How to Calculate the Full Load Ampacity of a Transformer

Knowing how to calculate the full load ampacity of a transformer is a very important calculation to have in your bag of tricks as a meter technician. Here I want to show you how to do the calculation as well as provide why you want to calculate the full load ampacity of a transformer. Finally, I will show you how you can use the calculation to troubleshoot a transformer-rated metering installation.

How to calculate the full load ampacity of a Transformer

There a couple of things that you need to know before you start to calculate the full load ampacity of the transformer in question. First, what are you even calculating? You need to know what your answer represents before you go punching numbers into your calculator. The full load ampacity describes how many amps the transformer is designed to handle. This is important because it helps determine what size transformer is needed to handle a particular load.

Many times we receive information about load in terms of amps. Well, most transformers are sized based on KVA, kilovolt-amperes. Since transformer are sized based on KVA we need to convert this number to amps in order to know what the transformer is capable of handling.

Next we need to know a couple of other things. One is the line to line voltage of the secondary output of the transformer. You also need to know if the transformer is a single phase transformer or a three phase transformer. Once you know all of this information you can start with the calculation. For simplicity we will start with 100 KVA single phase 240v transformer. To calculate the full load ampacity use the following formula:

KVA x 1000

Line to Line voltage

So, for a 100 KVA transformer we will multiply 100 x 1000 and then divide it by 240v.

100 x 1000


That gives us 416.67 amps. So, for a 100 KVA 240v single phase transformer the full load ampacity is 416.67 amps.

Next let’s calculate the full load ampacity of a three phase transformer. There is one more step that you have to do in order to find the full load ampacity and that is to use the square root of 3 which rounds out to around 1.732. Let’s do the same thing for a 120/208v three phase transformer. Use the following formula:

KVA x 1000

Line to Line voltage x 1.732

For a 120/208v three phase 100 KVA tranformer we calculate the full load ampacity as follows:

100 x 1000

208 x 1.732

That gives us 277.58 amps. So, for a 100 KVA 120/208v three phase transformer the full load ampacity is 277.58 amps.

Why Calculate the full load Ampacity?

Now that you know how to calculate the full load amps of a transformer you probably are wondering why in the world you did that in the first place.

One reason specific to metering is that it tells you the number of amps a transformer is capable of producing so you can size your CT’s accordingly. In both examples above you can get away with using 200:5 CT’s with a rating factor of at least 3. This covers the entire operating range of each transformer.

Another reason to know the full load amps is that it ensures that you are not over or undersizing your transformer. An undersized transformer is one that is going to have a shorter life span because of the excess heat that is generated due to being overloaded. An oversized transformer is a transformer that is being under utilized. This adds up in the form of increased system losses because even though the tranformer has plenty of capacity the coils still have to be energized and this can be thought of as waste.


Knowing how to calculate the full load ampacity of a transformer can help you troubleshoot the entire installation. You as the meter tech will most likely be going out and testing transformer-rated metering installations. Many of these will be installed on tranformers that are serving only one customer. When you test the site you will find out how many amps are on the service. You can then take this information and compare it to the full load capacity of the transfomer.

Another thing that you will do is look at the demand on a transfomer by looking at all of the meters being served by a particular transformer. Looking at each meter individually will only let you know what each service is pulling on its own. If you add each of these service together you will be able to tell whether or not the transformer is sized properly.


Finding the full load ampacity of a transformer is a very useful calculation to have on hand. It can alert you to problems that may arise on your system as well as help you install the right size CT’s.

Hot Sockets in Meter Bases

Hot sockets are one of the things hot socketthat you will encounter if you spend anytime working in self-contained meter bases or changing meters. Here I want to discuss a few things that cause hot sockets, what kind of damage a hot socket can cause and what to look for when changing meters to spot a hot socket.

What causes Hot Sockets?

The biggest cause of hot sockets seems to be in my experience, loose connections. Loose connections can be at a couple of different places in the meter base. One of the places is where the wire attaches to the lugs. This is a notorious spot that heats up over time when it is not tightened properly. What happens is over time little micro arcs occur between the loose wire and the lug causing it to overheat. This, in turn, causes the socket terminal where the meter plugs in to overheat and voila, you have your first cause of a hot socket.

Another cause is the terminal or socket itself. In most meter bases these are spring loaded jaws that apply force to the terminals on the back of the meter. When the meter is pulled and set these jaws open and close back. Sometimes plastic boots are installed on the terminals of the meter in order to turn off a customer for non-payment or for any other reason. The more a meter is pulled in and out of these jaws the looser they become. When they get slack then tiny micro arcs happen which causes the terminal to overheat and we have another cause of a hot socket.

