Noritz NR98-SV ideas requested

[Aliris19]

Hiya - I have a NR98-SV from approx 2010 installed and working fine. We have high water pressure, average gas AFAIK, and a bit of problem with scale that I've flushed a couple times (I didn't know to do this until recently).

With no warning it stopped working, no error codes. Simply isn't igniting I believe; you can hear it cycling but not catching. I should have thought it would be "three and out" or stop or throw some code but it just keeps going. You can smell gas and the gas on the stove works.

I shut off the gas, water and electrical breaker, put it all back: nothing. Did the same, released the water pressure and checked the filter: it was clean. Tried running several faucets to be positive of the water in the unit. Nothing. Interestingly, when I have three faucets open I do get it throwing an 11 code. Turning the machine off and back on resets that. And that's replicable - no code for one faucet, a code with three. Note, however, we have super-high water pressure from the street (bottom of a hill).

So .... now what. I've searched for manuals on troubleshooting and really can find nothing useful except they really quickly tell you to Call A Professional. There are a couple DIY things about changing the "heat exchanger", not that I really know what that means. Is it a fancy word for "burner"? I gather the fuse is some sort of wire and deeply embedded next to this heat exchanger so changing it out is a big annoying deal. I'm sure I could do it, but *should* I do it? Is there some way to trouble shoot that this is the problem? Can it be this wire/fuse and not the heat excahnger such that you tear the whole thing annoyingly open, change it out, and discover the whole exchanger should have been changed?

Yikes. Am I missing some super-simple step? I did try unplugging as well as throwing the breaker and there's no obvious reason there's an electrical problem anyway.

Thanks for any advice anyone might have to offer.

 

[Dana]

The heat exchanger is NOT the burner- it's the part that contains the water that is being heated by the burner.

A failure of the burner to ignite is absolutely NOT a heat exchanger problem, and de-scaling it will not fix that symptom.

Describe what you mean by " ...hear it cycling but not catching..."

The code "11" is (as you probably already have looked up), an indication that the unit senses that it failed to ignite.

A sticky/faulty flow sensor is one possible cause of the ignition failure, but the "...hear it c ycling". part may rule that out, if what your hearing is the initial flue purge and ignition cycle (attempt).

 

[Sponsor]

 

[Aliris19]

The heat exchanger is NOT the burner- it's the part that contains the water that is being heated by the burner.

A failure of the burner to ignite is absolutely NOT a heat exchanger problem, and de-scaling it will not fix that symptom.

Describe what you mean by " ...hear it cycling but not catching..."

The code "11" is (as you probably already have looked up), an indication that the unit senses that it failed to ignite.

A sticky/faulty flow sensor is one possible cause of the ignition failure, but the "...hear it c ycling". part may rule that out, if what your hearing is the initial flue purge and ignition cycle (attempt).

Thank you very much for replying.

What I hear - without technical language for which I apologize - is -- it sounds like blow torch, to be honest, that comes on, then clicks off, waits and comes on again, then clicks off. It's the process that I believe happens in order to ignite the gas. It's the process you hear happening "three times and out" in shutting off the heating system in order to descale it (what I heard termed "three and out").

The "11" code doesn't ordinarily get thrown and I was very puzzled by having no hot water and no code to go on. It was not until following trouble shooting suggestions to open multiple faucets that I get an error code. With three faucets (not two, not one) open, then the 11 starts to flash. It is reset just by pressing off and on (as opposed to needing to unplug the unit), and if just one faucet is open it will again fail to ignite and no code will display. So all that is replicable and reversible.

 

[Aliris19]

Thank you very much for replying.

What I hear - without technical language for which I apologize - is -- it sounds like a blow torch, to be honest, that comes on, then clicks off, waits and comes on again, then clicks off. It's the process that I believe happens in order to ignite the gas. It's the process you hear happening "three times and out" in shutting off the heating system in order to descale it (what I heard termed "three and out").

The "11" code doesn't ordinarily get thrown and I was very puzzled by having no hot water and no code to go on. It was not until following trouble shooting suggestions to open multiple faucets that I get an error code. With three faucets (not two, not one) open, then the 11 starts to flash. It is reset just by pressing off and on (as opposed to needing to unplug the unit), and if just one faucet is open it will again fail to ignite and no code will display. So all that is replicable and reversible.

