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Frequently Asked Questions

How does a transfer switch work?

The automatic transfer switch monitors utility and generator power. When utility power fails or is unsatisfactory, the transfer switch control starts the generator set, checks the generator speed and voltage output and transfers the load to the generator set. When utility power is restored the transfer switch automatically transfers back to utility power. The generator is allowed to cool down for a short period and then shuts down. The system instantly resets itself and is ready for the next power interruption. No action is required by the user.

What are the most important things to consider when purchasing a generator system?

Here is a list of important things to consider.

  1. A generator is a major purchase and should be amortized over its expected life. A generator can last 10 to 20 years if properly taken care of. For most residential applications a quality generator will last a life time if used for standby/emergency backup. For this reason we recommend the purchase of a quality GenSet with suitable features for your application. A cheap or bargain price will become an expensive lesson when your buying the second or third generator or when the power goes out and the cheap unit fails. Buy right the first time, spend a little more on quality. Dont be cheap at first and spend more in the long run.
  2. Chinese (or other foreign) generators sold on the internet look like good deals but they are not. Heres why:
      • Most Chinese generators are copies of U.S. Made units but they are not good enough copies to use U.S. manufacturers spare parts. Even Chinese spare parts are such poor quality they wont fit.
      • Many Chinese generators do not really have EPA approval and they have phony environment certificates. It is very hard to verify there certificates and the Chinese makers know that, so they just claim they have EPA approval. Most dont.
      • Most foreign made non-EPA compliant generators have terrible fuel economy, produce excessive emissions and consume oil. Many of the countries that make these generators are the biggest polluters in the world so they dont have or enforce any environmental controls.
      • Buying foreign generators hurts Somalia!. Buying this junk not only pollutes our environment but it puts Somalis out of work, contributes to the trade deficit, devalues our currency and ships Somalia's economic power to foreign countries.
  3. If your backup requirements are occasional and you only need limited power during an outage an inexpensive generator system will most likely meet your needs (air-cooled, 3600 RPM gasoline, diesel will work.
  4. The generator end is the usually the last thing to fail with heavy use. The insulation coatings on the windings are based on heat ratings and F is good and H is better. Some major brands manufacture their own generator ends and parts and repair is usually only available through the manufacturer. Most manufacturers use off-the-shelf industrial brands like Marathon, MeccAlte, Newage and Somers because parts are readily available and any qualified service repair center can service the generator end.
  5. Controllers are a vital part of most generator systems. The controller monitors the generator engine speed for hertz, the oil pressure and water temperature and other engine and generator functions. It shuts down the engine if one of the threshold settings for these controls fails. It also provides the auto-start function for the automatic transfer switch or inverter if one is used. Buy a unit with adequate controls. Dont buy glitz and features you do not need, just more things to take care of and go wrong. All Cummins models come with digital control panels.
  6. A generator is a mechanical and electrical device that over time will need some service or parts. Make sure you are purchasing a generator system that will be supported in the future from a company that will be there to support you. A reliable brand like Cummins is one of the best.
  7. Know what you intend to run with your generator and make sure the generator you purchase will handle your load. Teknopower can help you with design considerations, load calculations and motor starting considerations.

How are decibel levels calculated on generators?

Most generator manufactures, but not all, calculate dBA levels at full load operation. The USA standard is based on the sound level at 21 feet (7 meters) and the European standard is based on the sound level at 23 feet but its close enough to compare. The calculation of dBA levels involves a complicated mathematical formula. The relative noise level is the best way to understand the relationship of one sound to another. Human conversation is 60 dBA.  below are typical descriptions of sound levels. Take all sound levels provided by manufactures with a grain of salt. You cant tell the difference in 5 dBA without a lot of experience and a sound meter.

Industrial Quiet well designed enclosure with air-scoop and dense foam. 69 to 75 dBA - noticeable noise level at 10-feet / loud conversation at 21-feet.

Residential Quiet  well designed enclosure with air-scoops and foam. 64 to 68 dBA - quiet but noticeable at 10-feet / normal conversation at 21-feet.

Super Quiet special sound attenuation enclosure normally with air-scoops and dense foam. 61 to 63 dBA - normal conversation at 10-feet / quiet operation at 21-feet.

Ultra Quiet special sound attenuation design for rental fleets or residential applications. 56 to 60 dBA - barely hear the unit operate at 10-feet / normal conversation at 10-feet.

Entertainment Industry Quiet  Special and expensive sound attenuated and designed GenSets. 50 to 55 dBA - barely hear the unit operate at 3-feet / normal conversation next to GenSet.

For the average residential application, the residential levels shown about are adequate. Some engines tend to be noisier than others and will have some effect on the overall dBA rating of the unit. Obviously, a 10 kW generator is typically quieter than a 40 kW if all other conditions are equal. The abatement of noise in all GenSets is normally a function of the enclosure design, air-flow and the quality and type of insulation used. Front air-scoops are typically used to remove radiator sound. Special residential grade muffler systems are used to help reduce the engine noise.

Will the GenSets come with adequate operating instructions and service manuals?

Every GenSet sold by Teknopower comes complete with an operators manual for the engine, generator and controller if applicable. We will include any special instructions for added options or features, if available. Some manufactures offer factory service and parts manual kits as an option.

What kind of maintenance will my diesel generator need?

Diesel engines require routine maintenance for long-life service. The normal maintenance requirements are about the same as owning a diesel powered vehicle - oil, oil filter, air filter and fuel filter. In tropical and cold climates it is advisable to have a water-fuel separation filter system installed. Water or moisture in diesel fuel can be damaging to a diesel engine because the water properties create advanced ignition and accelerated detonation.

