Building Design and Construction Handbook - Merritt - Ventech!

13.42 SECTION THIRTEEN
TABLE 13.10 Recommended Design Indoor
Winter Temperatures
Type of building Temp, �F
Schools:
Classrooms 72
Assembly rooms, dining rooms 72
Playrooms, gymnasiums 65
Swimming pool 75
Locker rooms
Hospitals:
70
Private rooms 72
Operating rooms 75
Wards 70
Toilets 70
Bathrooms 75
Kitchens and laundries 66
Theaters
Hotels:
72
Bedrooms 70
Ballrooms 68
Residences 72
Stores 68
Offices 72
Factories 65
Choosing Heating-Plant Capacity. Total heat load equals the heat loss through
conduction, radiation, and infiltration.
If we provide a heating plant with a capacity equal to this calculated heat load,
we shall be able to maintain design room temperature when the design outside
temperature prevails, if the interior is already at design room temperature. However,
in most buildings the temperature is allowed to drop to as low as 55�F during the
night. Thus, theoretically, it will require an infinite time to approach design room
temperature. It, therefore, is considered good practice to add 20% to the heatingplant
capacity for morning pickup.
The final figure obtained is the minimum heating-plant size required. Consult
manufacturers’ ratings and pick a unit with a capacity no lower than that calculated
by the above method.
On the other hand, it is not advisable to choose a unit too large, because then
operating efficiency suffers, increasing fuel consumption.
With a plant of 20% greater capacity than required for calculated heat load,
theoretically after the morning pickup, it will run only 100/120, or 83 1 ⁄3%, of the
time. Furthermore, since the design outdoor temperature occurs only during a small
percentage of the heating season, during the rest of the heating season the plant
would operate intermittently, less than 83 1 ⁄3% of the time. Thus it is considered
good practice to choose a heating unit no smaller than required but not much larger.
If the heating plant will be used to produce hot water for the premises, determine
the added capacity required.