Yet another cause is the hot and the cold along with fluctuations in the load. As the metal in the terminals heats up and cools down due to the weather and load changes it expands and contracts. This over time can cause the jaws to loosen up and overheat.

A hot socket can also be caused where the terminal is put together or attaches to the bus bar in the meter base. Sometimes it is a screw or bolt and other times it is springloaded jaws that connect to bus bar. Either way, any slackness and you will eventually end up with a hot socket.

What kind of damage can a Hot Socket cause?

A hot socket is a very dangerous occurence. The worst thing it could cause is a house fire. You can see in the picures below that a hot socket in a meter base can lead to melted wire. It can also lead to overheated terminals on the meter itself. This causes irreversible damage to the meter to the point that the meter has to be replaced.

hot socket

Especially with the newer solid state meters there seems to be a lower tolerance for overheating of the terminals in a meter base. It is also not uncommon for customers who have hot sockets to experience flickering and dimming lights.

What to look for when changing meters?

When changing meters it is imperative that before pulling out any meter a quick visual inspection is done. This includes looking at the front of the meter and visually inspecting the wiring and terminals before pulling the meter out. It is very important not to take this step for granted. When terminals get so hot that they fail they can actually weld the terminals to the socket. This along with melted blocks in the meter base can cause a serious safety issue when pulling the meter.

So, look at the back of the meter the best you can before pulling it out. Once the meter is out you need to visually inspect the meter and the meter base before installing a new one. Some of the signs of an overheated terminal on a meter are discoloration and melting of the base plate. Likewise, some of the signs of a hot socket are discoloration and melted blocks and wire.

If you find this situation do not put a meter back in. The blocks, and possibly the wire and meter will all need to be replaced. Depending on you jurisdiction, this may be up to the utility or the homeowner to repair.


Hot sockets are something that every utility deals with. Be sure to be on the lookout for the causes and effects of hot sockets to keep those meters turning. As always, like us on Facebook and invite your friends!

3 Reasons Why You Should Be Using PT’s

Why use PT’s? That is a good question and this post offers three reasons why you should be using PT’s in your transformer-rated services. First, let’s review what PT’s are. PT stands for potential transformer. Some people call them VT’s which stands for voltage transformer. The names can be used interchangeably. PT’s are used to step down the voltage in a transformer-rated service to a safer and more manageable level. If you want more information on PT’s then check out our page on CT’s and PT’s. That brings us to the three reasons why you should be using PT’s.


The biggest reason why you should be using PT’s in your transformer-rated services is safety. Safety is very critical for your metering personnel and lineman. So, how do PT’s increase safety? Remember that PT’s step down voltage from a higher voltage to a lower voltage. For instance, if you have a 3 wire 480v delta service you could use 4:1 PT’s to step the voltage down at the meter base to 120v. This is much safer for utility personnel to work with.

Anything above 240v should be using PT’s to increase the safety of metering personnel and lineman. This means that instead of allowing 480v 4 wire wye and 3 wire delta self-contained services you should consider using a CT cabinet with CT’s and PT’s no matter how small the service is. This can help prevent exposure to 480v.

Prevent Catastrophic Meter Failure By Using PT’s

Below you can see what happens when a self-contained 480v meter blows up. This particular service was not even

Form 12s 480v meter blows up

Form 12s 480v meter blows up

in use at the time. The building that this meter serves is vacant. This is an Itron Sentinel form 12s meter installed in a 480v 3 wire delta service. Things like this can and do happen. If however, this installation had been metered with instrument transformers and used a CT cabinet or even overhead metering this meter would probably have not blown up. It does need to be mentioned however that if something in the service caused this meter to blow up then most likely had PT’s been used, one of the PT’s would have blown as well.

I can hear what you are saying right now. Well, if the PT is going to blow to then what is the point? The point is that when a PT blows it is generally not a catastrophic failure like shown in the pictures. Sometimes when a PT goes bad it is even hard to tell from the outside that anything has happened. Yes, you will still have a PT to replace but the failure will not be catastrophic. Although not the case in the pictures, often times when a meter blows like this the meter base needs to be replaced as well. Also, when a meter fails like this it can create fires as well. Which brings us to our last reason why you should be using PT’s.

