Electric Water Heater

[Teken]

Hello,

As some of you may be aware I have been using a special tool to monitor my electrical consumption in the home. Recently, I have been trying to trouble shoot a few devices which I believe is not wired correctly.

I have a electric hot water tank and believe its 240. I also believe in most hot water tanks there is no neutral, correct?

On the electrical panel there is only two wires going into the dual pole 30 amp breaker. On the electric water heater there is one orange 10-2 NM wire powering up this monster tank.

My question is this: With the CT's (current transformers) to measure the total wattage on this appliance all I need to do is measure one of the service feeds correct?

Or, does both service feeds for that circuit need to be monitored to obtain a true reading?

I am having a brain fart at 5:48 AM so any insight would be appreciated!

Teken . . .

 

[Highbeam]

It's AC so you only need to measure 1 leg. Your measurement output is amps and you will need to know that your amperage is being consumed at 240 volts. Volts times amps equals watts.

 

[wyliesdiesels]

It should be a balanced load so u only need to monitor one leg! If it needed a neutral like some 240v appliances have, then it would be different much like a utility meter operates! And 10-2 is the correct wire in case u were wondering!

 

[Teken]

It's AC so you only need to measure 1 leg. Your measurement output is amps and you will need to know that your amperage is being consumed at 240 volts. Volts times amps equals watts.

It should be a balanced load so u only need to monitor one leg! If it needed a neutral like some 240v appliances have, then it would be different much like a utility meter operates! And 10-2 is the correct wire in case u were wondering!

So after talking to the maker of the device. I have a couple of options to record and capture the wattage. I can leave both CT's on both feeds and accept that the wattage meter will show up on both.

I can use just one CT, and use the software to double up the wattage so both sides will be captured. But, only one of the GUI power meters will show the combined power being consumed.

I believe I will use the one CT approach and use the software to compensate and than display the combined load / power so it can be viewed.

Thanks Guys.

Teken . . .

 

[Charles (in GA)]

240 two wire is simply power in and power out, no different than 120v is. Measuring current on both legs would double the number you are looking for. I cannot see why you would need more than one CT on one leg of the 240v for this.

Charles

 

[Socophreak]

Wattage does not double. Current is the same through both legs @ 240V. Both legs are 120V to neutral or ground, and 240V across each other.

 

[Jim_No_Garage]

Wattage does not double. Current is the same through both legs @ 240V. Both legs are 120V to neutral or ground, and 240V across each other.

Total wattage used would be double - wouldn't it? He wants to know total usage by the tank. Mesauring and calculating based on 1 leg is giving him 1/2 of the power used.

Teken - I'm jealous of the work you are doing in HA, monitoring and Solar collection.

My goal is to find a house or building - preferably something with some architectural appeal and take it back to the frame and do it up with modern amenities and materials.

The problem is that nothing stands still . . . so it's like hitting a moving target.

Cheers

Jim

 

[Teken]

Total wattage used would be double - wouldn't it? He wants to know total usage by the tank. Mesauring and calculating based on 1 leg is giving him 1/2 of the power used.

Teken - I'm jealous of the work you are doing in HA, monitoring and Solar collection.

My goal is to find a house or building - preferably something with some architectural appeal and take it back to the frame and do it up with modern amenities and materials.

The problem is that nothing stands still . . . so it's like hitting a moving target.

Cheers

Jim

Jim,

Yes, that is my goal and intent. A lot of this is new to me and I am trying to configure and wrap my head around all of these elements. I'm just trying to make sure what I am measuring, capturing is indeed correct.

If not I would like to correct any mistakes in my install. I would rather be wrong and be told so, and be allowed to learn and correct it.

Than, to live through the next *** years thinking all of this is wired and captured right.

I rather not live in ignorance of the facts and wanted some feed back from the GJ collective.

Let me post some images for all to see and maybe this will make more sense. Also, I was mistaken in stating there were (2) CT's measuring the electric hot water tank load.

There is only (1) CT in place. Based on what I have read and see at home this is normal and expected behavior. Below is a screen capture of what I see on the meter.

EDIT: I will need to wait for the water heater to come on to screen capture the power being consumed BRB.

Teken . . .

 

[Teken]

Just wanted to close off this problem as fixed. I know a lot of this is hard to translate to others who don't have the same equipment or understanding of what I am trying to do and see.

So I hope this link will provide some insight and clarify my intent. If you scroll all the way down you will see the images of what I was trying to accomplish. Trying to explain something is much harder than providing pictures to see.

http://garagejournal.com/forum/showthread.php?p=2977587#post2977587

Teken . . .