Step 3. Negative Pressure Make-up Air
Negative Pressure warning: When negative pressure is present, an atmospherically vented fireplace (with a draft hood) may not function properly and it may down draft. In the case of a gas appliance, spillage of the combustion gases may occur. This may create a dangerous carbon monoxide situation in the house.
The causes of negative pressure to a house can include the following:
•Stack effect in the building.
•Exhaust only appliances (mechanically and atmospherically vented).
•Inadequate make-up air (which is increasingly more prevalent in new construction).
NOTE: This fireplace will operate correctly only if adequate ventilation is provided to allow proper draft to the fireplace system. Heat-N-Glo assumes no responsibility for the improper performance of the fireplace system caused by inadequate draft due to environmental conditions, down drafts, tight sealing construction of the structure, or mechanical exhausting devices which create a negative air pressure within the structure where the fireplace is located.
It is recommended that all natural venting non-air tight gas fireplaces have outside air connected to them. It is also recommended that the building be mechanically or passively balanced to allow atmospherically vented appliances, such as top vented gas fireplaces with draft hoods, to draft properly. If the home experiences negative pressure or is likely to experience negative pressure, connection to an outside air source is mandatory.
Installing Optional Outside Make-up Air: This unit is equipped to accept outside air. By using outside make-up air, the amount of room air used for combustion will be reduced. It is recommended that an AK-225 air kit be used with this appliance.
!WARNING: IN A NEGATIVE PRESSURE CON- DITION (LIKELY TO OCCUR IN NEW HOMES
THAT DO NOT HAVEADEQUATE MAKE-UPAIR) THE OUTSIDE AIR KIT MUST BE INSTALLED TO OB- TAIN PROPER PERFORMANCE AND TO HELP PRE- VENT SPILLAGE OF COMBUSTION GASES.
A4-inch side collar and a 4-inch flexible air duct must be installed to the outer wrap of the fireplace. See Figure 4. After removing and discarding the outside air cover plate attach the side collar to the outer wrap of the fireplace using sheetmetal screws. Attach one end of the flex duct to the side collar and the other end of the duct to the termination cap. Use plastic tie straps to secure the ends of the flex duct to the collar.
Detailed installation instructions for Model AK-225 Outside Air kit are found in the kit. This kit cannot be used in Canada.
OUTSIDE AIR
COLLAR
AIR DUCT
OUTSIDE AIR
COVER PLATE
Figure 4. Make-up Air
