Bosch 1600H Experience

[Atom]

I installed one of these in December of 2010. FYI,I am the owner and installer and not a plumber. I had no problems with the installation. There was an initial startup problem due to a stuck diaphragm, but the Bosch tech support was able to talk me through this and since then the unit has, by and large, performed well enough except for one thing. The unit is located some distance from the primary user. It serves the clothes washer, dishwasher, and the kitchen sink primarily. It can take up to 30 seconds to tell if you have hot water depending on where you set the water flow. Unfortunately, it doesn't always light. To get it to light, you have then cycle the water on and off until it does and eventually it seems to light. I've talked to Bosch about it and until something fails, there is not much they can tell me. This situation has been very frustrating, esp. for my wife, because you never know when it has lit, or even if it will. So, I rigged up circuit which uses a phototransistor to generate signal which then will turn light up an LED located at the kitchen sink. The PT uses the green indicator light on the control box to know when to turn on. Now we know right away if it's lit or not and cycling the water on and off to get it going is not such a big deal... wife happy. However, one should not have to do this and having unreliable hot water is totally unacceptable. I'm hoping to hear from other owners as to what they may done if they have this problem and decide if I should return the unit while it is still under warranty. If anyone should want to know how to set the indicator circuit, I'll be glad to supply you with details. It is very inexpensive.

[Dana]

I've recommended the 1600H to several people (some off-grid), but haven't heard anything like the misery you seem to be having with it. But they're all in cold-water New England, not the warm gulf-coast.

With most of the lower-end tankless units flame-out is common, particularly when incoming water temps are (relatively) warm and the flow rates are low. This is primarily due to their relatively high minimum modulation on the burner (in the 1600 series min-mod is ~30KBTU/hr). If you start the hot water flow at the tap with a fairly high flow it should light up every time without much hesitation, and you can back it off a bit while running, but a burner running at 30K is going to make scalding hot water at flows less than ~1gpm when the incoming water is a tepid 65-75F or warmer (which is common enough in a LA summer). When it can't regulate the temp down, it turns itself off for a period, then re-strikes, which is probably the cycling you're experiencing.

If you just crack the tap a little on startup it'll either not have sufficient flow to run the igniter, or take many seconds. Try just blasting the flow hard for a 3-count before throttling it back, and never take it down to a real trickle- always a good-ly flow. See if that gives you a more favorable result.

Intermittent dishwasher and front-loader clothes washer draws can be an issue for many tankless units in any price & burner range. The flows are often not long enough to complete an ignition cycle, or half the flow per burst is the ignition cycle, and the average water temp is lower than expected.

I don't know how much history they have on the flow-powered ignition system, but I wasn't aware that it had an LED indicator on it(?).

[Atom]

Thanks for the comments. One of the things that happened early on was that the Bosch technician had me set the water flow to minimum. I left it there on the assumption that he knew what the best settings would be. However, recently I changed the water flow from min to max. This seems to have had a positive effect on ignition reliability. The water temp is not bad, but a little lower than I would like. It was really too hot with the min water flow setting. The burner does not cycle at all. Once it's on it stays on. The cycling I was referring to was having to turn the faucet on and off to get it to light.

There are two indicator lights on the control box, a red failure indicator and a green one for burner on.

[jadnashua]

If the outlet water gets too hot, and you can't throttle it back, you should install a tempering valve (if there isn't already one there) to ensure the outlet water never gets dangerously hot. Where I live, they are required on any water heater. This valve essentially mixes some cold with the outlet of the WH if it is above the setting, to 'temper' it to a tolerable level.

[Dana]

The "flow" adjustment on the thing functions essentially an internal tempering valve. It also has a safety overtemp shutoff that will cut in to turn off the flame.

Their water-flow powered ignition design is less than a decade old, and may have manufacturing or design issues. It SHOULD be able to light it off reliably even at min-flow, but will have more power to deliver at higher flow. Sounds like they're wasting some of the power lighting up some LEDs, but that's a fraction of the amount needed to run the ignition. I suspect it's just a flaky or failing ignition/electronic control box- not sure how easy that is to swap out, but a Bosch technician should be able to diagnose it fairly easily.

I assume you've already walked through this stuff:

http://www.boschhotwater.com/Helpful...4/Default.aspx





http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/1600HTechSupport/ServiceBulletins/tabid/1100/Default.aspx

Low gas pressure or flaky pressure regulation may also be playing a factor in the ability of the pilot to light-off in the right time frame. (That initial stuck diaphragm issue may still be there in the form of fluctuating pressure.)

[Atom]

I have noticed that the igniter will sometimes spark and the pilot does not light. This was happening yesterday. I have measured the gas pressure so I'm confident that is not a problem.

[jadnashua]

To be accurate, you need to measure the gas pressure with the unit firing. A static reading is nearly meaningless, if that's what you measured.

[Atom]

I thought I'd add another chapter in this story. The latest thing to happen was finding that the wire leading to the igniter electrode was arcing through the insulation to adjacent metal parts on the unit. I discovered this when the unit failed to light after several tries. I fixed the problem by putting some much heavier insulation around the wire. I also called Bosch and they sent me a replacement part under warranty. I have to say their tech support is really good. The other thing I should mention is that the only way I discovered this was by being directly in front of the unit with the cover off and being able turn turn the water on and off locally while observing what the unit is doing. I regret that I did not install the test valves from day one, but you really need them for troubleshooting.

[Dana]

I like that explanation for the symptom, since it validates the generally satisfactory service they've been giving in the few installations I'm familiar with.

But I'm not thrilled that it happened on a brand-new unit- seems like a design or manufacturing flaw that is detectible in a factory test (just as the sticky diaphram shouldn't be an issue on any reasonable quality control.) That said, I lived with an E.L.M. (the tankless company that Bosch bought to get into this biz), and it gave me reliable service for ~15 years, and was retired working (replaced during the installation of an integrated heat/hot-water system.) Hopefully this is the last of the bugs you have with yours.

[Atom]

Here's another thing. We've had this almost a year and since I got the igniter working correctly, it's been giving very satisfactory service. But, recently we were doing some repair work in the shower that my wife and I primarily use. While we're doing this my wife starts using the shower that is supplied by the tankless unit. No one had used that shower since the tankless unit was installed. My wife complained that she could not control the water temperature and that it would get way to hot or too cold. I checked the water temperature at the tub faucet and it seemed to regulate just fine, but not from the showerhead. I removed the flow restrictor in the shower head and this fixed the problem.

[Dana]

The minimum flow requirement for firing the thing up is apparently above the flow rate of the low-flow showerhead at your water pressure. This isn't unique to Bosch- getting the flow high enough to fire up in some situations is common other units as well, but they've gotten somewhat better over time. Some require a high initial rate to fire up, but can continue at lower flow rates once flame has been established.

[Atom]

Yes, and complicated by the fact that the shower valve is a flow regulating device itself, plus a big lag time between the heater and a shower.

[Dana]

...and some shower mixers & anti-scald valves sense the pressure difference between the cold & hot side due to the higher head of the tankless causing annoying interactions or shut-down.

Sounds like you've successfully debugged your system though.