Reduce Customer Downtime By Using PT’s

When you have a meter failure like the one shown in the pictures what does that mean for your customers? That means that they are going to have some downtime while you make the necessary repairs. At a very minimum you are going to have to replace the meter. Many utilities now have policies that prevent their personnel from working on 480v services while they are still energized. This means that while any repairs are made power to your customers will remain off. This can be the case even in the event that you are using a transformer-rated service with PT’s. In the

Form 12s 480v meter failureevent of a meter failure on a self-contained service like the one shown above power will be turned off until a new meter can be set. If the meter base is burned up or if a fire is caused this can mean that an electrician will have to be hired by the customer and also that the fire department will come out and inspect as well. Sometimes this means that the customer will have to pass inspections before the service can be restored. This can be a few days sometimes. If however a PT fails, the power may only need to be off for 30 minutes while the bad PT is replaced and everyone can go on their merry way.


PT’s are an essential tool that can be used to increase the safety of utility personnel who work on metering installations. When used properly they can help prevent catastrophic failure of metering installations. On top of that when used, PT’s can reduce the downtime your customers experience by reducing the number of meter failures and by reducing the time it takes to make repairs when a failure does occur.

Form 12s Meter Wiring Diagram

The form 12s meter can be one of the more confusing meter forms out there. So, here I want to provide a form 12s meter wiring diagram in two different configurations. One is the 120/208 network service.  The other form 12s meter wiring diagram is the form 12s meter in a delta service.

Form 12s Meter Wiring Diagram Network Service

The form 12s meter can be used with the network service. The network service comes from taking two legs off of a three phase wye transformer and using the neutral. So, if you measure voltage from each phase to ground you should get 120v. Also, if you measure voltage from phase to phase you should get 208v.

This service is typically found in businesses that are located in a downtown area or businesses that are located in an industrial park. The reason for this is that many of these businesses do not require a full three phase service. So, the utility will pull two legs and a neutral off of the nearest wye transformer and call it a day.

Looking at the diagram you notice that there are two yellow terminals. These are either or terminals. Meaning that you connect the wire to one or the other in the meter socket. Also, some meter sockets do not come with this 5th terminal pre-installed. You have to purchase a 5th terminal separately and install it yourself.

With some form 2s meter sockets there are provisions to install a 5th terminal. The form 12s is also known as a self-contained meter. This means that the meter is installed in series with the load. Pulling the meter will also turn off the power.

Form 12s Meter Delta Wiring Diagram

For the form 12s delta wiring diagram we are going to talk about the service. This is the diagram for using a 12s with a delta service. Note that this is a three phase service. If you notice there is no difference in how it is actually wired. I used different colors here to denote the difference but it is actually physically wired the same way.

This could be a 120v, 240, or 480v delta service. My recommendation, as always, is against using a self-contained meter for voltages above 240v however. In the center of this diagram following the blue wire again this is an either or connection. You can connect the wire to the left center terminal or the bottom center terminal. Also note that the stab on the back of the meter is interchangeable.

Since this is a three phase service when measuring voltage across any of the three phases you should get the same voltage.

As always remember that the colors in the diagram are for illustration purposes only. You should always use the colors your utility uses.


Form 4s Meter Wiring Diagram

The form 4s meter is the meter form used to meter single phase three wire services. Below is the form 4s meter wiring diagram. As always remember that there is no standard on colors in the metering field. So, always use your company standard as far as the color code goes. The colors here are chosen at random so they show up in the drawing.

Form 4s Meter Wiring Diagram

For the form 4s meter wiring diagram let’s start at the bottom. Notice that we are going to be metering a single-phase three-wire service. We have two phase wires and a neutral. Make note that this is the same type of service that you find on most homes. The only difference is that it is larger. Homes are typically metered with a 200 amp meter base. Furthermore, anything above that normally requires CT’s.

Ok, so we have two phases. Using Blondel’s Theorem we know that since we have three wires we are going to need two CT’s. However, each CT is installed on a different phase. Remember that the orientation of the CT’s are important. The polarity marking needs to face back towards the line side or the transformer. Hence the old adage, “dot to the pot.”

Going up the diagram from the CT’s we have wires X1 and X2 on each CT. It is also important to note that X1 is connected to the meter socket terminals labeled “current in,” and X2 is connected back to the neutral. Wire these backwards and the meter will not register correctly.

Staying in the CT circuit we go to the current return terminals. These wires connect back to the neutral to create a return path for the current.


After tracing out all of the current wires we trace out the voltage wires. Notice that in this case the voltage wires connect directly to the service wires. If we were using PT’s in this service we would connect the voltage wires to the PTs.

What voltage should you expect in this service? You should expect to see a voltage of 240v between each phase. Also from each phase to ground or neutral you should expect to see 120v. Now there are some odd 480v services out there that use this service so be aware.

Where do we normally see the form 4s?

The form 4s meter is a transformer rated, also known as a CT meter, and is typically installed on large residences who have 400 amp or larger services.

It is also found on large businesses with the same requirements. Also, it can also be found on temporary services. These can include saw services or temporary trailers for schools.