I wonder if it is igniting and then immediately shutting off? [But a problem with that theory is I do smell gas...] That would imply a scaling problem. And having to turn on multiple faucets could too ... except turning on multiple faucets ought to get it to stay *on* which it doesn't; there's no indication it ever ignites.

I suppose it wouldn't hurt to descale, though it's time and some money and annoyance. The filter was pristine.

 

[Dana]

I have no idea what the ..."three times and out" in shutting off the heating system... even means. I've never had to run the burners as part of a protocol to turn off a heating system (for any reason.) Turn off the gas, turn off the power- it's off.

But it sounds like the Noritz is detecting flow and initiating an ignition cycle, trying and failing to light the burners on three (or more?) successive tries without actually lighting. Whenever that happens when the water is still flowing it SHOULD be spitting out code-11.

If there is a bunch of crud on the burners it may be lighting intermittently but can't stay lit. If there is varnish built up on the flame detector the controls might not be reliably detecting that the burners are firing, so it interrupts the gas flow, then re-initiates an ignition cycle.

It's possible that the unit is fine, but can't stay lit because the gas pressure is too low, too high, or the pressure isn't being well regulated or even air mixed in the gas line. You've stated that you have "... average gas...", but it's not clear what meaning was intended there. Have you measured the gas pressure? How old is the gas regulator?

 

[Aliris19]

Thanks again for sticking with me.
Noritz (or at least this unit) has some built in system for shunting the water elsewhere in a descaling protocol. It doesn't matter for this situation I don't think.

Yes, it seems to me that it ought to be flashing code-11 if it's not igniting. So it was interesting that it did so only under these specific circumstances of 3 faucets open (presumably meaning "more water pressure")... but as mentioned we have known very-high water pressure already.

I don't know about the gas pressure; I was only teeing off the known-high-water pressure (which is silly, they're not related). I know only that there's no noticeable disruption of gas at my gas-powered stove. I do not know whether flow rate is ever an issue with gas or whether it could be detectable by eye if it were.

There's a nipple underneath the unit separate from the water line filter - is that for bleeding the gas line? Is that something an amateur could safely do?

Unless you think it's dangerous, I'm willing to try to go inspect the burners for crud or the flame detector for varnish (presuming that these can be cleaned or changed should they wind up being a problem). Is there any reference or instructions to point to for such an operation?

It seems unlikely that the gas flow would alter; the unit's worked fine for 8 years now and it's seemingly fine at the stove. The gas regulator is ... something in the unit or something in the main house line? The gas meter appears fairly newish-looking; I think they installed new ones w/in the last five years.

I guess the question is whether it's worth inspecting the burners and flame detectors, whether I can affect any difference even if I find something there, and whether there's a safe way for a fairly-handy amateur to do so and whether there is any schematics or instructions for a NR98-SV. Well, and also I guess whether there's any way to rule out these problems shy of tearing the unit down.

 

[Dana]

There is never a need to bleed the gas line (which would indeed be quite dangerous!).

You are probably refering to the sediment trap, which is designed to capture grit before it can get into local pressure regulators & burners. If you turn the gas OFF and ventilate the space well, you can open it up and empty the sediment trap if you like, but it's pretty rare to have so much crud built up as to interfere with the functioning of the equipment even after decades.

Vacuuming the crud off burners (even taking a steel brush to them if they're really cruddy) is fine.

Cleaning the varnish off flame detectors is best done with a clean, new, plastic scouring pad (not steel wool, not sandpaper) such as 3M ScotchBrite or similar:

Using anything more abrasive than that can create surface defects that cause it to re-varnish or soot up quickly.

Modulating burners such as tankless heaters and modulating condensing boilers are much more sensitive to gas pressure fluctuations than single-output or things like gas ranges, etc. Most houses will have a gas regulator at the meter, and many appliances have a local regulator The all look something like this in general shape, but vary in size (the one at the meter is much bigger than one designed for an appliance):

 

[Aliris19]

Hi Dana - no, not the sediment trap, it's a little nipple. It's attached to (gotta go check) ... the top of the hot water line while the sediment trap is attached to the top of the cold water line. But having looked more closely, I do notice a bead of water below that nipple ... I wonder if it's significant?

