Thread: Crawl space furnace

I checked previous threads and nothing came up about requirements for furnaces when installed in crawl spaces. Is the unit required to be six inches above grade.

Thanks
Mat

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I don't know the Code req. for that one where you are but I would let the client know about:
- is the trunkline interior insulated or not at all? lots of heat loss
- sheet metal isn't fully under the unit
- premature deterioration of unit if crawl is damp
- annual repairs of small parts if crawl is damp; board, trans, flame sensor, hot surface, vent motor, etc.
- is that a yellow extension cord for power?
- plastic tarp?
- lack of fire separation
- flue pipe looks borderline

From the 2006 IRC. (underlining is mine)
- M1305.1.4 Appliances under floors.
Underfloor spaces containing appliances requiring access shall have an unobstructed passageway large enough to remove the largest appliance, but not less than 30 inches (762 mm) high and 22 inches (559 mm) wide, nor more than 20 feet (6096 mm) long when measured along the centerline of the passageway from the opening to the appliance. A level service space at least 30 inches (762 mm) deep and 30 inches (762 mm)wide shall be present at the front or service side of the appliance. If the depth of the passageway or the service space exceeds 12 inches (305 mm) below the adjoining grade, the walls of the passageway shall be lined with concrete or masonry extending 4 inches (102 mm) above the adjoining grade in accordance with Chapter 4. The rough-framed access opening dimensions shall be a minimum of 22 inches by 30 inches (559 mm by 762 mm), where the dimensions are large enough to remove the largest appliance.
- - Exceptions:
- - - 1. The passageway is not required where the level service space is present when the access is open, and the appliance can be serviced and removed through the required opening.
- - - 2. Where the passageway is unobstructed and not less than 6 feet high (1929 mm) and 22 inches wide for its entire length, the passageway shall not be limited in length.
- M1305.1.4.1 Ground clearance.Appliances supported from the ground shall be level and firmly supported on a concrete slab or other approved material extending above the adjoining ground. Appliances suspended from the floor shall have a clearance of not less than 6 inches (152 mm) from the ground.

- M1401.4 Exterior installations. Equipment installed outdoors shall be listed and labeled for outdoor installation. Supports and foundations shall prevent excessive vibration, settlement or movement of the equipment. Supports and foundations shall be level and conform to the manufacturer’s installation instructions.

- M1401.5 Flood hazard. In areas prone to flooding as established by Table R301.2(1), heating and cooling equipment and appliances shall be located or installed in accordance with Section R323.1.5. (I just found a problem in the code, the reference to Section R323.1.5 in the 2006 IRC references a section which no longer exists! However, below is that Section R323.1.5 from the 2003 IRC.)

From the 2003 IRC (because the referenced section no longer exists in the 2006 IRC). (underlining is mine)
- SECTION R323
- - FLOOD-RESISTANT CONSTRUCTION
- - - R323.1 General. Buildings and structures constructed in flood hazard areas (including A or V Zones) as established in Table R301.2 (1) shall be designed and constructed in accordance with the provisions contained in this section.
- - - - Exception:
- - - - - All buildings and structures in identified floodways as established in Table R301.2 (1) shall be designed and constructed as stipulated in the International Building Code.
- - - - R323.1.5 Protection of mechanical and electrical systems. Electrical systems, equipment and components, and heating, ventilating, air conditioning and plumbing appliances, plumbing fixtures, duct systems, and other service equipment shall be located at or above the design flood elevation. If replaced as part of a substantial improvement, electrical systems, equipment and components, and heating, ventilating, air conditioning, and plumbing appliances, plumbing fixtures, duct systems, and other service equipment shall meet the requirements of this section. Systems, fixtures, and equipment and components shall not be mounted on or penetrate through walls intended to break away under flood loads.
- - - - - Exception:
- - - - - - Electrical systems, equipment and components, and heating, ventilating, air conditioning and plumbing appliances, plumbing fixtures, duct systems, and other service equipment are permitted to be located below the design flood elevation provided that they are designed and installed to prevent water from entering or accumulating within the components and to resist hydrostatic and hydrodynamic loads and stresses, including the effects of buoyancy, during the occurrence of flooding to the design flood elevation in compliance with the flood-resistant construction requirements of the International Building Code. Electrical wiring systems are permitted to be located below the design flood elevation provided they conform to the provisions of the electrical part of this code for wet locations.

Mathew, here is the code for NC. Note the 4x8x16 block under the unit, this has been a code requirement for a very long time.. The passageway was 22" high by 36" wide in the 1994 SBCCI mechanical codes, somewhere the numbers got reversed and NC changed them back. (Just looked at this post and the number before the underlined number is susposed to be lined out, don't know why it did not show up on post?) 30" is changed to 22" and 22" is changed to 36".



101.1 Title.
These regulations shall be known as the North Carolina Mechanical Code as approved by the North Carolina Building Code Council on September 13, 2005, to be effective July 1, 2006. References to the International Codes shall mean the North Carolina Codes. The North Carolina amendments to the International Codes are underlined.



304.9.3 Crawlspace supports. In a crawl space, a minimum of 4x8x16 inch block or brick supports shall be held in place with mortar. Formed concrete or approved prefabricated steel units are acceptable.

306.4 Appliances under floors.
Underfloor spaces containing appliances requiring access shall be provided with an access opening and unobstructed passageway large enough to remove the largest appliance. The passageway shall not be less than 30 22 inches (762 559 mm) high and 22 36 inches (559 914 mm) wide, nor more than 20 feet (6096 mm) in length measured along the centerline of the passageway from the opening to the appliance. A level service space not less than 30 inches (762 mm) deep and 30 inches (762 mm) wide shall be present at the front or service side of the appliance. If the depth of the passageway or the service space exceeds 12 inches (305 mm) below the adjoining grade, the walls of the passageway shall be lined with concrete or masonry. Such concrete or masonry shall extend a minimum of 4 inches (102 mm) above the adjoining grade and shall have sufficient lateral-bearing capacity to resist collapse. The clear access opening dimensions shall be a minimum of 22 inches high by 30 inches wide (559 mm by 762 mm), where such dimensions are large enough to allow removal of the largest appliance.
Exceptions:
1. The passageway is not required where the level service space is present when the access is open and the appliance is capable of being serviced and removed through the required opening.
2. Where the passageway is not less than 6 feet high (1829 mm) for its entire length, the passageway shall not be limited in length.

So despite the fact this unit was about 4 inches off the ground, I am going to go out on a limb and say supporting the furnace with pieces of scrap wood is not an approved material.

Originally Posted by Markus Keller

I don't know the Code req. for that one where you are but I would let the client know about:
- lack of fire separation
- flue pipe looks borderline

What lack of fire separation do you call out for a crawl space furnace?