Form 2s Meter Wiring Diagram

By far the most commonly used meter in the United States is the form 2s meter. Here is a form 2s meter wiring diagram. I also want to offer some notes about the form 2s service here.

Where is the Form 2s Meter Installed

Being the most popular meter out there it comes as no surprise that the form 2s meter is installed on both residences and businesses. It comes in both regular Kwh only format and is available with a demand register as well. Regardless the meter socket for the form 2s meter is wired the same way.

The Form 2s Meter Wiring Diagram

Ok, now that we know where the form 2s meter is installed let’s take a look at the form 2s meter wiring diagram. Notice that the form 2s meter is what is known as a self-contained meter form. This means that the meter is in series with the load. So, when the meter is pulled out of the meter socket the power to the service will go off. Of course, this happens so long as there is not a bypass meter base installed.

Alright, the power comes in from the utility on the line side of the meter base which is the top side. There are two terminals that the two phase wires will attach to. These terminals connect to the jaws that hold the meter in the socket. The next thing that you notice is the neutral wire. The neutral connects to a lug that is normally but not always in the center of the meter socket. Continuing on we see the ground connection. Most meter sockets now contain terminals specifically for the ground wire. This wire is connected to a driven ground rod.

On the bottom side of the meter socket we have the load side terminals. This is where you connect the wires that go into the house and connect to the panel. Notice that you also have both phase wires and a neutral.

I also want to make note of the colors in this diagram. The colors were chosen so they show up on the diagram. Always be sure to follow local and national codes with regard to wire color codes.


The most common voltage for this type of service is 120/240. This means that if you check the voltage between the two phase wires you should get 240v. And if you check the voltage from each phase to ground or neutral you should get 120v. If you are having problems with the voltage on this service check out this post on flickering and dimming lights to help you with troubleshooting.

Form 9s Meter Wiring Diagram

One of the questions that I often get is about how to wire a form 9s meter. Since I get this question so often I thought I would put up a form 9s meter wiring diagram. Here it is with comments about the form 9s meter wiring diagram below.

About the Form 9s Meter Wiring Diagram

The form 9s meter is one of the most commonly used meter forms. S0, as you begin to study the wiring diagram I want to make note of a few things. First is that the colors that I chose were chosen at random. That is because there is no universally accepted color code. You need to make sure that when you are doing the wiring that you adhere to your utilities color code.

If you do not have a color code then create one. You can use the colors above with some important changes. If you use colors that are the same you need to make sure you have a way to tell the difference between them. One way to do this is to use a red wire for one and a red wire with a black or white tracer for the other. This helps with troubleshooting especially down the road.

Remember that the form 9s is typically used to meter a 4 wire wye service. If you notice you have phases 1, 2, and 3 labeled as well as the neutral. You will also connect the metering equipment back to ground.

Wire Groups

So, what are the different wires? When wiring a form 9s meter you can think about the different wires in groups. You have phase groups and you have voltage a current groups. This means that each phase will have two wires. The voltage wire connects directly to the service wire in this example. The current wire connects to X1 on the CT.

Follow the black lines. The smaller black line connects to the voltage terminal in the form 9s meter socket and the thicker black line comes from the CT and connects to the current terminal. These make up one phase.

Remember that with the CT’s you need to make sure that the polarity marking or “dot” as it is often called needs to point back towards the Line. Remember dot to pot.

Buy all Sell all Renewable Energy Metering

A buy all sell all arrangement of metering renewable energy seems to be one of the more popular ways of metering solar power and wind power these days. But what is it? How does it work? Is is right for me?

What is Buy all Sell all?

Buy all sell all is a way for small scale renewable energy producers to connect back into the grid. This typically uses a two meter setup. One meter measures what customers are consuming and the other measures what they are producing. It is pretty simple really.

How does it work?

As stated, in a buy all sell all arrangement two meters are typically employed. Normally when we think about renewable energy we think about solar panels on someone’s roof. This is accurate but often times customers think that as soon as they put the solar panels on the roof their power bill will go down. While this can be the case in a net metering arrangement it is not the case in a buy all sell all arrangement.

Surprising to some is that in a typical buy all sell all arrangement the normal electric bill does not change. This may be confusing. But what we are saying by buy all sell all is that we are going to buy all of the power that we use from the power company as usual. Then, all of the power that our solar panels or wind turbines produce will be sold back to the utility.

One of the easiest ways to think about it is if the solar panels or wind turbines were physically located in another state. You are still producing the power but it does not reduce your bill.

