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Beth Stackpole
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A scary, but necessary appliance
Beth Stackpole   1/4/2012 6:26:20 AM
That's a pretty scary story, especially for a generator that appears to be pretty new. Despite the helping hand generators can provide, there are some pretty frightening complications if they don't run properly. I'm somewhat surprised that the manufacturer didn't buck up for a full replacement as opposed to simply just fixing the defective model. It would seem that would be a more economical and PR-friendly route than subjecting themselves to a potential lawsuit.

Rob Spiegel
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Re: A scary, but necessary appliance
Rob Spiegel   1/4/2012 10:58:34 AM
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I agree, Beth. If nothing else, you'd think the insurance company would try to hold the generator manufacturer responsible. I can understand the manufacturer wanting to avoid responsibility, but the insurance company ended up covering costs that were incurred by another company's screw-up.

trawickim
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Iron
Re: A scary, but necessary appliance
trawickim   1/16/2012 3:51:51 PM
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I installed an natural gas fired generator based on widespread power outage and how are gas stations going to get power to pump fuel out of storage tanks?

After selecting and installing my 12KW natural gas fueled generator, I tested it by loading down with appliances, lighting circuits, and base heaters. It work fine except for the CPU driven gas furnace which I could not get it going at all. The gas meter had reserve capacity when both furnace and generator is going so that was not an issue. (Note: Make sure that your gas meter does not starve your generator & furnace when running at full power. Check specs online.)  The CPU board kept on giving me fault codes. I checked the output voltages on it loaded and unloaded as well as frequency, and they were within reason. But why? I decided to put a scope on the output of the genset and saw that there was a considerable amount of hash on the sinewave.  I installed a small CVT just for the CPU power supply to clean things up and the furnace started right up. I suspect that the CPU used line frequency for clocking.

Lesson learned: If you decide on getting a nat. gas fired unit, make sure that all desired equipment work before you really need it. If you get a electrical contractor, make sure that he knows with factory training how to properly install generators, transfer switches, size gas meters, load testing, and be able to trouble shoot issues before you realy need it.

tekochip
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Platinum
Re: A scary, but necessary appliance
tekochip   7/17/2012 8:10:41 AM
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Every appliance I have ever just worked on used linecross, not just as a time base, but also as a "power good" signal.  At Power On Reset the code looks for linecross and measures a few cycles to see if it's 50 or 60Hz.  If it can't find a stable linecross then it keeps cycling around until it does.  When linecross is established the control expects to see it at regular intervals.  It's normal to miss a few from noise and minor power interruptions, but after a handful the appliance assumes that power has gone away and begins a shut-down sequence.
Normally linecross is very, very accurate and that's why it's relied upon by so many parts of the system.  Of course, a gas powered alternator may not provide a stable source, and that can bring the whole system to its knees.


Alexander Wolfe
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Re: A scary, but necessary appliance
Alexander Wolfe   1/4/2012 1:03:02 PM
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If the manufacturer was aware of the flaw, and it sounds from this description that they were, this was clearly a design defect (not only on the part of Troy-Bilt, but also the maker of the VR). I can only infer that time to market pressures are at the root of these kinds of disasters waiting to happen. Either that, or non-deterministic testing techniques and poor QA procedures.

BillyBob
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Iron
Generator Safety
BillyBob   1/4/2012 3:42:32 PM
I am shocked (no pun intended) that a person would wire low rent generator into their power panel using the main breaker to isolate it from the municipal power.  That is just plain stupid and quite frankly, can kill an unsuspecting power worker just as easily as an "unloaded" gun.  It is absolutely illegal and I am surprised that the insurance company paid and/or the generator manufacturer.

The poor man's way to isolate is to install a second distribution panel.

 [NOT SURE OF THE LEGAL STATUS OF THIS TYPE OF INSTALLATION)

Pull out the wires from the main panel of the circuits  that you want to run with the generator and put them on breakers in the secondary panel.  Then run a 220 30 Amp dryer or welder socket out of the main panel.  Put the matching 30 Amp pigtail on the secondary panel.

From the generator, run a cord with the same type socket that is on the main panel.

In this way, you will be required to unplug the secondary panel from the main power source and physically plug it into the generator extension cord and when the power comes back on, unplug from the generator and plug into the socket from the main power panel.  

With this physical isolation, there is no way you could ACCIDENTLY feed AC back into the grid potentially killing a neighbor or power worker coming into contact with a down 13.5 kV line that looks like it dead ends on your transformer hanging on the pole.

