Gas Unit Location

[Brian G]

I just did one where a natural gas central unit (forced warm air) was located deep in one of those 1/2 closets with the return air underneath, then completely covered with a screwed-down piece of plywood. A shelf with music CD's and other little junk was in between, and speaker wires ran through a hole in the plywood. Not what I would call accessable. It is open to the attic above, but that doesn't seem like it would be great for air supply (sitting in a square hole). What does code say about accessability / locations of such units? Please tell me this isn't kosher.

Brian G.

P.S. The house is 10 years old. I wonder when was the last time anybody looked at that unit.

[Gerry Beaumont]

Hi Brian,

I was going to paraphrase this for you but it's way past my bed time, here's the code, enjoy the read.

BTW Codecheck HVAC is well worth the investment

M1305

APPLIANCE ACCESS

M1305.1 Appliance access for inspection service, repair and replacement.

Appliances shall be accessible for inspection, service, repair and replacement without removing permanent construction. Thirty inches (762 mm) of working space shall be provided in front of the control side to service an appliance. Room heaters shall be permitted to be installed with at least an 18-inch (457 mm) working space. A platform shall not be required for room heaters.

M1305.1.1 Central furnaces.

Central furnaces within compartments or alcoves shall have a minimum working space clearance of 3 inches (76 mm) along the sides, back and top with a total width of the enclosing space being at least 12 inches (305 mm) wider than the furnace. Furnaces having a firebox open to the atmosphere shall have at least a 6-inch (152 mm) working space along the front combustion chamber side. Combustion air openings at the rear or side of the compartment shall comply with the requirements of Chapter 17.

Exception: This section shall not apply to replacement appliances installed in existing compartments and alcoves where the working space clearances are in accordance with the equipment or appliance manufacturer's installation instructions.

M1305.1.2 Appliances in rooms.

Appliances installed in a compartment, alcove, basement or similar space shall be accessed by an opening or door and an unobstructed passageway measuring not less than 24 inches (610 mm) wide and large enough to allow removal of the largest appliance in the space, provided that a level service space of not less than 30 inches (762 mm) deep and the height of the appliance, but not less than 30 inches (762 mm), is present at the front or service side of the appliance with the door open.

M1305.1.3 Appliances in attics.

Attics containing appliances requiring access shall be provided with an opening and a clear and unobstructed passageway large enough to allow removal of the largest appliance, but not less than 30 inches (762 mm) high and 22 inches (559 mm) wide and not more than 20 feet (6096 mm) in length when measured along the centerline of the passageway from the opening to the appliance. The passageway shall have continuous solid flooring in accordance with Chapter 5 not less than 24 inches (610 mm) wide. A level service space at least 30 inches (762 mm) deep and 30 inches (762 mm) wide shall be present along all sides of the appliance where access is required. The clear access opening dimensions shall be a minimum of 20 inches by 30 inches (508 mm by 762 mm), where such dimensions are large enough to allow removal of the largest appliance.

Exception: The passageway and level service space are not required where the appliance is capable of being serviced and removed through the required opening.

M1305.1.3.1 Electrical requirements.

Alighting fixture controlled by a switch located at the required passageway opening and a receptacle outlet shall be provided at or near the appliance location in accordance with Chapter 38.

M1305.1.4 Appliances under floors.

Under floor spaces containing appliances requiring access shall be provided with 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) in length 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.

Exception: 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.

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.

M1305.1.4.2 Excavations.

Excavations for appliance installations shall extend to a depth of 6 inches (152 mm) below the appliance and 12 inches (305 mm) on all sides, except that the control side shall have a clearance of 30 inches (762 mm).

M1305.1.4.3 Electrical requirements.

Alighting fixture controlled by a switch located at the required passageway opening and a receptacle outlet shall be provided at or near the appliance location in accordance with Chapter 38.

M1306

CLEARANCES FROM COMBUSTIBLE CONSTRUCTION

M1306.1 Appliance clearance.

Appliances shall be installed with the clearances from unprotected combustible materials as indicated on the appliance label and in the manufacturer's installation instructions.

FIGURE M1306.1

REDUCED CLEARANCE DIAGRAM

Note: "A": equals the required clearance with no protection. "B" equals the reduced clearance permitted in accordance with Table M1306.2. The protection applied to the construction using combustible material shall extend far enough in each direction to make "C" equal to " A."

M1306.2 Clearance reduction.

