Navien CH240 ng

macplee

I am buying a house with a Navien CH240 ng system for heat and hot water. The home owner tells me the system would sometime shut down if it's cold and windy out. My question is, are the intake and exhaust vents too low to the ground and/or too close to one another? It looks to be 20"+ off the ground. Is it better to have the intake a foot or so higher? Also, has anyone ever build something to protect these vents? I don't mean boxing it, but something that keeps it from the elements but still give it free flow of air? Just curious.

Gordan

Whether they're too low depends on the snow line in your neck of the woods. This is definitely not a proper termination from the point of view of preventing exhaust recirculation. The exhaust (not the intake) should be at least a foot higher. It would also be good to check the clearances from operable windows and any other "ventilation openings." Check the venting instructions in the manual for proper clearances.

macplee

Well, we got like 8' of snow here in Boston this passed winter. I would like to extend these 1-2' higher. So exhaust higher than in take. Good to know. What about building something around to prevent the wind from blowing into the vents? Has done that? I know the housing must still allow amper air flow

Ironman

macplee said:

Well, we got like 8' of snow here in Boston this passed winter. I would like to extend these 1-2' higher. So exhaust higher than in take. Good to know. What about building something around to prevent the wind from blowing into the vents? Has done that? I know the housing must still allow amper air flow

The intake needs to be kept high enough that it won't get blocked by snow. But, I don't think you need to go 8 feet. You're looking to keep it above the expected level from one snow fall, not the accumulation from several.

Don't attempt to build anything around it, that's not recommended. If the wind really is an issue (doubtful), then a "Tee" could be used on the exhaust. But, your problem is probably exhaust gas recirculating.

The boiler should have been setup with a digital combustion analyzer when it was installed. Ask the seller if this was done and if so, to give you the print out results.

jonny88

venting requirements are all in the manual.Post a pic of boiler install.For venting mod/cons in my opinion it is better to use chimney as a chase when possible.Centrotherm makes a good product.I would rather a str 90 then a 45 on the air intake.Pity they dont make a concentric termination for the unit as it would have worked for you.

SWEI

Just checked with Centrotherm, and they have Navien approvals for SW only, no concentric.

BUT, the CH manual does show generic PVC concentric terminations as an option.

jonny88

Thanks @SWEI .Ii was not aware they had that option honestly I try and stay away from it.

Bob Bona_4

Navien is fine with "rocket ship" concentrics, they don't approve the flat side by side wall terms--which is unfortunate because they offer more flexibility.

macplee

I am sorry, what is "concentric" vs. "SW"? This is all new to me. So far I understand to double check the installation manual, and that exhaust should be higher than intake but both need to be high enough to stay off typical snow fall (3' - 4' should do). Attached is a pic of the system.

SWEI

Concentric vent uses a "pipe within a pipe" design to carry both intake and exhaust gases. Concentric vent terminations allow both to pass through a single opening in a wall or roof. The design of the termination mostly prevents reversion.

SW is short for Single Wall (one pipe having one wall.)

macplee

That's very helpful. Thank you SWEI. Since I already have two holes on my wall, I may opt for extending the height of both in take and exhaust, but have exhaust be higher by 1-2 feet.

Should I use a Tee instead of 45 or 90 to prevent wind blowing in the in take? Or Tee for both in take and exhaust?

Ironman

Turn the intake back down with a 90 or two of them so it's facing the ground. You can blow the exhaust straight out or put a Tee on it. In either case, the exhaust needs to be at least12" above the intake.