I came across this heating a 2100 square foot house last week. I can’t find anything online about sizing and the reviews aren’t good. It looks like a water heater to me, not something to heat an entire house. It has a max input BTU of 199,000. Is anyone familiar with these?
There’s a big label on the front of that unit that will tell you what it is.
I don’t think you want to get into that rabbit hole of determining if the unit is sized properly. The first step to understanding that requirement is to know what you’re looking at.
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Check the label, Joseph…
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Your right Martin, I read most of the label while at the house but didn’t see it. It has “suitable for space heating”. I have seen this type of setup for heat, but never with that small of a boiler. The realtor and buyer have both asked me if it will heat the home.
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It’s a cat3 micro boiler, so @ 200k btu and 80% efficiency you can get 160k btu out of it if the rest of the system is installed correctly. 160k BTU should be plenty for 2.1k sqft house.
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If you want to take on the liability of answering that question that’s your prerogative. I would refer that question to a licensed professional.
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Simon I would never make that assumption without a heat loss calculation. Just my two cents.
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I agree, I would never state the heater was adequately sized. What I meant to say is that I would not be alarmed if I encountered such heater in 2.1k sqft house. But, say, if it was 50k and there was no insulation in the attic, and maybe even areas of a wall where I could see, I would write it up hard. BTW, if 160k BTU is not enough for 2.1k house, it’s either made out of glass or you’ve got window-size hole(s) in the house. If that’s the case the OP should not be asking about heater size 
Lastly, we all know nobody (95% contractors) performs heat loss calculations, they just go by rule of thumb and oversize for the coldest or hottest day. Then, when the thing short cycles and dies prematurely or does not deliver proper comfort, the contractor makes more money by downsizing the unit (and in rare cases upsizing).
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I come across these quite a bit in Seattle. However, typically the end unit will be a wall unit with a fan, but heated by circulated water. Each zone has a wall thermostat to control the valve for that zone at a manifold. Each wall heater has a 2 speed fan. They do take a bit to get “Hot” and will usually limit out at 120° air flow (based on the setting of the boiler), but they traditionally will have a smaller boiler for the system. I know it is not comparing apples to apples, but I would guess that if that was left on for a bit longer, it would get plenty of heat produced. The fan will obviously help to distribute the heat in each zone.
Attached is a picture of the wall heaters with the 2 speed switch in the top left.
