ASHRAE Journal - December 2014 - 33

COLUMN ENGINEER'S NOTEBOOK

even pumps; instead they feature insulation only on
straight pipe lengths.
The energy losses from these uninsulated elements can
be substantial and is generally not allowed by ASHRAE
Standard 90.14 except for some elements of small piping. Moreover, these uninsulated surfaces pose a safety
hazard and may not meet code or OSHA requirements.
For our international readers, OSHA is the Occupational
Safety and Health Administration, an agency of the U.S.
Department of Labor. OSHA regulations5 mandate that
all exposed steam and hot-water pipes within 7 ft (2.1 m)
of the floor or working platform shall be covered with
an insulating material or otherwise guarded to prevent
contact.
Bare metal steam piping or hydronic hot-water piping is a burn risk for personnel assigned to maintenance
or repair work in the vicinity of those hot surfaces. It is
not difficult to imagine a mechanic performing maintenance in a crowded mechanical room on one piece
of equipment while accidentally making skin contact
with an adjacent uninsulated steam pipe. Or imagine a
worker on a ladder re-lamping a light fixture who begins
to lose balance and, as an involuntary human reaction,
reaches out a hand to the nearest object for self-bracing-and that nearest object is a bare steam pipe fitting.
Even above a lay-in ceiling, a worker may be assigned to
repair a VAV box and accidentally touches a nearby bare
reheat pipe fitting. In consideration of this, the author
does not recommend limiting insulation to the lowest 7
ft (2.1 m).
It is clearly not unreasonably difficult to insulate
valves, fittings, strainers, and pipe specials because it is
done frequently on chilled water piping systems for condensation control. The same should be done for hot surfaces, and it is even easier to accomplish since a vapor
barrier is not needed and because removable valve/fitting blankets and covers are available for hot water and
steam systems. OSHA allows issuance of personal protective clothing to workers in lieu of insulating nearby
hot surfaces, but it is difficult to imagine a mechanic
successfully rebuilding the seal on a pump near an adjacent hot surface while dressed in bulky clothing and
wearing heavy, thick insulated gloves.
OSHA does not specify a specific temperature threshold above which insulation is required nor below
which insulation is exempt, and this may be relevant as
hydronic hot water design temperatures in our industry

are falling with the growing application of condensing
boilers. For help in that regard, we can turn to ASTM
Standard C1055-03,6 which points out that touching of
a metallic surface at or above 158°F (70°C) causes irreversible injury to human skin almost instantaneously
upon contact, and faster than human reaction can
withdraw. Metallic surfaces at or below 111°F (44°C)
appear to pose no safety threat according to the same
Standard. 140°F (60°C) seems to be a reasonable threshold because it correlates to a first-degree burn (the least
severe type of burn) at a contact duration of five seconds. Furthermore, the Uniform Mechanical Code7 in
Paragraph 1201-3.8.6(A) establishes 140°F (60°C) as the
threshold above which pipe insulation is required.
Hopefully, this safety concern will eventually fade, as
energy concerns are driving designers and engineers
to specify high-efficiency condensing boilers operating
with low-temperature heating water systems. But steam
systems are still prevalent in health-care occupancies
and legacy non-condensing hot water systems will still
be encountered in retrofit work for many more years,
so this author recommends you include a clause in your
insulation specifications stating something similar to:
"For piping services denoted as 140°F (60°C) or greater, all
piping surfaces including but not limited to pipe, flanges,
fittings, valves of every kind, strainers, unions, and other
appurtenances should be insulated to avoid potential for
personnel injury via contact with a hot surface." Where
Standard 90.1 compliance is required, all piping elements
operating above 105°F (41°C) must be insulated except for
some elements of piping 1 in. (25 mm) and smaller.

Sidewall Grille Blade Spacing
If an air inlet or outlet is less than 7 ft (2.1 m) above
the floor, its maximum allowable blade spacing is 0.5
in. (12.7 mm). This is mandated by NFPA 90A8 in Article
4.3.7.3. Technically, that clause is worded as requiring a
grille having openings through which a 0.5 in. (12.7 mm)
sphere cannot pass; so a grille with wider blade spacing
could be used if a 0.5 in. (12.7 mm) mesh screen is placed
immediately behind the grille. Although the NFPA does
not explain the rationale behind this requirement, it
may be related to discouraging the use of an HVAC grille
as a place to discard trash or accumulations of other
materials that could later become a fire hazard. As is the
case with the Safety Guards near a Roof Edge, the cited
code requirement is taken from the 2012 edition, but the
D ECEM BER 2014

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