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Old Concord Horizontal replacement/placement of new furnace

Good afternoon all, I'm a new member here and I apologize in advance if this subject has been addressed in the past and if so, it would be appreciated to point me in the right direction because I could not find a post on this topic. I'm taking on a horizontal oil-fired furnace replacement in the near future and was curious as to what the "best practices" are for placement of the new furnace. My initial thoughts were a 4" to 6" thick reinforced concrete pad with either heavy gauge sheet metal risers or solid concrete block to put the furnace on top of for a a solid "foundation" vs. the existing makeshift cinder block "stand." Unfortunately I do not have any pictures available at this point in time but it is a sealed and insulated crawlspace (with the exception of the small area surrounding the existing furnace) in South Eastern Massachusetts. Any input would be appreciated.
Thank you in advance,
David Jr.


    EBEBRATT-Ed Member Posts: 13,433
    Concrete pad is ok. You could put some pressure treated lumber on top of the pad if need be.

    Many would hang the furnace using unistrut and threaded rod
  • Jamie Hall
    Jamie Hall Member Posts: 21,099
    One thing to check -- if that crawlspace is sealed, make sure you really have enough combustion air. Just because the old one worked...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 5,626
    Dave Jr.

    4" thick poured concrete pad is more than enough. Oil Fired furnace for a medium size home is less than 400 lbs. If you are placing the foundation more than 8" below the finished hight of the bottom of the furnace, you might want to think about using mortar on the cinder blocks between the foundation and the furnace. If you are more than 3 blocks high, think about hanging the furnace from the floor joist above the crawlspace as EBEBRATT ED suggested. Don't hang it right below the bedroom though. it may not vibrate too much when it is new... but as it gets older the vibrations may be annoying.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
  • Thank you gentlemen, your answers are very helpful. EBEBRATT-Ed I know in most crawl space situations unistrut would be the way to go. But I think the vibration would become an issue like EdTheHeaterMan mentioned as the furnace wasn't hung originally from the start. Although I'll keep it in mind as the customer may want to add an evaporator in at some point in the future and that could ease the install/service aspect. Jamie Hall I figured that in as well as soon as I dropped down into the crawlspace. It was definitely a pleasant surprise over the typical dusty cobweb infested crawls I end up in!