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Generator Realities For the guy who doesn't want to learn any thing about a generator or he simply doesn't have time to learn, the following happens more than you would think. One of my friends bought a new diesel pusher motor home with a nice complicated name brand generator that burnt up two expensive control boards in the first year and a half of ownership. see footnote The following is what happened to one guy who wrote me 5/2010.. I can tell he is a smart guy, and had he made time to get a manual for this generator set I think he could have made a few simple checks on his own and determined the trouble. He's just wasn't aware of what a lot of repair shops will do to you if you let them.. Here's snippets from the emails during our conversation.. What I am looking for is an economical replacement for the 7.8KW Power Tech brand generator head on my RV. I just got the unit back after spending way too much money to be told that the Kubota diesel is fine but the rotor and stator are bad and I need a new generator head to the tune of $1800 to $2300 plus labor. At that point, I decided to get smart and do it myself plus, I like the KISS principle. I was curious how he was treated by the repair shop, and Jay was kind enough to share the following with me when I asked for more detail. LOL.
They first threw a new regulator at it to the tune of nearly $400 including
overnight shipping and then when that didn't work, they determined that they had
to pull the whole generator unit out from under the coach. That took about 3
hours. After ohming it out and talking to the manufacturer in Florida, they
ended up charging me for a total of 6.5 hours of labor (included installing the
regulator, pulling it out, and "diagnosing" it) @ $110/hour plus the regulator
for a total of about $1150. All that got me was a non-working generator sitting
in the back of my pickup and a new regulator. To top it off, they told me that
this was an older brush-style generator and when took it apart, it turned out to
be an exciter type so I'm not necessarily taking their word as to what is wrong
with it either. They've quoted me about $2300 for a new 10KW generator head
plus $1100 labor to get it back in and running and that doesn't include
servicing the engine end. I've found an electric motor rewinding shop that said
they'd diagnose the rotor and stator for $30 once I have it apart so I may do
that just to see what's really wrong. It's very typical for these RV shops to hire less than a good generator tech. Here's some advice if you are stuck with an expensive and complicated generator set. Call the generator manufacturer and ask them who is qualified to work on your generator set! Ask them if they sell a manual for the unit. After you've read Jay's story you can see the value of paying money for a good manual and doing a little arm chair reading about it. An average tech should have proved the gen stator and rotor good or bad in 15 minutes. Looks to me like they had a less skilled guy do the work and they charged $110 an hour while they attempted to learn the gen set. Jay said they even had the wrong wiring diagram for his Generator! 6/11/2010 I heard from Jay, he took both rotor and stator into the rewind shop and they could find no fault with either part! Jay put the generator back together and mounted it up to the engine, he called the generator manufacturer and they were most attentive to his problem and guided him through some tests that proved the exciter, rotor, stator and more were good! Later they guided him through a Voltage Regulator adjustment and he has a proper output at no load.. more testing to be done, but I bet he is fine. One thing to note here when and IF you are buying a new or used Motor Home, there were a lot of companies that built Motor homes with near zero concern or consideration as to how an owner or repairman would gain access for repairs. If we analyze what went on here, the customer paid the RV repairmen a good chunk of money to gain access to the unit. Had the Coach Builder designed it even half way right, there would be access to test points to prove the gen head good or bad, and access to replace a bad VR, generator starter and solenoid etc. Certainly their diagnosis was bad.. but a large portion of the labor was spent in gaining access. Hats off to the generator head manufacturer for supporting the owner! If you buy a motor coach slapped together with little access, Murphy guarantees you'll need access soon! 7/2/2010 I received a nice email from Jay today. Good Evening George, His comment about the PMG? Jay had originally asked about a replacement for his generator head that was pronounced dead by a RV Shop Repairman. I knew there was a fair chance his gen head was just fine, and it would have been unethical to sell him anything without encouraging him to get a competent generator guy to look at the stator and rotor. I believe Jay's story is far more typical than we would like