I do remember it mentioned when looking into descaling a year or two ago; maybe not all units have this too. But I cannot imagine it would hurt to shut off the water and gas and unscrew that as well. I suppose it's not at all inconceivable something's cruded up there and that would be relatively easy.

The space is very well ventilated so I am not worried about residual gas puddles. It's got a nice cutoff valve too.

My only real question is how to access (and identify) the burners and flame detectors; thanks for the info about how to clean them and pitfalls there (so to speak). I'll check again, but I don't believe the "owner's manual" has such info and I cannot find a service manual.

Thanks.

 

[Aliris19]

They're calling the hot water nipple a "water drain valve" and the cold water trap a "water drain valve (water filter)" http://support.noritz.com/download....Manual/NR98SV IM.PDF&field=InstallationManual

I'll go try it, maybe I'll get lucky...

 

[Aliris19]

No success really. The nipple is clean as can be. However upon replacing it and firing everything back up, before any faucet was opened, there was a click ... so I was hopeful. But no go. And as before, no code thrown, which can be affected by opening not one additional but two additional for a total of three faucets. Then the code flashes (11). Lots of lovely gas smell. I think the first time it tried to ignite upon startup it spent longer before it shut off.

I think it does sound like cruddy flame detectors maybe? As if it is igniting, then not staying ignited... But ... why would super-high water pressure matter? BTW I did turn down the water temperature to aide in boosting water pressure; all this has been done under those lower-temp conditions.

 

[Aliris19]

Hah! Here we go ... it's a "parts list" I need. http://www.heritageparts.com/manuals/noritz/NR98-SV

 

[Dana]

Why do you think the water pressure is affecting anything? What is your static water pressure? The thing was working at your higher-than average static water pressure before, so it should still work.

Most tankless units have a minimum inlet water pressure requirement of 15 or 20 psi to prevent flash-boil inside the heat exchanger, but the maximums are usually pretty high. The last bulleted note on p16 and again on p.17 of the manual implies 29 psi is the minimum inlet water pressure for this unit (which is higher than most.)

The output temperature does not affect the static water pressure. Lower output temperature results in higher flow through the unit and a corresponding bigger pressure drop when the water is flowing, but I doubt either is related to the ignition failure. The pressure of the output after the drop is of no consequence to the tankless operation, only a practicality issue for the hot water user ( to provide sufficient flow at the faucet.)

 

[Aliris19]

I only have this empirical observation that when one faucet is open, and no hot water results, and the ignitor (presumably) can be heard cycling, then no code is thrown; while when three faucets are open code 11 flashes (and of course there also results no hot water). I have been told repeatedly over the years that our household water pressure is abnormally high - what that means precisely I have no idea. The only reason I think about it at all is that reading about these tankless heaters an important spec is water flow rate; if it's insufficient the burner won't ignite (0.5 cfm for this unit I think, maybe 0.4 cfm?). And in trouble shooting "no hot water" it is suggested to open more than one faucet in order to up the pressure and jump start the heater/ignition. That's how I came to notice the odd circumstance for when and when-not the code gets triggered. It may be a complete red herring.

Several sites (perhaps just mirroring each other) insist (though I think the Noritz site does too) that in trouble shooting it's best to drop the water temperature because that ups the flow rate and potentially enables the burner to kick on.

Anyway - yeah - all probably not related to what my problem is. Just trying to note that I've tried to do these things mentioned frequently elsewhere for troubleshooting. And hoping they'll be a clue as to what's going wrong.

 

[Dana]

This makes no sense: "... it is suggested to open more than one faucet in order to up the pressure..." .

That's the converse of what actually happens. The pressure is highest (and flow is lowest) when just one faucet is open. Opening more faucets doesn't change the pressure much, (which isn't being actively sensed anyway)- but it does increase the flow which is actively sensed by the tankless.

The flow sensor is one of the suspects here, and it's pretty common for them to fail after a decade or more of average use, sooner if the unit gets operated at or near its maximum flow much of the time. (When building heating systems around these things people tend to over-pump the tankless and burn out the flow sensors in five years or less, when they'd be better off running them at 1-3 gpm and a high temperature delta, but that's another can o' worms not directly related to your problem.)