On your power be you will get something like an avoided cost credit. This is paid at a predetermined rate set by the utility. Normally it is close to the wholesale rate they pay. So, if you pay $0.10 per Kwh they may pay you $0.05 per Kwh. This means that you are not getting the retail rate paid back to you.

Is a Buy all Sell all Arrangement Right for You?

If it is the only option available then yes. If net metering is available then it is probably a better option as you can trade retail Kwh per retail Kwh. Before agreeing to either or you need to make sure that you read your rates very carefully to make sure they make perfect sense to you.


Renewable energy metering can be confusing. You have buy all sell all and you have net metering. But which on is right depends on your circumstances and what is available from your utility.

Net Metering

Net metering is often times a confusing topic for many. But, it does not have to be. Many people try to make it more complicated than it really is. Here I want to define what net metering is. I also want to talk a little bit about how it pertains to renewable energy. Finally I want to help you decide if net metering is right for you.

What is Net Metering?

Net metering is used when some form of generation is used on the same service where power is being consumed. Confusing right? As always, I want to use an example. First, let’s talk about the term “net”. To net something out means to subtract what is used from the whole amount. For example, if you had $100 worth of sales but you had $45 worth of expenses then you netted $55. The same thing works with net metering. If you are generating power, be it from a generator, solar panels or wind turbines etc., and you are putting that power back onto the grid we need a way to calculate what you consumed versus what you produced.

Net metering typically uses one meter. Using a traditional electro-mechanical meter you can actually watch the disc turn backwards when you are producing more than you are consuming. This is an analog way of doing the math for you. When you are consuming more than you are producing the meter turns the correct way. When you are producing more than you are consuming the meter turns backwards.

Net Metering and Renewable Energy

I could not talk about net metering and not mention the role it plays in renewable energy metering. Most likely the first thing that popped into you head when you read the words “net metering” was solar power. So, is solar power metered with net metering? The answer is yes. This was the most common way to meter solar power. It is easier to do from a billing stand point and can be less work all together. With other types of renewable energy metering separate billing accounts need to be set up for credits and it can be very confusing. Using one meter however, allows you to read the same meter just like you did every month. As far as billing goes it looks like the customer is using less every month.

However, not all utilities offer net metering tariffs. That is unfortunate because from a customer’s view it is really the best of options for feed in tariffs. This is because you are trading retail Kwh for retail Kwh. What I mean is that if the rate that you pay for electricity is $0.10 per Kwh every Kwh that you avoid because of your solar panels or wind turbine reduces your power bill by $0.10 per each Kwh you produce.

Is Net Metering Right for Me?

It depends. If it is an option that is available to you from your utility then it is most likely the best option. There are many things to consider with the different rates that may be available but generally speaking, net metering is usually the best option.

Are you planning on trying to produce more than you consume? Many utilities protect themselves against this by making sure that they limit the size of your renewable energy service. They pay wholesale rates for electricity so why would they want to pay you retail for what you produce?


In conclusion, I hope this dispels the net metering confusion that is floating around out there. Normally one meter is used in this arrangement. This type of metering provides a simple and easy way for utilities and customers to enjoy the benefits of renewable energy systems. Also, if it is available where you are it is most likely the best option for you.

Edison and the Electric Chair: A Story of Light and Death A Review

Recently I read Edison and the Electric Chair: A Story of Light and Death. I wanted to give a quick review of the book in case anyone was thinking about reading it.


When I picked this book to read I thought that it would be more about the electric chair. Not that I am totally interested in the electric chair or the death penalty or anything. Also, I did not know that Thomas Edison had anything to do with the electric chair.

It turns out though that this book does not focus a ton on the electric chair. It does do a decent job offering a bit of biographical information on Thomas Edison. I feel like the book focused more on the battle between alternating current and direct current.

Obviously Thomas Edison was a proponent of his own direct current system over the alternating current of George Westinghouse. So, the book focused more on the war between George Westinghouse and Thomas Edison than it did on the electric chair. Which, in my opinion was not a bad thing.

The book talks about the discovery of the light bulb and how it changed the world. It also talks about how different electric companies started.

How does it relate to Metering?

There are actually a couple of mentions of meters in this book. One is from one of the metering pioneers Elihu Thompson.

What about Thomas Edison and the Electric Chair?

There is a good discussion of the electric chair and how it was chosen to become the new humane way of enforcing the death penalty. Several examples of different methods are described and there are pictures included as well. I am not going to spoil the book but it also talks much about Thomas Edison’s role.

Would I Recommend Edison and the Electric Chair: A Story of Light and Death?

The answer is yes. Overall I thought that it was a good book and I would recommend it. I was able to learn something and anytime you can learn something it is usually a good thing. If you are interested in checking this book out follow the link for Edison and the Electric Chair: A Story of Light and Death.

