ColoradoKid
New Member
What size boiler do we need?
We live in a New England Cape house built in 1968 in southern NH (Nashua). House is a 4 bedroom, two full bath, two story structure and was, when we bought it, electric baseboard heated. It has a "mostly" finished, walkout basement which was heated by a wood burning stove when we bought the house.
After the first winter in NH in 1988, we learned the error of our ways and removed baseboard electric and installed baseboard HW fed by natural gas boiler in 1989. The contractor installed a cast iron Weil-McLain HE-6 (DOE rating 137,000 Btu/hr capacity) and it only fed two zones, the first and second floors. At the time of install, only about 1300 sqft were "conditioned" space or heated by the boiler. The boiler is installed in the unfinished laundry room section of the basement (sits on concrete floor next to uninsulated concrete wall) and is directly vented out the side of the house above the foundation (we had no flues or chimneys being an all electric home with exception of wood stove). The contractor also installed a traditional gas HW heater next to the boiler with a power vent exhaust out the side of the house.
We haven't had to "heat" our basement very often, I assume due to the residual heat flowing off the boiler and water heater permeating through the basement spaces. It gets cool but never really cold in the basement unless outside temps go very low. When we have had to heat the basement, we use a Vermont Casting Radiance natural gas stove which we installed in place of the wood burning stove. This has been useful in times when we have lost power and hence the boiler (once for 6 days last winter). We cranked up the Radiance stove, open the door down to the basement, and kept the house from freezing. The basement is insulated from the first floor via R-19 batting in the floor joists above fiberglass suspended ceiling in the finished sections.
Combustion air for both boiler and water heater are fed from the ambient basement air volume.
We add a third heating zone in 2003 when we added a well insulated 4 season room onto our deck and heated it via baseboard radiators as with the rest of the house. Its worked great. We replaced the heating system expansion tank and relief valves and some rusty piping and failing gaskets about 10 years ago. All zonal heat piping has foam insulation tubes installed wherever possible.
The boiler has kept our house warm for 27 years with minimal maintenance but is now showing its age. An inspection by a local HVAC contractor brought in for maintenance advised the boiler may soon fail and there is much rust/corrosion on piping again, iron rust flakes on the floor, some leakage stains, and expansion tank and valves need replacing again. So we are looking a new boiler before the major snows & cold of winter hits.
Reading this forum, and other internet pages, I'm convinced the original boiler was way oversized for our house. Our kids are now grown and gone and the second floor bedrooms kept normally around 55 degrees. Main floor with living room, master bedroom, office (former bedroom), kitchen, and 4 season room is usually kept around 68 degrees.
For the winter time frame of Oct 14-Apr 15 with the above situation, I burned 692 Therms of natural gas. In the same window, I consumed approx 2,244 KW of electricity (eqiv, I think, of 76.6 Therms). I looked up the local Home Degree Days (HDD) for the above timeframe and it came to 6056.9. I'm assuming a boiler efficiency of 75% (probably high) for WM HE-6. HDD were measured against a 65 Deg norm and I used a -3 Deg 99% temp. Using an equation I found on this forum below:
Formula (excel spreadsheet) was btu/hr = ((((ThermsGas+ThermsElec)*100000)/HDD)/24)*(65-(-3)).
I calculated the period consumption at 26,964 btu/hr (adding the electricity therms to the natural gas therms) during the above winter time window. That gas consumption includes, of course, the natural gas Hotwater Heater, clothes dryer, cooking stove, and occasionally the Radiant Gas stove for the basement. Have I done the calculation correctly? Is it appropriate to add in the electricity therm equivalents? From what I've read, at least 75% of electricity flowing into a house turns into heat subsequently deposited in said house. If the 2nd floor bedrooms were utilized more and kept at 68 degrees, the above consumption would go up.
I next tried to estimate the Heat Loss of my house. I used a WM Boiler Replacement Guide, circa 1997, and also an iOS iPad App from Slant-Fin. With the 4 season room in the mix, sqft heated is now around 1460 for my 4 BR, two full bath home. First floor has 841 sqft, second floor 463, 4 season room 156. The WM "model" (as best I could match the categories) indicated heat loss around 40,200 btu/hr BEFORE adding the 4 season room. 4 Season Room has 90 sqft of Harvey Classic double hung new construction vinyl windows (U=.47) and 36x80 steel door, cathedral celling, floor area is 11'8" x 13'4". French doors connect to main floor of the house. Room floor is over deck with 6" fiberglass batting in deck joists beneath the floor, celling is 2x6 with batting, 2x4 walls have 2" batting with 2 " of styrofoam insulation installed.
