Generators

[HeyBub]

[email to a blog (Instapundit) ]

Having enjoyed about one-third of our lives on generator power, we decided to enter the discussion.

I have more than 40 years experience in electric power generation for prime power applications (seagoing vessels, forward operating bases, field hospitals) and critical standby power (healthcare facilities, emergency services, credit card transactions).

My wife has invested a similar amount of time performing research at sea, and in remote locations, on generator power.

We met shortly after 9-11, and we watched the Pentagon smolder for several weeks.

Note to deniers: It really happened!

This e-mail is my contribution to the generator discussion.

First, to all those who want a cheap, convenient way to charge their cell phones and other portable electronics: every motor vehicle includes a one kilowatt (1kw) alternator for battery charging.

Some vehicles are slightly less (a skinny kilowatt) others are quite a bit more (2kw) but all vehicles have a battery charging alternator.

The best way to charge portable electronics is to idle your vehicle and use

12 volt DC chargers.

To charge your cell phone, you do not even need to start your vehicle. Just plug the cell phone charger into your vehicle and let it charge.

To charge larger items, start your vehicle and let it idle.

To operate larger items which require 120 volt AC power, such as your computer UPS, a drip coffee maker, or a small microwave, use a 1200 watt (1.2kw) inverter ? available everywhere for less than $100.

Most vehicles today will run a 1200 watt inverter indefinitely while idling, but you may need to turn on the air conditioner (which increases the engine idle) or turn up the idle speed (not legal ? do not do this) to make sure the alternator is putting out full power.

Also, the family minivan (or coupe, pickup truck, or SUV) is the best survival pod ever invented ? heat, air conditioning, lights, etc. You already own it, and the fuel to run it is negligible compared to buying, maintaining, and feeding a generator.

Even more important, you can drive the vehicle to a fuel point to refuel it, and charge the battery while driving to and from the fuel point.

If you need more power than your vehicle produces, then and only then, consider a generator.

We can discuss how to size a genset for home use, based on how many items you desire to run during a power outage, and how much fuel you are willing to store and consume.

You can use a portable generator, or install a standby generator.

Whatever you do, please follow all safety precautions with respect to electrical hazards, thermal hazards, and fume hazards.

If you use a portable generator, please use extension cords to power your loads ? do not energize your home wiring unless you have installed an Underwriters Laboratory (UL) listed transfer switch!

I will discuss transfer switches later in this article.

If you choose to install a standby generator, and you live in an urban, or dense suburban area, a propane (bottle gas) or natural gas (city gas) powered system is the most popular and cost effective way to go. It is also the quietest.

Note well: City gas is often shut off during natural disasters. Propane is stored on your property, and can be stored indefinitely.

If you live in a rural area, you can go with a propane or a diesel unit, or if you have a tractor, a pto-driven genset.

For almost all tractor owners, I recommend a pto-driven genset. If you buy a Winco, Onan, or similar high-quality pto-driven genset, you can pass it on to your grandchildren. It will never wear out.

The beauty of a pto-driven genset is that many tractor owners are already adept at maintaining their tractors. Also, you can always find someone to repair a tractor, or, if you really need to, you can buy another tractor, new or used, almost any time.

It is extremely important to have a generator big enough to start and run your rotating loads, and to hold frequency and voltage as near constant as possible.

All rotating loads ? well pump, pool pump, air conditioner/heat pump compressor and fan motor, refrigerator and freezer compressors and fan motors ? require 60 hz alternating current (AC) to operate at the correct, constant speed, and require full voltage (120 or 240 depending on the motor) to operate at the correct current under load.

Incorrect voltage, and incorrect or varying frequency, can lead to failure of rotating equipment.

Let me put that more plainly ? a badly regulated generator will burn up expensive motors!

Home electronics (tv, computer, etc.) are not as sensitive to voltage, and are relatively insensitive to frequency (they all have power supplies that convert AC to regulated DC) but they can be damaged by very low or high voltage.

Most important is your transfer switch.

After the transfer switch is installed, and inspected by your county building inspector, send a copy of the electrical inspection to your insurance agent ? 2 reasons:

1. Liability ? If anyone is ever injured or killed while working to restore power on your distribution grid, you will have proof that there is no way it was a backfeed from your generator.

1. Risk Reduction ? If you ever have an electrical fire in your house, you will have proof that the transfer switch was properly installed and inspected.

My advice is to install a 200 amp (or whatever size your home electrical service is) manual transfer switch.

That way you will be able to use any lights, anywhere in your house, including in your basement, regardless of whether you power your house with a 5kw or a 50kw genset.

I do not recommend an automatic transfer switch for home use.

You want to determine that the power really is out, and will be out for more than a few minutes (or hours).

