Navien h/w cuts off

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New Member
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Toronto Canada
New member hi guys….I’m at a loss here on how fit my Navien NR 210A NG

Tankless is 7 years old with yearly maintenance.

Currently when I shower tank will shut off after about 5 mins. But if I run bathroom hot faucet and shower same time it never shuts down.

Get error code E030
So far I have replaced
1. Exhaust limit switch
2. High limit switch
3. Flow sensor
4. Check valve
I’m completely stuck and hope someone can help me out plz
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Licensed plumbing contractor
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San Francisco Bay Area
Dang, you have sure tried good ideas.
I just pulled a NR unit last Thursday because I so hate the poor design of those first Naviens.
The pushbutton method of running diagnosis and poor sensor feedback/troubleshooting is infurating.
The manual says to (sic, meaning all the typos are as written in the repair manual "Check the resistance betweenteo whit wires of CN13: (016E)
Check the resistance betweenteo white wires of CN 13: short-circuit (030)...Caution: Measuning should be done at least 30 minutes after an error."
The flow chart says to replace PCB if the HTL is (sic) "normally operation".
Is the heat exchanger overheating? Is the vent blocked? I've pulled one rat (dead) from a vertical exhaust vent.
Not worth replacing the PCB nor the heat exchanger on that old beast.
In case you don't know it, the newest series, the NPE A2, have a really easy interface in real English (or probably French in other areas), with multi lines of display to tell you with precision all the crap you might need to deal with.
And they haven't raised prices (yet?) the way so many other products have in the last few years.
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Wellston, OK
If your hot water flow rate through the shower is close to the minimum flow rate (usually about .5 gpm) required by the Navien, it can cause the unit to overheat before it shuts down and throws an error code. That could explain why when a lav is running concurrently with the shower it doesn't happen (the hot water flow through the tankless heater is higher for the two fixtures than shower alone). The minimum flow rate is required because the burner can only go so low and the water had to pass through fast enough to conduct the heat away from the heat exchanger so it doesn't over heat.
Hey, wait a minute.

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