Of course, the best method is to have a CERTIFIED/LICENSED electrician install a transfer switch or at least sign off on the work that you did installing the transfer switch. 

Tim
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Re: Generator Safety
Tim   1/4/2012 7:46:34 PM
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The use of a certified electrician is great advice. I have heard of a few fires in VA due to improperly wired transfer boxes. I am surprised to hear of issues with a Troy Bilt generator. These are higher dollar and usually higher quality than others. Briggss and Stratton's quick response and payout does look like they knew of the issue and were looking to avoid potential litigation.

bob from maine
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Platinum
Generators
bob from maine   1/4/2012 9:43:51 AM
Most small portable generators have the output fixed by design such that the output voltage is a function of speed, there is no voltage regulator. If the generator overspeeds the output voltage will climb proportionately. While it's far from common, it is not that uncommon for a standby generator that sits for long periods to have the governor stick due to rust,  animal hair, or other debris that falls onto the throttle/governor. It happens to lawn mowers and snow blowers as well. Thank goodness for insurance.

Rob Spiegel
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Blogger
Re: Generators
Rob Spiegel   1/4/2012 11:18:47 AM
Wow, Bob from Maine. Sounds like blowing appliances due to the generator could happen often. I would think that would take quite a toll on insurance agencies. I'm surprised insurers don't exclude coverage for customers who use generators that don't have voltage regulators.

bob from maine
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Re: Generators
bob from maine   1/4/2012 3:37:12 PM
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Yes, I agree, and insurance claims are fairly frequent, though some subtrifuge may be called for in making the claim: "voltage surge  during recent power failure". At the risk of TMI; Most portable gensets are self excited using permanent magnets so the output voltage is a function of engine speed and current is limited by engine power. An excellent, inexpensive system which works - usually. The governor is a vane type which takes air from the engine flywheel which blows to cool the enigne, the pressure on the vane needs to overcome the governor spring which is designed to pull the throttle to wide-open. There are several pieces in this mechanism, any one of which can jam and prevent proper governor operation. If the generator is used outdoors (it usually is) rain can fall onto the spring and cause some or all of the coils to rust together, thus the vane cannot generate enough force to break the rust apart. Older engines seemed to have somewhat stronger springs of a larger wire size and the vanes were larger. Lawn mowers, snow blowers and other such machines have throttles which usualy create enough force to break the rust but generators are designed to run at a single speed so unless you have a good ear, you can't detect an engine overspeed. Moral is, don't put the generator away wet, as a rule, WD40 sprayed around the carburator will prevent the parts from rusting, keep a 60 or so watt trouble light plugged into the generator, if it blows out, don't turn on the house breakers.

VA Mech Eng
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Iron
Re: Generators
VA Mech Eng   1/4/2012 7:36:41 PM
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If you would like to know more about generators you should check out the yahoo group "AC generators".  But first I would like to dispell some misconceptions the commentors here have about small portable generators.  The author of the article said the voltage regulator failed, which I beleive.  Many of the new, small, gasoline powered portable generators use a circuit called an "AVR" or Automatic Voltage Regulator.  This circuit attempts to limit the voltage output by the generator to acceptable levels regardless of the engine speed (within certain limits of course).  The original use was to prevent voltage surges and spikes when the generator has sudden changes in loading (i.e. the refrigerator compressor turn on, or even when it turns off).  Small lightweight portable generators do not have enough rotating mass to maintain rpm during these changes in loading. Although the mechanical governor will eventually bring the speed back to normal (which in the case of the US will either be 1800 or 3600 rpm, usually the higher for small gasoline engines).  The AVR's job is to compensate for the voltage dip (upon loading) or rise (upon unloading) while the governor gets the engines speed back to normal.  It's a good idea in theory, the only problem is AVR's require capicitors to function, these capacitors are usually mounted on the roating part of the generator!  Even if the are mounted stationary, they are still subjected to the vibrations of the engine.  All capacitors will eventually fail, and those subjected to mechanical streses will fail much sooner.  When the caps fail the whole circuit is doomed.  This is the part that most likely failed on the author.  Most light duty residential type generators will fail within 1000 hrs running time even if maintained impecably.   

 

If the generator did in fact have a self exciting permanent magnet setup, then the only component used in it would be a rectifier consisting of 4 diodes.  This arrangement almost never fails.  This is the type of generator that I bought for my house, unfortunately unless you are buying a very large generator to power a commercial building you will not find one made in the US.  The one I bought is chinese, where they still realize that sometimes old and simple (self exciting) is better than new and high tech (AVR).  If your interested in knowing more about this look up the ST style generator heads found on utterpower.com.  If you do a search for ST generator on google you find a link to utterpower follow it and read about a simple robust generator.  My generator also uses a disel engine outfitted with a 80lb flywheel so there is almost no noticble change in engine speed (and therefore frequency and voltage) when the generator has a sudden load/unload event. 

