Choosing a generator for off grid
If you build off grid you must always have a backup generator system. This is usually one of the first items that is purchased.
It’s important to note that many generator manufacturers don’t actually build their own motors. They use engines from well-known names like Ford, GM, and Honda to power their generator heads. When choosing a generator, look for one that comes with a brand name motor: it will be much easier to find parts and service for a well-established brand than for some no-name model. It is highly recommended that you DO NOT use a unit that is from China or some new company that has not proven its reputation.
I have listed some of the companies and rated them on what I have experienced and reports from others who have used these products.
John Deer - Good reputation, been building generators for decades, highly recommended.
Onan —— Good reputation, been building generators for decades, highly recommended.
Kohler —– Good reputation, been building generators for decades, highly recommended.
Baldor —– Good reputation, been building generators for decades, highly recommended.
Robin Subaru —- They make a good product and I have heard good things about them.
Winco —– They have been making generators for decades, myself I would not use them.
Coleman ——- I have no experience with their generators.
Mitsubishi —– I have no experience with their generators.
Yamaha ——– I have no experience with their generators.
Kubota ——— I have no experience with their generators.
Honda ———– I have no experience with their generators.
Guardian —— Cheaply made, not recommended for reliable power.
Generac ——–Cheaply made, not recommended for reliable power.
Northern ——- Cheaply made, not recommended for reliable power.
Yanmar ——– I have heard only bad things about their generators.
ProForce ——- I have no experience with their generators, and would not use them.
Stateline ——– I have no experience with their generators, and would not use them.
Duropower —– I have no experience with their generators, and would not use them.
Choose a generator that produces more power than will be drawn by the combination of lighting, appliances, and equipment you plan to connect to the generator including the initial surge when it is turned on. If you cannot determine the amount of power that will be needed to operate your appliances, lighting, and equipment, ask an electrician to determine that for you. (If your equipment draws more power than the generator can produce, then you may blow a fuse on the generator or damage the equipment.)
Once you’ve decided to purchase a generator, there are several considerations you must keep in mind when choosing which set to buy, where to install it and how to install it. Choosing the right system is not difficult if you take the time to analyze your requirements carefully. You will also need to know a few terms and have a basic understanding of the different types of generator sets and their operating principles. Installation requires expert assistance and a strict adherence to local codes and regulations. Its recommend that you have a contractor do your installation. Also to meet warranty requirements, you may have to have a licensed expert do the installation or void the warranty. In any case you want it done right the first time, the Generator is a major part of any Off Grid System, and needs to be treated as such.
Generator Sizing
Don’t push it to the max. Make sure you’re comparing the “rated” capacity of various models, not ”maximum” capacity. An electric generator can deliver its maximum capacity for no more than 30 minutes before starting to overheat – “rated” capacity is the level of power a generator can deliver on an ongoing basis, “continuously”. Usually, it’s around 90% of the “maximum” power.
Stand-By or Prime Power
There is only one right answer for this question as far as I am concerned. I only recommend the use of a PRIME POWER GENERATOR. I have seen a number of failures of Stand-By generators that were installed on Off Grid Systems. If you have a power system problem, the only alternative source of power is going to be the Generator. Everything will be relying on it as the back up power source, so you want one that can hold up and handle the load. It may have to run continuously for a number of days. A stand-by generator simply will not last under these conditions and will not be a dependable, reliable part of a well-designed Off Grid System.
A stand-by generator is a backup to normal Utility Power, because in most cases Utility power outages do not last more than a few hours. Stand-by units are designed to run for only a few hours per week, not 24 hours at a time. There is a price difference between Prime Power and Stand By units. Prime Power generators are generally built to last much longer than Stand-By units.
Fuel Choices
Generators can run on several different types of fuel. Many people recommend diesels due to their longevity and lower operating costs. What with today’s fuel prices, its hard to say which fuel choice is a cheaper way to go. Today’s modern diesels are quiet and reliable. Ideally, you may want to consider getting a generator that runs off natural gas or propane instead of diesel fuel or gasoline. Why? The major drawback to gasoline is that it can’t be stored for very long periods of time, or it will go bad and can varnish out in the engine components, requiring mechanical repairs.
Diesel fuel is popular for larger, commercial generators. They do require deliveries of diesel fuel and a tank to hold it, and while they’ve cleaned up their act considerably in recent years, diesel generators are still not as clean-burning as other types. In some areas, on-site storage of diesel fuel is strictly regulated because it carries the potential for spills and leaks. The Diesel can have problems due to condensation and moisture getting mixed in with the fuel. This causes starting problems and reliability issues.
Natural gas or Propane, however, emits far fewer exhaust emissions and because it burns so much cleaner, the wear on internal engine parts is “greatly” reduced as compared to Diesel and Gasoline fueled engines. Propane has practically unlimited shelf life. Using Natural Gas or Propane will cause the generator to produce a little less power than the other fuels, but if you plan for this when choosing the size of generator that meets your demand, there will be no problem. If natural gas does not exist in your neighborhood you may install a large propane gas tank that can be periodically refilled by a local distributor.
Generator Types & Features
Generator sets produces either single or three phase power. Choose a single phase set if you do not have any motors above five horsepower. Three-phase power is better for motor starting and running. Most Off Grid homeowners will require single phase. Single-phase sets are 120 or 120/240. You will want a 120/240 volt unit, to be able to properly connect it to your house breaker panel.
Operating Speed
Electric equipment is designed to use power with a fixed frequency: 60 Hertz (Hz) in the United States and Canada, 50 Hertz in Europe and Australia. The frequency output of a generator depends on a fixed engine speed. To produce 60 Hz electricity, most generator engines operate at 1800 or 3600 RPM.
