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Old 9th November 2012, 01:14 AM   #11
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Hi,
Remove all the loads and try to run only the furnace alone.
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Old 9th November 2012, 01:12 PM   #12
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If the furnace has a mains powered fan in it then this WILL burn out when run from a modified sinewave inverter...
I'm not too sure about that. Just ran my gas heater (forced venting) using a duracell 134 watt inverter, it's the size of a deck of cards. I assume it's a simple modified square wave inverter. The fan motor had no problem at all, there was not even excessive noise or buzz from the motor. I was concerned with it, exactly as you caution, but twas uneventful. I did use a 100 foot 12/3 extension cord, I figured it's inductance would help buffer harmonics a tad.

The motor was a simple 60 hz, .94 ampere rated shaded pole type. My biggest concern was whether the ignitor circuit would exceed the inverter's peak capacity of 175 watts, but it worked like a charm.

Good luck over there in jerseyland..I'm on longuyland, lost my power for 2.5 days, I'm one of the lucky ones.

edit: can you tell if your fan motor is 120 or 240? If it's 240, you may not be able to "get there from here".

Also, be aware that at turn on it will draw locked rotor current, which could be up to about 7 times it's continuous duty rating.

jn

Last edited by jneutron; 9th November 2012 at 01:16 PM.
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Old 9th November 2012, 02:09 PM   #13
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We had no power for 23 days after hurricane Wilma 6 years ago. I tried running many things from generator power during that time. I have two generators, one is a 6KW run 8KW surge Coleman Powermate. The other is a cheap 1.2KW (Chinese Watts) unit from discount store. Both use a primative mechanical governor system that tries to keep the engine at 3600 RPM.

If the engine speed varies, the line frequency varies by a proportional amount. So does the output voltage. Motors that use a run capacitor rely on the capacitor for a phase shift that will vary with a frequency change. This affects the motor's efficiency.

I could not get my home central AC to run the big generator, the compressors motor would not start causing a severe overload on the generator. The generator has a 240 volt 20 amp outlet.

A small wall unit (5000 BTU) would run from the big generator only if connected directly with a SHORT piece of 3 X #10 Romex. It did not seem to cool as well as it normally did when fed with line power.

My refrigerator ran from either generator, but did not get as cold as normal. The freezer stayed at about 30 degrees.

The swimming pool pump worked normally, but was connected directly to the generator with 4 feet of #10 Romex with alligator clips attached. The pump was the point where I feed generator power back into the house.

Computers, TV's and other electronics seemed to behave normally. There was constsant light flickering from the AC and refrigerators motors cycling.

I had to start the wall AC first, then the refrigerator, then other stuff if I wanted them all to work. Otherwise the gen would shut off when the AC was turned on.

Instruct wives and children not to plug in blow dryers, toasters, microwaves and coffee makers without informing you first! You get to repeat the start up sequence.

The big generator is LOUD and consumes 1 to 2 gallons of gas per hour. I ran it during the day for several hours. The little generator is quiet enough to run in the evening and powered everything that is really needed except AC. It will run for 4 hours on 1 gallon. We had to drive 50 to 200 miles north to get gas during the first 10 days.

We charged two car batteries during the day (the Coleman also has a 12 volt charging source) to run lights, a 12 volt TV and a portable fan at night.
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Old 9th November 2012, 03:30 PM   #14
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The main problem, and the reason why I was conservative, was that portable generators don't have flywheels on them, 99% of the time they are direct drive, so there is apsolutley no way that they will kick over another large motor unless you throttle up by a great amount first before applying the load, which is impossible/difficult and even dangerous when the choke is the only control that you have on automatic ones.

I've had a little portable gen break its direct drive coupling when trying to start a heavy load before.

Small generators are usually fine for small motor loads like fans, but inverters are very hit or miss, and this is mainly to do with their build quality.

The only generators that I know of that will power large air conditioners like as you describe for at least a week or more are the old 1 or 2 cylinder Diesel Lovson/Lister engines.

Just beware of the build quality of the Indian knockoffs (Lovson's), sometimes they can have casting sand in the sump when they arrive at your door, and oil/lubrication pipes barb fittings can leak like a sieve, but thats easily fixed, and the sump gaskets that arrive with them will also be useless (cut one out of cork, fixed.) and its a good idea to flush the sump before you fill it with fresh oil and run it anyway.

When you are trying to power A/C, a flywheel is the only thing thats going to get you over that huge plateau upon startup, they also have the great benefit of giving you pure-clean sinewave noise-free power and a steady voltage/frequency.

