Navien 240A Maintenance Question

[Vinny01]

My unit is 13 months old and I’m getting ready to do my first maintenance flush. I have watched a few YouTube videos and am pretty confident about the process except for one point. Back when my unit was installed the plumber poured some water down the exhaust vent opening to fill the interior condensation trap as described in section 3.5 of the manual.

On all the videos I watched they all removed the round white condensation drain lid on the bottom of the unit to clean. This allowed all the water to drain out of the interior trap. After the cleaning cycle no one ever mentioned refilling the trap before starting the unit. In fact this step is not even mentioned in the directions is the manual. Won’t CO flow out of the drain tube if no water is present in the trap at start up?

If that trap needs filled when the unit is first installed it only makes sense that it needs refilled if it’s emptied.

Thanks for any assistance
Vincent

 

[Bannerman]

You are correct, the condensate trap should be refilled. The unit's exhaust fitting will be usually removable at the top of the unit so you can add water there.

If filling the trap is not performed, because natural gas and the air used for combustion contains moisture, condensation will naturally form on the cooler plastic vent piping interior walls so that condensed water will flow back to the Navien unit where it will refill the condensate trap within a short time. Manually adding water initially will ensure the trap is filled from the start and additional condensation will continue to keep it filled. Once filled, additional condensation will be drained through the drain tube to either a building drain or condensate pump as appropriate.

 

[Sponsor]

 

[Vinny01]

Bannerman, thank you for your help. Just a follow up if I may. I understand that during the combustion process the condensate tube will get refilled but what about before it is? If you don't refill it manually wont CO flow out until water is in the tube to prevent this? Just wondering here because my vent pipe is pretty close to the joist. I can always go out side and pour some water in from out there.

If not filling the interior tube will allow CO to flow out of the condensate drain this is an important step these videos are missing. Im wondering if this is why not even mentioning cleaning that out is in the owners manual.

Thanks

 

[Bannerman]

Since you have easy access to the outside termination vent, recommend adding some water to ensure the trap will again be filled.

The exhaust gases will contain a high volume of air from the inducer fan so any amount of CO will be diluted and is likely negligable, but replacing the water in the trap should ensure there will be 0 exhaust gases entering your home.

 

[Vinny01]

Sounds good.
Thank You

 

[Breplum]

I am not quite sure the issue with CO blowing out the condensate drain near ground level on the exterior of a building.
I can see that the inducer fan could have a problem and introduce a error due to lack of back pressure so the pressure safety switch won't open.
But after installing at least 30 NPE A without ever adding water to the trap at start up and never having an issue, I would not worry.

 

[Vinny01]

But after installing at least 30 NPE A without ever adding water to the trap at start up and never having an issue, I would not worry.

I don’t mean any disrespect but if manual says to add water why do you skip this step especially on an interior install?