I have a bosch ae115tankless waterheater - the neon light will flash when turned on but when i reset the breaker it will work? any ideas/

iF YOU RAN OUT OF GAS, THE LINES MAY NEED TO BE PURGED OF AIR. dISCONNECT THE GAS FLEX AND TURN THE GAS ON TO PURGE THE AIR FROM THE LINE. dO THIS UNTIL YOU GET A STRONG SMELL OF GAS. aLSO, WHEN YOUR UNIT TRIES TO LIGHT, BUT THERE IS NO GAS, IT WILL TRY TO LIGHT THREE TIMES. aFTER THE THIRD ATTEMPT, THE UNIT LOCKS OUT. yOU MAY NEED TO RESET IT BY UNPLUGGING IT, OR IF IT IS HARD WIRED, JUST TURN THE BREAKER OFF FOR 10 SECOINDS AND THEN TURN BACK ON. tHIS WILL RESET THE GAS VALCE TO RELIGHT. gOOD LUCK!

http://www.worcester-bosch.co.uk/homeowner/literature/gas-boiler-literature/greenstar-15ri-literature. Hope this helps :)

no you do not, but it is a good idea to take the hydrogenerator apart and remove the waterwheel inside to protect it from damage(if you have anything that gets shot through the pump)
Connections are 1/2 inch.

All resets and breakers trip with high heat.
Do you mean the tankless unit is tripping the 40 amp circuit breaker?
Or the thermal cut-out, located on unit, is tripping?

Is this a new installation?
Or was the tankless working before and stop working?

Copy following link to check wiring.
AE 9.5 requires 40 amp breaker and 6 gauge wire.
http://waterheatertimer.org/How-to-wire-Tankless-electric-water-heater.html

If the unit is tripping the thermal cut, -out, then product manual says to call Bosch or service technician.
Call Bosch 866-330-2729
http://waterheatertimer.org/pdf/Bosch-Powerstar-AE3.4-7.2-9.5.pdf
Thermal cut-out can trip if water flow is too low.
Try changing power selector screw from Hi to Lo so only 1 element is ON. See diagram page 6 of manual.
Adjust the 'outlet service valve:' The manual recommends that a ball valve be installed between hot outlet and faucet. Adjust the valve so more water flows to faucet.
Remove aerator, clean aerator, don't use low flow restrictions or low flow shower heads, replace leaky faucet cartridge on single-handle faucet.

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

is this an area w/a threaded fitting?if so ,you turn off waterheater,drain,disconnect existing fitting,clean and rewrap with new teflon tape ,and retighten down.i only say to drain,because i am not sure if it is hanging and would not want to fall on you.teflon tape and rewrenching down should fix,unless soldered.then call your plumber.also if under warr.from installer ,less than 1 yr.,call them and tell them to fix it for free.i have over 13yrs in sheetmetal install,both in hvy.industrial down to many other types of home install of furnaces,a/c units,retrofits in /new and existing homes,waterheaters,garbage disp,refrig.water lines,gas etc

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

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

Test elements for short to ground.
Element that is shorted in center might not trip breaker.
Because thermostat only turns off one leg of 240V circuit, the element will continue heating using 120v to ground:
http://waterheatertimer.org/How-to-test-water-heater-element.html

Add a comment for more free help.
Also take advantage of fixya phone service.
For a price, expert speaks with you over phone while you work on water heater or any do-it-yourself project.
Fixya is always less expensive than a service call.

Look at the manual to see what code E4 is

Here is the run down>
Water too cold Neon light on:
Cause:
1). Water flow is too high-adjusting the water flow as follow; open fully both inlet and outlet shut-off valves at the heater, then turn on fully the highest flowing hot water faucet closest to the outlet connection. Adjust the outlet shut-off valve until the water flow from the hot faucet corresponds to the approximately 3.6gal/min at 105 degree.
2). One of the power supplies is not on-check the breaker box, there should be three ganged breaker, each corresponds to each of the heater power supply.
3). The power supply voltage has dropped-reset the breaker in the breaker box.
4). Temperature dial is turned too low- temperature adjustment is made using the dial on the bottom edge of the unit. The adjustment is between approximately 95 and 135 degree F. Turning the dial clockwise increase the temperature settings.
5). The inlet water temperature has dropped-readjust the temperature dial.

Attached link is for Bosch hotwater heater installation. This should give you idea as to what to look for.
http://www.boschhotwater.com/Portals/7/TechManuals/AE115_AE125_English.pdf
The following link is Basch Hotwater troubleshooting Q&A, this should also give you some help.
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/PowerStarModels/AE115AE125/Troubleshoot/tabid/632/Default.aspx

Please post back on this thread, If you still having problem.