You, just as with many other owners out there, have now discovered the harsh reality of those generators that have a carry handle or two on them when it comes to things like Hurricanes and heavy loads.

Me and my family have been without power for 7 days when the Pasha Bulker ran ashore on Newcastle's beach during that massive big storm we had, and it taught me one thing, the only thing that works is the good old Kerosene Primus stoves, or butane stoves, or Solar Panels, and good luck lasting a SINGLE DAY with a Generator...

I fed my entire family from a full to the brim chest freezer for those 7 days (which kept ice cold for 3 days after the power went out, and was a wedding heirloom from my mother's father 50 years ago) and a twin burner Primus stove, and 2 Litres of Kerosene, yes they are that fuel efficient.

And yes you can still buy the pump gaskets off eBay direct from India.

Just be careful of small children and the primus kerosene lamps, severe burns can be caused by the kerosene tipping onto a child and igniting, and yes kerosene especially poor quality stuff can ignite and spread out just like petrol especially if its at a high temperature when it becomes less thick/viscous.

And I take no responsibility if anything happens to anyone who has read any of this, you are responsible for your own safety and those around you.

http://en.wikipedia.org/wiki/Pasha_bulker
http://en.wikipedia.org/wiki/June_20...l_Coast_storms
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Last edited by freax; 9th November 2012 at 03:55 PM.
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Old 9th November 2012, 04:03 PM   #15
freax is offline freax  Australia
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Originally Posted by jneutron View Post
I'm not too sure about that. Just ran my gas heater (forced venting) using a duracell 134 watt inverter, it's the size of a deck of cards. I assume it's a simple modified square wave inverter. The fan motor had no problem at all, there was not even excessive noise or buzz from the motor. I was concerned with it, exactly as you caution, but twas uneventful. I did use a 100 foot 12/3 extension cord, I figured it's inductance would help buffer harmonics a tad.
Small generators are usually fine for small motor loads like fans, fridges, "disposable tv's, aka 34cm CRT.. a laptop, maybe a desktop computer if its not a gaming one, but inverters are very hit or miss, and this is mainly to do with their build quality and wether or not they will spew out a modified square wave, a pure square wave, or a pure sinewave, the pure square wave ones are the worst offenders for motors and can make them lock up and catch on fire!, the modified square wave ones can make the motors overheat or run slow, and the pure sinewave ones will usually run them perfect unless the motor is too high of a wattage for the inverter.

I'd say you got lucky, How long did you run it for? I've had plenty of inverters and none of them were able to run a simple cooling fan without making it run at least 1/2 the speed it normally is, maybe Australian's regulations are looser with chinese inverters, You might even find out that as soon as the components inside of the inverter heat up that the fan will seize or start to run slower, thats what happened with one of my inverters, it ran a fan just fine, but give it 15 minutes on a fresh battery and it was running slow as, and it wasn't the battery.

A modified square wave inverter will run large loads like a 68cm CRT tv (168 watt load), usually with the small inverters and generators you need to 'prime' the degauss circuit first before starting the tv set, but I wouldn't risk a fridge compressor on one.

Btw a "modified sinewave" inverter is exactly the same thing as a modified square wave inverter, they are just trying to trick you into thinking its a pure sinewave unit.

I try to keep everything on DC anyway during an extended blackout, and its a lot easier to replace a blade fuse than it is to replace an expensive inverter when the worst happens, I hate inverters, they are extremely RF noisy and long extension cords only worsens this.
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Last edited by freax; 9th November 2012 at 04:33 PM.
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Old 9th November 2012, 04:30 PM   #16
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Originally Posted by freax View Post
Small generators are usually fine for small motor loads like fans, fridges, "disposable tv's, aka 34cm CRT.. a laptop, maybe a desktop computer if its not a gaming one, but inverters are very hit or miss, and this is mainly to do with their build quality and wether or not they will spew out a modified square wave, a pure square wave, or a pure sinewave, the pure square wave ones are the worst offenders for motors and can make them lock up and catch on fire!, the modified square wave ones can make the motors overheat or run slow, and the pure sinewave ones will usually run them perfect unless the motor is too high of a wattage for the inverter.

A modified square wave inverter will run large loads like a 68cm CRT tv, but I wouldn't risk a fridge compressor on one.
For those not versed, a modified square wave inverter is simply a square wave inverter with a dead band between the positive and negative portions. It is a compromise between square and sine, but doesn't have the dissipation issue a pure sine would have.

There are two possible scenario's for "locking up a motor".

