Portable Natural Gas Generator Maintenance

To keep your generator in good working condition, you will need to perform routine maintenance. For specific instructions consult your owners manual.

In general, maintenance of a natural gas unit is pretty simple since the fuel never goes bad and you don't get residue like with gasoline or diesel fuel. The unit just needs to be started periodically and the oil needs to be checked and changed as needed. Personally, I set an email reminder to remind me to start the generator every 6 months. If your generator has a battery start, you need to keep the battery charged.

Instead of an installed battery, I prefer to use a Jump Start Battery which is always charged and ready to use.

Don't forget to keep some engine oil handy in case you run low or need to do an oil change.

How to decide what kind of generator to install for your home: What you need to install a Natural Gas Generator

Considerations in Installing a Portable Natural Gas or Tri-Fuel Generator and Parts List

[This information is meant to give the reader a general idea of the installation process and parts needed as well as the project cost, consult a licensed professional to design and install your generator system.]

After doing the research and reading reviews and specifications on the different generators available, I settled on a portable Tri-fuel generator rated at 6kW made by Winco. Tri-fuel means that it can run on gasoline, natural gas (CNG), and propane (LP). I plan on using it connected to the natural gas supply from my house. Here is a similar product rated for 10kW by Powerland:


I figure I can use gasoline if there is a problem with the natural gas supply. I recommend keeping a few gas containers handy, they are hard to find during an emergency.


I already have a hook-up for my outdoor bar-b-q and I planned on using that for the generator. Unfortunately, that is not possible. The generator requires more gas flow than a bar-b-q. A natural gas line for a medium power generator must be 3/4" or 1" diameter (check the owners manual for actual requirements). If you use a smaller line or the pressure is too low, the generator will not work properly. Check with a licensed professional to make sure the gas lines in your home are rated for the generator you plan on using. Example of pipe:


It is necessary to have a licensed plumber install the natural gas line for your generator. Since a portable generator is not meant to be left outdoors, a quick disconnect fitting is essential so that you can quickly connect (and disconnect) the generator in case of emergency. The gas line should also have a shut off valve right near the hook-up so that you can cut the fuel quickly if necessary. You will also need flexible gas line to connect the generator. Make sure all of the parts are designed for outdoor use. This is what a gas valve looks like:


Rather than running extension cords from the generator, it is best to wire the generator into your house's electrical system. This should always be done in compliance with local building codes and with permits. For a medium power generator, a sub-panel is needed that your electrician can move a few essential circuits to. This will allow the generator to power limited parts of your home safely. You will also need a manual transfer switch that will allow you to direct the electricity from the generator to the sub-panel when needed and switch it back to the power company service at all other times. This all must be installed by a licensed electrician. Transfer switches come in different power ratings and support different number of circuits. Figure out how many circuits you want to power and check your generator rating before purchasing. A 30 amp 6-circuit kit and a 50 amp 10-circuit model is shown below.



 An outdoor receptacle (inlet box) is necessary to plug the generator into so that the power can be directed into the house. Make sure it is rated for your generator, 30 amp and 50 amp models shown below.

You will also need a generator power cord rated for your generator. 30 amp and 50 amp cords shown below.

How to decide what kind of generator to install for your home: Natural Gas, Propane (LP) or Gasoline

Generator Fuel type: Natural Gas, Propane (LP), and Gasoline

Gasoline
Gasoline generators are the least expensive type and are available in the low to medium power range. They are best suited to occasional use. The main limitation is the size of the fuel tank. Most gasoline generators can only run for about 8 hours before the tank needs to be refilled. The other problem with gasoline is that the gas starts to go bad after about 3 months. You can't leave gas in a generator that is only used once per year since the gas will degrade and clog up the generator.

Examples of Gas Generators from 2,000 to 7,500 watt:



Natural Gas and Propane (LP):
Many natural gas (CNG) and propane (LP) generators can use either fuel. Some are portable but most are meant to be installed. There is a limited selection of portable natural gas and propane generators. The portable Generac LP model shown below is a very nice product. It is rated for 6,875 watts and takes up to 30 pound propane tanks. Propane can be stored indefinitely in tanks and never goes bad making it a better solution than gasoline. The CorePower model is 7,000 watts runs on natural gas or propane and comes with an automatic transfer switch and can turn on instantly in case of a power outage.The Guardian is 20kW and can power most homes. All of  of these models get great reviews.



Tri-Fuel Generators (Gasoline/Natural Gas/Propane): 
Tri-fuel generators are flexible, they can take any of the above fuels. That makes them very useful in emergency situations. Lets say you are planning on using your natural gas hook-up and there is an earthquake, damaging the gas supply. You could always use gasoline or store propane tanks as a backup. If it is portable, you could take it with you if you need to leave your home. They are often more expensive and can be finicky if not built right.


