Question about Noritz 6.9 Gallon Residential Direct Vent Tankless Water Heater - N

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My Noritz 6.9 flashes a 90 code. I was told by Noritz that this code relates to air flow.. and that the unit needs to be cleaned/serviced. Is this something I can do myself? If so, how do I do it? If not whom should I call?

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I recently started getting an error 90 on my N69-M unit. I finally got a hold of someone at Noritz tech support and they state this error is a general combustion/exhaust/air flow error. Here is what they suggested to look at.
Gas Pressure – The unit has a minimum flow rate for the incoming gas and if the system is gas starved, then you have some sort of obstruction or restriction. If this is a new install and you are getting an error 90, this is likely your problem but if this is an existing install that suddenly started getting this error, unless someone was monkeying around with any values you might have in-line, this probably isn’t your problem.
Air Flow – This is a ventilation issues caused by the build-up of dust, lint, etc that chokes the flow of cool air to the unit and causes the burner to overheat. If your unit runs for a while and then pops an error 90, this is probably your problem. They told me they get a lot of these errors when the unit is installed in close proximity to a clothes dryer, which makes sense. To resolve this, remove the front panel and blow out the intake holes and slots (I tried to shop-vac mine before blowing them out and I was amazed at how much the vacuum didn’t remove). After removing the cover, the first thing you should see is a system board that is covered by a black dust shield. The board is held to the unit by 3 screws (one on the top left and two at the bottom). Remove the screws and let the board dangle by the wires plugged in it. You should now be staring at the fan assembly. They suggested that I either remove the whole unit and clean it out or use compressed air to blow it out. I went with the compressed air route because getting the fan assembly out requires removing and eventually reinstalling 2 relatively small screws way in the back of the unit that you have no real easy way to get to. Blow/clean the fan out and then blow out everything else inside the unit. Reassemble and you are good to go, provided this is your problem.
Exhaust – You might see an error 90 if the exhaust can’t freely flow. Two things can cause an exhaust issue to throw this error. One is that the flapper valve on the outlet of the system sometimes gets stuck closed. This should be easy enough to fix. The other is an obstruction in your exhaust ducting or using too small of a diameter duct to exhaust the unit.
Hope this was somewhat helpful and prevents you from having to wait on hold forever for Noritz support or having to pay someone to fix your problem.

Posted on Jan 22, 2010

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I have a N-084M also shows error code 90. The heater had been used for 3 month then stored for 2 years. The gas is 3/4, about 30ft from the meter. When I mount a loaner, a Rheem 7.4 gpm, it works fine. Tried a Rinnai, it works too. But this Noritz keeps shutting down 5 minutes after the burner starts and displays error 90. I can reset the msg by push on/off on the remote, it will work for another 5 minutes before shut down again. If gas is the problem, I would think the error code should show up winthin 10 seconds. I had the front cover removed, vent disconnected. So air is not an issue here. The problem appears even when the water flow is low (which translate to low on gas useage). I measured the gas pressure at the heater, it's about 10"WC.
But, after move the heater out, mounted on top of the gas meter, it works fine. This has been bothering me for a week. Why this unit demands more gas for the same amount of heat?

Posted on Feb 13, 2010

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Contact Noritz for a certified repair company most plumbers do not know how to repair these I do but you need to have a qualified person in your area

Posted on Nov 15, 2009

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I have a Noritz tankless water heater (model n-132m). I am getting an error code of 71. What does that mean?


The Noritz Manual shows fixed for the following error codes:
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For all other codes this is the recommendation:
Contact our sales agent if:
• Any other error code appears.

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Tip

Error Code 90 Solution


Over time after about 5 to 6 years many Noritz heaters tend to display error code 90 and stop working. The unit has to be shut off and back on for it to work again for a short time. Error code 90 is indication of abnormal combustion and can have a few causes, including blockage in the exhaust vent. However the problems lies mostly with the combustion fan. that is the fan that you hear when the unit is running. It is unable to deliver enough air to normal combustion.
Replace the fan and while doing it clean the air pathway with compressed air. In addition remove the ignition and heat senors (all in one assembly, in the middle of the unit) and sand them very slightly with very fine sandpaper (400 or higher) to remove build up on them.
While the fan is being ordered you can at your own risk operate the unit with the cover slightly open (about 2 in.) at the bottom and the unit will run without code 90. It is highly recommended to hire a trained technician for the above work as gas appliances pose a significant danger to human life and property if not installed or maintained properly. This solution is for informational purposes only. Please be safe.
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Working on a N1321-ASME unit installed in a Taco Bell. Getting error code 21. Unit gas pressure is at 8.5wc and manifold pressure spikes to 2 when it come on but unable to see what it remains at because...


I recently had a similar problem with my N-132M-ASME heater. The unit would come on, then shut down and flash Error Code 21. According to the owners manual, that code indicates the unit is not getting enough air. I tried vacuuming the unit, blowing it our with air and checking to be sure the exhaust lines were clear. Nothing helped. A service technician came out and recommended I descale the unit and clean the burner. I did this but the problem did not go away. He also suggested I replace the Burner Sensor. It's not an expensive part, around $20. I ordered the part and have not had a problem since I installed it. Hope this helps.