Rob Spiegel
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Re: Generators
Rob Spiegel   1/5/2012 9:38:26 AM
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Connecting a light bulb to the generator is a great idea. Simple and effective. You would think this could be built into generators as the canary-in-the-coal-mine warning.


Amclaussen
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Platinum
B & S quality, a thing of the past...
Amclaussen   1/4/2012 9:53:52 AM
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Sadly, the quality of execution in recent products by old, previously good Brigs and Stratton is aparently going down... vertically.  Friends report me that their Pressure washer by Sears, powered by a Brigs and Stratton gas engine has given them a lot of trouble, in an otherwise "light" home use.  It appears that some parts in the carburetor now come in plastic, and do not perform adequately anymore.  I avoided it, and ended up purchasing a little more expensive Kärcher brand gas engine pressure washer, powered by Honda. so far, my unit always starts at first pull, works beautifully, and produces almost no odor in the exhaust. After some operating hours, the spark plug is very clean, and the exhaust hasn't a trace of soot. Overall, I'm happy with my purchase.  BTW: I've seen a much older 4-cycle Brigs and Stratton engine powering a firepump ina 25 year old building, and it stills works beautifully, proving that previously the quality was there. Amclaussen.

Jerry dycus
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Gold
Re: B & S quality, a thing of the past...
Jerry dycus   1/5/2012 9:35:46 AM
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  B+S makes good quality unit but you were too cheap to buy it, instead bought the cheapest thing you could then blame them?

Had you bought the better B+S grade that still costs less than a Honda, the most overpriced brand with parts costs so high you have to junk it when it does quit, you'd unlikely to have the problem. 

You get what you pay for.

Walt
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Gold
Re: B & S quality, a thing of the past...
Walt   1/5/2012 9:55:14 AM
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I've also had bad experiences with B&S engines that were not of the rugged old vintage.  After having the B&S V-twin engines of two Simplicity tractor/mowers self destruct (though well maintained), I've moved to Kohler...

I do still have an old push mower with a B&S that still runs great, but will be hesitant to buy a new one.

Bullsofchgo
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Re: B & S quality, a thing of the past...
Bullsofchgo   1/5/2012 10:18:32 AM
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I don't think the price of a particular model by a manufacturer should govern the quality and safety of a product. There should be some baseline for that regardless of the model. Generally there should only be enhancements and additional bells and whistles. Maybe the life of the product of say 5 years vs 10 years or something. Any company that does differently is only hurting their reputation and will end up on the trash heap of deceased companies.

dmpflumm
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Iron
Inexpensive Solution
dmpflumm   1/5/2012 10:59:51 AM
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A low cost panel meter that displayed the AC voltage for both the 110 & 220 VAC would have made the design more safe... not foolproof but more safe.

At the very least a warning lamp for over/under voltage conditions could be implemented relatively cheaply... but still not foolproof as the user would have to read the manual and be aware of it's indication.

Possibly the best solution would be to include a under/over voltage contactor, but this would add expenses to an already very competative market.

Ken E.
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Similar woes experienced.
Ken E.   1/5/2012 12:36:48 PM
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Yes, one has to know what they are doing when hooking these things up, but I expect I'd have done it the same way for my home.

As plant engineer, I was asked to install a fairly small (10kva) 120/240v/1Ø back-up generator and transfer switch for a small computer equipment room, which contained servers, network switches, and telecom equipment, most of which is UPS backed for the short term.  Even 'qualified' electricians can make mistakes, in this case misidentifying the generator ground lug as the neutral lug.  Without a neutral, when the two 120v loads are not balanced (and they never are) the voltage will go high on the least loaded side, low on the other.  We lost some minor equipment, similar to the case here.

But that was not the end of the problems.  Although the generator was 3x oversized for the connected load, we experienced problems with stability.  When a transfer to generator was made, all the UPS's saw the voltage and frequency return to 'normal', and they all switched on.  This caused the generator to suddenly load, slow down, voltage and frequency went outside acceptable range, all the UPS's turned off, then the whole chain of events repeated.  What I need is the 80 pound flywheel that another reader mentioned, but that's not an option at this point.  There were occasions when we did actually stabalize and everything ran, but the reliablility isn't up to snuff.  And every switch of any UPS change of state triggers an automated email!

