europe and we never put different valves on European machines. I would think you would need to be a long way off frequency before you have a problem.

Keith
 
If it is a 3600 rpm class generator, then one cycle per 60 rpm.

If it is 1500/1800 rpm, then one cycle per 30 rpm.

I don't see how it could be that far off as far as frequency.

Maybe it is not a true sine wave or something.

I could run several thousand watts of light, and run my Dewalt 1/2" right angle drill on 300' of 16 ga. extension cord. But 100 feet of cord on my Dewalt 1/2" D handle gear reduction drill smokes the brushes and destroyed the rotor.

If I could, I'd check the output waveform and frequency with an oscilloscope.

regards.....casey
 
Alternators

I just know that 4 years (well 3 yrs, 10 mos, 28 days - but who is counting) experience operating and reparing alternators on a submarine would come in handy.

Would assume single phase 120 / 240 1500 watt unit, gas powered, Honda or other "low cost" unit.

Lets see 11 amps on 120 line is about 1330 watts. That is a nice healthy load for a 1500 W unit. Engine has to be in real good shape good fuel, plugs etc. Honda etc I would not have huge expectations for engine life carrying this much load constantly.

BUT then they are better than lugging a heavy diesel unit around I guess.

What is allowable wattage KW on unit??
What is allowable KVAR on unit (if so rated)??
Last rated for PF??

If this glow bar is a truly resistive load (and I assume it is) then resistance and therefore power care not about frequency PROVIDED volts and amps stay the same.

Alternators have a voltage regulator.
They also have a "frequency regulator ie the engine governor. IF engine not running well then governor cannot govern well engine will hunt slow down etc etc.

The few times I put an O scope on an alternator (portable) it put out a nice clean sine wave - just as good as that of the power company.

NOW IF
the governor is real sloppy or out of adjust (or cannot compensate for sickly engine) the voltage regulator may not be able to overcome low speed -- just like car alternator --speed up engine and volts go up lites get brighter.

GOOD IDEA to check volts amps and freq at varying loads. Use a couple heaters (toaster, baseboard, hair dryer etc etc) to increase load. Freq should hold at 60 maybe give or take a half cycle per sec.

Volts - depends on droop of alternator -- if drop 3 to maybe 5 from no load to full load dont think I would get excited.

Also let heaters heat up before readings - cold heaters have lower resistance thus higher amps and power

Dan Bentler
 
Thanks Guys/Gals, seems allot for a camp stove, but will do the checks. I did read the 'trouble shooting' section and stopped.

It just simply works on normal 120VAC from the utilities. There must be one characteristic between that and the Gen Voltage. There is 'zero' voltage drop. Oh, yes, I do believe the thermostat switch is electronic. Perhaps a Thermistor, RTD, or who knows?

Any control voltage would have to be 120VAC, but perhaps not. I will look at the schematics once again. It just seemed rather useless to look at them if there is not a possible solution.

Why trouble shoot something that works, or trouble shoot 'it' when it does not, with no possible solution. Oh well, stupid stove.

I really like the UPS idea. And the load is resistive indeed. The glow bar just draws allot of current, which made this type of stove a 'thing of the past', because of that.

As I recall, the glow bar may not have 'gotten up to temp'. But that is from 'others'. The 'old' boys are not stupid, and I just wanted to fix it for them.

Why would Gen Voltage cause this?

Gen is 5000 Watts, very very well maintained. Not only that, Propane Technicians have heard of this issue many times.

John
 
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Heater

Johnny

What are equivalent readings on city power??


OR does unit have solid state controls? What other loads are you running ??

Maybe some things are just beyond comprehension.

Dan
 
I've got a 7,000 watt generator powering a 3000 sq ft home. When the wife turns on the oven, stove, dryer (all electric) and all three AC units, gen slows under load, frequency drops and HVAC & fridg compressors/fans burns up.

Good expensive newer Honda will have electronic true sine wave form. Cheap (enexpensive) Generic (like mine) is regulated by a governor. I vote for frequency problem with gas coil. SWAG.

If you change to dc for the coil then you might have to double the voltqge to get the same henerys.

Mike
 
The circuit should be pretty simple. Turn the stove on and you start to heat up the glow stick. When it gets hot enough, it trips a thermal switch which closes to allow current to flow to the gas valve. So, either the glow stick isn't getting hot enough to trip the thermal switch, or the gas valve doesn't like the fluctuations in voltage or frequency. My opinion is that the thermal switch is not tripping, but if you can get at it with a meter, you can verify that.

How accessible is the control wiring and the burner? Is converting the stove to manual operation a possibility?
 
Had the same stuff back in the 70's in the UK when we changed from coal gas to natural .
I think if you do a bit of checking , you might find propane doesn't appreciate being lit with a flame rod.................
 
I missed this and I am pretty sure Johnny's headed out for the weekend already.

Everyone talked about generator freq, etc. That propane doenst like a glow bar.

I dont care if the genset is a 1000 watt Coleman from Wally World, a 20K Onan or a 1000KW from CAT. If its running at rated speed an you have 120vac output at the genset then a purely resistive load should work with no problem. If requency fluctuates voltage should too.

I will assume something else. The meter reading was taken at the genset. What kind of "cord" or wire is being used from the genset to the stove?

This is my theory. lets say the glow bar is 1500w at 120vac the current would be 12.5 amps. Lets say your "cord" is giving a voltage drop of 10v so at the stove you only have 110vac...even if you draw the 12.5 amps at 110vac you will get 1375 watts which may not make the bar hot enough to trigger the thermal switch.

If the genset is powering the panel then verify "cord" and conncetions.

Sometimes the simple things get overlooked.
 
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Mike, I hope you are correct. The stove is at the camp, so wont get there until next weekend. Did not go last weekend, ignition is messed up on snowmachine. I will get the gen/stove manuals today.

Eventually I will make it to the camp, think I will change that 120V valve to DC. Of course that may not be the problem, but I will be prepared.

Thanks Johnny
 
Had similar problems on mobile equipment I have worked on. First check your earthing at the generator and your neutral, some circuits don't like to float. If that doesn't work try putting an isolated transformer between the supply and the load, some circuits do like to float and it will absorb any high frequency spikes coming out of the generator.


Regards


Bryan
 

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