You want to start your genset and make sure it is running right ? all engine gauges (oil pressure, battery voltage, coolant or cylinder temperature) and generator gauges (voltage, FREQUENCY, current) registering correctly, and then and only then transfer the load.

If the engine parameters are incorrect, you run the risk of destroying the engine. If the generator parameters are incorrect, you run the risk of destroying expensive items in your home.

Even if you never have a power outage, throw your transfer switch once a year to make sure it moves.

Also, open it once a year and blow out the insects. Leave a piece of no-pest strip or a livestock ear tag with pyrethrins in there to keep it insect free.

I recommend testing a home generator twice each month.

Just connect an electric stove or similar load to it, and run it under load for 30 minutes.

If you can start it and run it every 2 weeks, and it takes a full load, you can depend on it for a power outage when you transfer the house load using your manual transfer switch.

Takeaway ? Generating your own power during an outage requires serious investment in time and money, and significant fuel and maintenance expenses.

At present prices, we spend about $90/day for fuel and oil changes during extended power outages.

We can discuss this stuff further if you like.

We have a 200 amp transfer switch to transfer our house between the electric grid and generator power, and a second 100 amp transfer switch to transfer between main generator and auxiliaries. Main generator is a 15kw 1800 rpm diesel. Auxiliaries are 25kw Winco pto unit (more power than either of our tractors can provide, but superior motor starting capability), 8.5kw 3600 rpm gasoline powered welder, 3.5kw 3600 rpm gasoline powered welder, 2kw

1800 rpm continuous rated gasoline powered genset (perfect for overnight refrigeration and entertainment loads, if we don?t need heat or air conditioning).

[Vic Smith]

Good article, but the above needs checking out. Way too simplistic. I looked fairly hard at this when I was considering buying an inverter. A typical 100A alternator (I think the alt in my Lumina is 105A) won't put out nearly that much at idle, so you want to put a meter on your alternator to know what you're getting. From what I've seen alt amp ratings assume about 3000 rpm. You might get 2/3 of rating at idle. There's some inverter loss. High output alts are available for most cars, but it's an expense. Some car ECU's will limit alternator output to gain efficiency, so check that out. Inverters should to be wired correctly to the car's charging system right, with heavy gauge wire and lugs. Getting by with jumper cables might work, might not. You'll probably want to add permanent connects to the car. Good sine wave inverters cost more. No surprise there. Anyway, you have to check out all the factors to get a realistic assessment of what you can actually power continually. I liked the idea, and it's doable, but decided to just buy a couple extra flashlights and some more candles.

--Vic

[Han]

"HeyBub" wrote in news:wMednTF_Y4miJOTTnZ2dnUVZ [e-mail]:

Thanks for the informative and comprehensive post. The difficulties you point out have indeed prevented me from going forward with getting a gen set. That and the uncertainty what capacity I really need, e.g. should it be able to run my whole house A/C?

[Frank]

Decent post but not aimed at occasional needs that I have.

To test it by running under load for a half hour twice a month would be a PITA and use more gas than I usually use in a year.

Also if I ran mine full time, it would cost $900 to 1,200/month depending on price of gasoline. Not to even count oil changes specified every 25 hours. Plus, it is only big enough to power half my house.

I run mine every couple of months just to clear gas in carburetor and sometimes under load to run yard equipment.

[trader4]

[e-mail]:

You live in NJ, no? That's where I am and I wouldn't size a generator to run my central A/C. Only in the hurricane last month did I really even need a generator at all in the past 35 years. Power was out for 3 1/2 days. All other times, it's been out a few hours at most, except one other time when it was out for 24 hours. Also, around here, it's far more likely for power to be out for an extended period due to winter weather, eg an ice or snow storm, than it is to be out in summer.

Sizing it for the A/C means it's going to have to be a lot bigger, cost more, heavier, burns more fuel, etc. For my needs a portable unit, about 5 or 6KW that runs on natural gas appears to be the most cost effective solution. Seems you lose about 20% power when running on natural gas vs gasoline, so if you're converting one over you have to keep that in mind.

A neighbor had one of the whole house automatic Generac natural gas units which was capable of running his A/C. Paid $7K for it and it was about 5 years old. During the hurricane it ran for about 4 hours, then had a major failure in the gen section. It's totalled. He's buying another one. That seems like overkill too unless you have a situation where it's critical it automatically powers up without someone being there.

[Han]

Frank wrote in news:j5clt1$s3t$ [e-mail]:

Indeed. The bad, but not terrible outages we've had here have occurred about once a year the last 3 or so years. I'm not going to run a gasoline hog once a month just to make sure it'll work right. That's why I'm looking really only at NG or propane. As I said, my plans are fueled by fears that at some point in the future we'll be without power for days on end in the middle of winter. I know that is highly unlikely, since we are in a very densely populated area, but somewhat away from the flood- prone part of town. I expect PSE&G to re-connect us sooner than people out in the boonies.

