Bosch Aquastar on-demand overheating


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Old 09-13-07, 11:40 AM
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Bosch Aquastar on-demand overheating

Hi. I have a Bosch Aquastar Tankless on-demand water heater that has worked great for about 3 years.
Now, it has ceased to work. After some experimenting, I have determined what the problem likely is: it is overheating water and the safety switch is shutting it off.
I was just wondering if anyone has any experience with this issue. Would it be a bad thermostat? I don't really know how this thing works that well..anyone have any idea if I would be able to replace that thermostat or would I need to have it serviced?
Thanks for any advice/insight you can give!!!
Josh
 
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Old 09-13-07, 12:11 PM
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Does the heat exchanger in it require periodic cleaning?

If so, has this been done?
 
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Old 09-13-07, 09:58 PM
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it's been quite a while since i've been inside a bosch tankless water heater but these heaters are computer controled. there isn't a thermostat perse. what can happen on the ones i'm most familiar with is the thermistors can get lime scale built up on them and not register the correct temp. this tells the computer that the outgoing water is cooler than it really is and it keeps heating. before tearing into it i would, at the very least, get your hands on a service manual and call the tech support line for help. most times that is a long drawn out nightmare spent listening to hold music but as i remember, the bosch tech line is quick and easy.








paul
 
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Old 09-15-07, 11:23 AM
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Originally Posted by Who
Does the heat exchanger in it require periodic cleaning?

If so, has this been done?
I did clean out the little oxygen intake screen..what is the heat exchanger?

Originally Posted by p-nor
there isn't a thermostat perse. what can happen on the ones i'm most familiar with is the thermistors can get lime scale built up on them and not register the correct temp. this tells the computer that the outgoing water is cooler than it really is and it keeps heating. before tearing into it i would, at the very least, get your hands on a service manual and call the tech support line for help.
paul
Thanks paul, that sounds like a likely possibility. Any idea how to go about cleaning the lime out of it? Is this a pretty involved process.
 
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Old 09-16-07, 05:35 AM
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Tankless water heater installs should include accessible flush connections on the supply and return side. Paloma, for example, recommends flushing with white vinegar at least annually. If you do not have ports, then it will be a more difficult process, but can be done.
 
 

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