But yes, dropping the temperature increases the amount flow through the tankless needed to deliver a given temperature at the tap. But in areas where summertime incoming water temps are 80F or higher it can take well over 1 gpm for the thing to deliver anything but scalding water even at it's minimum firing rate, so when it tries to regulate the flame it ends up turning the flame off. Is it possible your incoming water temperature has been unusually high this summer? (Not that it ever gets HOT in California... )

The minimum gas input to the NR98 is 12,000 BTU/hr or 200 BTU per minwhich at ~85% efficiency is 170BTU/minute delivered to the water. At 0.5 gpm (= 4.17lbs per minute) that's a minimum rise of 170/4.17= 41F. So if the water is coming in at 80F and the unit is set to 110F that's only a 30F rise, less than the minimum firing rate and won't work at that flow rate- it would light up then shut itself down fairly rapidly as it tries to regulate temp. That could conceivably cause the symptom of multiple ignitions in a row without spitting a code. But at 1 gpm the minimum rise at the lowest firing rate is only 20F, and so it should be fine and regulate the output temp well even with 80F in, 110F out. If the output temp were boosted to 125F (there is a scalding risk here) it should also work fine at 0.5 gpm with 80F incoming water, since that's a 45F delta, and it theoretically can dial back to 41F at minimum fire.

 

[Aliris19]

Actually, I had it set at 135 because I happen to like *hot* temperature. And yes, I'm in SoCal and I'm not exactly sure, however, whether the "tap" water has been unusually hot this summer. I mean, yes, it's been 3-digit temps last week, but no it's since cooled down and no, even though this is more than usual, it's only incrementally more so .... I think.

Someone convinced me to call Noritz; I was sure they wouldn't help but they've been very helpful stepping me through codes and opening up the unit and checking for a spark: there is one. Now I'm tasked with cleaning it with compressed air. I'll keep you posted....

OK, all this video suggests is just routine maintenance, cleaning the fan, etc. And also the spark rod, so ... I'll do it. It seems simple enough...

 

[Aliris19]

Noritz helped me to see it's sparking then recommended a routine service which just cleans out lines and the fan but crucially, also the ignitors - I used a 320 paper on that (I don't have the pad recommended handy). I think the most interesting thing I found inside is (1) everything's really pretty clean but (2) it also seems maybe to be wet where it shouldn't be. Behind the plate that holds the ignitors is a gasket and that's wet. Doesn't seem good. There is a window above the ignition plate and there's a little dust to be seen there but I couldn't get at it. Then above the box that houses the ignition plate is what looks like an engine head; I imagine it may function a little similarly? Dunno - anyway, that attaches to the piece below with a spongy gasket and there's a break in the metal 2/3 from the left along the front edge. It doesn't look wrong, the metal looks shaped. But the gasket that pokes through is wet. Is that correct? I am thinking maybe not.... I am assuming this must be the heat exchange box up top, it's above the manifold.

Thanks for any thoughts if anyone has any to offer. I appreciate the help, Dana. It might be looking bad for this appliance maybe?...

 

[Aliris19]

Noritz helped me to see it's sparking then recommended a routine service which just cleans out lines and the fan but crucially, also the ignitors - I used a 320 paper on that (I don't have the pad recommended handy). I think the most interesting thing I found inside is (1) everything's really pretty clean but (2) it also seems maybe to be wet where it shouldn't be. Behind the plate that holds the ignitors is a gasket and that's wet. Doesn't seem good. There is a window above the ignition plate and there's a little dust to be seen there but I couldn't get at it. Then above the box that houses the ignition plate is what looks like an engine head; I imagine it may function a little similarly? Dunno - anyway, that attaches to the piece below with a spongy gasket and there's a break in the metal 2/3 from the left along the front edge. It doesn't look wrong, the metal looks shaped. But the gasket that pokes through is wet. Is that correct? I am thinking maybe not.... I am assuming this must be the heat exchange box up top, it's above the manifold.

Thanks for any thoughts if anyone has any to offer. I appreciate the help, Dana. It might be looking bad for this appliance maybe?...