Generator

[mm]

I guess that is your reward for being nice to her.

Folks with the same furnace arrangement you had?

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

[m Ransley]

Only inverter style gens have voltage dependant rpm. Your standard unit runs at 3600 a small unit may use 1/4 to 1/3 gallon on a light load of

400 watts for a furnace. Honda EU or a Yamaha inverter may only need 1200-1600 rpm to make 400 watts and get much better run time and much more engine life. Idle control on my unit only cuts no load run from 3600 to apx 3300 not much of a reduction.

[TheMightyAtlas]

Of course I meant 3750 watts!

[TheMightyAtlas]

Of course I meant 3750 watts!

[Tom Horne, Electrician]

RBM wrote: > Your furnace will run just like it normally does. You need to have an > electrician install a male plug at the furnace, connected to a single > pole double throw switch. In one position the furnace gets its power > from your electrical system, and in the other position it will get its > power from an extension cord plugged into your generator.

That male plug is called a flanged inlet. Best practice is to use a double pole double throw switch that switches the neutral as well as the hot conductor. That avoids grounding the neutral on the load side of the service disconnecting means. While your running off of the generator the Service disconnecting means is the generators main breaker. The generator will be grounded through the Equipment Grounding Conductor of the cord.

[L. M. Rappaport]

On Tue, 13 Dec 2005 21:31:41 -0500, mm wrote (with possible editing):

Actually that would be very rare. I've never seen one that does that, and I've used many of them. They usually run constantly at one of two speeds: 1800 rpm or 3600 rpm. That is necessary to maintain the 60 hz that they produce. They certainly use less fuel when no load is being drawn, but the speed remains the same. An alternator designed to run at 1800 rpm is more expensive than one designed to run at 3600, but typically the engine will last longer due to reduced wear.

We have an automatic 18kw diesel for backup here and I own a gas driven Honda used for construction. I've also used two Generacs and a few other gas driven models.

[Pop]

... : >Yes, but more slowly, right. Don't they have speed regulators that : >somewhat depend on the load. Cars use far less at idle than they do : >when moving the car. : : Actually that would be very rare. I've never seen one that does that, : and I've used many of them. They usually run constantly at one of two : speeds: 1800 rpm or 3600 rpm. That is necessary to maintain the 60 hz ...

No, not so rare. MANY generators idle during periods of no-load. Most generators around here do, including mine. If there is ANY load though, it jumps up to speed incredibly fast.

So, it depends on the particular generator design. A 5 gallon tank of gas can last me a day during power-outages IFF I only power the furnace & fridge. When they're all off, the generator drops to a fast idle and stays there. It still puts out 130Vac, but I have nothing to see the frequency with because my test equipment triggers it up to speed. Too lazy to drag out my scope to look at it. Just a 4W nightlight is enough to cause it to spring up to speed. As long as they're supplying any current though, they will definitely be at speed, and that speed is usually governed in some way to remain pretty stable; that's how they get the 60Hz frequency.

I've no experience with generators that vary motor speed with load, but I do know there are some - they've been discussed on various groups. So I don't know how those work. I suspect they're more DC systems than anything else.

HTH,

Pop

[BocesLib]

Errrr... Your having flashbacks to the old days...

Most modern UPS's either use a stepped wave (cheap ones) or the more expensive units do make a sine wave. These sine waves can be cleaner than what you get out of the power grid.

Think about it... The square wave would be a problem with transformers... In modern computers they ALL use transformers to convert the power down to 5v and 12v. They dont make UPS's to blow up computers, but to save them from power spikes and voltage dropouts. One side you can look at though is that square sine waves do their damage over the long periods of time. Almost any UPS can work well for a little while.

This makes me want to look at my APC ups now.... Geeez

[Chris Lewis]

According to Pop :

These generators tend to be slightly upscale (as in commercial grade) rather than the cheapos you see at HD. Usually not _big_ ones, because they're usually used in circumstances where you're always drawing power. The big ones often operate full time at 1800 RPM.

I recall reading about 3600->1800 or 1200 RPM idle step-downs on mid-range commercial Onans, Generacs and Hondas. It's advertised as a feature to make the generator last longer.

The idea being that the generator itself is much cheaper to make if it's operated at 3600 RPM (eg: most engines produce peak power near to

3600), but the wear level is considerably increased over 1200 or 1800 - hence the compromise of idling lower.

There's an analogous situation with electric motors. It's cheaper to make a 3600 RPM motor than an 1800 RPM one. But most applications need 1800 RPM rather than 3600 RPM, and the cost of gear/belt reduction of 3600RPM is more than the cost savings of 3600 over 1800. Hence, most motors are 1800 except with certain applications.

[Chris Lewis]

According to :

Errrr..... Virtually ALL modern computers use switching power supplies. Which is direct rectification of the AC to DC (at 160V), filtering, and then AC modulation at some high frequency (20Khz-60Khz or even higher) through a toroidal step down transformer, then rectification back to DC, filtering and regulation.

[The advantage to this is that the toroidal transformer can be very small at this frequency. At 60hz, a "normal" step down transformer at these power levels would weigh 20 pounds or more. In contrast, at 60Khz the toroid weighs well under a pound. The economics are such that these switching power supplies are vastly cheaper to build and smaller than "classical transformer" supplies]

These power supplies are fairly insensitive to line quality, and really don't mind square wave at all - in fact the high voltage filtering is much more effective.