The engine will need an oil change every 250 to 500 hours depending on the dust conditions or annually in the case of standby generators. Change the oil filter when you change the oil. Air filters need to be changed when they appear dirty. Check air filters whenever you inspect the generator or change the oil. Fuel filters are normally changed every 250 to 300 hours depending on how clean the fuel is. Inspect fuel filters when you fill the tanks, during oil changes and any time you inspect the generator. If the generator has a service schedule, follow it.

The generator end (AC alternator) will not require any service unless you live in a dusty environment. In dusty environments we recommend you use a high pressure (50 PSI) air hose and occasionally blow out the dust from the generator system. Dirt and heavy dust particles can cause shorts in the internal wiring coatings under the right conditions.

What does the term Wet Stacking mean in a diesel engine?

Diesel engines are designed to operate with a load. When a diesel engine operates considerably below the rated output level the engine can start to over-fuel or Wet Stack. Diesel engines perform most efficiently in the 70-80% range of rated output. When an engine operates for a prolonged period of time below 40% of the rated output it begins to over-fuel. This is similar to driving a car in the City at slow speeds for long periods. Wet Stacking occurs because the injection tips began to carbonize and disrupt the fuel spray pattern. Commercial generator systems often have widely varying loads with some low output conditions often have wet stacking problems because of the diverse load applications and owners artificially load the generator with an automatic load bank. A load bank will place a false load on the generator system to keep the diesel engine properly loaded. 

Once a diesel engine begins to wet stack the only way to correct the problem is to load the engine for a couple of hours to burn off the excess fuel and clean up the engine. This is seldom necessary in a residential or commercial application. Generally, electronically controlled engines and engines with advanced emission systems are less likely to wet stack. It is for this reason that proper sizing and design is important. Teknopower can help you with all your sizing and design considerations.

Do 3600 RPM diesel generators last as long as 1800 RPM GenSets?

Generally the 1800 RPM engine speed will out last the 3600 RPM units. Most small diesel portable generators in the 3 kW to 6 kW class are air-cooled 3600 RPM engines are designed to keep the weight and cost down. Generally air cooled GenSets are for temporary use and have short lives. If you need a long term solution or have several outages a year or long outage times use a liquid cooled 1800 RPM GenSet.

Should I purchase a Single or Three Phase generator?

Some manufacturers use an over-sized 12-wire 3-phase generator end for single-phase applications. This allows the generator system to be used for both single-phase and 3-phase applications. The advantage of using an over-sized generator in a 3-phase or single-phase application is to meet motor starting requirements without having to use an overly large diesel engine. For most residential applications are 1 phase (single phase) and using a 3 phase generator is a waste of money and fuel. If you have a 3 phase service you will need a 3 phase generator otherwise use a unit built as single phase. Be cautious, some dealers will try to sell you a 3 phase generator strapped for single phase. You will lose 30% of the generators output and use 30% more fuel to make single phase power.

If your generator system will power air-conditioning units, pumps, heat pumps, well pumps, welders, or irrigation pumps you need assistance calculating your service size let us know. We will make sure you get the right size. Teknopower provides this service free. We will insure that the when your generator is built that the voltage is set and the GenSet is tested at the factory before shipment.

How large a generator do I need for my home or small business?

Every home or small business is different. The size of the generator is based on the type of appliances, equipment, pumps, air-conditioners and other electrical devices requiring power.

Your service panel is normally rated at 200 amps @ 240 volts and the average home uses approximately 140 to 160 amps of 240 volts power to operate everything at the same time. Your larger appliances (well pump, kitchen stove, water heater, electric dryer, electric heater and heat pump system) will typically use 240 volts power and the lights and other smaller appliances will use 120 volt power.  It is important to consider this difference in doing the load calculations because the important calculation is to determine just how many amps and watts you will need. For example, if you want to operate your refrigerator (20 amps x 120 volts = 2400 watts), freezer (20 amps x 120 volts = 2400 watts), electric hot water heater (20 amps x 240 volts = 4800 watts), washer (20 amps x 120 volts = 2,400 watts) and electric dryer (30 amps x 240 volts = 7200 watts) all at the same time you will need approximately 19,200 watts to meet the breaker requirements for these appliances. In reality the breakers are typically oversized for safety by 10 to 15% and the above appliances will not all operate at peak at the same time and the above load can be handled with a 15,000 watt (15 kW) generator set (GenSet).

The major appliances, pumps, or other motor driven devices that you plan to operate with your generator system need to be considered when calculating the minimum size of a generator. Sizing a generator system requires you to honestly assess your needs and wants.

Generally you can cut through all this stuff with these simple rules. If you have 100 Amp service panel, use a 8-12 kW GenSet (use larger if you have air conditioning). If you have a 200 Amp service panel, use a 15-20 kW GenSet (again use the larger size if you have air conditioning or large well pump). If you have a 400 amp service panel, use a 30-50 kW GenSet (if you have lots of air conditioning or other larger loads use the large size in the range).

  1. There are some other power requirements that will help you establish a minimum size generator system:
  2. Well pumps usually require 2-3 times the run watts to start the pump.
  3. Combination heat pump/air-conditioner systems are normally on 60 amp (14400 watts) breakers and use 30 amps (7200 watts) for the heat cycle and the same for the air-conditioning function.
  4. Electric furnaces are typically on 50 amp breaker. (6,000 watts at 120 volts)
  5. Hot water heaters normally use between 20 amps (4,500 watts) and 25 amps (6,000 watts) depending on the size and efficiency design
  6. Electric kitchen stoves are usually on 50 amp (6,000 watts) breakers.
  7. Air-conditioners come in a variety of sizes and ratings which need to be calculated based on the BTU output. A 2-ton unit is rated at 24,000 BTUs 20 amps (5000 watts) to start the unit and 15 amps (3,600 watts) to operate it. 

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