Heating, Air Conditioning, Fridge, HVAC/sizing a furnace

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Question
Hello, I am converting my homes heating from oil to gas. I live in south central NJ in a wooded rural area. I currently have an oil fired hot air furnace, 105kbtu @ 80% efficiency which produces 84000btu. Also a 3.5 ton AC It keeps the house warm but struggles on those rare 5 - 10 degree nights that we rarely have. My house is a colonial, finished basement, not included in the measurement, 2150 square feet ( I measured it myself, twice to be sure.) It was built in 1980 and has the standard insulation for a house built at that time.  6" in the attic and 3 1/2" in the exterior walls. It has Anderson narroline double pane windows that were also built in 1980. I have gotten 5 estimates from reliable , licensed hvac contractors. 2 have come in at 100k 95% furnace, 2 have said  I need an 80k furnace. One said I need a 60k furnace after they re insulate the entire house.  They are way too expensive and I can't swing that right now. None of the contractors did a manual J but some measured the rooms. I don't want to be over sized or undersized. All of the furnaces the contractors recommended were 2 stage, variable speed, 96% AFUE They run at lower btu s a majority of the time so I don't know if too large a furnace would be that much of an issue vs. too small. Any information would be appreciated. Thanks, Bill

Answer
Bill,

I would go with a two stage furnace 95-96% with a one stage 13-15 SEER A/C either variable or multi speed furnace blower motor. There are state and federal rebates for high efficiency A/C and furnaces. Some rebates are tax credits while others are cash in your pockets. I personally would not go higher than 15 or possibly 16 SEER ( if replacing the A/C )living in New Jersey ,you have a relatively short cooling season. Do not get an overly complicated system ,as they tend to be expensive upfront and have many expensive specialized parts. Future repair cost will be more, minimizing your energy savings over a less complicated system repairs. I would spend $50.00 and do an accurate manual J heat loss and heat gain calculations yourself. Hvaccomputer.com has a residential software package that you can do yourself. Then compare your correct manual J calculations with their less than accurate calculations ? . Get all the manufacture warranties in writing, including the labor warranty and t-stat warranty.  

Heating, Air Conditioning, Fridge, HVAC

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40+ years diversified experience.An HVAC/Refrigeration Self Employed Contractor since 1986. NATE Certifield. Answer questions pertaining to Residential and Commercial Air Conditioning , Warm Air Heating, Heat Pump systems.Mechanical and Electrical troubleshooting of these systems.Be as detailed as possible when describing problem.Packaged unit or split systems.No appliance questions.

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Installation and Troubleshooting, Mechanical and Electrical, in following areas, Refrigeration ( Walk In and Reach In Coolers and Freezers ) Commercial Roof Top and Packaged Heating/Cooling ( Natural Gas,Propane, Electric, and Heat Pumps ) Computer Room Air Conditoning Systems,Commercial Residential Packaged and Split Systems Air Conditoning and Heat Pumps.Warm Air Oil , Natural and Propane Gas Heating systems.

Education/Credentials
Graduated from Private Technical School in 1975. An HVAC/Refrigeration Contractor . Have Unlimited Heating/Piping and Cooling Contractor License.Limited Sheetmetal Contractors License.NATE Certifield. York Certifield Master Heat Pump Technician 1986. Served 33 years combination Active Duty Air Force , Air Force Reserves and Air National Guard in the HVAC/Refrigeration Shop/Mechanical Shop. Troubleshooting/Installing HVAC/Refrigeration Equiptment Worldwide. Retiring in 2003 as a Senior NCO ,and a Mechanical Superintendent.

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