Each has its advantages and drawbacks. For 1800 RPM, four pole sets are the most common for large generators but small units usually run 3600 RPM. Most 1800-rpm water-cooled diesel units operate on average 12,000-30,000 hours before major maintenance is required. 1800 rpm water cooled, gas powered units normally operate 6,000-10,000 hours because they are built on a lighter duty gasoline engine block. 3600 rpm air-cooled gas units are normally replaced, not overhauled at 500 to 1500 hours.
My advice would be to purchase an 1800 RPM unit over a 3600 RPM unit because of less noise, less vibration, longer life, lower fuel usage. Just from personal experience. The 1800 RPM units offer the best balance of noise, efficiency, cost and engine life. 20 kW and larger generators are typically liquid-cooled, 1800 RPM units, which give the best combination of quiet operation and reliability. In some cases, you may be able to choose between the two RPM settings – I always recommend going with 1800.
Engine Features & Benefits to Look For
Engine block is one of the most important items. For long life and quiet operation I recommend four cycle, liquid cooled, Prime Power Systems. Air-cooled engines require a tremendous amount of air movement, and may require ducting. They’re noisy too. Liquid cooling offers quieter operation and more even temperature control. Time and money savers include a large, integral air cleaner with replaceable filter element and a residential muffler. The lubrication system should have a full flow, spin-on oil filter with bypass. Make sure the generator used a “Major brand” of engine.
I do not recommend you purchase a Chinese built unit or off brand engine. You will not be able to obtain the necessary off the shelf parts and service. The DC electrical system should be a standard 12 volt system, starter motor, battery, and charging alternator, also you will want to have the option of remote starting so you can start the generator from inside your home and the Off Grid System can also start the generator should system need to. Diesel units should come with a pre-heat switch, which is used during cold weather starting.
Other important features would be a Safety Shutdown System to protect the engine in case of oil pressure loss, generator over-speed or over-crank and high water temperature. Like any motor, a generator motor creates quite a bit of heat and needs a cooling system to prevent overheating. Liquid cooled systems are quieter and more dependable - and also more expensive to purchase and to maintain. The lubrication and coolant fluids will need to be checked and replaced as per the manufacture recommendations.
For noise abatement, I recommend a residential (not industrial grade) muffler. A good primary fuel filter/water separator is a must to protect your engine’s fuel system. Some generators may require a block heater to keep the coolant/water mix at an adequate temperature for easier starting. One overlooked item is a trickle charger for the starting battery, I highly recommend it.
Generator End
AC generator should have a 4-pole revolving field. An automatic voltage regulator will provide, clean, power. Normal utility power is +/- 5% voltage regulation; most 1800-rpm generator are even better, at +/- 2%.
GOOD VENTILATION IS IMPORTANT - Generators produce carbon monoxide, a colorless, odorless, toxic gas that can result in serious injuries, or even death if levels become to high. For this reason, the generator should never be operated inside your home, garage, or other enclosed space. It should always be located outside in a dry location. Proper ventilation is not only for exhaust gases, but also for the air that will be passing through the radiator. If air movement is restricted by shrubs, or spacing from other buildings, than the cooling system may fail to do its job keeping the engine temperature under control. Keep this in mind when determining the generators location.
AC Switchgear and Controls
Switchgear can be as simple or complex as you want, or can afford. For most Off Grid Systems I have found the most cost effective and simple switch controls are Gen-Tran transfer switch panels. They are easy to install and allow you to simply switch each breaker circuit between the Off Grid Power Source or the Generator. All generator systems require a circuit breaker and a distribution panel. The circuit breaker protects the generator set from short circuit and unbalanced electrical loads. The distribution panel (breaker panel) divides and routes the connected loads and includes circuit breakers to protect these loads.
Installation, Service Contracts & Warranties
Turn to the pros for installation. Experienced interior electricians may not be as familiar with electric generators as they are with other types of electrical systems. Choose someone who has installed generator systems before and make sure they are licensed and do all work up to code.
If well maintained, a generator can last quite a long time. However, they do require maintenance. Most of the wear is concentrated on the motor: changing oil and spark plugs, checking coolant, and other engine maintenance all need to be done on at least an annual to semi-annual basis. For this reason, it’s best to choose a dealer who offers a service plan that includes yearly visits. Pricing for a service plan will vary according to the size and type of generator you select - for example, large, liquid cooled generators take longer to service. Your dealer should offer at least a two year parts and labor warranty with the sale of a new generator.
Make sure you know what the warranty covers: some are bumper-to-bumper, while others cover only certain parts of the generator. Because maintenance and service are so important, you’ll most often want a generator dealer in your local area. A more distant dealership can sometimes connect you with licensed service technicians who are in your area, which can be okay but is generally not the preferred arrangement. Ask what maintenance services they’ll provide
- How many technicians do they have? How many trucks?
- How long have they been in business?
- How many commercial generators similar to yours have they installed in the last year?
- Which brands do they work with the most?
- How long have they carried the brand you’re interested in?
At a minimum, a generator requires an annual checkup of oil levels, air flow, and other factors. For Off Grid Systems it is always a good idea to start the generator at least once each week and run it for about ten to fifteen minutes to allow all the fluids to come up to operating temperature. This helps keep the fluids from going bad and helps keep the generators ready for use.
This information was compiled as a guide for those who are planning to put together an Off Grid Power System. The information is readily available on the Internet off various web sites and also from information acquired through personal experience.