[Han]

" [e-mail]" wrote in news: [e-mail]:

Yes, I live in Bergen county, a mile and a half east of the Home Deppot on the Passaic river, 75 McLean Blvd, Paterson, NJ 07514. The bridge there, and Rt 20, become impassable during flooding ...

[George]

innews:wMednTF_Y4miJOTTnZ2dnUVZ [e-mail]:

You might mention to your neighbor that Generac makes big box versions to meet their price point and better versions that are sold through generac dealers.

[Tony Miklos]

I heard new code calls for generator sizing dependent on full load for all circuits powered, and no allowance for rotating loads. Not hard wiring it in and using extension cords instead would be the only way around that. Don't know if it's true but that's "watt" I heard.

[RogerT]

Thanks for the comprehensive write-up. I printed it out and saved it.

I have a few very basic questions, if you don't mind my asking.

One is about the car inverter idea. Does that mean that I could buy a car inverter and use that to power an oil or gas fired home heating system during a power outage? -- and/or maybe a few lights and the refridgerator?

Another is about the possibility of buying a portable generator. I have been thinking about buying a portable gasoline generator like the ones that I see contractors using on job sites where there is no power. I don't know anything about them, but it seems like that would work as a way to power an oil or gas fired home heating system during a power outage, and/or maybe some lights and the fridge. I would have to look and see how much they cost and what size to get. Since it would be portable, I'm thinking I could bring it to wherever it may be needed during an outage (my home, my relative's home, etc). If I did that, could you suggest what size or type/brand to consider getting?

And, what does "pto" mean in the part you wrote about tractors etc?

Thanks.

HeyBub wrote:

[gfretwell]

That is only for generators with automatic transfer equipment that do not also have automatic load management. If you manually switch the generator on line they assume you can also do your own manual load management.

[Frank]

Lot of sites discuss this. Here's just one that I found when I looked up capacity of car inverters:

There are numerous sites that detail general wattage requirements for what you want to run and you also need to consider starting watt requirements. Generators will be sized for continuous and starting watts.

[HeyBub]

"PTO" = Power Take-Off. Think of it as an extension of the tractor's drive shaft.

Many attachements towed behind a tractor need power to do their thing, big rotating wheelie-looking gizmos, giant hedge-trimmer thingies, etc. Of course the attachment doesn't have to be towed; a sizeable water pump, for example, might be stationary. PTOs are (I think) fairly standardized so almost any brand of tow-behind (or stationary) whatcha-macallit will fit any tractor.

[Tony Miklos]

Ah! That makes sense. Thanks.

[bud--]

I know these generators exist. How do you regulate the frequency - just tractor RPM? Would think that wouldn't be very accurate or stable. They could generate DC and invert it - seems excessively complicated.

[RBM]

I think that the PTO on the tractors maintain a steady 540 RPM. If you needed 50 hz, you'd probably use a different generator. I don't know how quickly the tractor can make adjustments to the changing loads, as compared to the regulators on self-contained engine/generators

[dpb]

On 9/21/2011 3:08 PM, HeyBub wrote: ...

_Very_ much so...540 (6-spline) and 1000 (21-spline) rpm are US standards; virtually all larger tractors now have both as standard equipment (interchangeable spindles, not two separate drives); smaller utility tractors of the homeowner variety will generally be limited to

540 rpm.

--

[bud--]

How do you get variable land speed and constant PTO RPM?

[dpb]

On 9/28/2011 8:59 AM, bud-- wrote: ...

PTO RPM has nothing to do w/ ground speed--independent drive train gearing from that to axle drive shaft.

Older tractors (and a very few new/current inexpensive) did generate the PTO gearing off a transmission gearing such that PTO also free-wheeled when clutch was in. This is ok for light equipment but definitely not so much for present large equipment--the inertia there can continue to power the tractor and lead to real control issues. Modern tractors have "live" PTO that is fully independent of transmission clutching and is engaged/disengaged w/ a separate control (generally magnetic-controlled hand clutch lever altho have seen a few recent w/ just a push-button on the control panel).

To clarify, on those with both 540 and 1100 RPM the two speeds are obtained by physically interchanging the tractor external drive shaft in the same drive hub; the two stub spindles have different spline patterns on the drive side that match up internally to get the RPM, it is like two transmission speeds but by actually changing gearing by swapping spindles, not by an external shift mechanism like transmission. IOW, one operates at either/or, not selectable "on the fly". Any one piece of gear is designed for and only uses one or the other drive speed.

[dpb]

...

Well, nothing related outside the obvious that both are (for a given gear) directly proportional to engine RPM...for the pedants :)

--