Superstor Ultra vs Slant Fin heat loss calc.

Roland_4

OK so I did the Slantfin heat calc for my house and came up with a heat loss of 38,000Btu/Hr. This number was achieved after really trying for a worst-case situation. The boiler installed by the heating contractor is rated 104,000Btu input and 94,000Btu output. so this makes it nearly 3 times more boiler than I need. But hold on. I took a look at the ratings for my SSU-30 indirect and it has a specification: MinimumBTU/Hr required to achieve first hour rating: Gross output-120,000Btu/Hr. Is this the required output of the boiler? Can someone help me make a bit more sense of these ratings? Thanks,Roland

ALH_4

Water Heater

That is the heat output to maximize the output of the water heater. You can certainly have less input, but the water heater will perform below the published specs. That number is an indication of the performance of the heat exchanger in the tank. Their heat exchanger cannot transfer more than 120,000 btu/h at their published temperatures.

For reference, many residential gas water heaters are only 30,000 to 40,000 btu/h input, and the output is generally much less than that (70% to 80% efficiency range). Even with the 94,000 output, your Superstor will recover approx 3-4 times as quickly as a typical water heater. Of course showers with multiple heads will require more than a typical water heater can supply. If you require more than your boiler can supply, I recommend looking into a simple solar domestic hot water system to supplement. In fact, it's a good idea to plan for it even if you don't install a solar system right now.