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Question DetailsAsked on 4/4/2016

do hvac units need a certified base or curb?

a general question, do the bases or curbs that units sit on need to certified or safety verified?

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2 Answers


This is a nationwide forum. Here in Florida, yes for "wind" , so it depends on where you live.


Answered 3 years ago by BayAreaAC


Check the installation instructions in the manuals that came with it - or online at manufacturer website. Will tell you clearances around and under the unit to combustible materials and absolute clearances for airflow, and bolt sizes to bolt down. (Plus as BayAreaAC said, some Gulf states have separate requirements for fastening down for hurricane protection). Some specify their own design base for certain purposes, others sell a fire-resistant base but also specify alternative clearance measures you can build yourself out of angle iron and plate steel.

Also - if sitting on combustible materials (like wood) you commonly, especially with boilers and some upflow furnaces and many older, lower-efficiency units, have to put down a separate stand for it to sit on, which is metal and has airflow passages through it to prevent the radiated heat from the burners from catching the wood on fire.

The building code defers to manufacturer designs on appliances - so it just says you have to meet the clearances and support required by the manufacturer, not a specific design.

The only specific design I know of is many jurisdictions have instruction sheets on their websites about pedestal heights and construction materials to get the units the required 18" from combustion sources to the floor (24" in a few areas) in garages - and also mandate barrier posts so a car cannot hit the furnace, boiler, or hot water heater without hitting the posts first. If your locale has has otehr specific requirements about base or curb it would presumably be on there - and of course local HVAC contractors and plumbers "should" certainly know about such requirements too.

Answered 3 years ago by LCD

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