I’d greatly appreciate feedback on this. I’ve had a pro heat loss done, have attached a pdf that shows heat loss and gain room by room, zone by zone from OT 0 degrees through 60º, for 68º indoor set temp. Design day is 10ºF. For a mod-con we are hoping we can do an AWT of 130º, meaning SWT of 140º. Models using a lower AWT didn’t look promising but, since heat losses are often overly conservative, we might get lucky. We’ve insulated about as much as we can with closed cell foam in the attic, dense pack cellulose in the walls, and fiberglass in the basement rim joists.
Total heat loss is about 38.6K btu. The cast iron emitter gain to loss ratio is good for the main and second floors. Basement zone design day loss is about 1100btu, slantfin baseboard gain only 6760. I am seriously considering replacing slantfin with CI rads.
[Using the O’Brien virtual heat loss method by usage, last year’s total gas btu usage for heating to maintain 65º daytime set temp and 63º night setback was:
725 HTH x 100Kbtu = 72,500,000btu x .75 old boiler AFUE = 54,375,000btu/5215DD = 9,857 btus per DD/24 = 411 btus per DH x 55∆T = 22,605 Heat Loss/1800sq ft house = 12.55btus per HDH per sq ft.]
Wild cards:
1-Zone 1 and 2 are series ¾” copper piping—with insulated old 1 inch gravity risers. With our current 170Kbtu old oversized boiler, no problem with uneven heating @160º SWT, 150º AWT.
2-Under-insulated and under-radiated Sun Room is kept at about 50 degrees, so our ‘virtual heat loss’ would certainly rise to at least 26Kbtu if we heated that room as it is now. (The pro heat loss assumes that the under-insulated room will be heated to set point.)
Note that the plan is for an ECM circ with three zone valves, outdoor reset.
Major questions:
1. The two options so far are the HTP Versa Hydro PHE130-55 or the HTP UFT-80 with a Turbomax 23 Reverse Indirect to act as both indirect HWH and Buffer Tank. Note that my wife and I have been using a 50 gallon stand-alone gas HWH which fires at 30Kbtu set at 140º mixed down to 120º and even on the prior heater which we kept at 120º we have never run out of hot water even with back to back showers. Our makeup water hardness is 126.67ppm and chlorides 83.5ppm. Ph is 7.28. The UFT/Turbo Max appeals to me a)is more closely sized for my heat loss and b) With the turbomax the heating system will stay sealed—probably filled with inert water--and though the indirect waterways will have to be cleaned annually, it will be less expensive to replace if and when it fails.
2. With either of the above systems, my concern is the ability to work around the low basement emitter gain without short cycling or having to install a valve to mix in a higher SWT for the basement. Can the buffer of the Versa Hydro or Turbomax handle this on design OR shoulder day? Smallest zone loss at 60ºF is 1349btu, with a gain of 3300btu. I’ve read that sometimes you can lower the ∆T SWT/RWT to accommodate this problem.
3. Assuming that all heat losses are to conservative, when the Uponor program spit out the losses at the non-design day OTs—in addition to my ‘projected’ losses for the 50º and 60º OTs—the losses all seemed too linear-ly proportional. Meaning I was always told that as OT goes down, proportional heat loss will rise due to ∆T of indoor and outdoor temps causing increased infiltration/convection. If so, then this heat loss is not only too high on the cold OT end but also on the shoulder end, so if that smallest zone loss turns out to be only 1000btu or 750btu, how will either system handle that?
4. Highest zone loss at 0º OT is about 21Kbtu which would seem to require 2gpm, which seems easy for the 3/4” to handle.
5. The hard water gives me pause for any mod-con, both for longevity and for annual maintenance costs. All the above units are supposed to be easy to clean, but the DHW side of things seems tricky. We are in our mid-60s hoping to remain in the house.
Total heat loss is about 38.6K btu. The cast iron emitter gain to loss ratio is good for the main and second floors. Basement zone design day loss is about 1100btu, slantfin baseboard gain only 6760. I am seriously considering replacing slantfin with CI rads.
[Using the O’Brien virtual heat loss method by usage, last year’s total gas btu usage for heating to maintain 65º daytime set temp and 63º night setback was:
725 HTH x 100Kbtu = 72,500,000btu x .75 old boiler AFUE = 54,375,000btu/5215DD = 9,857 btus per DD/24 = 411 btus per DH x 55∆T = 22,605 Heat Loss/1800sq ft house = 12.55btus per HDH per sq ft.]
Wild cards:
1-Zone 1 and 2 are series ¾” copper piping—with insulated old 1 inch gravity risers. With our current 170Kbtu old oversized boiler, no problem with uneven heating @160º SWT, 150º AWT.
2-Under-insulated and under-radiated Sun Room is kept at about 50 degrees, so our ‘virtual heat loss’ would certainly rise to at least 26Kbtu if we heated that room as it is now. (The pro heat loss assumes that the under-insulated room will be heated to set point.)
Note that the plan is for an ECM circ with three zone valves, outdoor reset.
Major questions:
1. The two options so far are the HTP Versa Hydro PHE130-55 or the HTP UFT-80 with a Turbomax 23 Reverse Indirect to act as both indirect HWH and Buffer Tank. Note that my wife and I have been using a 50 gallon stand-alone gas HWH which fires at 30Kbtu set at 140º mixed down to 120º and even on the prior heater which we kept at 120º we have never run out of hot water even with back to back showers. Our makeup water hardness is 126.67ppm and chlorides 83.5ppm. Ph is 7.28. The UFT/Turbo Max appeals to me a)is more closely sized for my heat loss and b) With the turbomax the heating system will stay sealed—probably filled with inert water--and though the indirect waterways will have to be cleaned annually, it will be less expensive to replace if and when it fails.
2. With either of the above systems, my concern is the ability to work around the low basement emitter gain without short cycling or having to install a valve to mix in a higher SWT for the basement. Can the buffer of the Versa Hydro or Turbomax handle this on design OR shoulder day? Smallest zone loss at 60ºF is 1349btu, with a gain of 3300btu. I’ve read that sometimes you can lower the ∆T SWT/RWT to accommodate this problem.
3. Assuming that all heat losses are to conservative, when the Uponor program spit out the losses at the non-design day OTs—in addition to my ‘projected’ losses for the 50º and 60º OTs—the losses all seemed too linear-ly proportional. Meaning I was always told that as OT goes down, proportional heat loss will rise due to ∆T of indoor and outdoor temps causing increased infiltration/convection. If so, then this heat loss is not only too high on the cold OT end but also on the shoulder end, so if that smallest zone loss turns out to be only 1000btu or 750btu, how will either system handle that?
4. Highest zone loss at 0º OT is about 21Kbtu which would seem to require 2gpm, which seems easy for the 3/4” to handle.
5. The hard water gives me pause for any mod-con, both for longevity and for annual maintenance costs. All the above units are supposed to be easy to clean, but the DHW side of things seems tricky. We are in our mid-60s hoping to remain in the house.