Navien Tankless Hotwater Heater Leaking

We have a slow leak from the outlet for the Navien's Recirculation Return Connection (RCC). We don't employ an external (through the home) recirculation system, so the return is capped. It's the cap with yellow duct tape on it, next to the Cold Water Inlet Connection (CWIC), in the photo below (I insulated the cold water copper piping in case it was collecting condensation).

Navien NR-180A Tankless Hotwater Heater from the front

We are using the internal circulation mode to speed up hot water delivery to our bathroom outlets. I'm concerned that the circulation pump or 3-Way Valve may be leaking, and water collection in the bottom of the tank is leaking through the capped RCC. The Inlet Water Filter may also be dirty, and this could cause a leak.

Note also the venting for the room, which runs right along side the water and drain pipes (the Navien will sit above this vent). I'm not sure this venting is required. The vent drops very cold air into the room during winter, and may freeze water in the pipes. There is a gas furnace in the room, but it is vented separately.

Vent to outside right under where the Navien will be installed.

Another Navien Repair

I'll say this for the standard hot water heater -- the kind with a tank -- it doesn't have a lot of moving parts and it certainly doesn't have a lot of electronics. The same can't be said for the typical tankless hot water heater. Just look at the Navien.

Navien NR-180A Tankless Hot Water Heater

The more stuff you cram into these 17" x 28" x 14" boxes, the more can go wrong. We've had problems with our system ever since it was installed in December 2010. The last fix was replacement of the flame rod assembly. Before that, we had to cut into the wall and pull the exhaust pipe down to create an incline for the condensate to drain properly.

This time around the problem was the air pressure sensor (APS). The new APS Pt# was 30000663A, and replacing it also required replacing the whole damned printed circuit board (PCB), Pt# 30000182A.

The APS is located at the top, right side of the unit.

This job went fast, less than an hour, once the problem was diagnosed, and it took time on the phone with Navien tech support to figure out what was wrong. We had, at different times, error codes 3, 10, and 12; ignition failure, abnormal air pressure, and flame loss. None of these codes made reference to the APS or the PCB.

Navien Tankless Water Heater Flame Rod Replacement

Due to continued "failure to ignite" problems (Error Code #3), we recently had the flame rod assembly on the Navien NR-180(A) replaced.

Old flame rod assembly showing oxidation and increased gap

Flame Rod Assembly Pt#30004680A

Adjusting Inclination of Navien Exhaust Pipe

See a previous post for an explanation of why this repair is being done.

Removing Navien connection to exhaust pipe

Sheet rock cut out around inlet and exhaust pipes

Condensate (~1.5") trapped in exhaust pipe

Original set of exhaust pipe

Exhaust pipe hole expanded and pipe lowered

Cover placed over open sheet rock space

Piping refit to Navien

Studying the Navien Problem

As indicated in an earlier blog post, we have had problems with our Navien NR-180A-NG tankless hot water system each winter since its installation. The system fails to ignite (Error Code E003), and thus won't deliver hot water. This happens only during winter weather, i.e., when it's very cold outside. The last time it happened was in January 2013. The error code displayed then was E027, "Abnormal activity of the air pressure sensor."

One of the theories for why we're experiencing this problem is buildup of condensate in the flue that exhausts hot air from the Navien. The flue piping has a long level section that elbows up (see photo) and water could collect here in the winter, since outside air will be cold and make the pipe cold. If enough water is collecting there, it may be blocking exhaust enough so that the system senses an air pressure problem. We've been able to reboot (unplug and plug) the system and get it working again.

Matt and Chris Q of Campbell & Company were out today to examine the system and discuss what might be done to correct the problem. It was generally agreed that the long run of the vent pipe and failure to slope the pipe the designated amount (1/4" per foot) is the major contributing factor in the system failures during cold weather. However, Matt hypothesized that another factor may be the fact that the cold air in the winter is harder to move through the long exhaust pipe. The combination of the condensate building up in the pipe and the added difficulty of moving the heavier cold air may be causing the air pressure anomaly and failure to ignite.

We hesitate to go in and realign the exhaust pipe because it is housed in a chase for cosmetic reasons (see photo below).

Matt disconnected the intake pipe on the Navien so that warm air is being drawn from inside the home (see photo below), rather than outside. We'll see if this fixes the problem when the weather turns cold. If not, we'll have to cut a hole in the chase where the vent pipe is located and attempt to incline the pipe and exhaust it directly under the deck instead of on the roof.

Water Collecting Under Wall Below Navien Tankless Hot Water Heater

We've noticed water collecting under the baseboard below the Navien Hot Water heater. The problem is intermittent; it isn't constant, and it's a small amount of water. We've noticed the water collecting during the day, when water is being used in the house, and when the heating system is more likely to be running. As an example, there was water on the floor along the baseboard yesterday. The water had dried up overnight.

Although the water is below the tankless hot water heater, it isn't coming directly from piping on the hot water heater itself. We've checked the hot and cold water piping, the drain, and cycled the pressure relief valve (in case water is splashing), and found no leaks. The water is definitely collecting inside the wall.

Water is collecting along the baseboard below the Navien
tankless hot water heater. Notice the vent on the wall.
Cold air pours through this vent during the winter.

The water runs all along the baseboard.

Drains (black), main water (blue), and plumbing
for the tankless hot water heater

Drain pipes

Intake and exhaust for tankless hot water heater. Line above
white pipes is HVAC power and condensate drain.

Exhaust goes into garage

and up garage wall

up through roof

Installation of vent ducting.

Installation of Navien tankless hot water heater.

Navien tankless hot water heater as it stands
today. Line above system is condensate drain
from furnace and power to HVAC units outside.

Condensation line exiting storage room to outside under deck.

Condensation line drain by AC unit.

Given the situation, the best guess as to the nature of the problem is condensation forming on the cold water pipe inlet coming to the Navien unit from inside the wall. There's also possibility of condensation forming on the exhaust pipe from the unit.

Pipe insulation can prevent condensation forming, as the surface temperature of the insulation will vary from the surface temperature of the pipe. Condensation will not occur, provided that (a) the insulation surface is above the dew point temperature of the air; and (b) the insulation incorporates some form of water-vapor barrier or retarder that prevents water vapor from passing through the insulation to form on the pipe surface.

Of course, another possibility is a slow leak in one of the water lines. The fact that the problem just showed up in the winter cold weather seems to mitigate against this, but doesn't rule it out.

The Navien Tankless Hot Water Heater

We're having a tankless hot water heater installed in our new house. These systems heat the water only when needed, rather than keeping a supply of water heated all the time. We used this sort of system when we lived in Vienna, Austria, and it worked fine for us.

The diagram below shows how the system works.

1 - Exhaust

2 - Heat exchanger

3 - Burner

4 - Fan

5 - Control panel

6 - Flow sensor

7 - Hot water to faucet

8 - Gas supply

9 - Cold water coming in

10 - Cold water to faucet

Plumbing for tankless hot water heater in in storage room downstairs

The Navien tankless system is much smaller than a hot water heater

The large diameter pipes above the unit are intake and exhaust pipes

The intake and exhaust pipes for the Navien exit the house under the deck. A chase has been built to hide these pipes.

The exhaust pipe travels along the back wall of the garage up to the roof 

Bottom of the Navien unit showing water inlets and outlets, as well as circulation inlet, and gas inlet.

Navien energy guide

Navien cover has been removed to permit testing

Closeup of insides of Navien unit

Mother Board -- Error codes show on display (showing 8888)