to think. The more you know about your own equipment, the better off you are. One last note....if you don't own a 'kill A Watt' why not? I remember trying to run a pellet stove with a small generator during a power outage (years ago). It wasn't long and the combustion chamber scooted up and stove just didn't run right. Later I checked the frequency with an old reed type instrument and found it to be running at 55hz, and low voltage of course. The control board was expecting 60hz, I think the sine wave was the basis for timing as per other functions the board controlled as well. The combustion fan was powered by an induction motor, and of course it was running off 55hz and NOT providing the combustion air the stove needed. Had I had a $20 kill_A_Watt I would have whipped out a screw driver and adjusted the governor. On this particular unit, I ended up drilling a hole in the plastic side cover to insert a screw driver into the governor adjustment. As a final note: Jay is a DIYer, we can see from his last email message he is a busy man and decided to rely on others to do the basic trouble shooting... the more complex the generator is, the more likely you are to involve others in the repair process. Jay has problem solving skills.. Just imagine how much more he would have paid if he didn't have the DIYer background. We are now the minority, most Thirtyish men barely know where the oil fill is under the hood of their own cars...no matter how challenged you are, the KillAWatt and an access point between the PMG and breaker would have given you all the information you needed. The engine either runs or it doesn't, the generator either spins or it doesn't. --------------------- If you look at the PMG testing, you can see that you can prove it good or bad in a few minutes even if you can't spell lectricity. Most are not aware that there is a high end generator set available (called an APU) that uses a PMG, it sells for about $7000 and is used in a mission critical application where conventional smaller generators are considered too failure prone. Building your own PMG is a possibility if you have the basic skills.. read on. Once you've reached some level of maturity in your thinking, you'll wonder how the term 'whole house generator' was ever phrased? One quickly realizes that you manage loads, you don't buy a huge generator just in case you want to run everything at once. There is seldom a reason to run your two largest loads at the same time and you can set up a simple relay to assure that you strip one load automatically before the other starts. It all boils down to efficiency, running a 15KW generator at 10% load will quickly break the fuel bank, and of course the initial cash layout of the generator will be significant. Lots of people learn that having too big of generator is a 'big' problem. People with experience know they must have a generator that can >Start< their largest load. They Also understand that it takes a lot more power to start some loads than it does to run them, so they factor this. People with well pumps often make their generator purchase based on what it takes to start and run their well pump. In North America, most people have a one horse power submersible Pump or something easier to start like a 1/2 HP surface mounted jet pump. If you have too small of generator, you can damage the pump. Going by the name plate rating of the generator is not always a good idea, some generators rated at 5kw or more fail to start one of these pumps, others rated at 3kw continuous can start them with ease. Most of us understand, we need the power source (prime mover) to develop the power to drive the generator through that inductive moto start up which can draw current 3 to 5 times as much as what it takes to run the pump motor. If all is right, this >start up< is short, maybe four tenths of a second. Once you understand this, you can see that the stored energy in a heavy flywheel can help deliver the power to cover the large demand for current. If you have a generator with a very light flywheel, the engine will need to develop this energy on it's own, and the governor will need to respond quickly. In the case of the heavier flywheel, it is helping cover this short event, and the governor has more time to react and open the fuel rack. Let's look at a two wire 1 hp submersible pump, in my opinion people buy these because they are a little cheaper, the 3 wire 'down the well' pumps often have a little better power factor and take less current to start, so I think this is a good test for the little PMG, if it can start this pump, it can start most of them. In this case, we are going to use the Yanmar Clone, our drive ratio is 5:4, so we are running the engine at less RPM and lower power than its horsepower rating of 10 HP at 3600 rpms. We do this to increase the longevity and the efficiency of the generator set. This 5:4 ratio is about as low as you want to go with the PMG and still start a big load like this with other loads on line.
