No hot water

Error E02 indicates that the water temperature exceeded high limit.

Switch off the house circuit breakers dedicated to the water heater and then press the reset button located behind the control panel on the water heater.

Switch house circuit breakers back on.

If error persists, call a service engineer.

good luck

One leg is hot all the time. The second leg switches through a contactor or sequencer & goes through a high temp limit. Each element is wire this way.

Testing voltage on heater can be tricky since elements can test 120Volt to ground all all times.
This is because thermostats only turn off 1 Hot leg in the 240Volt circuit, while the other hot leg remains live. Each hot leg in 240Volt circuit is 120Volt.
http://waterheatertimer.org/B220C.html#120-240
Troubleshoot electric water heater:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#reset
Try following things in order: Press reset button. Test elements. Replace thermostats.
http://waterheatertimer.org/How-to-test-water-heater-element.html
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html
Add comment.

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

1) Check across top two screws on upper element for 240volts.
Circuit breaker can be tripped on one leg so water heater appears to have power, but only has 120Volts to ground, and not full 240Volt potential across both wires.
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html#electricity

2) Move wires to another same-size circuit breaker
http://waterheatertimer.org/How-to-replace-circuit-breaker.html

3) Add comment and say what you find, and for more assistance Dec 2012

If you need further help, I’m available over the phone at https://www.6ya.com/expert/gene_9f0ef4df2f9897e7

You probably could but my question would be "why?" Water heater timers are made to turn power off to waterheaters during the times that we dont need hot water, like in the middle of the night or while you are at work. This keeps the hot water heater from working during those times and wasting energy (gas or electric). Tankless water heaters already have this builtin because they only work when you actuallty turn on the hot water. If the hot water faucet is not turned on, the tankless heater never comes on. It does not use a bit of energy until the hot water is actually turned on. So it will not be using energy during the night or while you are at work. So there really is no reason to do what you are thinking about unless you have another reason that I cant think of. Tankless heaters are great and this is why they save 60% of energy of conventional tank heaters.

First of all, you have 240V water heater because tank has two elements.
You have no hot water, and tank has power to upper element.
Lower element has no power.

Something doesn't sound right.
You're not testing correctly.

Before doing anything, test across top two screws of upper element for 240Volts.
This will eliminate electrical problem as suspect.
Breaker must deliver 120V on both legs to complete the 240V circuit.
Every single-phase household circuit takes 2 wires to complete the circuit.
With 120V you need 1 neutral wire and 1 hot wire to complete circuit.
With 240V you need 2 hot wires, one from each hot busbar, to complete circuit.
Your water heater can appear to have electricity if breaker is delivering power on one leg of the 240V circuit.
To check breaker for sure, move wires to another similar size breaker to see if water heater functions properly.
http://waterheatertimer.org/B220C.html

If 240V circuit is good, then next thing is take 30 minutes and do full test of water heater parts.
This will identify exact problem(s) without guessing.
Buy 5$ multimeter from Home Depot. Install battery.
When test calls for continuity, rotate dial to Ohms (upside down horseshoe is ohms).
When test calls for testing voltage, rotate dial to 240-250-277 VAC
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

Add a comment for more help.

You have water heater with two elements.
Two-element water heaters are 240Volts.

1) Lets talk about what makes a 240Volt circuit
See basic water heater circuit:
http://waterheatertimer.org/B220C.html

Open link, and illustration at top of page is your water heater circuit

Notice that two insulated wires come from the circuit breaker and go to the water heater.
These two wires are 120volt each. When these two 120Volt wires combine, they create 240Volts
These are called hot wires because they come from the hot busbars.
There is also a bare copper wire that comes from neutral busbar.
The bare copper wire is a safeguard, and is not necessary for the 240V circuit to work.

Inside each circuit breaker box is 1 neutral busbar, and 2 hot busbars.
Open image below, and it shows typical residential breaker box
http://waterheatertimer.org/images/Inside-Main-Breaker-Box-420.jpg

In a residential home, each circuit takes two wires to complete the circuit.
For 120Volt circuit, you need 1 neutral wire and 1 hot wire to complete the circuit. These are usually a black and white wire. The bare copper wire is a safeguard.
For 240Volt circuit, you need 2 hot wires to complete the circuit, and each hot wire comes off a different busbar. These can be a black and white wire, and sometimes a black and red wire. The bare copper wire is a safeguard.

With a 240Volt water heater the two hot wires connect to the black and red wires located on top of water heater.

2) Let's talk about wiring inside a water heater.
http://waterheatertimer.org/images/WH-w-combined-530.jpg

Open image on link above, and it shows your 240volt water heater wiring.
The 2 hot wires from breaker box connect to the red and black wires on top of heater.
Inside each water heater, the wires are color-coded and will appear the same, or nearly the same, as shown on link above.
As long as your wiring appears like the image, and the hot wires from breaker box connect correctly, and the circuit breaker is working fine, then your water heater will work.

Add a comment any time.

