Navien CH-240 drip mystery: combustion, ventilation, condensation?

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Joe B

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I'm getting to know my Navien CH-240 and I appreciate much of the feedback and insight from some of my other posts. Here is a new one. I am hoping to get some tips on how to troubleshoot this.

The other day, I noticed about 1/4 of water on the garage floor beneath the unit. Oh no! It was in the same spot where I had been catching a significant drip due to a failed 3-way valve about 1.5 months ago. That got replaced, and it seems to have been replaced properly. Had no issues since then, until now.

But then, there is this new puddle indicating a new leak or drip. Since I spotted it three days ago, it has not dripped and I see no existing moisture inside the unit. The only moisture I saw was a few lingering water droplets on the rear mounting bracket. The bracket rests on a rubber-lined block which is in turn attached to the wall.

2022-02-06 20.48.59.jpg


Here is another view at an angle.

2022-02-06 20.49.11.jpg


I thought, there must be water accumulating inside the bottom of the unit, and then flowing out the back. I had seen this before when water accumulated inside the bottom of the unit due to the failing 3-way valve. So my first suspicion was a poor installation of the replacement valve.

I have looked inside with a flashlight, and it is hard to see in there, but I see no drip marks or signs of water inside the bottom of the unit, on any of the short pipes, the 3-way valve, etc. BUT, I do see some "rust colored" streaks from what looks like water dripping down the back interior of the unit. I do not know if those are old, new, or recently recurring.

I then climbed the ladder and looked on top of the unit.

2022-02-06 20.47.55.jpg


Top of unit exterior, exhaust

I could not detect moisture here, but there sure are some signs.

This unit has one of those two-in-one concentric vents. They join near the garage wall, and the single intake/exhaust thing is on the outside, approximately a total of eight to ten feet of length from the unit to outside air.

I had been actively troubleshooting a problem where it seems combustion is too rich - I am smelling lots of gas out the exhaust, and the gas man said 90% LEL and 110ppm CO, which is apparently way too high. My technician has yet to come out with the manometer, but will be doing this soon. Others have advised me to have the technician adjust the gas mix.

It has also been quite cold at night, in the 20F - 30F range.

I have yet to catch the drip or moisture accumulation in action since I first discovered the drip three days ago (the unit has indeed been running both hydronic heat and dhw plenty since that time).

Has anyone else seen symptoms like this? Is the root cause the poor air/gas mix, causing too much leftover condensation and/or maybe the concentric vent is faulty? Perhaps it is not letting enough air in nor enough condensation / exhaust out?

Thank you for any insight or tips on how to troubleshoot this!
 

John Gayewski

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I'm getting to know my Navien CH-240 and I appreciate much of the feedback and insight from some of my other posts. Here is a new one. I am hoping to get some tips on how to troubleshoot this.

The other day, I noticed about 1/4 of water on the garage floor beneath the unit. Oh no! It was in the same spot where I had been catching a significant drip due to a failed 3-way valve about 1.5 months ago. That got replaced, and it seems to have been replaced properly. Had no issues since then, until now.

But then, there is this new puddle indicating a new leak or drip. Since I spotted it three days ago, it has not dripped and I see no existing moisture inside the unit. The only moisture I saw was a few lingering water droplets on the rear mounting bracket. The bracket rests on a rubber-lined block which is in turn attached to the wall.

View attachment 80816

Here is another view at an angle.

View attachment 80817

I thought, there must be water accumulating inside the bottom of the unit, and then flowing out the back. I had seen this before when water accumulated inside the bottom of the unit due to the failing 3-way valve. So my first suspicion was a poor installation of the replacement valve.

I have looked inside with a flashlight, and it is hard to see in there, but I see no drip marks or signs of water inside the bottom of the unit, on any of the short pipes, the 3-way valve, etc. BUT, I do see some "rust colored" streaks from what looks like water dripping down the back interior of the unit. I do not know if those are old, new, or recently recurring.

I then climbed the ladder and looked on top of the unit.

View attachment 80818

Top of unit exterior, exhaust

I could not detect moisture here, but there sure are some signs.

This unit has one of those two-in-one concentric vents. They join near the garage wall, and the single intake/exhaust thing is on the outside, approximately a total of eight to ten feet of length from the unit to outside air.

I had been actively troubleshooting a problem where it seems combustion is too rich - I am smelling lots of gas out the exhaust, and the gas man said 90% LEL and 110ppm CO, which is apparently way too high. My technician has yet to come out with the manometer, but will be doing this soon. Others have advised me to have the technician adjust the gas mix.

It has also been quite cold at night, in the 20F - 30F range.

I have yet to catch the drip or moisture accumulation in action since I first discovered the drip three days ago (the unit has indeed been running both hydronic heat and dhw plenty since that time).

Has anyone else seen symptoms like this? Is the root cause the poor air/gas mix, causing too much leftover condensation and/or maybe the concentric vent is faulty? Perhaps it is not letting enough air in nor enough condensation / exhaust out?

Thank you for any insight or tips on how to troubleshoot this!
If a had to guess there's a joint that isn't quite sealed up there. Either right at the unit or very near.
 

Joe B

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I caught it. It was an internal leak at one of the o-rings. Very hard to see without taking the unit apart, but it was in there. Dripping down and out the back. Replaced multiple o-rings and the issue was resolved.
 

breplum

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You will be lucky to get 5 to 7 years out of that unit. YouTube mikeypipes navien
mikeypipes videos are impressive for that particular leaky issue, which was a mfr's transient quality control issue.
Just seeing the old Navien corrugated condensate tube makes me think the unit is possibly over 10 years already, and could easily keep going for a good long time.
Joe B...good job following the leak.
 
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