I prefer Winco models. Examples:
Winco 8,000 Watt TriFuel Power System w/ Electric Start B&S Vanguard Engine $2,788 on back-order as of 7/23/2013

How to decide what kind of generator to install for your home: How much power do you need

How much Power do you need in a Generator?

Obviously, it depends on what you plan on powering. A low power generator (1-5kW) will work fine for powering extension cords to a small appliance and for some lights and emergency equipment like phones, radio, etc. Medium power (5kW - 10kW) can power most of the appliances in a small house or an emergency circuit in a large house. High power (10kW - 20kW) can power a small house or dedicated circuits in a large home.

It all comes down to what you want to power - some emergency equipment vs entire house and what your budget is. If your budget is $1,000, you will be buying a portable low to medium power generator and will run extension cables to the important appliances and devices in your house.

If you are willing to spend more $, you can have a larger portable or installed generator and run dedicated circuits on a sub-panel with an auto transfer switch and remote start that will automatically start the generator when the power fails.

Keep in mind that gasoline generators consume a lot of fuel if they are run continuously. The more powerful the generator, the more fuel you will need. A small generator may use 10 gallons of gasoline per day. A medium power unit can use 20-30 gallons per day. There are sometimes fuel shortages during black-outs, making it difficult to keep the generator running.

Here is an example of a Low Power gasoline generator: It is rated for 4.4kW. It can run a small appliance and other equipment. It is connected with extension cords. It has an electric start which means you don't have to pull a cord to start it.


 Medium Power gasoline generator: This generator is rated for 7.5kW. It can run appliances in addition to other items. It will not run an entire house. It is used with heavy duty extension cords. Also has an electric start.


High Power natural gas generator: This generator is rated for 17kW. It is meant to run most or all of your home and comes with an automatic transfer switch so that it turns on automatically in an emergency. It runs on natural gas or propane so you will not have to buy gasoline and constantly fill it during a power outage.
This type of generator needs to be professionally installed. Installation can cost $5,000.

How to decide what type of generator to install: measuring power use for the whole house

Calculating whole house power usage

There are a few ways to calculate the power required to run a whole house on a generator. First I would recommend finding out what level of service your house currently has. Most homes have 150A or 200A service. Larger homes could have 300A or 400A service. This number is usually printed on the main breaker in the breaker box. You may have to call the power company to ask them if you are not sure.

If you multiply that amperage (A) number by the voltage (120), you get the maximum service that the power company can deliver to the house. For a 200A service, that would be 24kW. Most whole house generators are 20kW or less, so one could not safely run the entire house on a generator. Most installations only power certain important circuits in the house to get the power requirements below 20kW.

If you know the maximum wattage for your house, the actual use should be much lower than that. If you have a mechanical electric meter with a rotating disk, you can calculate wattage by timing how long the disk takes to make a full revolution. There is a black line on the disk which you can use for this. Most meters have a Kh factor of 7.2, check your meter to make sure.  Here is a picture of a meter, you can see the spinning disk in the middle and the Kh factor of 7.2 written on the side:

I took a video showing the rotating disk in the meter.

You can see it takes about 5 seconds for a full revolution.

The equation to calculate wattage is:

(Kh factor x 3600)/ rotation time in seconds = wattage

For this meter:

7.2 x 3600 / 5 = 5,184 watts. That is not bad for 2 air conditioners running, television and lights on and all appliances plugged in. This does not mean that a 7,500 watt generator would be sufficient. This is a steady state value, the peak load when a compressor kicks on or when all of the lights and appliances are on at the same time - ovens, toasters, etc could be much higher.

How to decide what type of generator to install: measuring powerrequirements for large appliances

Large Appliances: hard-wired or heavy duty plugs

In my last post I talked about figuring out the power (wattage) required for small appliances that have labels on them. There are other devices in your home that are more difficult to figure out and the best way to determine the power needed is to measure it directly.

Measuring wattage:
You will need to buy a Kill A Watt power meter to do this. The Kill A Watt works simply. You plug the Kill A Watt into the wall and plug your device into it. It displays the watts being used. You can also measure electricity consumed in kilowatt-hours using this meter. Keep in mind that you are interested in the peak wattage which often occurs when a device is active, not the steady state or idle wattage. If you use the lower wattage for your calculation, when the device uses more power (like when the AC compressor turns on) you could draw too much current from your generator thereby damaging it and possibly damaging the appliance also.

