tropostudio
Member
This is a great resource and a great forum. I'm a couple weeks away from starting into a major renovation on our 1915 bungalow in St. Paul, MN. It's currently a 1-1/2 story and we have opted to top the house and add a full second story. Drawings and spec are done, and we have a contractor on board to do the framing and structural stuff. I'm doing the mechanical, plumbing, electrical, HVAC. Not a stranger to most of it, as I have reno'ed a 1904 church into a studio/workshop.
House is currently hot water heat with cast iron radiators and a 70's vintage gravity boiler system. It's going away, along with the old gas water heater and the chimney. I've done 2 heating and cooling calcs using 2 different Manual J programs for the whole house. Heat loss is 57-59kBtuH for a -10 F outdoor temp and 70 F indoor temp. I assumed an "Average' sealed house. We may get a bit better than Average, but I'm not banking on it. We did fine with a family of 3 using a 40 gallon water heater with a 38kBtuH burner. But 50 gallons might be nice.
I'm looking at installing a WM Ultra 80 or Ultra 105 boiler with an WM Aqua Plus 45 indirect tank for DHW. I'm not locked into that set-up yet, but I figure it's going to be a 93-95% efficient condensing modcon with a 4:1 or 5:1 modulation ratio. If I want to bump up to a 50 gallon indirect DHW tank, should I look at going with a 100 kBtuH boiler, or would I be OK with something in the 75-80 kBtuH range? My thinking is with such a large modulation ratio, the bigger unit wouldn't be oversized like it might for a single stage boiler. FWIW, I'll be using new panel radiators for both floors in the reno, and will probably oversize them to keep water temps down. No in-floor loops going into this job.
Thanks,
Chris Krumm
House is currently hot water heat with cast iron radiators and a 70's vintage gravity boiler system. It's going away, along with the old gas water heater and the chimney. I've done 2 heating and cooling calcs using 2 different Manual J programs for the whole house. Heat loss is 57-59kBtuH for a -10 F outdoor temp and 70 F indoor temp. I assumed an "Average' sealed house. We may get a bit better than Average, but I'm not banking on it. We did fine with a family of 3 using a 40 gallon water heater with a 38kBtuH burner. But 50 gallons might be nice.
I'm looking at installing a WM Ultra 80 or Ultra 105 boiler with an WM Aqua Plus 45 indirect tank for DHW. I'm not locked into that set-up yet, but I figure it's going to be a 93-95% efficient condensing modcon with a 4:1 or 5:1 modulation ratio. If I want to bump up to a 50 gallon indirect DHW tank, should I look at going with a 100 kBtuH boiler, or would I be OK with something in the 75-80 kBtuH range? My thinking is with such a large modulation ratio, the bigger unit wouldn't be oversized like it might for a single stage boiler. FWIW, I'll be using new panel radiators for both floors in the reno, and will probably oversize them to keep water temps down. No in-floor loops going into this job.
Thanks,
Chris Krumm