My gwh 2700 keeps freezing at night,and takes about 2 to 3 mins to reach a warm temp. had it for a 2 years no problem. just started with freezing. how do i fix it.

Check pilot is clean and strong Also check sensor is clean and connections are clean and tight .

A lot of pilot lights have a thermal coupler... the pilot light must be lit for several min to open the coupler so the pilot light will not go out.... the newer systems use an electronic ignition and no pilot light and need power to autostart but the coupler may be gone if you are holding that pilot start button down for several min and the pilot light is still going out..ps.. leave it in pilot mode for several min after initial start up before turning turning full burner operation operation operation operation operation operation operation it will snuff out the pilot light.

Stupid me but could you be a little bit literate in asking a question.

My dog write better questions that I can understand than this scribbling.

A GWH 2400 is the little brother of the GWH 2700 much like the 635ES. If you have an LP model be sure to use the overpressure protection valve supplied by Bosch as overpressure in LP (above 10-14" WC) can completely destroy this unit.

And you can use a TPR or PRV for 170,000+BTU being sure you get a House Pressure valve of 60-80-100 PSI+ and not the boiler PRV for 30 PSI

Beyond that your questions above states nothing recognizable as a technical question

Check for obstruction in your watervalve. It has a flow meter, that needs to spin freely. Remove the watervalve and blow through it, you should hear it spin.
Also make sure you dont have an error code showing. Hold down your reset button for 5 seconds to reset an error code and get back to your set temp.

CHECK LIST

- is the BTU'S enough for the space
- is there proper flow through boiler
- should have 20'F-30'F difference between inlet and outlet temp
- is there air in the system
- is there a lock on via controls that is set to lock out under 20'F
- no matter what if boiler is working properly it should be able to maintain 20-30'F temp difference from inlet to outlet
ex. 60'F in, 85'F out = 25'F split boiler is working right, if temps do not rise means house insulation my be so bad BTUS calculated for the coldest conditions was to low

Yes. Contact Bosch.
Error codes are considered start-point for troubleshoot.
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

Tankless are complex electronic machines.
If on-site plumbers cannot figure out problem, then you need trained service technician with a service manual for your specific product, who can ohm-test the electronics.
Bosch will have a list of trained service technicians. And maybe Bosch has another step for fixing problem yourself.

Fix most tankless problems yourself, same day, for $330.
http://waterheatertimer.org/How-to-install-gas-water-heater.html

im leaning towards the thermo coupler its like a eye only it measures the heat at the pilot tight if it tells the unit its off it shuts down and turnes the gas off thats why you have to keep relighting hope this helps.

A lot of factors, internal and external, can cause this problem ranging from bad PC board to plumbing problem.

Since you have no error code, it could be plumbing,
http://waterheatertimer.org/pdf/No-Error-Code.pdf

Open following link for useful Bosch troubleshooting information including Bosch support and typical manual for 2700 gas tankless:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

For folks with Rheem tankless:
http://waterheatertimer.org/Troubleshoot-Rheem-Tankless-water-heater.html

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Hi,
The unit is plugged up with mineral buildup from the water going through it... it will need to be cleaned internally....this is done by running an acid solution through it to clean out the mineral buildup...

Then it will work again...

heatman101

are u using well water or hooked up to city line if well water --may be to cold for unit if water is below a certain temp unit usually goes into error or shuts down if un heated space where water heater is u may have to warm [ insulate ,heat tape etc]the incoming water usually water that around 40 degrees causes problems