Desa VTP22R User Manual

www.desatech.com

113261-01C

1. Determine the volume of the space (length x

width x height).

Length x Width x Height =__________cu. ft.

(volume of space)

Example:

Space size 20 ft. (length) x 16 ft.

(width) x 8 ft. (ceiling height) = 2560 cu. ft.

(volume of space)

If additional ventilation to adjoining room is

supplied with grills or openings, add the volume

of these rooms to the total volume of the space.

2. Multiply the space volume by 20 to determine the

maximum Btu/Hr (kw) the space can support.

__________ (volume of space) x 20 = (Maxi-

mum Btu/Hr the space can support)

Example:

2560 cu. ft. (volume of space) x 20 =

51,200 (maximum Btu/Hr the space can support)

3. Add the Btu/Hr (kw) of all fuel burning appli-

ances in the space.

Vent-free heater

________ Btu/Hr (kw)

Gas water heater*

________ Btu/Hr (kw)

Gas furnace

________ Btu/Hr (kw)

Vented gas heater

________ Btu/Hr (kw)

Gas ﬁreplace logs

________ Btu/Hr (kw)

Other gas appliances* + ________ Btu/Hr (kw)

Total = ________ Btu/Hr (kw)

* Do not include direct-vent gas appliances. Di-

rect-vent draws combustion air from the outdoors

and vents to the outdoors.

Example:

Gas water heater ___________ Btu/Hr (kw)

Vent-free heater ___________ Btu/Hr (kw)

Total

___________ Btu/Hr (kw)

4. Compare the maximum Btu/Hr (kw) the space can

support with the actual amount of Btu/Hr (kw) used.

___________Btu/Hr (kw) (maximum the space can support)
___________Btu/Hr (kw) (actual amount of Btu/Hr used)

Example:

51,200 Btu/Hr (15 kw) (maximum

the space can support)

62,000 Btu/Hr (18.2 kw) (actual

amount of Btu/Hr used)

The space in the above example is a conﬁned space

because the actual Btu/Hr (kw) used is more than the

maximum Btu/Hr (kw) the space can support. You must

provide additional fresh air. Your options are as follows:
A. Rework worksheet, adding the space of an adjoin-

ing room. If the extra space provides an unconﬁned

space, remove door to adjoining room or add

ventilation grills between rooms. See Ventilation

Air From Inside Building.

B. Vent room directly to the outdoors. See Ventila-

tion Air From Outdoors, page 7.

AIR FOR COMBUSTION

AND VENTILATION

Continued

C. Install a lower Btu/Hr (kw) heater, if lower Btu/Hr

(kw) size makes room unconﬁned.

If the actual Btu/Hr (kw) used is less than the maxi-

mum Btu/Hr (kw) the space can support, the space

is an unconﬁned space. You will need no additional

fresh air ventilation.

WARNING: If the area in which

the heater may be operated is

smaller than that deﬁned as

an unconﬁned space or if the

building is of unusually tight

construction, provide adequate

combustion and ventilation air

by one of the methods described

in the National Fuel Gas Code,

ANSI Z223.1/NFPA 54 Section 5.3

or applicable local codes.

VENTILATION AIR

Ventilation Air From Inside Building
This fresh air would come from an adjoining un-

conﬁned space. When ventilating to an adjoining

unconﬁned space, you must provide two perma-

nent openings: one within 12" (30.5 cm) of the

ceiling and one within 12" (30.5 cm) of the ﬂoor

on the wall connecting the two spaces (see options

1 and 2, Figure 2). You can also remove door into

adjoining room (see option 3, Figure 2). Follow the

National Fuel Gas Code, ANSI Z223.1/NFPA 54,

Section 5.3, Air for Combustion and Ventilation for

required size of ventilation grills or ducts.

  40,000 (11.7)
  + 22,000 (6.4)
  = 62,000 (18.2)

Figure 2 - Ventilation Air from Inside

Building

Remove

Door into

Adjoining

Room,

Option 3

Ventilation Grills

Into Adjoining Room,

Option 2

12"

Ventilation

Grills

into Adjoining

Room,

Option 1

12" (30,48 cm)