Emax ex280t2t tankless heater every so often they get cold water when you reset the breakers in the house panel it works fine the manufactuar says it does not have a a duty cycle why does it do this and where can i get a schematic on the electronics to see if it has a duty cycle that may be faulty

Turn circuit breakers fully off and then back on.
Use nose to smell for burning inside main panel.
Make sure you are getting 240Volt and not just 120V from one leg of the breaker.
Do stress test on breaker panel.
http://waterheatertimer.org/Troubleshoot-household-electricity.html#stress

Least expensive solution: Replace tankless computer for $285 buying tank-type electric water heater from local box store.

If tankless computer is new, then call installer.
If you installed it yourself, call professional installer.
http://waterheatertimer.org/How-to-wire-Tankless-electric-water-heater.html

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

Check for small fuse on circuit board:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html
Water heater circuit boards are NOT protected from surge. And reset button does not protect from surge. Nearby lightning can put out any household appliance, especially since more of these things are electronic instead of mechanical.
Install single-use whole house surge protector and replace it after each surge event instead of replacing appliances.
http://waterheatertimer.org/How-to-wire-Whole-house-surge-protector.html
The quickest solution for tankless is to replace whole thing with more reliable tank-type electric heater for $275 from local box store.

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

You need three #8 wires for AE125. Two #8 wires for AE115.

1) Copy following link for wiring information:http://waterheatertimer.org/How-to-wire-Tankless-electric-water-heater.html

2) The AE125 has 3 elements, and requires 3 wires.Each wire is sized #8 copper, and is connected to 40 amp breaker, up to 100 feet. Over 100 feet, use 50 amp breaker and #6 wire. Oversizing breaker and wire is smarted and more efficient than undersizing.

3) Often a separate subpanel is installed to provide 3 extra spaces.

http://waterheatertimer.org/images/Main-subpanel-Tankless-600.jpg


4) Makes sure main breaker panel can accept additional 120 amps of draw without overampping panel ... and starving other appliances of full power.... that will damage appliances, overheat motors, and damage main panel and overheat main breaker. You want to oversize, not undersize electric service when installing tankless electric, which is why I do not recommend tankless electric installation, including issues of costing more to operate, and expensive repairs, and general money risk-nuisance of owning tankless vrs tank-type heater.
http://waterheatertimer.org/Troubleshoot-household-electricity.html#stress


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

I don't have specific suggestion for tankless tripping breaker or if that is a circuit breaker problem or a tankless problem.

1) Move wires to another same-size breaker and see if problem persists.

2) Compare amp draw on tankless label with wire size and breaker size amp rating.
For example 30 amp breaker using 10ga wire is rated for 80% of listed amps or 24 amps.

3) If you are drawing full 30 amps, then 30 amp breaker is getting hot. Breaker trips with heat. Older breakers can trip more easily.
http://waterheatertimer.org/How-to-replace-circuit-breaker.html

4) Before calling service technician, open following link for Bosch troubleshooting steps.
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

5) Be sure to read manual for yearly maintenance requirements.

6) Add a tempering tank for incoming cold water problem.
http://waterheatertimer.org/Tempering-tank.html

7) All gas tankless brands can be repaired by homeowner for $330.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

the price will vary in different localities.

you should call a plumbing wholsaler in your area. Home depot and Lowes will not carry these, neither will you local hardware store.

the replacement is faily simple. Eemax is a nice heater, although faily expensive to opperate.

It seems you have had little luck with a direct answer or chat...perhaps their website will help? Try here.

to what

check circut breaker reset it then chek for power on both legs.

in and out hooked up right?

Sounds like you are either getting power surges to the unit or there is an excessive amount of moisture around the control board. There also and probably is a short somewhere in the unit.