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HELP A NEWBIE GET IT RIGHT - DHW AND SPACE HEAT
Hope you can help. I have a Vitodens 200 with a 53 gallon single coil tank right now - radiant panel heat. Family of 4, avg to above age DHW use (2 girls). We plan to add evac tubes to our New Hampshire home but get conflicting reports on how much space heating we will get. Some say 2 panels of tubes (60 total Viessman or Thermomax) will give us DHW plus ample swing season heat, while others say 3 panels, or even more are required. Then there is tank size (80 gal dual coil for the 2 panel, 115 for the 3 panel) and cost. $14k for a 2 panel, but $21 k for the 3 - I assume because of a larger tank and piping?
The question is - how much space heating do people in the north realistically get with 2 vs 3 panels, and is the extra cost justified? Should I be specing a different tank size for a 2 or 3 panel than what is proposed?
Are there different ways to pipe this too? I have seen standard Viessman 2 tank schematics, but also hear of alternate approaches where solar water is injected into system just before the boiler, but the tanks are not connected to each other...is that OK?
I know you need more specifics but looking for a rough guess to help - 2800sq ft home, southern exposure, home insulated well and has slightly better than average air loss on a blower door test.
Any help appreciated!