This will work for anything in your house that has a standard plug. That means there are appliances that you will not be able to measure.

Some appliances are hard-wired to your house's electrical system. Examples include a wall-mounted oven and the central AC system. Other appliance use a bigger plug with 3 or 4 prongs. We will discuss these two issues separately.

Hard-wired appliances:
Your best bet is to find the sticker on the appliance that has the power information since it is difficult and possibly dangerous to measure the power requirements for large appliances that are hard-wired. There is a risk of electrocution when working with live wires and this is best left to an electrician. You can look at the breakers in your breaker box for some ballpark numbers (at your own risk).

Breaker Box:
[These instructions are for the modern breaker box pictured below. They may not apply to your setup. There is an electrocution risk when coming into contact with electric power even if you are careful. Use caution. There is a risk of injury or death. By reading this, you accept all risk for damages, injury, death, etc.]

You need to access the breaker box for your house and find out which breakers control the appliance that you are interested in. There are usually labels on the breaker box, however, not always. You may have to test which breaker goes to what appliance by turning the breakers on and off until you isolate the right breaker for that appliance. Once you know what breaker you are interested in, figure out if it is a double breaker or a single breaker. Double breakers are 240 volts since they use two 120 volt live wires. Single breakers are 120 volts and use one live wire.

Here is the outside of the breaker box. The door is closed.

 This is the box with the door open. On the back of the door, you can see a table with the numbered breakers and the labels for each breaker. On the right side there is a very big breaker on top with two rows of smaller breakers on each side.

This is a close-up of the top breaker. It controls the entire panel. If your house has only one panel (like mine), it will control your entire house. You can see 200 printed on the switch. That means that this is a 200A panel. If more than 200A (which is 120 x 200 = 24kW of power) goes through the breaker it is supposed to trip (turn off) and cut power to the rest of the breakers on the panel.

 To figure out how much power your appliances use, you can look at the breaker for that appliance. This will give you an over-estimate since the breaker should always be rated for more than the appliance being powered. In this example the top four slots on the right side are labeled "oven." If you look at the breakers in those positions you will see two double breakers taking up the four slots. Each double breaker is labeled 30A. That means that the oven is sitting on a total of 60A of breakers with a maximum wattage of 120V x 60A = 7.2kW.

Measuring power inside the breaker box
So now you know how to figure out what the breaker for your appliance is rated which gives you the maximum wattage for that circuit. If you want actual numbers, you will need to open the box. This is where you could get electrocuted. Only licensed electricians should open a breaker box. I do not recommend it. I will not show pictures since I don't want to be responsible for people injuring or killing themselves trying to figure out wattage for their appliances. One device comes in really handy for doing so. It is a clamp meter. See image below:

A clamp meter is placed around one hot wire (by an electrician) in the circuit being tested and can display the voltage V and amperage A going through that wire. The power going through the wire can be calculated by multiplying V x A. One can not place a clamp meter over a power cord since power cords have at least two wires inside that have electricity traveling through them. The electricity is going in one direction on the hot wire and going in the reverse direction on the neutral wire. Since the flow is in both directions, it cancels itself out and the clamp meter will read 0. 

Measuring power for Large Appliances with non-standard plugs:

NEMA5-15
A standard plug is called NEMA 5-15. The plug and socket looks like this

NEMA 5-15P

NEMA 5-15R

The Kill A Watt works for standard plugs and sockets pictured above. They carry a maximum current of 15A with maximum wattage of 15A x 120V = 1.8kW.


For window air conditioners and other large appliances, different plugs and sockets are used. They carry 20A - 30A in most cases. They are usually 3 pronged like the NEMA 5-15, however, some appliances are 4-pronged.

NEMA 5-20
This is for heavy appliances requiring 20A of power. It is three pronged with one hot wire, a neutral and a ground. One of the prongs is sideways so that it will not fit into a standard 15A outlet. Maximum wattage is 20A x 120V = 2.4kW.

NEMA 5-20

NEMA 5-30
This is also a 3 pronged plug but it has a higher amperage. It is rated for 30A. This is a twist-lock type of plug with projections coming off two of the prongs. Maximum wattage = 120V x 30A = 3.6kW.

NEMA 5-30P

NEMA 14-30
If an appliance uses a 4-pronged plug, it is usually 240 volts. Two of the wires inside the cable will be hot and will carry 120 volts each. There is one neutral wire and also one ground wire. The 14-30 is rated for 30A. Since it has 2 hot wires carrying 30A each at 120V, the total maximum wattage is 2 x 30A x 120V = 7.2kW.