What is the difference between voltage and current?

Voltage and current are two different measures that are found in electricity. They are both present in every electrical circuit from the flashlight all the way to refrigerators. But, the question is what is the difference? To illustrate the difference between voltage and current we will look at the age old comparison of electricity to water.

Current Flow

Current is a bit easier to illustrate. We can compare it to water in a garden hose. Imagine you have a simple water wheel. To make this water wheel turn you need to pour water over it. Let’s say we have two different sized water hoses. One is 3/4″ and the other is 1″. Now, let’s pour the water over the water wheel with the smaller hose and see what happens. The water wheel turns. Now, the larger hose. What happens? The water wheel turns faster.

This is a result of more water flowing in the larger water hose. More water = faster water wheel. Pretty simple. We need to make sure that when we think of current in the same way as water in a hose that we always think of the hose as full all the time. That way when you turn the hose on you instantly have water flow.

In the early days of electricity it was a commonly held belief that electricity was a fluid. This fluid was made up of tiny particles that would flow into different materials.

Voltage, the Driving Force

Again we are going to compare voltage to the water system. First remember that voltage is the driving or electromotive force that is a part of electrical circuits. How does this translate to water? Think of the voltage as the pressure in a water system.

With the two hoses from the example above how can we make the smaller hose move the water wheel faster? With more pressure of course. So, with more pressure the smaller hose can make the water wheel turn faster. How does this relate to voltage?


Look at the distribution lines above your head next time you are out and about. The wires on these lines carry thousands of volts. However, they are not very big. Remember Ohm’s Law? Let’s say you have a 2,500 watt motor. This is a multi-voltage motor. Meaning that you can wire it a couple of different ways depending on the voltage available. You need to run new wires to this motor, but what size do you need? That depends on the voltage.

Wait, I know what you are saying. Wire is sized by the number of amps. You are correct. However, depending on the voltage we may be able to run a smaller wire therefore possibly saving money. If the voltage in this case is 120 then the amperage will be 2,500/120 = 20.8 amps requiring a 10 gauge wire. If the voltage is 240 then the amperage will be 2,500/240 = 10.4 amps requiring a smaller 12 gauge wire.


Voltage and current are two different quantities that go hand in hand. Voltage is the driving force while current is the flow of electrons in the circuit.

What is Electric Current and how it relates to Metering

What is electric current? A good question indeed. What is the unit of measure for electric current? How can we measure electric current? And finally how does it relate to metering? These are the questions that will be tackled in this post. So, let’s get started with the first one.

What is electric current?

Electric current is the flow of electrons in a circuit. It is also what is used to power our stuff. Remember that in a circuit we have both voltage and current available. But, without the current flow our electrical stuff does not move. So, now that you know that electric current is the flow of electrons in a circuit what is the unit of measure used?

What is the unit of measure?

Current is measured using what are known as amperes, or amps for short. This is typically notated as an “A” in formulas but can also be notated as an “I”. This “I” stands for intensity of current. As with any unit of measure amps can be smaller or larger. So, it is not uncommon to see milliamps or kiloamps. Milliamps is typically notated as mA and kiloamps as kA. So, now that you know the unit of measure, how do you measure amps?

How do you measure Amps?

Amps, or electric current, are measured using what is known as an ammeter. An ammeter can come in a couple of different varieties. There is the common clamp on ammeter. The clamp on ammeter comes with a spring loaded jaw that enables you to open the jaw and place it around the conductors. This places the ammeter in parallel with the circuit. Clamp on ammeters can be found in digital and analog variants.

Another type of ammeter is placed in series with the circuit. These are typically found on multimeters. Also, when an ammeter is placed in series in the circuit it typically is not able to measure a very substantial load. Make sure you read the specs on your meter before you place it in series in any circuit.

How does electric current relate to Metering?

Ah yes, finally, the meat of the article. Electric current is very important to metering. This is because we are essentially measuring the changes in current flow. Remember that using Ohm’s law and the power formula that Watts = Volts x Amps. This means that the amount of watts used are in direct proportion to the amount of current that is being used. As the amps go up, so does the watts. As the amps go down so do the watts.

We as meter techs should know how amps relates to watts and how to convert amps to watts. We should also know how to go the other way and convert watts to amps. This will help us in troubleshooting with customers. Let’s have an example.