Above: Here's a graph produced by a power analyzer, it's hard to see, but there's two inputs being recorded here... these are both of the 120 volt legs. you can see that the pump looks a little like a crow bar has been dropped across the power leads of the generator, but about two tenths of a second into the start, We see there's some CEMF shutting off the current as the pump rotor starts to build RPM. At about four tenths of a second the pump is running near maximum speed and current has dropped off with voltage stabilized. Setting up your governor on the CF186 or other prime mover to produce a voltage of 127 volts at the distribution point gives you an ANSI standard voltage and allows the PMG to produce power all the way to 4.2 KW continuous and still be ANSI legal. Please note, the Power Factor on this Pump is not optimum, and adding some run capacitance across the pump leads between the pump relay and the pump could lower the start current and use even less generator capacity. Bill Rogers has written an excellent book about what Off Gridders and those who run back up power frequently should know, and you can learn how to optimize your loads and why you do it by reading his book. The above example has about 675 feet of wire between the pump and the generator. Added note: 7/3/2010 I recently added more load bank to the utterpower test bench, this allowed me to explore further the real load starting capacity of the utterpower 3KW PMG. With the PMG soaked to a temperature of 110F, the power analyzer saw power at >6KW for 10 seconds delivered at >220 volts. I don't suggest that all PMGs are certified to deliver this kind of starting current, but I picked this unit at random for this test. As we know, we typically need far less than a second to start the typical 'hard to start' inductive loads, and then the rotation of the shaft quickly cuts off the high current. Circuit breakers take a little time to react to high current, and the properly sized breaker will handle start current and still protect the PMG. Of course there are other considerations, we know that our prime mover MUST be up to the task of delivering the torque to maintain RPM through this short duration when we start a large Induction motor. In stationary applications, this is where High Mass Flywheels shine, it is why so many Mechanical Engineers are fascinated with the old prime movers, the high mass stores energy, many loads take three to five times as much power to start as it does run, this info is usually provided for pump motors and other loads we must power during outages or off grid. What the ME and seasoned DIYer understands is the high mass flywheel allows us to provide high starting torque, and still run a power plant that is generally loaded at eighty percent or more where we see the best efficiency. If we deploy a prime mover with a low mass flywheel with larger cubic inches OR at far higher RPM to assure enough power to start these big loads, we typically lose efficiency and the amount of fuel we burn to produce a measured number of KWHs over time goes down. I remember being a far younger man and having all too little appreciation for the marvels created by men of past generations who had a deep understanding of the science long ago. Of course there are other considerations, and one being that some of these old engines were designed to be rebuilt in place with simple tools, no need to unbolt them from their mounts, or haul them to a repair facility, many have access doors big enough for the largest hands to gain access. the best of field mechanics might replace a cylinder liner, rings and new big end rod bearings in less than an hour. Keep water out of the fuel, keep the sun from shining directly on your gen set, and the injection pump might outlive you. Still we need consider the application, we all understand that these engines are not best suited for use in a motor home, or a number of other applications where light weight and portability and other factors are a consideration. Imagine a motorcycle with a 24 inch 200 pound flywheel, the first corner you try and make should be on video... Note: As a comparison, I started a one horsepower 3 wire down the well (more typical) pump down 130 feet with 200 feet of wire between generator and pump. In this case, the CF186 was fitted with a 5" : 4.2" utterpower drive. the no load voltage was 254volts (within ANSI standard), and the pump brought the voltage down to 240 volts for running. In this case, we have more horsepower available, and in this situation I can run a lot of stuff in my shop and still start the pump when it wants to run. If there's a point to the story, it's that you can tune your drive system to start your largest load safely and often you can do this with a little less rpm and greatly increase the longevity of your machine and save fuel as well. the danger is going too far and not developing the power necessary for starting inductive motors. What's obvious to you is the direct drive doesn't allow you to do this, there are advantages to low loss belt drive systems :-) dropping the belt also isolates the engine and generator which can be valuable in location a noise like a bearing going bad, vibration, etc. Having two totally separate units greatly simplifies repair and replacement when necessary. The belt driven PMG is also a very compact package and should fit nicely into the old engine compartment should you decide to make your own replacement. One of the worst case stories I have told in past years happened about 12 years ago. A friend had a blower motor that fed a glass blowing furnace powered by natural gas. The Motor was rated at only two horse power but it was part of a custom blower designed by a glass blower. The blower fan was made of heavy cast iron, it was directly mounted to the motor shaft and took a long time to spin up to speed. The owner needed a backup power for this blower and ended up buying a natural gas powered 8KW rated generator with auto transfer. Over the next year, there were several restarts of the blower on commercial power and each failed, the breaker tripped out, the motor found bad and expensive replacement ordered and down time for the furnace. The cause was a very poorly designed blower that was nearly cooking the start windings with great commercial power. The 8KW generator would start the motor, but unknown to the customer, it was