# Need help picking a generator......



## wordmanjay (Oct 8, 2015)

We're looking for an inverter generator for our coffee trailer.

We've calculated our max Watt requirement at around 9,000 watts. That's if all the machines surged at the same time- 
1675 watts- espresso machine
1600 watts- 2nd expresso machine
1100 watts- coffee grinder
200 watts- espresso grinder
1600 watts- coffee maker
1600 watts- 2nd coffee maker
1400 watts- Hot water heater

Need it be quiet as the generator won't be far from business operations inside the trailer.
We've seen generators with multiple fuel options- that would be nice, but not required.
The inverter generator idea- we'll probably be operating a computer and we thought the espresso machines might constitute "delicate equipment". We need info on that topic as well.

Thanks in advance for your help.


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## Osviur (Sep 7, 2015)

*Reliable generator*

Hello wordmanjay,

As you are requiring to feed a commercial installation, for long periods of operation in a daily basis, I would recommend you to think in a rugged, long lasting machine, high efficiency, low noise and very reliable.
The first point calls for a diesel engine, then low RPM for durability, diesel fuel for efficiency, liquid cooled for quietness and free of spark plugs, high voltage coils, wires etc. subject to frequent failures.

Fuel consumption is another factor to evaluate. Taking as an example: A Kubota diesel gen 12.5 KVA prime power (continuous duty) model KJ13 at ¾ load, (9375 W Power factor 1) will use .98 US gal. per hour. With a 9.8 gal tank capacity it means 10 hours of operation . A Honda gen model EB 10000, gasoline fueled, at full load (9000 W rated output) will consume 1.78 US gal per hour. With a 8.19 gas tank capacity, it means 4.6 hours of operation. The first one runs at 1800 RPM, the second, at 3600 RPM. Useful production time is related to the number of cycles or revolutions done. Consider this too, especially if this gen is going to run several hours daily. Sound level is very similar 75.5 diesel vs 76 gas.

For the delicate loads, as a computer and some smart machines, you may use a line conditioner, to protect the electronic equipment against, basically, spikes due to commuting loads.

A low speed generator, 1800 RPM, 10 KVA, 4 poles, with a good quality design and construction, will provide a long lasting power source with a clean sinusoidal wave, that will feed correctly almost any electronic load in your installation. The extra protection needed is because it is a small grid, prone to generate spikes due to commutations in the equipment, especially with inductive loads, as motors, universal ones (those using brushes, very noisy).

Check this link: 
http://cumminsonan.com.br/pdf/a-1474.pdf

It runs at full load emmiting only 68 dB at 10 Feet! not at the standard 23 feet. Really silent. Fuel consumption: At 3/4 load , 0.84 US gal/hour.

Regards.


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## Osviur (Sep 7, 2015)

*Line conditioners*

Hi wordmanjay
With respect to the electrical protection for your “delicate” equipment, I would like to explain you why and when to use a line conditioner.

Electric power is supplied normally under the Alternating Current or AC form. In its ideal “presentation”, comes in a continuously, but smooth, voltage variation with the form of a sinusoidal wave , changing amplitude and sign from 0 to +170v then to zero and -170v to return to zero, sixty times in a second (in a 120v AC 60 cycles per second or Hertz, circuit). Any deviation from this shape and amplitude is called a disturbance.

The most common forms of these alterations are spikes and surges. Spikes are very fast shots of voltage, that easily can reach thousands of volts during fractions of milliseconds, but enough powerful to destroy sensitive electronic equipment, like transistors, diodes, etc, found by billions in computers, memories, smart devices etc.

Surges are slow variations in the voltage level, or amplitude of the wave, beyond the normal limits (+- 10%), from fractions of second to seconds, but maintaining the normal shape and frequency.

Line conditioners, or surge protectors, in its simplest form, are really spike protectors, that work blocking voltages over 200-300 v or more by means of many types of devices, being the most common MOVs ( metal oxide varistors). They start conducting current above the mentioned 300v and derive it or to ground or shorting it between conductors, avoiding higher levels of voltage to reach the electronic components. They are usually built in a disc form, ¾” diam, with two terminal wires and a bright color.
Protection against voltage or power surges can be obtained by means of voltage regulators (bulky) or opening power lines, cutting power to the protected circuit.

Voltage spikes, in an isolated grid as is your case (a coffee trailer) are caused by devices using wire coils, which have a characteristic called inductance. Any variation in the current flowing through the coil will cause a reaction against this change. The faster the change, the stronger the reaction, converted in volts . The smooth sine wave causes to appear a opposite voltage near the applied. A sudden cut of energy, like switching off a coffee grinder will generate a spike reaching easily several hundreds of volts, enough to damage a computer or any smart device installed and switched on in the same circuit fed by the generator.

Voltage surges, in this specific case, only can be produced by a failure in the generator’s AVR (automatic voltage regulator). This is a very uncommon failure, controlled internally by the internal generator’s control (overvoltage-under voltage sensors), very difficult to control inside the trailer.

The sensitive loads are the computer and its peripherals (CPU,display, printer,KB etc.). They can be protected feeding all of them in one branch circuit, protected by a line conditioner.

If your espresso machines are fully automatic, that is, if it is only necessary to push a button to obtain a shot of espresso, yes they need to be protected, but instead of avoiding to enter the disturbance using a 2 KW line conditioner, you may avoid the spike going out from the coffee grinders using a 300 W line conditioner in its power input . 

The water heaters don’t require any protection. You don’t mention illumination, and it is an important load, and the kind of lamps used is important too.

Modern lamps (fluorescent, compact fl, LED) use electronics and fast switching devices, they introduce some alterations in the circuit and it is recommendable to group them in a branch, and protect it with another line conditioner. 
Well, sorry for the extension of this note, but it was the shorter way that I found to explain in simple words why and when to use line conditioners.
Regards


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