The Slant-Fin app comes up with a household loss of 34, 279 btu/hr including the 4 season room. The iPad app provides a lot more flexibility in options than the WM guide and I tend think it more accurate (opinion?). The Slant-Fin app indicated the 4 season room heat loss at 8885 btu/hr with indoor 68 deg, outdoor 1 deg, design water temp 180 deg which seems reasonable to me.
Bottomline is the HDD & gas consumption based formula as well as the house heat loss calculations are all WAY LOWER than the 137,000 btu the Weil-McLain HE-6 boiler is supposed to be capable of delivering by a factor of almost 3. So, from this site and others, I'm assuming I have some great heating system inefficiencies in play, short cycling on the boiler, etc are going on (What is "short cycling" anyway?) . How do I tell by boiler observation (boiler and heating system are now on given its 28 degrees outside) if this is the case? When working, HE-6 has heated the house very well over all these 27 years. I have no complaints with reliability of the Weil-McLain boiler.
Given the circumstances (venting, location, heat demand), what size and type boiler do you recommend? NH has run out of funding for 2015 rebates for boilers but may reinstate $1000 for 2016 installed boilers above 90% AFUE ($1500 for >95%). That said, 90% seems to imply condensing boilers, I believe, requiring a drain for condensation and the closet drain is near washing machine 30+ feet away. What are the pros/cons of condensing vice non-condensing boilers? Is the increased boiler complexity, failure/maintenance, etc, worth it? We only intend to live in this house another 5-10 years max so we have short ROI window.
I'm not sure I can wait for 2016 (think of last winter) and hate to have the system fail in the midst of another El Nino driven winter in New England. I'm also going to replace the 10 year old traditional water heater (sits next to boiler) with a indirect storage tank fed off the boiler. Any recommendations on brands and capacity with respect direct hot water storage systems?
Two boiler models have caught my attention. Burnham ESC and Weil-McLain GV90+. Given the above, are these too much boiler for my needs? Do you have other boiler recommendations? I (and my wife) are skittish about going to low and I want some heating reserve should I add a further addition to my house in the future.
Thanks,
We live in a New England Cape house built in 1968 in southern NH (Nashua). House is a 4 bedroom, two full bath, two story structure and was, when we bought it, electric baseboard heated. It has a "mostly" finished, walkout basement which was heated by a wood burning stove when we bought the house.
After the first winter in NH in 1988, we learned the error of our ways and removed baseboard electric and installed baseboard HW fed by natural gas boiler in 1989. The contractor installed a cast iron Weil-McLain HE-6 (DOE rating 137,000 Btu/hr capacity) and it only fed two zones, the first and second floors. At the time of install, only about 1300 sqft were "conditioned" space or heated by the boiler. The boiler is installed in the unfinished laundry room section of the basement (sits on concrete floor next to uninsulated concrete wall) and is directly vented out the side of the house above the foundation (we had no flues or chimneys being an all electric home with exception of wood stove). The contractor also installed a traditional gas HW heater next to the boiler with a power vent exhaust out the side of the house.
We haven't had to "heat" our basement very often, I assume due to the residual heat flowing off the boiler and water heater permeating through the basement spaces. It gets cool but never really cold in the basement unless outside temps go very low. When we have had to heat the basement, we use a Vermont Casting Radiance natural gas stove which we installed in place of the wood burning stove. This has been useful in times when we have lost power and hence the boiler (once for 6 days last winter). We cranked up the Radiance stove, open the door down to the basement, and kept the house from freezing. The basement is insulated from the first floor via R-19 batting in the floor joists above fiberglass suspended ceiling in the finished sections.
Combustion air for both boiler and water heater are fed from the ambient basement air volume.
We add a third heating zone in 2003 when we added a well insulated 4 season room onto our deck and heated it via baseboard radiators as with the rest of the house. Its worked great. We replaced the heating system expansion tank and relief valves and some rusty piping and failing gaskets about 10 years ago. All zonal heat piping has foam insulation tubes installed wherever possible.
The boiler has kept our house warm for 27 years with minimal maintenance but is now showing its age. An inspection by a local HVAC contractor brought in for maintenance advised the boiler may soon fail and there is much rust/corrosion on piping again, iron rust flakes on the floor, some leakage stains, and expansion tank and valves need replacing again. So we are looking a new boiler before the major snows & cold of winter hits.