A search of the net bore very little fruit, except to suggest oversizing the generator even more.

My next option is to add some timers and relay's to sequentially load the various equipment in three steps, reducing the load spikes to somewhere within the working envelope of the rotating inertia and regulation capacity available. 

My reputation has taken a quite a hit with our I.T. department, they are suggesting they should have had it done 'by a professional', which up till now I had considered myself.  Yeesh!

Ken

 

Rob Spiegel
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Re: Similar woes experienced.
Rob Spiegel   1/5/2012 12:45:21 PM
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Hi Ken,

This is a good story. I'd like to use it as a Sherlock Ohms posting. Is there an end to this story? Sounds like it's close.

Could you send me permission to use the story? Also, I would need a short bio (three or four sentences).

Send to: rob.spiegel@ubm.com

Ann R. Thryft
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Re: Similar woes experienced.
Ann R. Thryft   1/5/2012 12:50:15 PM
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Wow, sure glad I read this MBM and especially all the comments. We are looking into various power supply, marine battery and inverter combinations to deal with the occasional power outage here in the redwood forest. Since our main purpose is to keep computers going, and for other reasons, generators aren't always the best option. Their power is usually too dirty for computers, mostly, as I understand it, because of that lack of voltage regulation. But this instance really takes the cake. Sounds like more lousy quality control, or rather, a lack of QC. 


Ken E.
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Re: Similar woes experienced.
Ken E.   1/5/2012 3:53:41 PM
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Ann, you are right to be worried, yet generators do computer back-up all the time, all the way up to huge units on big server farms.  The simplest way to cya, is to oversize considerably, say 5x expected load.  This essentially adds enough rotating inertia to ride through power consumption surges, and it also tends to get you into a bigger generator with more sophisticated controls.  I spoke to several generator installation 'professionals' who had experienced pains identical to mine, and that's their general work-around.

In your situation, i.e. a remote area, where you may be using the generator to power other equipment as well as electronics, the 5x number refers only to the electronics, particularly the UPS's, which may be switching groups of equipment. I did another back-up generator that supports a call center plus I.T. equipment, and the I.T. equipment was a small enough percentage of the total, that a generator only 2x the connected load worked without a hitch.

If you really want clean power, spring for a Constant Voltage Transformer between the generator and electronics.  They are pricey, but very effective, reliable passive devices, offering very clean power output, no matter the trashy input you apply.

Good Luck, Ken

Ann R. Thryft
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Blogger
Re: Similar woes experienced.
Ann R. Thryft   1/6/2012 12:09:12 PM
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Ken, thanks for the detailed feedback--it's very helpful. I know computers run off generators, the problem is how to do it at home with usually lower-end, non-server-farm-quality equipment, especially when running other stuff off the generator, as you point out. We will check out the CVT--sounds like just what we need.


bdcst
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Platinum
Re: Similar woes experienced.
bdcst   1/11/2012 3:57:44 PM
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CVT's typically are power hogs as they run at full saturation with 60Hz resonant windings.  They can run hot and add a lot of acoustic noise.  But they do the the job well of isolating output powe from line transients.  Just remember that there are two types.  One delivers fairly dirty distorted AC while the other provides a fairly clean sine wave.

A fairly new technology in inexpensive standby power is the gasolene driven DC generator/AC inverter combination.  Honda has several models.  The inverter produces a true clean 60 Hz sine wave without regard to generator speed!  And that's the key.  The motor can idle when the energy demand is low and yet the generator will still put out 120 VAC at 60Hz.

Honda has lightweight 1-2 kW had carried generators up to a dolly mounted 6 kW 120/230 VAC model that'll also run your well pump using the same inverter technology.

There are also a bunch of far less expensive versions now on the market though I'm not sure about ultimate quality and reliability.

I assume the Honda inverter circuitry has built in regulation control and fail safe shut-down.  It does control motor throttle when it needs more energy from the DC generator/alternator.  At any rate it kept my fridge cold, my home entertainment center running, computers and Internet working and my ham station on the air during hurricane Irene with no smoke emitted.

cvandewater
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Re: Similar woes experienced.
cvandewater   1/11/2012 11:13:16 AM
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@Ken E:

Typically in a setup for a computer room, the generator does not feed the loads directly, but the genset (as well as the incoming grid) power the UPS'es which will provide uninterrupted power to the computer equipment.

So, a bad genset connection will fry UPS'es (and other non-critical loads that are on raw power, such as lights) but should not affect the computers.