3) More electric water heater links about water heaters, thermostats and tank wiring:
http://waterheatertimer.org/How-electric-water-heater-works.html
http://waterheatertimer.org/How-water-heater-thermostat-works.html
http://waterheatertimer.org/How-to-wire-water-heater-thermostats.html

If water is totally cold, then upper element is not getting 240V. Since element tested for 120V, then that says upper element is burned out, upper thermostat is bad, or circuit breaker is bad.
Best thing is to buy multimeter and do 30 minute troubleshoot:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

Also read information below for understanding how water heater works.

Testing elements for voltage can be misleading.
If water heater has 2 elements, then tank is 240Volts.
240V water heaters have 120V on each element at all times.
So elements have hot 120V power, but they are not turned on until the circuit is complete with 240V.
Open following links to read specifics about 120V and 240V
http://waterheatertimer.org/B220C.html
http://waterheatertimer.org/How-water-heater-thermostat-works.html

240V is made from two 120V Hot wires from breaker box.
Each 120V line from breaker is called a 'leg.'
So 240V circuit has two legs, and both legs need to be turned on to complete 240V circuit.

Water heater thermostats turn off only one leg.
The other leg is Hot all the time.
So when you test screws on an element, for example test between a screw and any bare metal part of tank, then the screw will always show 120V.
That is just one leg of the 240V circuit.
But the 240V circuit is not turned On until both legs are connected.
Every residential circuit needs two wires to complete the circuit, and in the case of 240V, those two wires are both 120V.

When the thermostat turns on, it turns on the second leg to the element and that completes the 240V circuit.
http://waterheatertimer.org/How-it-works.html

Your water heater has 2 elements so its 240Volts.

1) If breaker is delivering power on one leg of the 240Volt circuit, then water heater can appear to have electricity, but tank is receiving 120V. Both 120Volt legs are needed to complete the 240V circuit. Double check for 240Volts.

2) Review electric Load.
Water heater label shows wattage of tank.
If tank is 4500Watts for example, you installed 3500 or 4500 watt elements.
With 5500 Watt elements you need 30 amp breaker and orange-colored 10 gauge wire
With 4500 Watt elements you can get by on 20 amp breaker and 12 gauge wire up to 75 feet away.

3) Check ECO red reset button on upper thermostat. If reset is tripped, then ECO is reading high temperatures. Suspects at this point are defective upper thermostat, shorted wire or bad lower element.

4) Also note that insulation and cover must be re-installed over thermostat. Thermostat reads temperature through wall of tank. If outside air circulates around thermostat, that can cause a mis-read and cause tank to overheat and ECO trips.

If you don't want to test the heater, replace both thermostats for about $25. Return the upper thermostat for a refund. Then see of problem persists.

Here's what I would do.
1. Check breaker for 240
2. Check water heater for 240 across 1 and 3 screws on upper thermostat
3. Note wiring and breaker size.
4. Note label on side of tank.

5. Look at end of new element to see wattage printed on each element. Look for sings of high heat and burning. Tighten screws on elements.

6. Check ECO reset button. Look for high-heat and burning. Tighten screws on thermostat.

7. Test upper thermostat as follows:
http://waterheatertimer.org/images/Electric-diagram-water-800.jpg
Test left-side #1 screw to right-side middle #4 screw. Test should read 240V at all times. If not, then ECO is tripped, thermostat is bad, or electricity is OFF

8) Water heater is cold so upper element should be ON. Test upper thermostat.
Test right-side #3 screw to left-side bottom #2 screw and it should read 240V
Test right-side #3 screw to right-side bottom #4 screw and it should read 0 volts

8. If upper thermostat checks out. Test upper element for 240 across both screws. If upper element does not read 240 when water is cold, then element is bad or there is a shorted wire between element and upper thermostat.
How to test element:
http://waterheatertimer.org/How-to-test-water-heater-element.html

9. Do a full troubleshoot on electric water heater
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

The controls of electric water heaters are designed so that at no time are both the top and bottom heating elements energized. Nearly all electric water heaters of this capacity in the US & Canada (other places, too) operate on 240 Volts.

When the water in the tank is below the set point of the thermostat (in your case - 120 degrees), the top heating element is expected to be on - (unless there is an issue with the top thermostat or limit switch). The top most control is the "high temperature limit". It is identified by the reset button on it. Make sure this isn't tripped by depressing the button. If it clicks - it was tripped and should start to make hot water at this point. If not tripped, you should check for the presence of 240 Volts between the heating element terminal screws. Do not measure from ground to a terminal screw and believe 120 Volts is "good". To make heat, you need 240 Volts - not 120 Volts measured across the terminals - not to ground. The amount of heat created running at 120 Volts is only 1/4 of what it will do at the correct voltage.

If you don't measure 240 Volts on the top element, check the bottom element in the same manner described for the top element.

If unable to measure 240 volts on any element, either there is a problem with the power source (blown fuse or circuit breaker), high temp limit switch, or thermostat(s).

If 240 Volts is present on either heating element, and water is not warm / hot in 30 minutes or so, a defective heating element is suspect. You can change controls without draining a tank, but replacing elements will require draining the tank first. Do not power the water heater without first filling it.

You can read a very detailed "how to" article about checking water heaters here.

I hope this helps - and good luck!