Tankless Combi Boiler First Start

[Dave Alessandria]

I’m nearing the end of my project replacing an old conventional combi boiler with a tankless combi boiler (a Westinghouse WBRCNG140W 140k BTU condensing unit. I plan on hiring a pro to come out, give it a once over, and use a combustion analyzer to fine tune the gas pressure and burner but before that, I’d like to fire it up and and at least make sure that everything is working properly to troubleshoot any issues that may exist. I’m i going’s to damage or mess up anything if it runs for a few hours before I I get the burner dialed in? Thanks in advance,

Dave

 

[Dana]

You're unlikely to damage it by firing it up, the -140W has a fairly high minimum fire output, which can make it oversized for the radiation at condensing temperatures in many homes. How much of what type of radiation do you have (zone by zone, if more than one zone)?

The ~26-27,000 BTU/hr minimum-fire output needs at least 125' of typical fin-tube baseboard to balance the BTU-in to BTU-out without cycling on/off. (The -199W would only need about 90'.) If you're radiation limited there may be some programming options to help limit the cycling, but if it's broken up into a bunch of sub-30' zones some of that will need to be combined to keep it from short-cycling itself into an early grave. If it's high volume cast iron radiators the thermal mass may be enough to save the day even when under-radiated.

 

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[Dave Alessandria]

I’ve got a lot of old cast iron radiators all on one zone for the whole 2300 sqft home so I think I should have enough of thermal mass to keep it from short cycling. I just don’t want it to run lean enough to burn overheat components or rich enough to foul up the heat eachanging surfaces.