I have a Bosch GWH 425 HNO propane Tankless Water Heater I bought 3/2009. It began intermittent exploding when demand for hot water occurs. Has happened 3 times in maybe a week. Also lately no hot water...won't lite for afew times, then can get it going from another faucet. Any ideas?
Call a qualified service tech immediately.
Gas explosion indicates dirty combustion parts, and gas is not fully igniting when tankless turns on the gas. So gas builds up and then explodes causing serious damage to tankless, and serious risk to homeowner.
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Thanks for sharing this. I had a similar problem with my Bosch, so I called a company that does water heater repair in Salt Lake City. Glad it's all fixed now.
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SOURCE: I have a Bosch GWH 425 HN Tankless Hot Water
I have the same problem with the same model. The problem has been identified by a friend of mine, correctly, I think.
This is a very dangerous problem involving Bosch's much touted safety feature, ironically enough. IT IS THE FLAME SENSOR IN THE GAS VALVE. The flame sensor is supposed to confirm that the pilot has lighted BEFORE the main gas line sends gas to the main burners, after which the pilot shuts off. The pilot light is not coming on, the sensor that shouldn't let gas fto the main burners is failing and the main gas is flowing and ignighting from the spark that is supposed to light only the pilot in a big explosion.
This is the 2nd unit of this model that has failed. I think Bosch should do a recall
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I've called a few servicemen. Concerned with the other 2 posts on this subject, as they both spent a lot of $ on servicemen with no good results. Since have cleaned water screen (wasn't dirty), & blew out unit with a blower for dust and webs...wasn't that bad. Also tried to have it reoccur, turning on- off faucets several times, sometimes with very low flow. Didn't happen, sometimes slow to ignite,. With trickle on wouldn't ignite but heard noise in heater. Working fine now for a few days. Sounds like I should clean the combustion parts. Found a service bulletin booklet online.
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