Question about Bosch PowerStar AE115 Tankless Water Heater...
I have AE125 that I decalcify (delime, descale) once every 3-4 months. If you don't you will get gray gravelly discharge if your water has high calcium content, in a short time this will clog all your faucets creating low water flow conditions which prevents your heater from turning on. To prevent this problem you should install a high temperature filter with a stainless steel screen on the hot water discharge side of the heater & flush it once a month.
Next you MUST descale the leftside heater element or it will literally burnout from rockhard scale deposition on the copper coil of the heater element. This scale is the same stuff you've seen coming out your faucets & is the surest sign if you don't act within a few days to descale the element that it will soon burnout.
The ONLY good way to descale is to remove the 6 screws around the top of the canister & pry the coil out with a flathead screwdriver, remove electrical connectors first & label them with tags to remind you what terminals to reinstall them on. Immerse the coil into a suitable depth of white distilled vinegar for several hours. When you see bright red copper up through the center & all around the coil then you're good to go.
While the coil is basking in the vinegar bath you need to clean out the canister from which you removed the coil, it will probably be filled with the loose gray gravelly stuff that's been coming out of your faucets.
Posted on Nov 01, 2016
Increase your flow, sounds like you are right at your activation rate.
1 way is to turn down the temp on the machine, so you dont have to mix in so much cold at your shower. Check to see if your mixing valve is bad, or your showerhead has restriction/scale built up in it.The other way is to turn on your lavatory fixture full hot before showering(which will keep hot water flowing through the machine as you adjust your temp to be comfortable.
Posted on May 06, 2014
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Posted on Jan 02, 2017
the circuit board is gone bad, try this, with power off reset the overload on the heater.Turn power back on and turn on water to the unit. with no taps open hold the pipe near the left element for a few minutes. it will most likely getting verry hot and trip the overload.(this is done with no water running and power on to the unit).you may even hear the water in the left elemnet start to boil or sizle. the reason for this is the triacs on the cir board are bad.I have troubleshoot this troblem many times. the design is bad and their in now a new unit (redesign) out . bosch knows their junk and wont cover them beyond 1 yr. one way around it is call tech at bosch and tell them its leaking. the u will get one of the new designs. Also applies to the AE125, Rp27pt
Posted on Mar 07, 2012
Product manual shows electro-mechanical thermal cutout page 9 but offers no troubleshoot steps except to say that overheating is cause.
Remove both wires off element.
Set multimeter to read ohms.
Watt and volt rating appear on side of each element.
Ohm = Volts squared divided by wattage.
Assume 240Volt circuit (240 Volts squared = 57600)
Assume 9000 watt element > check side of element for rating.
So 57600 divided by 9000 watt element = 6.4 ohms
Have you de-limed this unit?
Is there a check valve causing closed system in the plumbing, that might also cause decreased water flow?
Are there reduced-flow faucets or clogged aerators?
What happens when suspect cut-out element is no longer connected? The unit should continue heating.
Posted on Sep 26, 2012
Heating water can peculate chemicals out of water, such as metals and organics.
Especially above 138 degrees.
Have well water tested.
Turn down thermostat temperature.
Or reasonably harmless well-water bacteria can react with anode rod, or other reaction in softener, to produce colored water, and smells.
Different water can produce different sludges, brown, red, gray, black, yellow.
The sludge can also combine with deteriorating pipe flakes to clog water flow.
Sludge can accumulate over years in low spots in pipes, or at elbows and constrictions.
Have plumber flush pipes.
Or run new pipes.
Also delime tankless yearly, and flush with white vinegar as shown in product manual, and treat bacteria with H2O2 hydrogen peroxide.
Posted on Oct 30, 2012
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