Clean genertor power

[Stormin Mormon]

A friend of mine bought a generator from Harbor Freight. Enclosed was a warning about running "sensetive electronic equipment". The generator was for power cuts, to run the furnace (boiler with some kind of circuit board) and the microwave (about 1985 or so vintage).

He contacted the Harbor Freight guys, who didn't know how to tell if it was clean enough for a furnace. And contacted the local power company who also wasn't sure.

Anyone out there know? How can you tell if a generator is clean enough to run a furnace?

It's got me thinking, too. I ran my last furnace on a generator, but it was a Miller downflow furnace with nearly no electronics. The new Luxaire by York has circuit board. How to tell?

[Toller]

When I bought a new furnace a couple years ago the installer told me that they had 6 furnaces burnt out by generators during a recent power outage.

I wouldn't let a HF anywhere near mine. I suppose you could hook it up to an oscilloscope and check the waveform, but even then, who knows how consistant it will be.

[Bob]

Even the new Miller furnaces now come with a Honeywell electronic primary (safety) control. Try posting this on alt.hvac, one of them may know. (I know a couple of those guys are assholes - just kill file them.)

[SQLit]

You have provide little to no information to help. Would you call McDonalds for information about a Jack in the Box product?

If there is a notice about sensitive electronics then the generator might not produce a sine wave. Or the notice is there for CYA. Most generators bond the neutral to the frame to establish ground. This passes Oh Shit Wisconsin and the place in Illinois. When connecting a generator to a residential load with electronics. There arises several issues.

You might have to remove the bonding internally to the generator, AND CONNECT the generator to the house grounding. With out specific generator information and a tester I can not tell you what do to. Of course if you use the generator for anything else it IS UNSAFE. The micro wave will not really care, cause you have remove all grounding when you plug in the generator. The electronics on the furnace are different. The duct work can be grounded by proxy. If the generator and the furnace are NOT AT THE SAME POTENTIAL then there will be problems.

Start the unit up, put it on 50% load and get an o'scope and look at the sine wave. Watch the HZ as well. Any readings taken with out 50% load are BOGUS.

[m Ransley]

Simply use a volt meter to check swing of voltage from no load to full load, what they refer to is unregulated power that swings with rpm. 3600 rpm is 120v 60 hz, unreglulated or non voltage regulated gens of small hp can swing 50v-60v and 10+ - hz from no load to full load damaging sensitive equipment, Regular regulated usualy only 10-20v. Most gens you see were designed for job sites saws, bulbs etc before electronics were everywhere. A Honda EU series may only swing 2v, it has power quality of your utility. There are waveforn isues im not familiar with that probably also affect certain things. Your cheapest regulated gen avalaible may be apx 700 a Generac Exl 4000. Larger gens are more stable in total swing and many can be used for electronics but its up to you to check voltage and calibrate it for how you use it by setting rpm. Ive heard of new gens not being calibrated for 120v outputting 160-320 ruining a friends tv set up in 5 minutes. Its up to you to see that V and HZ are safe at no load and full load for what you plug into it. A cheaper unit may damage things by swings in voltage also. Cheap is for jobsites, AVR models cost more, but can also swing to much for all equipments saftey. For saftey get a Honda EU series, They have load dependant rpm, at low load their low rpm can make them last 10000+ hrs, vs 350 for a cheap B&S or techumpsee , and 1-5000 hrs for commercial grade 3600 rpm units . With gens you get what you pay for. Yamaha inverter type are equaly as good as Honda EU

[Stormin Mormon]

Thanks for the suggestion to post on alt.hvac, I'll include them in. Wow, you mean some of the folks at alt.hvac are impolite? I can't quite imagine that.

The Miller furnace in question was already installed when I moved in, 1994. I'm guessing the newer ones are electronic.

Thank you for good ideas.

[Stormin Mormon]

Would it make sense to use a three wire cord off the generator. Use a three wire appliance cord, and wire to the black, white, and bare wires off the furnace? (Wirenuts, temporary application)?

From what I could tell, the two generators were a gas engine spinning a magnetic field inside a coil, wh ich is the traditional way to make sine wave. Now, a mod sine inverter isn't sine wave, for sure.

[Bob]

If you have reversed polarity, a lot of the new heaters won't run.

[m Ransley]

Post to alt hvac , thats a joke. Start with proper procedure, does your unit require ground, and check it out , hook it up as it says. Coleman puts those warnings everywhere, im sure they lost a few court cases from damage. But seeing Harbor Freight is involved I bet its cheap in all respects. Go get an inverter type, Honda or Yamaha and quit playing games with jumk.

[Joseph Meehan]

I suggest you get a better generator and make sure it is set up so you can safely and legally use it. What you have is good for running a few lights, but I would not trust it for anything else. Oh yea, not florescent lights, only the regular ones.

[mm]

They're pretty much telling him the generator is mediocre, so I don't see the point in testing the generator. I think he should contact the maker of the furnace and get their opinion how sensitive it is. It's out of warranty, so they shouldn't be excessively cautious.

And their only motive for being excessively reckless would seem to me to be so that he would burn out his furnace and buy a new one from them. I don't think the chance of that -- esp. since he might buy another brand, is high enough to make anyone lie.

So I think they would give the best answer.they coudl. Maybe they could compare the electronics of his furnace with new ones, in terms of sensitivety.

Even my '79 Carrier furnace has a bit of electronics, maybe to control the timng of the fan, or to accept the lack-of-flame signal from the photocell. Don't know how sensitive it is, though.

Remove NOPSAM to email me. Please let me know if you have posted also.

[Mark]

I think SOME new generator designs actually use an inverter to make the AC. These might not put out a good sine wave.

With a standard generator I would think the only issue is how high the voltage may surge when you suddenlty go from full load to light load.

When the furnace kicks off, the heavy load is removed but the electronics are still connected and if the genny regulation is poor (or slow to respond) the voltage may rise for a short time. (It is bassically a mechnical governor after all)

Any GOOD electronics desgn should be able to tolerate a high line volatge surge. Lightning is gonna be worse than this. This is as much a statement about bad furnace electronics design as it is about bad genny's.

Mark