My "Giant" electric hot water heater's reset button is stuck in, i never opened the cover to press the button until a couple of days ago, so not sure how it wound up pressed in, and with no hot water at all, how do i get it unstuck to work?

Bets say you have an electric water heater. shut off the electricity to the unit (typically in the breaker box), and then the water inlet valve. Locate the TPV valve, either on top of or near the top on the side, of the unit. Generally they have a small lever attached.

Depending on where in the home the heater is located, if indoors it should have thawed by now, outdoors it may still be frozen, remove the panels covering the elements. each of the elements will have a thermostat, each may be equipped with an independant reset button. press these. if one or the other seems to reset (a noticeable 'click), replace the covers.

ONLY if you were successful in resetting the thermostats, restore power, and wait 30 minutes. SLOWLY open the water supply, and watch for water leakage, listen for water flow(make sure all faucets are OFF first) Freezing can rupture the tank, ice can hold the TPV open, so there is a good chance your water heater is trash. Exercise caution.

In freezing conditions with a power outage, ALWAYS open the hot water someplace in the home to allow water flow(not full stream) to prevent freezing.

Press reset button located under topmost cover.
Replace thermostats if problems continue.
Test elements if problems continue after that
Open following link for links and images:
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

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Open top cover, and pull back insulation, and push in ECO red reset button firmly.
http://waterheatertimer.org/images/No-hot-water-1-275.jpg
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

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

Problem with overheat cutoff. Press reset button on the control panel.
Before calling service technician, open following link for Bosch troubleshoot resources.
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
Recommend that people not install tankless water heaters, or heaters they cannot repair themselves since all costs are energy.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

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Press the reset button located on upper thermostat
Following link has troubleshoot for electric water heater
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

Gene

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Check 240 circuit breaker.
Open top cover on water heater and push in ECO red reset button.
If reset button will not reset, then replace thermostat.
If reset is not tripped out, then either upper thermostat is bad, upper element is bad, or water heater might be getting 120V instead of 240V.
If you have some hot water, then best suspect is lower element.
http://waterheatertimer.org/How-to-troubleshoot-electric-water-heater.html

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Fixya is always less expensive than a service call.

Electric water heater is not making hot water.

That gives 4 suspects.

1) Breaker is not delivering 240V to water heater on both legs.
Open following link for checklist troubleshoot.
http://waterheatertimer.org/Test-electricity-to-water-heater.html

2) Upper thermostat ECO reset button has tripped. Open top cover and push in reset button. Put insulation and cover back so thermostat not exposed to cooler air. If problem persists, replace both thermostats.
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html

3) Upper element is bad. If upper element goes bad, the tank will not have any hot water, even if lower element is good.
http://waterheatertimer.org/How-to-test-water-heater-element.html
http://waterheatertimer.org/How-it-works.html

4) Water heater is overheating and ECO reset is tripping.
http://waterheatertimer.org/How-to-troubleshoot-electric-problems-with-water-heater.html

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Also take advantage of fixya expert assistance live.
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Fixya is always less expensive than a service call.

Well there should be a circuit breaker in your panel. Be sure it is on. If the water in the house was OFF while the heater was on, the element(s) could have burned up. You can go to Reem's web site and download a manual for the water heater. It will depend on your experience as to whether or not to work on this. On must follow safety procedures to work on a energized water heater for testing. There is a high limit reset button under the cover that houses the thermostats. I would recommend turning breaker off before opening this cover. The rest is a red button. Remember electric and water don't mix.

If your water has NO hot water, then click circuit breaker

Next, click red reset button.
Turn off power.
Open cover on water heater.
If heater has 2 covers, open top cover
After re-seting water heater, insulation must be put back over thermostat to prevent cooler air from affecting thermostat.

1) Reset button is a good starting place to check water heater.
Reset clicks off for a number of reasons, including overheated water.

2) Reset will not reset, then replace thermostat.
http://waterheatertimer.org/How-to-replace-thermostat-on-electric-water-heater.html

3) Resets clicks on, but clicks off again later, you should diagnose the problem.
Clicking reset is not a hazard
Click the reset as often as you want until you have time to diagnose.
http://waterheatertimer.org/How-to-troubleshoot-electric-water-heater.html

4) Reset is not tripped, and you still do not have hot water:
Then use tester on top two screws (T1 - T3 screws -or- 1 and 3 screws) of upper thermostat to check if you have power.

If you have power, then replace thermostat.
If problems continue, a full diagnosis is needed as per the link above

If you need more help, add a comment and I will respond

it is located on the thermostat. Take the cover off the side and you will see a little red button in the side of the themostat.