A customer is complaining of a high bill. You go to the meter and notice it is spinning pretty fast. So, you take the cover off the meter base and check the amperage. Let’s say that it is 30 amps. How do you convert this 30 amps to watts? Using Ohm’s law we plug in the numbers. Assume this is a 240v service. W = 240 volts x 30 amps = 7,200 watts. Let’s convert that to kilowatts and divide 7,200 by 1,000. We get 7.2 kw. This means that whatever the customer has on is pulling 7.2 kw and if left on for one hour it will use 7.2 kwh. A load like this could mean that an appliance like the air conditioning is not functioning properly and is running all day.


Electric current is one of the most important units we have in metering. It is measured by using ammeters and its unit of measurement is the amp. Using Ohm’s law we can convert amps to watts and back again.

What is Voltage and how it relates to Metering

What is voltage? This is certainly an important term to know in the electrical field. You hear it all the time. What is the voltage on the machine? Or, can you check the voltage on that circuit? We hear it, we say it but, what is voltage and how does it relate to metering?

What is voltage?

The most commonly used voltage definition states that voltage is the difference in potential between two points in a circuit. What a definition of voltage right? Another way that voltage is defined is by talking about water. Some find it easier to understand the voltage definition when we talk in terms of water pipes. Voltage is the driving force in an electrical circuit. We can think of it as the pressure in the circuit. So, what is voltage? It is the driving force in an electrical circuit.

How is voltage measured?

Voltage is measured using a voltmeter. With a voltmeter we can choose two different points in the circuit to measure the difference in potential across those two points. The unit of measure for voltage is known as the volt. The volt is named after Alessandro Volta who created the first battery known as a voltaic pile.

How does voltage relate to metering?

Ah yes, the big question is, how do we use voltage in metering? Well, we have to remember that meters measure kilowatts. So, what does that have to do with voltage? To find the kilowatts, we first need to find the watts. To calculate watts we need to know the current and the, you guessed it, voltage. Using Ohm’s Law we know that power is equal to voltage times current or stated mathematically, P = I x E. There are several ways you can remember this formula. One is by remembering the word PIE. Another is to change the letters to W = V x A.

In the first example, P = power measured in watts, I = current measured in amps, and E = voltage measured in volts. Just a quick fact here, E is the letter used because it stands for electromotive force which is a fancy way to say voltage.

In the second example, W = watts, V = voltage, A = amps. So, the two equations are equal they are just using different terms. The easy way to remember W = V x A is to think of West Virginia or W VA. Pretty simple right.

So, now that we know the terms we need to know how they relate to metering. Well, the nominal voltage in a typical metering circuit remains pretty much constant. A common household voltage is 120/240. So, the meter measures this voltage and then multiplies the voltage times the current in the circuit to get watts. And then as if by magic the readout is in kilowatts.


Look at the equations again and go back to algebra I. If the voltage stays constant and the amperage goes up that means that the wattage will go up. If the amperage goes down, the wattage goes down. To get kilowatts from watts, divide the watts by 1000. In the older electromechanical meters the voltage coil, also known as potential coil, produced a magnetic field in the meter. When current flows through the meter it produces a magnetic field as well. The interaction between these two fields are what causes the disc to turn. So this is why it is important to make sure that the meter chosen for each installation is crucial.


Voltage is the driving force behind each and every electrical circuit. We can use Ohm’s law to calculate watts using the power formula. It is the interaction of voltage and current in a circuit that causes the meter disc to spin. To check the voltage in a circuit we use what is called a voltmeter.

Portable Generators – All Your Neighbors Will be Jealous as they Sit in the Dark

Portable generators are becoming a very popular way to keep the power on. There are many things that can knock the power out. The biggest being storms. Whether they are ice storms, thunderstorms or just plain windstorms, a power outage can be a major inconvenience. So what do you do? You go shopping for a portable generator. But, with all of the choices available where do you start? How many watts do you need? Do you need 120v or 240v? How do you connect it to your house?  Read on as we tackle these questions.

Check out this great way to harness electricity from the Sun!

When Shopping for Portable Generators, where do you Start?

If you are keen on making your neighbors jealous when their power is out and yours is not, you need to start shopping and buy your portable generator before the storm. So, that is the first place to start. Make sure that you are not waiting on the natural disaster to begin shopping. Prices can be higher during a natural disaster and supplies may be limited.

You can do your shopping at many of the big box hardware stores or even online at sites like Amazon. There are several things that you need to consider when buying a portable generator. The biggest two are watts and voltage. When looking at these quantities you need to first decide what it is that you want to power when the power is out. Which leads us to our next point.

How many Watts do you Need?

To decide how many watts your portable generator needs to put out you first need to decide what you want to power. Do you want just lights so you can see at night? Does your refrigerator need to have power so your food does not spoil? Do you want to have heat? These are all considerations to take into account when deciding how many watts you need. All of your appliances have wattage ratings. So, decide what you want to power and then go and check the ratings of each appliance.

