240V Water Heater

[EEC]

The water heater has two elements rated each at 240V, 4500W. The current reading draw is 18 amps with amp meter. The element resistance is 12.5 ohms each. Using ohms law the two elements resistance total is 6.25 ohms. The current should be E/R=I or 240V/6.25=38.4A. So that's about 19.2 amps per hot line. Question is aren't the elements supposed the cycle from top only to top and bottom elements together. I never noticed any difference in the amp meter reading to indicate any cycling.

 

[infinity]

It should be that only one element operates at one time. What is the rating on the nameplate of the heater say?

 

[jumper]

Top and then bottom, never together.

 

[EEC]

How when the elements cycle from one to the other?

How when the elements cycle from one to the other?

How is the water heater tested to be certain both elements are working and cycling when they suppose too?

 

[EEC]

220-240 volt-ac watts upper element 4500 watts lower element 4500

 

[jumper]

How is the water heater tested to be certain both elements are working and cycling when they suppose too?

Turn the T-stats up and down, back and forth, and check amperage.

 

[infinity]

220-240 volt-ac watts upper element 4500 watts lower element 4500

The nameplate should tell you the total wattage. Typically it's the same as each element indicating that only one can be energized at a time.

 

[EEC]

There is no themostat on the lower element compartment. There is one in the upper compartment along with a reset button. Why is there a reset button?

 

[jumper]

Is this a standard residential WH?

 

[EEC]

Yes standard resisdential

 

[EEC]

I could post picture but I donot know how

 

[jumper]

You should have a lower T- stat, it is about 1/2 the size of the upper one.

 

[augie47]

The reset button is on a safety over-temperature thermostat and breaks all conductors ahead of any elements and operating thermostats.

 

[jumper]

I could post picture but I donot know how

Here ya go:
http://forums.mikeholt.com/showpost.php?p=760873&postcount=45

 

[EEC]

My network blocked me from photobucket

 

[winnie]

The water heater has two elements rated each at 240V, 4500W. The current reading draw is 18 amps with amp meter. The element resistance is 12.5 ohms each. Using ohms law the two elements resistance total is 6.25 ohms. The current should be E/R=I or 240V/6.25=38.4A. So that's about 19.2 amps per hot line. Question is aren't the elements supposed the cycle from top only to top and bottom elements together. I never noticed any difference in the amp meter reading to indicate any cycling.

A couple of small but important errors:

1) If the load resistance is 6.25 ohms, then the load at 240V should be 38.4A, as you write. This means _38.4A_ per leg. Both legs must carry the full current to supply a 240V load.

2) Since only one element is on at a time, you need not take the resistance of the two elements together; the load at any given time is only a single element.

3) The difference between 240/12.5 = 19.2A and the measured 18A is probably a combination of measurement error (is the resistance really 12.5 ohms, and not 12.6??) and the fact that resistance will tend to go up with temperature. The resistance of the element sitting in hot water is greater than the resistance of the element sitting in cold air.

4) We can check: 4500W / 240V = 18.75A; if the load is rated for 4500W, I would expect 18-19A at a nominal 240V.

-Jon

 

[Charlie Bob]

you can hear the elements cycling, as you hear a click noise when they do.
You have a upper and lower thermostat. If you lower both thermeostat to the lowering setting you speed up the cycling, that's how i do it.You can measure amperage while they cycle.

 

[Charlie Bob]

My network blocked me from photobucket

I've been using my pictures in my compure to unload pics.
You can click the manage attachments below, then it'll take you to a screen, look for upload from your computer. go look for your picture and upload it.
Hope this works for you.

 

[Dennis Alwon]

How is the water heater tested to be certain both elements are working and cycling when they suppose too?

Normally you have an upper thermostat that feeds down to the bottom thermostat.

The upper element is a priority. Power is given to the upper element until the thermostat has been satisfied. Once that happens it switches over to the bottom thermostat which will stay energized until the bottom half of the tank is satisfied or unless the upper part of the tank calls for more heat.

This is the upper element , reset button and thermostat. The reset button prevents he tank from getting too hot if the thermostat fails. It will kick out if the temp. gets too hot.

 

[Charlie Bob]

Normally you have an upper thermostat that feeds down to the bottom thermostat.

The upper element is a priority. Power is given to the upper element until the thermostat has been satisfied. Once that happens it switches over to the bottom thermostat which will stay energized until the bottom half of the tank is satisfied or unless the upper part of the tank calls for more heat.

This is the upper element , reset button and thermostat. The reset button prevents he tank from getting too hot if the thermostat fails. It will kick out if the temp. gets too hot.

I believe the device on top of the upper thermostat is called "high point" or something like that, i don't recall on top of the head, but like dennis said, it controls the thermostat. I've seen them sticking and sending power to both thermostat before tripping the 30 OCPD.