Regarding the load transfer of the UPS'es: indeed, if all UPS'es are of the same brand and type then they are likely to all detect good power at the same moment and according to Murphy, go for the maximum damage (all switch for max load and battery charging at the same moment, to increase the results of their synchronization).

What I would suggest is to review the voltage and frequency limits that the UPS'es accept - often they are set very critical to make the UPS'es look like they are needed a lot, while they can actually work with a much larger variation of voltage and frequency.

If the delay of the individual UPS'es to "jump" on the generator cannot be staggered to spread the load changes, then I suggest to configure the individual UPS'es with slightly different parameters when they consider power "good" again, so they will switch at different times. For example if power is nominally 230 +/- 10% then set 4 UPS'es to 207; 208; 209 and 210V so they likely will sequence their switch from battery backup to generator accordingly. Also try to set the frequency they accept as wide as possible so they don't trip off when another UPS is jumping on the genset, or you get an instable system as you have experienced. Success.

bdcst
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When is an UPS not an UPS? Answer: often!
bdcst   1/11/2012 4:16:42 PM
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I hate what the industry calls an "UPS", uninteruptable power system as most are not truly uninterruptable and should be instead be called an SPS (standby power system).  These so called UPS's are line interactive devices lying in wait to pounce on a loss of a couple of cycles of AC power and fire up their inverters whilst switching the load from the power line to the inverter's output.  This does not happen instantaneously.  The result is a glitch to the equipment being protected.  Depending upon the energy storage capacity of the protected equipment's own power supplies this might be acceptable, or not!

I've seen too many instances where "Smart" UPS's, (without naming names :-), fail to switch rapidly enough if at all when a power loss isn't a draconian cut but rather a slow brown-out to nothing.  Then there are the units that auto test their batteries weekly by switching the load to the inverter for a few seconds.  Some of these have been responsible for odd seemingly random equipment lockups.  Worse yet is the test that fails due to a battery with a shorted cell such that the DC power drops low enough to cause the controller to lose it memory of the failed test.  So, the bad battery indicator light doesn't stay on long enough to warn you that a test in your absence had failed!  How smart is that?

I've been replacing all of my so called UPS's with true double conversion units which are always powering the load from its batteries and inverter.  The one big drawback might be MTBF for the inverter since its always running.  But the benefit is truly uninterruptable power that is fully isolated from power line transients.  In addition I specify external automatic bypass switches to restore power around a failed UPS and to permit routine swapping of UPS's without having to power down critical loads.

Ann R. Thryft
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Re: When is an UPS not an UPS? Answer: often!
Ann R. Thryft   1/13/2012 12:25:40 PM
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bob from maine, we've looked at UPS in the past and the ones we saw are insanely expensive and don't last long enough for the home user who only needs an occasional 1-2 days during a power outage. The ones targeting clean computer power, at least what we have found, are also hard to buy. Meaning, if you're not a specialist in power, trying to translate all the terminology into the features and specs *you* want is too big of a headache. The buyer should not be having to do so much work! I'm surprised that an industry that's been around this long, selling stuff to non-techie consumers for this length of time, is so bad at communicating well enough for potential buyers to buy something. Even though I used to work in high-end UPS 30 years ago in marketing, my eyes glaze over and my mind goes blank every time a salesman starts talking to me about joules.

bdcst, thanks for the redefinition--I agree. Yet more reasons why we stopped looking at "UPS."


cvandewater
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Re: When is an UPS not an UPS? Answer: often!
cvandewater   1/13/2012 2:48:33 PM
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I often get frustrated at the clumsiness of the industry, just like Ann indicates - why can't you simply buy a true UPS/backup/genset unit that does exactly what it says and why do you have to piece a system together to do what should be a standard solution?

I have considered for a while now to start a new company to produce a product that I have been toying with for some years. In essence it would be the solution to all these questions: a simple unit that will always generate 100% clean sine-wave power from a large backup battery (at least 1 hour nominal power storage) so there is never a problem with compatibility or glitches on the output power.

This unit is not intended to be installed inside an air conditioned data center, but this unit will include a backup generator, in fact I want to integrate everything in the housing of a backup genset, so that you avoid buying two independent units (generator and UPS) and need to install and maintain all kinds of transfer switches and generator start signaling from grid power failure - everything should be integrated, power can be drawn from the grid when available (double conversion!) to charge the battery bank, but also solar or wind or other locally generated power in addition to the genset, such that the genset only needs to power up if all else fails and the battery energy level gets low - then the batteries can be charged at the optimal load level of the generator so that its efficiency and run time are optimized.

