TAB Journal Fall 2020 - 16

It should also be noted that the flooding
of HVAC air handling equipment,
cooling coil condensate drain pans can
lead to stopped-up condensate drains,
which in turn leads to the pooling of
water within the equipment. Pooled
condensate drain water will become
stagnant and ultimately result in
ideal petri dish conditions within the
equipment for cultivating potentially
dangerous organic growth such as
Legionella. 1
6.	Greatly increased potential for
organic growth in HVAC air handling
equipment cooling coil sections, as
well as all sections located downstream
of the cooling coil such as the supply
air fan section and the discharge air
plenum section.

The Occupational Safety and Health
Administration website Legionnaires'
Disease page indicates that " improperly
draining condensate pans may produce
the ideal tepid conditions that can
encourage microbial and fungal
growth. "

Wintertime Operation
1.	Lower HVAC air handling equipment
discharge air conditions, and lower
(i.e. dryer) space relative humidity
levels in the areas served by this

2.	Increased complaints from facility
occupants concerning cold space
temperatures and very dry air resulting
in space static electricity issues.
3.	Greatly increased potential for freezing
the HVAC air handling equipment
cooling and/or heating coils due to
the significantly lower mixed air
temperatures entering the equipment.
Typical Scenario Example
By way of example, a typical
commercial 20-ton HVAC air
conditioning unit (floor-mounted,
ceiling-suspended or rooftopmounted equipment) sized for a typical
minimum outdoor airflow of 20 percent
of the equipment's total airflow, has the
following typical operating parameters:
1.	Unit cooling capacity = 20 tons or
240,000 British thermal units per hour
(BTUH) (Note: 1000 BTUH = 1 MBH).
2.	Unit heating capacity = 521 MBH.
3.	Unit nominal rated airflow = 8,000
4.	Unit outdoor airflow = 1,600 CFM (i.e.
20 percent).
5.	Typical HVAC equipment OA entering
temperature & humidity conditions
during the cooling season: 80°F dry
bulb (DB)/67°F wet bulb (WB)/50

percent relative humidity. (Note:
temperature units = °F = degrees
Fahrenheit, humidity units = percent).
6.	Typical HVAC equipment OA entering
conditions during the heating season:
10°F DB.
7.	 Typical indoor space conditions in an
area served by HVAC equipment: 75°F
DB/50 percent relative humidity.
8.	Typical cooling coil discharge
air conditions during the cooling
season: 55°F DB/53.75°F WB.
9.	 Typical heating coil discharge air
conditions during the heating season:
122°F DB.
The percent of this HVAC unit's 20-ton
cooling capacity represented by the
minimum OA airflow load component is
approximately 5.42 tons, or approximately
27.1 percent of the unit's total cooling
capacity. Every incremental increase of
100 CFM in the amount of OA handled by
this unit adds approximately 4,000 BTUH
of additional cooling load or roughly a
third of a ton.
If service personnel were to simply
increase the amount of OA ventilation
airflow on this typical HVAC air
conditioning unit to say, 50 percent of
total unit airflow (i.e. increasing OA
airflow from 1,600 CFM to 4,000 CFM),

Need a Better

Test & Balance Spec?
■	 Specify for Independence

■	 Recommended, achievable tolerances

■	 Detailed contractor
responsibilities to ensure
readiness for T&B

■	 Detailed procedural requirements
■	 AIA format, MasterSpec approved

For more information:
Email, or call 202-737-0202

TAB Journal Fall 2020

TAB Journal Fall 2020

Table of Contents for the Digital Edition of TAB Journal Fall 2020

TAB Journal Fall 2020 - Cover1
TAB Journal Fall 2020 - Cover2
TAB Journal Fall 2020 - 1
TAB Journal Fall 2020 - 2
TAB Journal Fall 2020 - 3
TAB Journal Fall 2020 - 4
TAB Journal Fall 2020 - 5
TAB Journal Fall 2020 - 6
TAB Journal Fall 2020 - 7
TAB Journal Fall 2020 - 8
TAB Journal Fall 2020 - 9
TAB Journal Fall 2020 - 10
TAB Journal Fall 2020 - 11
TAB Journal Fall 2020 - 12
TAB Journal Fall 2020 - 13
TAB Journal Fall 2020 - 14
TAB Journal Fall 2020 - 15
TAB Journal Fall 2020 - 16
TAB Journal Fall 2020 - 17
TAB Journal Fall 2020 - 18
TAB Journal Fall 2020 - 19
TAB Journal Fall 2020 - 20
TAB Journal Fall 2020 - Cover3
TAB Journal Fall 2020 - Cover4