I am new to the forum and it looks great. I am looking to replace my 50 year old oil boiler with a gas boiler that will give high efficiency and will be low maintenance. I live in a 50-year old ranch with full basement in an area just north of Boston, Massachusetts. The total square footage of the ground floor is 1,700 ft2 and the basement is 1,500 ft2. The house is currently heated with a tankless American Standard oil boiler (Arcoliner 3B J3 series) and a forced hot water Mono Flo baseboard fin system on two zones. We currently run out of hot water quickly if two showers are taken back-to-back or if the forced hot water heating system kicks on when in the shower. The house had no insulation when we moved in back in 1993 and at the time had treated cellulose blown into the walls and attic. This year we are planning to remodel the kitchen and family room and will have two walls measuring approximately 40 feet total that will be mostly large windows. I am currently refinishing the basement and it will be fully insulated (floors, walls and ceiling) to R-13 or better. On average we keep the temperature in the house at around 58 F when we are not home and at night (pretty chilly). We burned about 720 gallons of oil in 2010. I tried the NORA Fuel Savings Analysis (FSA) calculator and it gave me a very low design day heat load of ~30,000 btu/hr when I input oil usage of 720 gal/yr with a temp of -2 F as the design day temp.
I received a quote from a local HVAC contractor that specified a gas-fired Heat Transfer Products (HTP) Elite HTPEL-110 High Efficiency (94%) heating boiler and a 45-gallon HTP SSU-45 indirect water heater (Super-Stor). As far as I can tell he only use the total lineal footage of the baseboard heating system to figure out how to size the boiler. I asked him if he used the Manual J method to calculate the heat load and did not get a straight answer. Another contractor told me that the new high-efficiency boilers are over-rated and that you are lucky to get 90% efficiency – and therefore, why worry about 5% when you can get one of the regular 85% gas-fired boilers installed for much less up-front cost. He also told me that since I want to install a self-heated 70-gallon Jacuzzi in the basement, that I will need to upgrade from a proposed 45-gallon Super-Stor to a 120-gallon Super-Stor. The first hour rating of the 45-gallon HTP SSU-45 indirect water heater (Super-Stor) is 200 gallons, therefore, that should be OK, right? When I asked how he will size the boiler, he told me that he will base it on the existing oil boiler size.
I am committed to switching to gas since I am convinced that oil prices will continue to rise at a much greater clip than natural gas. I would like an efficient gas-fired boiler to save dollars in the long-run and an indirect water heater so we do not run out of hot water, can heat both the ground floor and basement , and can safely fill a 70-gal Jacuzzi with warm water in one shot. However, I am also concerned about incorrect sizing and/or configuration of a high-efficiency gas-fired boiler with an indirect water heater that will consequently break down and need continual maintenance. Can you help me with the heat load calc, decide how to find a good HVAC contractor, size and configure an appropriate system? What do you recommend? I really appreciate it.