Reduction of clearances shall be in accordance with the appliance manufacturer's instructions and Table M1306.2. Forms of protection with ventilated air space shall conform to the following requirements:

1. Not less than 1-inch (25.4 mm) air space shall be provided between the protection and combustible wall surface.

2. Not less than 1-inch (25.4 mm) air space shall be provided between the protection and combustible wall surface.. Air circulation shall be provided by having edges of the wall protection open at least 1 inch (25.4 mm).

3. If the wall protection is mounted on a single flat wall away from corners, air circulation shall be provided by having the bottom and top edges, or the side and top edges open at least 1 inch (25.4 mm).

4. Wall protection covering two walls in a corner shall be open at the bottom and top edges at least 1 inch (25.4 mm).

FIGURE M1306.2

WALL PROTECTOR CLEARANCE REDUCTION SYSTEM

TABLE M1306.2

REDUCTION OF CLEARANCES WITH SPECIFIED

FORMS OF PROTECTION a, b, c, d, e, f, g, h, i, j, k

For SI: 1 inch = 25.4 mm, 1 pound per cubic foot = 16.019 kg/m3,

a. Reduction of clearances from combustible materials shall not interfere with combustion air, draft hood clearance and relief, and accessibility of servicing.

b. Clearances shall be measured from the surface of the heat producing appliance or equipment to the outer surface of the combustible material or combustible assembly.

c. Spacers and ties shall be of noncombustible material. No spacer or tie shall be used directly opposite appliance or connector.

d. Where all clearance reduction systems use a ventilated air space, adequate provision for air circulation shall be provided as described. (See Figures M1306.1 and M1306.2.)

e. There shall be at least 1 inch between clearance reduction systems and combustible walls and ceilings for reduction systems using ventilated air space.

f. If a wall protect or is mounted on a single flat wall away from corners, adequate air circulation shall be permitted to be provided by leaving only the bottom and top edges or only the side and top edges open with at least a 1-inch air gap.

g. Mineral wool and glass fiber batts (blanket or board) shall have a minimum density of 8 pounds per cubic foot and a minimum melting point of 1,500°F.

h. Insulation material used as part of a clearance reduction system shall have a thermal conductivity of 1.0 Btu per inch per square foot per hour per °F or less.

Insulation board shall be formed of noncombustible material.

i. There shall be at least 1 inch between the appliance and the protector. In no case shall the clearance between the appliance and the combustible surface be reduced below that allowed in Table M1306.2.

j. All clearances and thicknesses are minimum; larger clearances and thicknesses are acceptable.

k. Listed single-wall connectors shall be permitted to be installed in accordance with the terms of their listing and the manufacturer's

Regards

Gerry

[Jim Katen]

Originally posted by Brian G.

I just did one where a natural gas central unit (forced warm air) was located deep in one of those 1/2 closets with the return air underneath, then completely covered with a screwed-down piece of plywood. A shelf with music CD's and other little junk was in between, and speaker wires ran through a hole in the plywood. Not what I would call accessable. It is open to the attic above, but that doesn't seem like it would be great for air supply (sitting in a square hole). What does code say about accessability / locations of such units? Please tell me this isn't kosher.

Brian G.

P.S. The house is 10 years old. I wonder when was the last time anybody looked at that unit.

If it had six inches clearance in front of it and if the closet ceiling was open to the attic and if the panel in front of it could be removed by taking out a few screws (no matter how inconvenient), then I'd say it was within the margins of an acceptable installation.

Early '90s furnaces were generally listed for zero inches of clearance at the sides and rear and for six inches at the front.

If the closet is truely open to the attic, that's almost certainly plenty of combustion air.

As for the screwed-in-place plywood panel, we see access panels that are screwed in place all the time on whirlpool baths, sewage ejector pumps and, occasionally, water heaters. I don't consider that much of an impediment to access.

That said, there's no reason you shouldn't recommend improving the access to this unit. In fact, I believe that's the sort of advice our clients hope we'll give them. Just don't step into a trap by saying that the existing installation is "wrong" because it probably isn't.

I'd say something like this:

Access to the furnace is difficult. It involves removing CDs, speaker wire and other debris. The disruption necessary to get to this furnace may make you less inclined to have it serviced regularly.

1. Improve access to the furnace.

- Jim Katen, Oregon

[Brian G]

Thank you gentlemen.

Brian G.