Navien Ncb 300 Installation Manual

[Zee Petty]

Awhile ago we had a plumber/friend install a Navien tankless water heater. We trusted him and thought everything was just fine as we were getting hot water throughout the house. There is a circulator pump, but it still takes a long time for hot water to reach the upstairs bathrooms. Also, as I'm taking a closer look at it, I'm concerned that some key things may be amiss.

The cold water pipe coming from the wall goes into the domestic water inlet on the tankless heater, as it should. However, the plumber branched this off into the circulation water inlet. Is this correct for the function of the system?

When attempting a flush of the system, I shut off the hot and cold valves that lead into the heater. When I hooked hoses to the service pipes, the system still produced a strong, steady flow of water, seeming to not drain. This made me suspicious that water was coming from the mains. Is there a way to tell if the cold pipe is circulatory/return line or cold water from the mains?

You will see in the photo that the cold water valve shuts off water into the domestic water inlet but doesn't have a shut off into the circulation water inlet. Therefore, I can't drain the system. Is this incorrectly installed?

I'm fairly handy with DIY plumbing, but not and expert and I know when I am out of my league. If pointed in the right direction, though, I might be able to solve this. I would appreciate any help and insight you can offer.

The user manual for these devices (of which I own two) provides a pretty good plumbing diagram for proper install. Consider yourself lucky if this installation hasn't damaged your circulating pump inside the unit.

Actually the only real issue is the lack of isolation valve on the recirculation connection, resulting in the constant water supply to the water heater.Depending on the age of your Navien NPE-A model, he did you a favor.You need a crossover valve installed under one of your faucets that is far away from the water heater (there are a few different styles but they all have four connections and get installed under a faucet). Also the unit needs to be set to utilize the recirculation feature. It's unfortunate he's not around to explain all this to you. If enabled you would find that your hot water is ready to go almost anytime you need it, without a long wait. Most of information is available in the install manual but some of it requires a phone call to Navien support.Also you need not be concerned about pump damage. That install is exactly as specified in the newer manuals. Perhaps not everyone is familiar with the newer manual.

The only problem you have is there is no check valves in place check valves or like stop signs that direct traffic check valves, direct to flow of water. You need a check valve on the cold inlet 3/4 pipe also from the looks of the picture, you do not have a true designated recirculation line from your furnace fixture. All you have is a crossover valve underneath a sink somewhere also when plumbed correctly, all of that will only function with proper dip switch settings, perimeter settings, which is Pacific per heater model

Tankless Water heater manuals can be complex. At Hoffmann Brothers, our Navien contractors are available to help identify the very technical language found in popular Navien water heater manuals and break them down into easy to understand terms, highlighting the most important elements for your Navien products. Our goal is to clarify when maintenance, repairs or a replacement of your Navien tankless water heater might be recommended.

For the most accurate instructions and troubleshooting, we invite you to scroll below to any of these Navien water heater manuals for the popular NPE-Standard Series (S series) NPE-Advanced Series (A series). Hoffmann Brothers and Navien manufacturers recommend keeping a digital or printed copy of the required manual near your water heater for personal reference when maintenance or service becomes required.

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Are these 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.

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