What these power supplies (and ordinary transformers) intensely dislike is fast transients, or things that can cause them (eg: _very_ sharply square square waves lead to inductive spiking especially through ordinary transformers). These spikes tend to blow holes through transformer insulation or blow rectifiers and high-side capacitors.

"square sinewave" is an oxymoron ;-) The correct term is "modified squarewave".

[m Ransley]

Idle control on my 7500w generac is only from 3600 to 3250. You dont get much increase in life with that reduction. Idle is 6-800 rpm. Idle control must spool up to 3600 immediatly on demand of a draw so they cant allow them to really " idle" at 600. For long life a honda or Yamaha inverter style does better as it can run at 900 rpm generating, if minimal current is needed.

[Pop]

Huh? Are you addressing me? I suspect not because I have NO idea what you're talking about! ;-). Unless I got really mixed up, I haven't even seen a UPS mentioned in this thread.

Pop

[Pop]

Hmm, no big points to make, but a few comments inline:

"Chris Lewis" wrote in message news: [e-mail]... : According to Pop : : > ... ... : : > No, not so rare. MANY generators idle during periods of no-load. : > Most generators around here do, including mine. If there is ANY : > load though, it jumps up to speed incredibly fast. : : These generators tend to be slightly upscale (as in commercial grade) : rather than the cheapos you see at HD. Usually not _big_ ones, because : they're usually used in circumstances where you're always drawing power. : The big ones often operate full time at 1800 RPM. ===> lol, I have an upscale generator? First I've heard of it. It's a Coleman 5000W, one of their "Industrial" lines (not "Commercial"; industrial), a term they seemed to use for anything over 5kW & with all the receptacles, at the time I bought it, on sale, at Lowes. It cost almost a hundred less than the no-name

5.5kW sitting next to it, but it was the only one left. They seem to use the "industrial" on anyh of them that have the duplex receptacle plus a 3-wire and a 4-wire receptacle on the panels. To me, that would make it a "jobber's" generator, more than industrial. ;-) : : I recall reading about 3600->1800 or 1200 RPM idle step-downs on mid-range : commercial Onans, Generacs and Hondas. It's advertised as a feature : to make the generator last longer. : : The idea being that the generator itself is much cheaper to make if : it's operated at 3600 RPM (eg: most engines produce peak power near to : 3600), but the wear level is considerably increased over 1200 or 1800 - : hence the compromise of idling lower. : : There's an analogous situation with electric motors. It's cheaper : to make a 3600 RPM motor than an 1800 RPM one. But most applications : need 1800 RPM rather than 3600 RPM, and the cost of gear/belt reduction : of 3600RPM is more than the cost savings of 3600 over 1800. Hence, most : motors are 1800 except with certain applications. ===> Uhhh, I don't know about that. Besides, it's 1725 and 3450, not 1800 and 3600, right? With an electric motor, the application much more than the speed determines its life. Stresses on the bearings laterally and longitudinally, and % power output are much more the determining factors of the life of an electric motor. So it really only equates to load, not speed, with an electric motor. You have many more varaibles with a generator and I don't feel qualified to speak to any more than "intuition" and educated guesses about most things generator wise.

Are you implying that my idle speed is 1800? I really doubt that from the sound of the motor, but then again I do feel it's well over 600 rpm, but - that sounds pretty high.

You're really getting me curious now; guess I'll have to find a way to measure rpm's after all. I can't stand not knowing some things! ;-(. Up to now, I've figured 60Hz was the only number I'd bother with checking, but, well, curiousity and all that ... knowledge is power (who said that?).

Pop

: -- : Chris Lewis, Una confibula non set est : It's not just anyone who gets a Starship Cruiser class named after them.

[Chris Lewis]

According to Pop :

It may be a new line, or someone is trying to cash in on touting the "feature".

I don't know whether it's really idling at 1800, it's just the specs I've read for other generators spec it. The speed is effectively irrelevant, because it doesn't have to retain regulation. Just needs to be fast enough so that it doesn't hesitate and gets up to 3600 FAST. Yet another design compromise.

The 1725/3450 speeds are under rated load - sync slip. With no load it's 1800/3600.

If it's the motor alone, true, but it's the whole thing to consider with wear. And it's not that big a factor with electric.

Speed matters far more with internal combustion engine wear.

[Stormin Mormon]

Hmm. Since a 10 HP Tecumseh supplies about 5 KW, what would you need to run

3750 KW?

Typically generators will run with no load. And the thermostat is either battery, or powered from the furnace.

Are you having your 3750 KW generator delivered by semi trailer, and off loaded by crane?

[Stormin Mormon]

That would be some kind of battery!

[Stormin Mormon]

If oil won't burn without electricity, what are they doing at the refinery in England, at the moment? And how many watts did it take for Sadaam to burn his oil wells?

[Stormin Mormon]

Soudns like you have what I call an "octopus". Which some folks call a millipile generator gas valve furnace. Glad you had heat. Incidentally, get th at old energy hog replaced some time, you'll save enough on the gas bill to afford a generator.

Tongiht we are doing freezing rain in NYS. I'm wondering if we have a power cut in the near future. The octo across the street has a gas range, and has heated her kitchen with the range. While worrying silly about carbon monoxide.