This means that the genset will run as little as possible (Where I spend most my time in India, rotating power outages typically last 1 hour, so the battery pack will carry the UPS through this and the grid will typically come back to recharge the battery bank before it is depleted) and solar or other RE can minimize the use of fuel which reduces pollution, spending on fuel purchase and transport and maintenance of the generator.

Another application of the double conversion with battery backup technology is in grid storage devices, where they can be installed in homes that are on a weak branch of the grid, so when it needs some help (usually in the afternoon) then the grid storage unit will start pumping power back into the grid. The higher sale price of afternoon power versus nightly recharge can easily offset the cost-price of the unit. Large benefit to the home where such a device is installed is that in case of a power outage, the unit can isolate itself from the grid and start power the home as UPS for a very long period (typically a day). In addition to these benefits is the avoided cost for the power company, who does not need to upgrade the transformer(s) and may be willing to pay for the installation of such grid storage devices.

The technology is not essentially different between these two different applications of a double conversion unit and incidentally the same technology can even be found in the electric truck that I have driven for several years, which was equipped with a grid-interactive inverter for both charging and V2G (Vehicle to Grid) capability. Typical power levels of electric vehicles are around 200kW which is also an interesting power level for data centers and a lot of other applications, but the power is easy to scale down (for example 10kW) or up. Battery technology today allows lifecycles of up to 10 years of daily cycling and inverter technology does *not* have a fixed MTBF, in other words: if the product needs to run continuous for 10 years then you can design the electronics to have long life, it is a design trade-off, not a fixed parameter of the equipment! The cost price is typically below $1/W and below $1/Wh.  Let me know if you are interested in such products.

Ann R. Thryft
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Re: When is an UPS not an UPS? Answer: often!
Ann R. Thryft   1/17/2012 3:47:42 PM
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I'm very curious to see what others think about cvandewater's proposal to help non-specialist people like us not have to go through the piecing together process. However, my concern is that our situation sounds like a pretty different one from the first application. Our outages tend to last 1-3 days.

I do like cvandewater's second application, the grid storage one that isolates us from the grid and pumps power back in. We're not technically on a weak part of the grid, but we're at the end of a section, such that when the power goes out 20 miles away in a totally different community so does ours. But we would need it to potentially last as long as 3 days, possibly 4.

Another thing: One big need we have in the quiet country is quiet generators. That's one of the several reasons we haven't gotten one, aside from 1) expense and 2) stealability in our location. Surely they can be engineered to be quieter?


cvandewater
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Re: When is an UPS not an UPS? Answer: often!
cvandewater   1/17/2012 4:37:39 PM
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Ann,

The time that a battery backup lasts is a design parameter - reduce your loads and the backup lasts longer (don't light up the whole house, just the rooms that are used) or invest in a larger battery and the backup lasts longer. Or use a genset to recharge the bank and you have virtually unlimited run time. The min 1 hour battery backup is just another choice to minimize generator run time - when it can recharge the battery to >80% in 1/2 hour then it only needs to run 1/3 of the time.

Of course gensets can be made low noise - again another design choice. Most people accept a noisy genset and they are cheap to make, so that is what the majority of the manufacturers deliver, else they are forced in the small niche for expensive high quality, low noise gensets, which typically are only used a few hours or days every couple years.

Ann R. Thryft
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Re: When is an UPS not an UPS? Answer: often!
Ann R. Thryft   1/18/2012 11:45:29 AM
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I was afraid someone would tell me that, cvandewater. I mean the fact that we've got to always pay way up at the Rolls Royce end for features that, it seems to me, should be the default in all models and price points, in this case, quiet operation.


shadow1701
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Re: When is an UPS not an UPS? Answer: often!
shadow1701   7/15/2012 11:08:56 PM
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I did a professional instalation of a manual transfer switch, even before I got my residential electrical contrator license.  I have a Honda 2500 W generator.  To set up a "legal" manual switch-over, you can get various kinds of mechanical interlocks so you don't even need a subpanel.  There are interlocks that make the main breaker mutually exclusive with on of the side breakers at the top of the breaker box, where the generator is connected.  I used a subpanel (main lugs box) with two interlocked side breakers.  Now this does not solve the problem for sophisticated computers and home entertainment.

In my working days, I was a hardware AND software guy building process control interfaces and occasionly fixing minicomputers.  It seems like there is a market for this kind of engineering even in the home market, or serious work-at-hme situation.  I am making note of this since I am a retired engineer (No PE unfortunately).  In many cases, it would appear to need two subpanels--one with an electromechical (manual or automatic) switch-over for the furnace, fridge, and sump pump, with another one connected to the double-conversion UPS, perhaps with extra batteries for computers and serious home entertainment centers.