NEMA 14-30P

NEMA 14-30R

NEMA 14-50
This is the highest power you will see, I think it is more of a commercial type connection. It has 2 hot wires with 50A rating. No picture shown.

Measuring Power with Clamp Meter (Electrician only)
To measure any of these heavy duty appliances with the clamp meter, an electrician will have to isolate the wires in the power cord. Since it is not advisable to cut open an appliance power cord, the best option is to buy a short extension cord which can be cut open and temporarily hooked up to test the current and voltage in each of the hot wires. The resultant amperage from each hot wire is added to get the power draw for that appliance. Do not add the amperage from the neutral or ground wires, only from the 1(for 3 pronged) or 2(4 pronged) hot wires in the cord.

For example, I bought a 5-30 extension cord to measure power to an appliance using a 5-30 power cord. Image below:

I carefully sliced open the insulation on the extension cord and found the three wires inside. One of them is hot. Using the clamp meter, the amperage A for that wire can be measured and the wattage calculated. If you accidentally nick one of the wires you can easily electrocute yourself causing injury or death. Only an electrician should attempt this.

Clamp meter isolating the hot wire of a NEMA L5-30 power cord

If no extension cable is available, an electrician can unscrew the outlet from the wall and use the clamp meter on the house wiring that is attached to the plug. Also very dangerous! This is similar to opening up the circuit box while it is live which I do not recommend.

How to decide what kind of generator to install for your home, calculating power requirements for small appliances

After superstorm sandy hit we lost power for a whole week. I was able to acquire a small gasoline-powered generator and run power to our essential services. This gave us heat and some degree of normalcy. Getting gasoline was rather difficult due to fuel shortages and long lines. This was not the first time we lost power in New Jersey and it certainly will not be the last. I decided that a generator was necessary.

I started to research generators looking at what would best suit my needs and be a cost-effective solution. I have broken down the analysis into the following considerations: power level, fuel type, portable vs. permanent, type of transfer switch and connection to the house.

Power Level:
Types: low 1-5kW, medium 5-10kW, high 10-20kW

For residential use, generators come in various sizes ranging from 1,000 watts (1kw) to 20kw. Keep in mind that generators are not meant to be run at maximum capacity for extended periods of time.

Definitions:
Power is measured in watts (w) or kilowatts (kW). A kilowatt is 1,000 watts.
Voltage is measured in Volts.
Current is measured in Amps (A) or miliamps (mA). An amp is 1,000 miliamps.

Low power: Generators between 1-5kw (low power) are portable and designed to power a few outlets. They are generally not designed to patch into the home's circuit box. They can run things like lights, computers, modems, televisions, refrigerators, and other appliances, however, probably not at the same time. You plug in one or two extension cords to the generator and plug in your electric devices. It is important to calculate the power requirements for each device before plugging in so as not to overload the generator. It is best to research this before you lose power. two tools that come in very handy for this are the Kill A Watt meter and a clamp meter.

How to measure the power needed to run an electric device:
First, look on the back of the device or check the owners manual. There is often a sticker that gives the voltage, current, and wattage rating of the device. If you can't find the information you can estimate or measure it. Here are three examples:

This is from the bottom of a Blentec blender. The label is very clear, it uses 1,560 watts.

This is from the power supply from my Asus laptop. It gives information about voltage(V) and current(amperage)(A). It does not give wattage. It is easy to determine wattage from this information.
The equation is Power(P)=Current(A) x Voltage(V).
This adapter gives a range of input voltage since it is designed for a global market. In the USA, residential voltage from a standard outlet is 110-120 VAC (volts alternating current). So I would use 120 for voltage. 120 volts x 1.0 A = 120 watts. So this laptop can use 120 watts. I suspect the actual usage is much less, 50-80 watts but this is the max number.

 This is from the back of my Panasonic cordless phone. It gives the power source input requirements. I checked the wall adapter(power source) and it says 120 volts, 100mA but does not specify W (wattage). mili-amp mA is 0.001A. So from the power source the wattage is 0.100A x 120V = 12W. The phone consumes 0.500A x 6.5V = 3.25 W. As you can see, there is a discrepancy between the maximum wattage consumed by the power source and the wattage needed for the phone. I recommend always using the higher wattage or measuring the power requirements directly with a Kill A Watt meter. For small values it doesn't really matter, a 9 watt difference is not going to affect a 3,000 watt generator. A larger error like 500 or 1000 watts could cause problems.

How to use the Kill A Watt meter:

Here is the meter plugged into the wall with my Asus laptop. It is reading 39.6 watts. BTW, the power supply is rated for 120 watts max based on our calculations above. As you can see, actual usage is much less than maximum numbers printed on the power supply.