Small motors will be shaded pole motors, no startup capacitor. It starts rotation in the proper direction by a loop of copper around part of the field iron. This loop generates eddy currents and as a result, delays the magnetic field that goes through it a bit. This is the impetus for the rotor wanting to go in a specific direction. Square wave drives will have more high frequency content, and this can cause more dissipation in the iron as well as more rotor dissipation. Eventually, the entire structure may heat up more than design, and bronze or leaded brass bushings can expand to the point where they will start to bind. Rotors generally are not close enough to the field laminations to bind through thermal expansiion.

Given the manufacturing tolerances of typical small motors, the fact that they are either impedance protected, made with sufficiently thin laminations, or the inductance is too high to draw excessive harmonic currents means in general, there should be little problem.

Very large single phase motors use a centrifugal switch and startup caps. They will usually have lower inductances, draw more startup current, and will in general have thicker laminations which eddy more. I suspect it might be easier to kill the cap with a square wave high harmonic content excitation, and if the cap goes south for the winter, the motor will remain locked rotor.

Compressors for a/c's are definitely more severe at startup.

Your warnings are good advice.

One question though...what's a CRT??

(I give tours..I use the example of CRT's to show how even at home particle beams are deflected by magnets... Problem is, the students are aging out, less and less even know what it is..

jn

ps..ah, you added.. I was NOT lucky, I was skilled....make no mistake Had it blown up, that would of course been a result of bad luck despite my formidable skills...

Hey, my wife was a happy camper when she could take a hot shower..of course I'm gonna play it up...who wouldn't??.


I ran it for two days off and on, connecting it up whenever I wanted the hot water heater to cycle to completion. The inverter ran just fine, as did the heater.

As far as RFI, the extension cord I used was 12/3 with spiralled conductors. Not trying an AM radio, I've no idea how much the little unit broadcast. But a twisted cord will reduce field generation significantly, a parallel flat one is not good however.

j

Last edited by jneutron; 9th November 2012 at 04:44 PM.
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Old 9th November 2012, 04:37 PM   #17
freax is offline freax  Australia
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These might be of help to someone:
Lister CS slow speed cold start diesel generator** India
Lister CS cold start diesel generator LOVSON India

Whats a CRT? why its a cathode ray tube. A doohickey thats got a high vacuum though not as high as it used to be in the olden days, and this tube thingy has a doohickey in it called an electron gun, which spits out these things called electrons and accelerates them towards the front of the tube to strike a thing called phosphor, which when hit by this dancing little electrons light up like the dickens they do, like the dickens!

Then of course they went and ruined it by putting a grid thingy infront of this doohickey and called it a shadow mask, but I don't see no shadows in mine.

I'll sell you a few for a bob, I need to get my shoes shined.

I'll tell you a funny story for free, once my uncle was working on the back of one of these thingamabobsits and he put a hammer ontop of the set, don't ask me why a hammer was near a tv set he never said why, sure enough he went to grab his morning coffee and the hammer went plonk onto the back of the neck, next thing you know he's doing the upside down charleston as his chair and him is flung back from the fright of getting a face full of high speed glass and he nearly falls off the balcony of a 4 story apartment building.

Again, don't ask me why he was working on a tv set with a hammer ontop near the window of a balcony atop of a 4-story apartment building while drinking his morning coffee.

Yep, we a high flyer us bunch. And I'm off to bed, have yourself a good one
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Old 9th November 2012, 05:01 PM   #18
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The power is back on for us. I want to work out a good solution for this before the next time we lose power. I tried my 750 watt inverter and it seemed like it was going to work until the ignitor for the gas came on and blew a fuse. My old generator did not work the furnace, but I have to say that I could see a flickering in the lights and hear a lot of extra noise from the fish tank circulation pumps when using this generator. Maybe its at the end of it's life. I am looking to invest in a Honda inverter generator. The specs look good....clean power, quiet, and better on gas then what I have now. I will be converting the furnace from hard wired to plug in for ease of switching over when need too.
Thanks again for the help, Evan
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Old 9th November 2012, 05:39 PM   #19
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Again, don't ask me why he was working on a tv set with a hammer ontop near the window of a balcony atop of a 4-story apartment building while drinking his morning coffee.
Well, probably because he ran outta gin..

Cheers, jn
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Old 10th November 2012, 05:12 AM   #20
freax is offline freax  Australia
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The power is back on for us.
Just watched a story on the News Hour here (its 5:12PM here atm) Click the image to open in full size.

The power companies certianly had quite a bit of work cut out for them! Sparkies came in from all over the states to repair downed lines.

Makes me think about how big our thunderstorm season will be for this year, its beginning to start for us, from now until January.
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