Reading this forum, and other internet pages, I'm convinced the original boiler was way oversized for our house. Our kids are now grown and gone and the second floor bedrooms kept normally around 55 degrees. Main floor with living room, master bedroom, office (former bedroom), kitchen, and 4 season room is usually kept around 68 degrees.
For the winter time frame of Oct 14-Apr 15 with the above situation, I burned 692 Therms of natural gas. In the same window, I consumed approx 2,244 KW of electricity (eqiv, I think, of 76.6 Therms). I looked up the local Home Degree Days (HDD) for the above timeframe and it came to 6056.9. I'm assuming a boiler efficiency of 75% (probably high) for WM HE-6. HDD were measured against a 65 Deg norm and I used a -3 Deg 99% temp. Using an equation I found on this forum below:
Formula (excel spreadsheet) was btu/hr = ((((ThermsGas+ThermsElec)*100000)/HDD)/24)*(65-(-3)).
I calculated the period consumption at 26,964 btu/hr (adding the electricity therms to the natural gas therms) during the above winter time window. That gas consumption includes, of course, the natural gas Hotwater Heater, clothes dryer, cooking stove, and occasionally the Radiant Gas stove for the basement. Have I done the calculation correctly? Is it appropriate to add in the electricity therm equivalents? From what I've read, at least 75% of electricity flowing into a house turns into heat subsequently deposited in said house. If the 2nd floor bedrooms were utilized more and kept at 68 degrees, the above consumption would go up.
I next tried to estimate the Heat Loss of my house. I used a WM Boiler Replacement Guide, circa 1997, and also an iOS iPad App from Slant-Fin. With the 4 season room in the mix, sqft heated is now around 1460 for my 4 BR, two full bath home. First floor has 841 sqft, second floor 463, 4 season room 156. The WM "model" (as best I could match the categories) indicated heat loss around 40,200 btu/hr BEFORE adding the 4 season room. 4 Season Room has 90 sqft of Harvey Classic double hung new construction vinyl windows (U=.47) and 36x80 steel door, cathedral celling, floor area is 11'8" x 13'4". French doors connect to main floor of the house. Room floor is over deck with 6" fiberglass batting in deck joists beneath the floor, celling is 2x6 with batting, 2x4 walls have 2" batting with 2 " of styrofoam insulation installed.
The Slant-Fin app comes up with a household loss of 34, 279 btu/hr including the 4 season room. The iPad app provides a lot more flexibility in options than the WM guide and I tend think it more accurate (opinion?). The Slant-Fin app indicated the 4 season room heat loss at 8885 btu/hr with indoor 68 deg, outdoor 1 deg, design water temp 180 deg which seems reasonable to me.
Bottomline is the HDD & gas consumption based formula as well as the house heat loss calculations are all WAY LOWER than the 137,000 btu the Weil-McLain HE-6 boiler is supposed to be capable of delivering by a factor of almost 3. So, from this site and others, I'm assuming I have some great heating system inefficiencies in play, short cycling on the boiler, etc are going on (What is "short cycling" anyway?) . How do I tell by boiler observation (boiler and heating system are now on given its 28 degrees outside) if this is the case? When working, HE-6 has heated the house very well over all these 27 years. I have no complaints with reliability of the Weil-McLain boiler.
Given the circumstances (venting, location, heat demand), what size and type boiler do you recommend? NH has run out of funding for 2015 rebates for boilers but may reinstate $1000 for 2016 installed boilers above 90% AFUE ($1500 for >95%). That said, 90% seems to imply condensing boilers, I believe, requiring a drain for condensation and the closet drain is near washing machine 30+ feet away. What are the pros/cons of condensing vice non-condensing boilers? Is the increased boiler complexity, failure/maintenance, etc, worth it? We only intend to live in this house another 5-10 years max so we have short ROI window.
I'm not sure I can wait for 2016 (think of last winter) and hate to have the system fail in the midst of another El Nino driven winter in New England. I'm also going to replace the 10 year old traditional water heater (sits next to boiler) with a indirect storage tank fed off the boiler. Any recommendations on brands and capacity with respect direct hot water storage systems?
Two boiler models have caught my attention. Burnham ESC and Weil-McLain GV90+. Given the above, are these too much boiler for my needs? Do you have other boiler recommendations? I (and my wife) are skittish about going to low and I want some heating reserve should I add a further addition to my house in the future.
Thanks,