FAU in attic

[Marc M]

Im in California. I cant find anything regarding the minimum requirements for the install or clearances of the FAU when placed in the attic. I know about the platform and vent.

[Jerry Peck - Codeman]

[Marc M]

I was referring to the clearance of the combustion chamber to the deck and also the way in which the FAU is supported ( or lack of in this pic). I don't have other pics, but it just does'nt seem correct to simply have the FAU sitting ont he deck supported by two 5/8 pcs of wood.

[Marc M]

Hey Jerry, I was able to locate a few of the manufactures installation guide lines. So I assume that the IOR will use this as the install requirements? Also, in the pic, it wasnt visible but there were a start collars off the plenum. There was mastic so the clooar was not visible however, it was not strapped. In addition, all of the ducts were incorrectly supported as you stated. This is new construction.

[Jerry Peck - Codeman]

Hi Marc,

I suppose the manufacturer's installation instructions specify clearance to combustible material, which may be zero inches clearance all sides, but maybe not, and if not, the clearance may vary depending on the side. It is quite possible that there many need to be 3 inches to 4 inches of clearance to combustible material underneath, and, if so, that installation would not be correct. I am just making some suggestions for things to look up in the installation instructions.

Regarding the metal collars to the duct work and stating that the duct did not look to be properly attached, I was not referring to there not being a metal collar, but to the appearance (hard to tell in the photo) that the insulation around the duct was crushed down, taped and sealed crushed down, during installation - which is not allowed, the insulation is supposed to be left at fully expanded size around the mechanically attached and sealed inner core (no longer visible) and the attached and sealed outer duct covering (which is still visible). The outer diameter of the duct seems to get smaller as it approaches the metal collar, indicating the insulation is crushed. That 90 degree bend which is visible looks odd, almost like it is a metal 90 elbow inside the outer duct covering.

It also looks like there are two ducts crushing together to fit in that space which is not large enough to accommodate both ducts.

The closest duct coming out the top is not going vertical, supported, then bend ... it is pulling sideways on the attachment, sealant, and fitting and will come loose/unsealed and is not allowed to be that way either.

[Marc M]

You are correct with respect to the ducts. I also suspect zero clearances for the furnace but conventional wisdom just seems to tell me there should be more clearance of the burner chamber. It's funny, if I see 30 horizontal furnaces in a month, 90% will be supported by the rafters or trusses and 10% will be anchored to the platform. This one has neither. And by the way, what's the deal with the wood supports inside the pan? I understand that there should'nt be water in there anyway but it just seems odd.

[Jerry McCarthy - California Codeman]

Hi Marc
I'm a California building code instructor from College of San Mateo, in San Mateo CA and Jerry Peck sent me a copy of your question for my take.
All of what Jerry P said is basically correct and if you have a copy of the MII (manufacturer's Installation Instructions) that is what is required because MII trumps code. Those blocks of wood in the drain pan are obviously wrong and the duct connections are not correct as already discussed. Looks like an amateurish install and I would contact your local building department for a review. If not them, then how about a qualified HVAC contractor for a look-see?
I’m adding the current CA Mechanical Code requirements regarding FAU in attic installs along with a diagram. Hope this info helps,
Jerry McCarthy

2007 California Mechanical Code:
931.0 Attic Furnace; (Upright and Horizontal)
Upright furnaces may be installed in an attic or furred space more than five (5) feet (1,524 mm) in height, provided the required listings and furnace and duct clearances are observed. Horizontal furnaces may be installed in an attic or furred space, provided the required listings and furnace and duct clearances are observed. Clearances of a warm-air attic furnace from combustibles shall be as specified in Section 304.1.
931.1 An attic or furred space in which a warm-air furnace is installed shall be accessible by an opening and passageway as large as the largest piece of the furnace and in no case less than thirty (30) inches by thirty (30) inches (762 mm x 762 mm) continuous from the opening to the furnace and its controls.
Exception: The access opening into the space may be twenty-two (22) inches by thirty (30) inches (559 mm x 762 mm), provided the largest piece of equipment can be removed through the opening.
931.2 The distance from the passageway access to the furnace shall not exceed twenty (20) feet (6,096
mm) measured along the center line of the passageway. The passageway shall be unobstructed and shall have continuous solid flooring not less than twenty-four (24) inches (610 mm) wide from the entrance opening to the furnace.
931.3 A level working platform not less than thirty (30) inches (762 mm) in depth and width shall be provided in front of the entire firebox side of the warm-air furnace, and if the furnace temperature limit control, air filter, fuel-control valve, vent collar, or air-handling unit is not serviceable from the firebox side of the furnace, a continuous floor not less than twenty-four (24) inches (610 mm) in width shall be provided from the platform in front of the firebox side of the furnace to and in front of this equipment.
Exception: A working platform need not be provided when the furnace can be serviced from the required access opening.
931.4 A permanent electric outlet and lighting fixture controlled by a switch located at the required passageway opening shall be provided at or near the furnace.

[Marc M]

The info here is invaluable, thanks for all the help.

[Jerry McCarthy - California Codeman]

Your most welcome Marc and while I'm at it here's a bit more:
California 2007 Mechanical Code:
304.0 Installation.
304.1 Listed Appliances. Except as otherwise provided in the code, the installation of appliances regulated by this code shall conform to the conditions of its listing. The appliance installer shall leave the manufacturer’s installation and operating instructions attached to the appliance. Clearances of listed appliances from combustible materials shall be as specified in the listing or on the rating plate.
304.3 Unlisted Appliances. Unlisted appliances shall be installed with the standard clearances from combustible construction specified in Table 3-1. Unlisted appliances may have the standard clearances of Table 3-1 reduced by employing the forms of protection specified in Table 3-2. Forms of protection specified in Table 3-2 may be utilized to reduce clearances to combustible construction for all applicable appliances.
304.4 Anchorage of Appliances. Appliances designed to be fixed in position shall be securely fastened in place. Supports for appliances shall be designed and constructed to sustain vertical and horizontal loads within the stress limitations specified in the Building Code.
305.1 Accessibility for Service. All gas utilization equipment shall be located with respect to building construction and other equipment so as to permit access to the gas utilization equipment. Sufficient clearance shall be maintained to permit cleaning of heating surfaces; the replacement of filters, blowers, motors, burners, controls, and vent connections; the lubrication of moving parts where necessary; the adjustment and cleaning of burners and pilots; and the proper functioning of explosion vents, if provided. For attic installation, the passageway and servicing area adjacent to the equipment shall be floored.

[Marc M]

Beautiful, thats a sheet that I needed. I appreciate that. By the way, here's a pic of another one a today. I get all the good ones.

[Jerry Peck - Codeman]

Hi Marc,

You got the missing sediment trap, and the white pipe thread tape used at the gas line fittings, I am sure.

And the condensate lines, missing traps, tied in to each other, no pan, not insulated, etc.

And the lack of 1" spacing between the Type B Gas Vent and the insulation.

Question: What is that strap for which goes up from the corner of the FAU to ?? I know it is not supporting FAU, it must be strapping something to it for support?

[Jerry Peck - Codeman]

Looks like the questions have been answered, so ...

Jerry McCarthy,

Thank you for providing the California code information and answering Marc's question.

Thank you,