burning out the start winding in the motor when doing so! Of course the motor might run for six months or a year before shut off, so no one suspected the motor was actually bad all that time. This is more evidence that you should know your loads. This was rare in deed, but the Generator salesmen was consulted to size the generator required and naturally he assumed the 2hp motor blower would start with the 8KW generator just fine, (so did I :-) Moral of the story, Glass blowers are not always good engineers? Had someone put a power analyzer on that blower and consulted the motor manufacturer, they would have realized they had a product that was on the edge of destroying itself during the first 10 starts on good commercial power. In all likelihood, a few starts back to back would have taken it out at the factory had they done so. Motor specs give you all the data you need to assure you have a proper start. I am left to wonder how much quicker the start would have been had they used aluminum instead of cast iron for the blower? You can apply this story to air compressors, and even a fridge! If these items are started before the pressure is bled off the output of the compressor, they can draw a lot more current than normal to start. unplug some refrigerators in the middle of a run, and then plug them back in, and you'll see the lights dim. 7/2/2010 what does a Sears brand refrigerator have to do with a generator? I think a bunch. In 2009, we bought a new fridge from Sears. Due to a sticky crisper drawer and carelessness, I cracked the front of the plastic drawer when I was in a hurry and closed the fridge door with the drawer partially open.. I immediately called my wife and warned that I had just broke her fridge. she said.. "you get to order the new drawer" :-) I was shocked to find the part would cost me $112 delivered, I'm not sure the drawer weighs even a pound. But there is more to the story, Sears said the drawer may not be an exact match, but they would send a "suitable replacement that fits". What I received for $112 was a subassembly. Thank goodness I didn't break the trim and decor on the front of the drawer or the little adjustable vent that adjusts air flow into the crisper drawer. We were able to remove the pieces and build a complete drawer. In my mind, this is equivalent to a dead canary found in the cage. I am seeing other signs of stress where companies look to see what corners they can cut, and vestments in spares is an area where cuts can be made. I am left wondering what would have happened if I had asked for the replacement after two years of ownership? People who take the time to read this page have likely suffered outages in the past, they may have suffered through a hurricane with no power after losing a modern disposable wonder they eventually threw away because the parts were either so costly or the parts were not available at all. A KISS engineered two bearing Generator/Alternator should be the heart of your emergency power. Many of us are or have been active in armature radio, we know we are now coming out of a very quiet period as per Solar activity, and we expect a lot more Solar Flares and even a return to some of the bands that worked so well in the past. Along with this activity is uncertainty. We now have so much riding on a digital network, when a major elements lose timing, there's going to be problems. In today's world, if the data link fails at the gas pump, you don't pump gas. what happens at the bank? What happens at the grocery store?Over the last few years you have seen things happen you never expected, you've learned how vulnerable you are, and how empty the promises are that your elected officials made to you. Will you do nothing? It might be time to invest in durable goods. Here's an example of a pump house powered by a KISS and EMP proof Generator. http://www.youtube.com/user/georgeutterpower. This one will work, it will even run on highly filtered used motor oil IF it is the only fuel you can find. Newest DIYer in training, (Grandson Zach)... basics first.. he already has more DIYer skills that some of the posters on forums :-)
more to follow... back to PMG main page
foot note* Gen Parts are often made in lots under contract. The best price is normally obtained when circuit boards are made for the production line, the company decides what the failure rate might be and asks for a certain amount of spares to be made at that time as well. When spares leave the shelves faster than expected, there are times when the price is raised quite high to slow the trend. The options the company might consider: Claim the unit is now 'manufacturer discontinued', or spend a lot more money per part to make another (often smaller lot). Sometimes the quote the company gets to have a short run made is reflected in the price of current spares on the shelf. I once was gifted a really nice (like new looking) Makita Generator, the repair shop told the owner there was no spark at the plug and the electronic igniter module was manufacturer discontinued, the company did not have any kind of replacement part to fit. In other brands, I have seen that the price of these little modules were so high, people would naturally ask themselves.. "If I buy that piece, what will fail next and how much will the next part be?" Again, if it isn't part of the design, it can't fail. Some will continue to tell you that all this sophistication is necessary. I suggest all you need to do is meet the standards for Electric power as expressed by the ANSI standard, and you need enough generator to start your loads. Outside of Electronic modules in engines, most generator failures are the result of a gen head failure. If you break failures down into categories, you'll find most problems= engine OK generator head makes no power just as in Jay's situation above. The reason they threw the voltage regulator at the problem was it has a high probability of failure based on their experience. Of course they were wrong in Jay's case, but Jay was paying for the new part and labor, so why not throw parts at it? After the VR, we see failures like the diode being bad on the rotor in brushless designs, lack of excitation voltage because the rectifier is bad brush types and more. PMGs have none of these parts in their design, but it is more expensive to make a high performance PMG.
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