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I have a Nortitz natural gas water heater, model #N-063s-1. Acouple of days ago it stopped heating the water. what can I do myself to fix this matter. Thanks, lynnatheana@hotmail.com


There are many reasons a tankless heater will stop heating water. The first thing I would look for is a flashing red light on the burner indicator. The flash break down goes as follows

continuous blinking - typically means ignition failure or the unit is overheating; look for visible water inside the unit, have your gas pressure checked, or check the flame rod/igniter for buildup of debris

three blinks - typically indicates 16 error code; typically resolved by performing a descale

4 or 5 blinks - exotic error codes; for these you should definitely contact Noritz tech support

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1 Answer

Will not try to lite


1) First make sure you are getting power into the unit.
2) Then check for any visible water inside the unit which might indicate a leak.
3) The third possibility is the flow sensor being stuck. Try opening a large flow of water (bath tub, two sinks and shower) and see if the unit fires. Otherwise you may want to contact a servicer to clean this component.

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My Noritz N-084M-NG residential/commercial indoor/outdoor Hot Water Heater does not heat the water when I get up in the morning. I have to go and switch it on and off again to get it to heat the...


That unit has two flow sensors. It needs to register flow through both sensors in order for it to fire. If one of the flow sensors is stuck or if there is scale blocking flow through the heat exchanger, it will not fire. I'd recommend contacting a servicer to clean the unit.

May 21, 2010 | Noritz 8.4 Gallon Residential Tankless...

1 Answer

Sometimes the hot water just goes cold


Here are a couple things to look for:

1) flashing burner light - a flashing burner light indicates the unit is getting an error code
common error codes:
A. continuous flashing - ignition failure or abnormal combustion; look for visible water in the machine indicating a leak, check gas pressure, debris or buildup on flame rod/igniter plug, or clean unit with compressed air
B. 3 flashes - error 16, abnormal outlet water temperature; typically this code indicates you'll need to descale you unit
C. 4 or 5 flashes - exotic error codes; you should contact Noritz technical support to deal with these codes

2. If there is no flashing code, try increasing the hot water flow. In the summer time you typically use less hot water; this can result in intermittent operation of your tankless heater. Increase water flow by either: A. cleaning your showerhead and removing scale deposits B. widening your flow restrictor C. Remove your flow restrictor in the showerhead

3.If none of these resolves your problem, you probably have debris in your flow sensor. Contact Noritz technical support for a walkthrough on removing debris from a flow sensor.

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1 Answer

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You are actually getting a 90 error code. This error code occurs if the unit is dirty and overheating. I'd recommend contacting a servicer to clean your heater with compressed air. They'll need to remove the fan motor and manifold plate to fully clean the burner chamber and heat exchanger.

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1 Answer

Flashing code 90 .


The 90 error code is caused by two conditions:

1) the unit is under heating the water (not hitting the set temperature)
2) the fan is encountering resistance to air flow, which causes it to over correct

The most common causes for this conditions are:
1) insufficient BTU supplied to the unit
2) clogged fan motor or vent
3) insufficient makeup air
4) improperly installed exhaust vent

Nov 10, 2009 | Noritz Tankless Water Heaters N-0931M

3 Answers

Water Heater Won't Fire up


I had the same problem with my Noritz 751M, I called the plumber and after he talked with Noritz and ran a bunch of tests (for $150) he told me I needed a new unit ($4,000 installed). They implied it was my fault cause I never flushed it over 8 years. They were unable to tell me the flow rate though (which should be very low if scale was my main issue). I decided to take over as I am very handy and an engineer. Here is what I found:

1. The unit is 8 years old and was never descaled (orig installer did not install the bypass valves nor tell me to flush annually). So, I installed the valves ($70) and bought a pump/hoses/bucket/Zep CLR ($150) and did the flush. There was tons of flow thru the exchanger (I did not measure how much).

2. I called Noritz myself (they were very helpful) and cleaned up the igniter rod with sandpaper (it was very discolored due to 8 years of sparking). This did the trick and my unit fired up but it was very sporadic (sometimes yes & no). The difficult part is that while the igniter is installed you CANNOT actually see (nor definitively hear) the sparking. It seems like sometimes the spark happens (unit fires right up) and sometimes it doesn't (unit cycles and ends in a Code 11 after a couple of minutes).

3. INFO: Per the field manual (Search google for: docslide.us_noritz-field-manual-2009) you can read the flow rate data from Data #14 on the remote control. It needs to be >0.5 GPM for the sparking to happen which then triggers the gas flow. You can live monitor Data #14 by following the instructions in the field manual on pp.46-47. The startup logic is: Flow > 0.5 GPM then Sparking Happens then the Gas Flows then Flames start in the combustion chamber


4. I got mine to successfully start by loosening the ignitor rod PN 101 and jiggling it while still inserted into the combustion chamber (holding it with insulated pliers while still against the case) - somewhat dangerous and startling when after sparking the gas flows and flaming starts but not too bad.


5. BOTTOMLINE: I got it working but it would not "always" light (even though my flow was always >0.5 GPM). Noritz told me that it is probably because I have the older black ignitor (PN 126 = EHEJ003). They have a new and improved gray ignitor (PN 126 = EMUJ004). I ordered it with a couple of other ignitor parts for a total of $35. I just installed them and they work great - ignition all the time from every faucet.


6. ENDGAME: Order the new ignitor parts, verify your flow rates using the field manual. See the pics below for some insight. I spent 20 hrs troubleshooting and wanted o share. If you want more info just email me at: tmorganjets@gmail.com

You can monitor the flow rate and flame by doing a skype (PC at faucet to Phone place in front of Noritz) - you will be able to see the Noritz turning on (with flow rate displayed) each time you turn on a faucet - it is very helpful for troubleshooting and verification
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Feb 15, 2009 | Noritz 6.3 Gallon Residential Tankless...

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