What if I have a too-small boiler installed?
You’ve seen my posts elsewhere on this forum: I’m shopping for a new gas FHW furnace with indirect domestic for my 2200 square foot Massachusetts colonial. I want a good, efficient, direct vent furnace. My gas use suggests that I don’t need more than 28kBTU/hour on the coldest winter days, so my current 95kBTU/hour output boiler is three times what I need. Almost everything I’ve read here and elsewhere agrees with this.
But, plumber after plumber wants to install something as big or bigger than what I now have. They’re worried that they’ll put something in too small, I’ll complain loudly, and they’ll get burned. It’s a reasonable concern, even if misplaced. I doubt they get many call-backs for too-large boilers.
So here’s my question: what if I prevail upon my plumber, and then find that the boiler I demanded is too small? Either I run out of hot water during the morning’s second shower, or the house starts cooling on cold windy days, or both. What are my options for fixing it?
I ask because I want to know how dire a fix I’d be in. If I’d need an electric booster that only kicks in a couple of times a year, then that’s not to bad. If I’d need a swap for the next-size-up plug-compatible boiler, then that’s pretty bad. But if I’d have to rip everything out and start from scratch, then that would really be nasty.
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