ASHRAE Journal - August 2008 - 72

How Not to Smoke Test Fan Support. After consulting with the manufacturer of a small utility set fan about the fan’s suitability for a project, the alternative design was used, supporting the fan upside down (Figure 1). Slot Air Diffusers. In a school’s large auditorium, the architect wanted a sawtooth roof-ceiling system comprising concrete beams (Figure 2). Each beam was an inverted “V.” We created a supply air ventilation system by using some of the roof valleys with horizontal roof segments, creating triangular By Carl H. Jordan, Fellow/Life Member ASHRAE air ducts. The air ducts were tapered to reduce cross-sectional any of us, particularly as young engineers, have areas throughout their lengths. The gap between the beams experienced situations resulting in interesting, per- became the supply air slots. Flat, horizontal, linear, sheet metal haps even unique, design solutions (and problems). elements became slide-dampers. Satisfactory performance I know I did. The following column describes a few of my was conﬁrmed with smoke testing. Air Diffuser. To me, a typical exposed duct diffuser instalexperiences. lation can be unattractive. For Smoke Testing. A banking a high-end restaurant with an space had a mostly open ceilexposed wood truss roof, no ing system composed of many ceiling and exposed ducts, our vertical, metal plates (~3 in. by design dropped the diffusers to ~6 in. [8 cm by 15 cm]), each below the lower chord of the suspended from a metal grid. truss (Figure 3). Above the ceiling, we had deHVAC Replacement. The signed a supply air-distribution object was to replace an exsystem, which we hoped would isting HVAC system with a not cause the ceiling plates to Traditional Alternate new one for an entire floor vibrate or ﬂutter. of hospital operating rooms To conﬁrm the design, we Figure 1: Fan support using traditional design and alternate design. (OR) while maintaining alused smoke testing. It worked. But, we experienced problems resulting from the timing of the most normal operation of the surgical ﬂoor. The oversimplismoke testing. We were doing the test in the morning before ﬁed illustrations (Figure 4) reveal the process. Looking at the longitudinal section, the work progressed from right to left, the bank’s grand opening. First, not everyone on the bank’s staff had been notiﬁed about replacing the old with the new. Temporary air bypasses were the test, so a few of them, upon seeing the smoke, exited the used while the equipment was required to operate at reduced building through security doors, which set off alarms and called capacity for fewer ORs. Pipe and Pump Sizing. Desiring to optimize the efﬁciency of the ﬁre department. Second, the smoke did not clear before opening time. Visitors to the grand opening were greeted by a a pumping system to pump chilled water across site from one part of a building to another, the following approach was used: smoke-ﬁlled space and the ﬁre department. Editor’s note: Practical Pointers provides solutions and answers to common problems. We welcome submissions at practicalpointers@ashrae.org. Short columns are encouraged. The columns will be published as they become available. Letters and comments about this column should be sent to practicalpointers@ashrae.org. M Duct Traditional Alternate Figure 2 (left): Roof/slot system used in an auditorium. Figure 3 (right): Exposed duct/diffusers. The alternate was used in a restaurant. 72 ASHRAE Journal ashrae.org August 2008

ASHRAE Journal - August 2008

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