As y'all have noticed, there are UPS's, Inverters, and crap.  Many hardware store Inverters are "Modified Square Wave" which means that the waveform is 0,+,0,-,0,+,0... [only three stair steps] which is OK for motors and resistance heat including incondesant light bulbs.  Haven't tried one with CFLs; I use the Honda.  BTW my Honda has a voltmeter and a voltage knob--you can set it for 100 volts (Japan Standard) or 120 volts (USA), and it is very quiet.  I run the essentials of a four bedroom house with it.

Thank you for the discussion, I have gotten some more ideas for my retirement work as an electrician.

 

 

Ken E.
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Gold
Re: Similar woes experienced.
Ken E.   1/13/2012 12:47:35 PM
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Sorry, I gave Ann some bad advice I want to correct.  Constant voltage transformers use 'ferroresonent technology', a phrase which nagged at me.  In checking it out, they in fact use resonance at exactly 60Hz as part of the control scheme.  A generator may vary output frequency significantly for variable loads resulting in poor performance, thus generators are not a good match for these power conditioners.

After confirming this with Sola/Hevi-Duty tech support, they recommended 'double conversion' UPS's for mission critical electronics with standby generators.  These, as I understand it, eliminate any 'switch' between line power and battery, instead the output inverter runs continuously on the battery supply voltage, and the incoming power only charges the battery.  Somehwere in the description of a UPS you are interested in, you might also look for 'compatible with generators', before purchase.

We also did a bit of experimenting in my plant, and found that sequenced power-ups seem to have eliminated our instability problems.  (We tested by hand, and will automate it shortly.  We also did everything we could with software in the UPS's to reduce sensitivity to volts and frequency, as cvandewater suggested.

Appended are links to a couple of technical white papers from Cummins. The first may make you despair of ever using a generator with a UPS, but take heart, and go for it with eyes wide open.  The second one has some mild contradictions with the first, but both are the best reads I found, if you are trying to spec a back-up generator for electronics.

http://www.cumminspower.com/www/literature/technicalpapers/PT-6014-genset-ups-compatibility-en.pdf

http://www.cumminspower.com/www/literature/technicalpapers/PT-7007-SizingGensets-en.pdf

Ann R. Thryft
User Rank
Blogger
Re: Similar woes experienced.
Ann R. Thryft   1/17/2012 12:10:45 PM
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Ken, thanks for the correx. My electrically-inclined husband is tackling the white papers.

I find it ironic that we are learning more in a few (though highly detailed--thanks again!) posts from the commenters on this article than we ever did reading company literature and/or talking to salespeople of inverters, UPS, etc. We're not just learning about "products," which we don't really care about anyway, but solutions, and even more important, figuring out how to determine what to get for what we need. That initial figuring out is the 101 and pre-101 info we can't seem to find anywhere else.


robatnorcross
User Rank
Gold
MECHANICAL GOVERNORS...
robatnorcross   1/5/2012 5:33:59 PM
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I figured "engineers" would know better than this. "Homeowner" type generators use the same type mechanical governor that's on your LAWNMOWER. These things barely run power tools within their limits. Most are self excited with diodes used in the armature and only produce 120V at 60 Hz if your lucky on a good day. Larger (spelled more expensive) units have electronic controls that control the throttle to regulate the frequency. Another circuit is needed to regulate the voltage by changing the excitation.

VA Mech Eng
User Rank
Iron
Re: MECHANICAL GOVERNORS...
VA Mech Eng   1/5/2012 7:34:25 PM
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Rob,

 

Go to the 2nd page of comments and read my remarks. In short, there is nothign wrong with mechanical governors and self exciting windings.  I actually prefer them, and is what I have on my home back up generator.  You do need to make sure that the two are designed to work with each other first though.  I work at a VA hospital and almost none of our generators (and we have something like 15 of them) have electronic controls to control their speed. Most of our generators are between 10 and 40 years old and work just fine to back up even our entire IT department!

Rob Spiegel
User Rank
Blogger
Re: MECHANICAL GOVERNORS...
Rob Spiegel   1/6/2012 11:01:44 AM
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Interesting, VA Mech Eng. I would imagine you have a lot riding on your generators, since life-sustaining medical equipment would depend on the generators during a power failure. Have you received any concerns about the quality of the power from the generator? I would imagine both IT and the medical equipment team would need some reassurance. 

mechantronic101
User Rank
Iron
An off the shelf over/under voltage relay can help protect
mechantronic101   1/6/2012 1:31:40 PM
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Something like the magnecraft 831VS-120A and a contactor or breaker with shunt trip as a disconnect could have prevented the damage.

