Can Someone Explain Navien's "ComfortFlow" Technology?

I just had installed (yesterday) a Navien NPE-240A. After 24 hours I'd say it's doing great - but I sure would hope it's doing great after only 24 hours. LOL

Can someone explain how the internal tank and internal recirc actually works? (I don't have a recirc loop in the house - so it's not doing any external recirc.) The manual and product documentation only says it's purpose is to eliminate/reduce cold water sandwiching.

Does it keep the buffer tank hot all the time? Or does it only do the internal recirc if the buffer tank is hot and water is called for? I think the benefit in this scenario is some of the buffer is used to pre-heat the cold incoming.

It's the details of exactly what happens and under what scenarios is what I'm trying to understand.

Thanks.

Jim

The buffer tank is hot at all times. But as far as tanks, it is very, very small. It is also super-insulated, so it is not being heated all the time. It is just enough water to provide the initial burst of hot water

i just went thru the basic entry stuff at my job for these units the "buffer tank" does actually get heated, but not often because of how well its insulated that is what the pump inside of the unit is for and also for a hot water reserc loop in the house .. the comfort flow tech in these units.. how it works it that the unit will do everything in its capability to keep that outlet temp at its set temp. it has diffrent phases in the heat exchanger and it can controll its own water flow and gas flow to keep the set output temp (if the unit is heating in high rate, and the output starts to drop it will back the flow rate down to bring the temp back up) its a really cool unit well worth the money, we have alot of happy customers with one of these

The internal recirc doesn't do a whole lot. Works quite well though with a return line.

It has been 3 months and the unit is still doing great. I have a possibly related question........

This evening I happened to be standing by the exhaust vent (outside the house) and noticed warm air coming out. There was no hot water running in the house. I went and checked the unit and confirmed the water output at that moment was 0 GPM.

Would it be doing this because it's heating the internal storage tank? I assume it's considered normal to occasionally blowing out warm air when it's not in use but I'd like to confirm. (I figure the chances of me worrying about a non-issue is greater than the chances of there being a problem with the unit. )

Thanks.

Jim

The water keeps the water in the buffer tank hot at all times. This does help with getting hot water sooner but not to a great extent. A tankless can take a few seconds to react to a water flow but with the tank hot water enters the pipes immediately so you basically save a few seconds. The real good thing about the buffer tank is the elimination of the minimum flow requirement. Without a buffer tank, the unit will just stop when the flow is below 0.5 gpm and cold water will run through the hot water pipes. Buffer tank eliminates that problem.
As for how it works, whenever the temperature of the water in the tank falls below the set temperature (usually 120 °F), the sensors tell the unit to start running. Water is circulated through the heat exchanger until the temperature in the tank is restored. At that small interval the unit will run even though there is no water use and warm fumes will be blown out. That must be what you have witnessed.