Ncb-h Installation Manual

[Hildegard Lobach]

Arethese failures due to cut through of the gasket, or thermal degradation? A fix might be as simple as using a different material for the gasket. Hopefully the manufacturer is, or can be made, aware of this issue and can come up with a fix.

The vent gasket issue seems to only occur over time. The gasket between the heat exchanger and burner may be quality control failure at the factory, given that Mike aka "Mikey Pipes" was able to make multiple turns on multiple screws before they snugged up, and it STILL leaked. Mind you this was on a BRAND NEW heat exchanger that had been shipped as a warranty replacement.

Reports of oily residue inside Naviens have been increasing over the past few years. The distributors try to claim improper vent installation whenever possible, but have been very good about sending replacement heat exchangers when there is video or photo evidence that the gasket between the combustion chamber and heat exchanger is leaking. I'm not sure if that will be how they treat it going forward, given the amount of publicity Mike is generating. This could be a serious recall, a serious enough safety problem to be taken up by state Attorneys General etc if Navien doesn't take preemptive action on it in a big way.

Mike used to be Navien's biggest fan-boy, now he seems to be scrambling to cover his OWN potential liability, having promoted and installed many dozens (even hundreds?) of Naviens over the past several years.

1> cross contamination of the intake air and exhaust due to improper location of the intake & exhaust venting terminations outside being too close to one another. READ THE MANUAL to verify whether this is a possibility, since this is what Navien will try to point to as the proximate cause, voiding the warranty.

2> The rubbery gasket around the exhaust pipe where it exits the cabinet at the top is leaking. If it's been going on for awhile there will be corrosion/rust on the cabinet at that gasket. That gasket is just under the plastic exhaust vent collar in this picture, the dot marking labeled " 2" venting up to 65' "

3> The gasket between the heat exchanger and combustion chamber at the top of the heat exchanger is leaking. This can be tested with a soapy water mix in a spray bottle. (There are commercial products designed for testing for gas leaks available at most box stores that won't corrode metals, but unscented liquid hand dishwashing liquids mixes with water would do. Just be sure to wipe it off with a clean wet sponge to remove any residue when you're done.) To test it, completely power the unit down (pull the plug, or throw the wall switch), count slowly to ten then power it back up. On the power up sequence it will do a flue purge running the combustion blower, starting at low then ramping up to max before stopping. Spray the seam under test with soapy water about mid-way through the ramp up and look for any bubbles forming along the seam.

The easiest place to test first is on the upper left of the heat exchanger, at the seam between the two screws, by the dot labeled " Fully modulating metal fiber premix burner " in that picture. Try to avoid getting anything on the screws just right of center where the flame sensor wires come down. The sides are also testable, but harder to get at. If it's leaking and you call the tech line Navien will tell you to tighten all five screws in the front holding those parts together (only three of which actually hold it together, the other two hold the flame detector asssembly) , but there are three screws on the far side that can't be reached without completely removing the heat exchanger/burner assembly, nor is it possible to test the back side for leakage in-situ. Loose screws are apparently common, even on brand new units according to Mike, but tightening them rarely (if ever) fixes the leak.

These parts are similar across all of their water tube heat exchanger products. That is essentially all Navien tankless water heaters, boilers, and combi boilers EXCEPT the "NFB" series that have a cylindrical fire tube heat exchanger instead of that rectangular stainless steel box shape of their water tube heat exchangers. See:

So, I watched Mikey Pipe's videos a couple more times and I noticed he is using a CPVC vent with multiple elbows. His install makes me think he may be exceeding the vent length limits for the boiler or running them at higher burner temps (>149 degrees F). Both of these conditions fall outside the installation manual requirements for the boilers and would probably generate additional pressure that could force flue gas by the burner gasket.

>"So, I watched Mikey Pipe's videos a couple more times and I noticed he is using a CPVC vent with multiple elbows. His install makes me think he may be exceeding the vent length limits for the boiler or running them at higher burner temps (>149 degrees F)."

Personality characteristics notwithstanding, he's not an idiot (though clearly a character!), and knows how to set water temps for both boilers & tankless water heaters. (He has also taken the factory training at Navien distributor to become Navien-certified.) He admits right out when the installation isn't up to spec.

Mike posted a few more videos over the past several days covering this problem, some of which (like the longer video in the original post this thread where he replaced the heat exchanger in his own water heater at home) BRAND NEW heat exchangers, both on brand new units or warranty replacement heat exchangers are leaking fresh out of the box on the initial power-up flue purge, even before turning on the gas or filling the tankless with water. The blower ramps up, suds appear along the seam, even on brand new, never fired, stone cold equipment.

This is more likely to be a factory quality control problem than a design error, but both could be factors. I'm glad none of YOUR 2 year old units exhibit the problem, but it's worth re-checking when doing annual maintenance.

Thanks for creating this forum and making people aware of this massive manufacturing and design defect with Navien water tube systems. One BIG issue here is the burner gasket leak on brand new systems - out of the box. Navien has know about this for months and continues to sweep it under the carpet than possible deal with a billion dollar recall. Please, if you have a Navien CH, NPE, NCB or NHB the burner gasket must be tested ASAP.

In the manufacturers' home country (Korea) Navien competes head to head with Kiturami, imported into the US by Noritz and HTP, distributed Noritz HTP and Westinghouse, as well as Noritz, and in Canada by Laars. Some of the Kiturami/HTP/Laars/Noritz water heaters with water tube heat exchangers look very similar to the water tube Naviens inside, but most (or now all?) of the units HTP is importing are fire tube types.

I don't know of any comparable issues with the issues with Kiturami design/manufacturing, but they're priced competitively with Navien. The fire tube models have a good reputation in my area, but nowhere near the local market penetration as Navien. Navien NFB/NFC s are very similar to the Kiturami fire tube units:

I have replaced the exhaust gasket per Navien on my 240 unit that was covered in the oil. Cleaned it all up and let it run again. A year later it is covered in oil again. I tried to watch your videos to test the heat exchanger, but they say they are private when they open. How can I get access to this?

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