Grainger has them for less than $70.

 

 

William K.
User Rank
Platinum
Generator Fries appliances
William K.   1/6/2012 7:06:07 PM
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I am amazed that anybody would connect a generator without first checking the output voltage. Universal-motor appliances will work well with anywhere between 80m and 140 volts, and any noisy waveform that you can imagine. The ultimate protection is indeed a "constant voltage" transformer of the resonant-saturated-core type. Not only do they hold the voltage fairly constant, they also stop some of the generator harmonics. Unfortunately they demand that the frequency be held very close to the design target value. Also, they are fairly expensive, and not "wonderfully efficient". 

Another option would be to use a good quality DC powered inverter and have a generator charging batteries to power the inverter. THat would be a lot more complicated, but it would have the big advantage of not needing to run the generator constantly. IN addition, using an automotive style regulated charging system and commecially available inverters allows a great deal of flexibility, and the option of switching to backup power with very little effort. In fact, using the DC charging system to hold up UPS batteries could be a very cost effective system that would also avoid the need for a large transfer switch. The main downside to this approach would be the need for heavier conductor wiring to the various UPS packages.

dougspair
User Rank
Gold
Generator/s
dougspair   1/10/2012 11:15:35 PM
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..Interesting, as just recently I converted a motor-home type generator to stationary/portable use for my brother, who lives in a remote area subject to outages.

  The unit is a 5KW Onan..2 cyl opposed gasoline. Fairly decent sine-wave output from 4-pole wound stator and slip-ring rotor. The speed control is a mechanical unit on camshaft..appears to maintain 2-3% @ 1,800 RPM. No electronics in this unit to fail. Small fluctuations in speed affect frequency much more than the output voltage.

  The output is 2, 120 volt windings that can be connected at junction box, to series or parallel..50 amps @120, 25 amps @240. The output/s are through 2 30 amp circuit breakers. The generator ground (green) is not connected to the neutral. The two slip-ring 120 rotor outputs are completely isolated from each other, or the frame ground. The start winding is a heavy copper, brushed commutator, on the same rotor as the 120 output, and that start winding is also used to generate the rotating field current. A relay works from the oil pressure, to switch this winding from 'start' to 'run'.  

  I'd guess some of the...um...low-cost units would use a (permanent magnet?) alternator for the generator, and 'speed control' maybe just by adding some load, or the cooling air-vane flap attached to the carb..?..?

bob from maine
User Rank
Platinum
Stand-by power
bob from maine   1/11/2012 1:03:24 PM
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I've installed back-up power for public safety departments and the best way to absolutely guarantee power never, ever goes down is to install a high-end battery powered UPS which powers the radios and computers all the time, the batteries are charged from whatever power comes into the building; the UPS output is sine-wave, voltage and frequency regulated. Generator output power quality is typically directly proportional to cost. A good 4 pole 1800 RPM generator that is electronically governed/regulated and provides noise-free AC costs up to 10X a (relatively) cheap 3600 RPM 2 pole portable generator. If you want good, clean, uninterruptable, reliable power, go to a professional, talk it over and evaluate your options. Inverters, batteries, wind or solar or diesel or gasoline, flywheel/motor/generator sets all are designed to meet a particular end-user need. Single and dual cylinder Briggs, Honda, Kohler, Kawasaki (etc.) engines are providing excellent, relibable power (when maintained) for 1500 to 10,000 hours with no issues, diesel engines frequently run for 12 to 15,000 hours between overhauls. You pretty much get what you pay for.

Jack Rupert, PE
User Rank
Platinum
Testing
Jack Rupert, PE   1/22/2012 2:27:33 PM
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I guess that means another item to add to my test list.  I have a Generac generator which I usually run at idle about once month or so, just to make sure it starts in the case of an emergency.  I never thought to actually test the output.  During the summer, I'll plug the edger into it during the test, just so I can get some useful work out of it.  Unfortunately, that might not be enough to find the problem described here, since it is a different plug that goes into the house.

SethDesmarais1
User Rank
Iron
precautionary
SethDesmarais1   7/25/2013 5:02:52 PM
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thanks for the tragedy.. there thould be a breaker or fuse installed in the generator to cut off the output supply when it crosses the desired limit, i dont know why it did not stop it and fries your applianes.. is there was a fault in the generator or something else.. anyway thanks for the post, and i will use the generator after a long time before check the outpout supply .


ac & heating



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