If ventilation and/or combustion air must be supplied to the
•'Confined Space" from inside the building structure, two
permanent openings to an additional room of sufficient volume
as to combine the volumes of the spaces to meet the criteria for
an "Unconfined Space" must be created. Each opening must
have a free area of not less than one square inch per 1000 Btu per
hour of total input of all appliances within the "'Confined Space"
(but not less than 100 square inches). These openings must be
located 12 inches from the top and bottom of the furnace area
respectively and must be at least 3 inches long on the smaller side
of the opening. Neither opening can be blocked at any time.
If ventilation and/or combustion air must be supplied to the
"Confined Space" from outslde the building structure, two
permanent openings to the outdoors must be created. Each
opening must have a free area of not less than one square inch per
4000 Btu per hour of total input of all appliances within the
"Confined Space". These openings must be located 12 inches
from the top and bottom of the furnace area respectively. Neither
opening can be blocked at any time.
When ducts are used to supply air, they must be of the same
cross sectional area as the free area of the openings to which they
connect. The minimum dimension of rectangular air ducts must
notbe less than 3 inches.
;_ARNING :
DO not biock tfie com6usti6_ or ventilatid_: a!_ : :
openings,in:tlie furnace. Any: bloCkag_:,_ii:
result in impfope_ cOmbustion and ma_:re_:_lt :
n ; :
WARNING
If the blocked vent pressure switch (P1)
activates to shut the furnace down, the vent
system must be checked and cleared.
Failure to do so may result in serious bodily
harm or nuisance furnace shutdown and/or
a hazardous condition that may lead to
property damage, personal injuryor death.
WARNING
If the blocked drain pressure switch (P2)
activates to shut the furnace down, do not
attempt to operate the furnace until the drain
line is checked for blockage. Failure to clear
the drainage system could lead to nuisance
furnace shutdown and/or hazardous
conditions that may lead to property
damage personal injury or death,
Figure 1.4 PRESSURE SWITCH LOCATION
AND CONNECTION
may be combustible.
Blocked Vent & Blocked Drain Pressure Switches This
furnace is equipped with two (2) pressure switches that perform
several safety functions. The pressure switches are located in the
vestibule of the unit (see Figure 1.4). The switch labeled P1 will
turn the burners OFF in the event of a blocked inlet or a blocked
outlet condition. The switch labeled P2 will turn OFF the burners
in the event of a blocked drain condition. In addition, the P2
switch insures that the unit has combustion air flowing through the
unit prior to initiating the ignition sequence.
I °
| MINUS
P2
Y
PLUS
20246506 Issue 9939 Page 4 of 22
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