I've mainly installed Navien. I can tell you that their tech support and customer service is far and away the best of any manufacturer I've ever contacted. I won't bore you with stories but trust me they stand behind their product like no other company I've ever seen.

Maintenance... there's typically a water inlet screen to clean once a year. And descaling should be done once a year, that requires a submersible pump that runs cleaning agent and water thru the heat exchanger. You mix up the cleaner with 4 gallons of water into a 5 gallon bucket, the pump goes into that and the water pumps into the cold inlet side and out the hot back into the bucket. Let it circulate for 45 minutes. Then flush with fresh cold water. There should be bypass valves on the thing so you isolate the street inlet and the house hot outlet and you can just circulate thru the machine. You can probably buy the kit for the average price of a contractor to come out and do it twice so if you're in any way handy I'd say buy the pump kit. You'll clean the flame sensor and spark electrode while the system is flushing. It's an hour of maintenance once a year. There's also a fresh (combustion) air intake screen you should check and clean every couple years.

I hung my NPE 240 A2 on the wall today.

hey Darkside come back!!

my furnace wouldn't turn on this morning.
dead as a doornail
it's one of those fancy electric ignitions where there's just a switch, no pilot to light . I reset everything but no response, nada
got a call into the heating place, at this point ill just eat a service call/repair
but i suppose lesson learned in the future i should turn it on a few weeks before its supposed to be cold so if something is wrong it's not an emergency. I guess its not an emergency it won't be -11 tonight, but 38 is pretty damn cold to have no heat on.