We have had a love/hate relationship with our water heater for 2 years now. It’s a Bosch 635ES (aka 250SX) tankless, which for the most part, we love. It’s energy efficient and is great when we have guests and need to do 4 or 5 showers in a row (or even run 2 showers at once). So what’s the problem?
Noise. Since day one, this heater has made one of two different noises:
- A loud, combustion-engine-sounding, house-shaking groan/grunt upon startup, and/or
- A loud whistle during operation that can be heard a block away
The noises are related to the gas valve in the unit. It is apparently very finicky and tough to get adjusted properly. If the gas delivery is too little, it’ll groan; too high, and it’ll whistle. We are often lucky enough to get both. Our next door neighbor has asked questions such as “did you know your house farts?” and “why did you have a 1kHz tone coming out of your house?” (He works for a radio station, so I guess he listens to sine waves in his spare time). While they’re laid back enough not to let it bother them too much, it bothers me that we keep projecting noise out into the neighborhood. Since we already have 2 dogs and a 4 year old, it’s best not to add to the list of noise makers! The part that drives me insane is that we paid a ton of money for this thing, so I don’t think it’s unreasonable to expect it to be quiet.
I have called Bosch tech support a couple of times, and they’ll walk me through the adjustment procedure. One time I even paid an “expert” listed on the Bosch website to make the adjustments. He turned out to be an ordinary plumber who also had to call Bosch to learn how to adjust the valve. Big waste of $$. Each time it’ll work great for as long as 24 hours, then it’ll start making one of the noises. I’ll then adjust it so it only grunts, since it only happens when firing up vs. a 10 minute whistle during a shower. I have probably tried adjusting it at least 20 times, but I can never find the sweet spot.
Earlier on, there was a possibility that the unit was not getting enough gas, since our heater is on the opposite side of the house as the gas meter. To rule out the possibility, I changed out the 3/4″ line with 1″. No change. A year later, I changed over half the 1″ line to 1 1/4″. Everywhere I tried to find it, I was asked “you want it for what??” Nobody had ever heard of someone putting 1 1/4″ in a residential application, but I pressed on until I found it at a local plumbing supply shop. There was a slight lingering doubt due to our being about 1′ over the Bosch-recommended length for 1″ line, once all the elbows were factored in. I was pretty sure it wouldn’t even make a difference, but I had to find out for sure. And besides, even though I was often mad enough to rip the heater off the wall, it was maybe $60 to change out the pipe again vs. the $1000 that the heater cost. Guess what…even the mammoth line didn’t fix the problem. Even with the furnace and gas dryer running full blast, the heater is still getting well above the minimum pressure it needs. I know, because I found a way to make a homemade manometer on the net and tested it out.
I’m not sure how we ended up 2 years down the road, not really any closer to solving our problem. The only thing that has changed is my willingness to do something drastic, if necessary. I just sent Bosch a long email today, basically as a plea to hopefully have them send someone out to replace (or somehow adjust) the gas valve. To really adjust it properly, a CO2 meter is required, but neither I nor the “expert” had one. In case worse came to worst, I found the valve online, and it’s a $350 part! For that money, we could almost buy a new (smaller) heater once the new Federal Tax credit is factored in. We’ll see if Bosch responds favorably to my email and how long my drive to replace the heater lasts. It usually dies out just as soon as I figure out how much we’d have to pay, at which point I start thinking “well, it’s just a little noise…”
Picture of the water heater right after being installed (with the original 3/4″ gas pipe) [note: the install was not quite finished, so you don’t need to comment about the partially-finished temp-pressure release or the lack of pipe insulation]
Picture of the insane 1 1/4″ gas line (the black line running to the right) as it transitions to the 1″ line. It doesn’t look too big in the picture, but keep in mind that our joists are true-dimension 2×10’s!
Feb 2, 2007 update:
This story did end happily. See the new post here.
The short version of the story is that Bosch offered to replace our two year old unit with a brand new one in an effort to take care of the problem. The new one works perfectly.
Aug 19, 2008 update:
We’ve now gone through two summers since installing the new heater. Around August, we’ll find that the heater will turn off at least once during a shower. I’m assuming it has something to do with the incoming water temp being higher than the rest of the year, but it still doesn’t make sense as the flow rate for a shower is well above the heater’s minimum. Since it has happened two summers in a row, I am further convinced that there is a design flaw in this heater.
September 2012 update: I realized that I never wrote anything about the fan on our water heater. Instead of turning on the fan in conjunction with the burner, it seems to be coupled to water pressure instead. So any time any water is run in the house, hot or cold, the fan comes on for 30 seconds. It’s a little annoying when we turn on the house outside, and then noise will start coming out of the exhaust vent, which is right next to the hose reel. I once asked a Bosch rep about this, and they said that the solution would be to install a check valve to ensure that fluctuations in the cold line wouldn’t trigger the fan. That just didn’t seem worth the bother. It’s a relatively minor issue, but I really question why they designed it this way. ..