After you have checked the wattage ratings of your appliances add them up. This will give you the amount of wattage that your generator needs to put out. A word of caution here. Most people want to power their entire homes with a portable generator. While there are some models that are capable of doing this for smaller homes, that is not their intention. The intention is to run critical loads or essential loads. These are the loads that are most essential. If you live in a very cold climate your heating system may be a critical load. Most people choose their refrigerator and a few sets of lights as critical loads.

Should you buy a 120v or 240v Portable Generator?

The answer here depends on what you have chosen as your critical loads. If they are all 120v, such as lights and the refrigerator, then a 120v generator will work just fine. If you are wanting to power your heating system, water heater, or stove then you should consider a 240v generator. Some well pumps are also 240v. So, if you need to power a well pump you need to check the voltage of it as well.

How do you connect your Portable Generator to your House?

Connecting portable generators to your house is a job for a licensed electrician. They will install a transfer switch along with new breakers for the essential loads that you choose. This ensures that when the power does go out and you use your generator that no power will be put back on the grid. Keeping your generator power separated from grid power keeps the lineman safe.

Do not just fashion a drop cord with two ends that plug in and plug it into the wall. First of all this is illegal. Second, you can put power back on the grid this way and cause serious injury or death to someone working on the power lines. Also, if you do this you will try to run your whole house off of it. The extension cord is not rated for this and neither is the receptacle that you have it plugged into. You can burn your house down doing this.

This should be a no brainer, but make sure your portable generator is outside when using it. The exhaust from the generator can be deadly.


Portable generators can be a great addition to your home. They can keep the lights on and make your neighbors jealous. They can also be used to make sure that your food does not spoil during a storm. Make sure that when you are deciding what you want to power that you add up the wattage of each appliance. Then decide if you need a 120v or a 240v generator. Finally, once you have made your purchase, contact a licensed electrician to get everything installed in a safe and professional way.


Truper Automatic Wire Stripper Review

An automatic wire stripper can really add to your arsenal of electric tools. The ability to quickly, easily and cleanly strip wire can increase your productivity and reduce waste. Until the automatic wire stripper came about, you really had two options. You could use your knife to strip wire, or you could use a regular wire stripper like the Klein Tools 11047 Wire Stripper/Cutter. What I want to do is give my review of the Truper Automatic Wire Stripper.

Using a knife to strip wire works but there is always the risk of cutting yourself in the process. There is also the risk that you may nick the wire and degrade its capacity. You can also use the standard wire strippers. They work well but there is some skill involved with those as well. You need to know your strippers to know which slots correlate to which size wire. There is also a risk of cutting into the wire as well.

Truper Automatic Wire Stripper

truper automatic wire stripperThese wire strippers can be used to skin wire from 22 AWG – 10 AWG. This gives you a very wide range of wire sizes to choose from. And the best thing about them is that they are automatic. This means that you will not need to squint really hard to see which hold in your regular wire strippers you need to use. You just lay the wire in there and squeeze. That’s it!

I have used normal wire strippers for most of my career. I have also used a knife to skin wire for most of my career as well. So, when I bought these automatic wire strippers I was a bit skeptical. But, they really do a great job of stripping the wire.


truper automatic wire stripper jawsThe Truper automatic wire stripper features a guide that can be set up so all of your strips are the same length. This can be very useful for really anything you are doing. If you are making up a panel and you want all of your strips to be the same length so that just the right amount of bare wire is under the connector, you can do that. All you have to do is move it until you get the right length. Then set it and forget it. It really is that easy.

These automatic strippers also feature a wire cutter. However, it is not the best. It is located between the handles so you do not get a ton of leverage. When I was using them there were a few times where it did not cut all the strands of the stranded wire I was working with. But, these are not really made for cutting wire, they are made for stripping wire. If you are looking to cut wire then check out my review of the Truper Lineman’s Pliers.

Another feature of the this automatic wire stripper is the ability to crimp wire. It offers three different positions for crimping. Again, these are in the middle of the handles. I have never had good luck with any strippers or wire crimpers where the stripping, cutting or crimping is in between the handles.

The grips on these automatic wire strippers are comfortable. They offer plenty of leverage to carry out fast and precise wire strips.


The Truper Automatic Wire Stripper is a tool I wish that I would have had many years ago when I started in the meter field. I think about all of those meter bases I have wired up through the years where I used my knife or regular wire strippers to skin the wire. All of those CT’s and PT’s that I have wired up through the years could have been done much faster.

I highly recommend this tool. After using this tool on the first job you will not regret buying it. It makes stripping wire practically effortless.