Bosch Appliances 125B LPS, 125B NGS operating instructions Combustion AIR Requirements, Clearances

WARNING: Flammable materials, gasoline, pressurized containers, or any other items or articles that are potentially fire hazards must NOT be placed on or adjacent to the heater. The appliance area must be kept free of all combustible materials, gasoline and other flammable vapors and liquids.

COMBUSTION AIR REQUIREMENTS

The AquaStar water heater holds cold water in its copper heat exchanger and brass water valve when not in use. Because of this, any cold air that comes in through the unit’s vent pipe is capable of freezing these components. This Installation Manual specifies the minimum vertical vent pipe and the amount of combustion air required for this unit. When all requirements are followed, the unit will operate properly and safely. However, there may still be a risk of freezing due to negative draft if all the combustion appliances in the area are not being supplied with a sufficient amount of make-up air. A wood stove or furnace can rob the make- up air in the AquaStar’s vent pipe, leaving the cold infiltrating air capable of freezing the cold water in the AquaStar heat exchanger. More make up air is the solution. Follow the instructions on venting and checking adequacy of make up air. A HVAC specialist should be used to design solutions for providing more make-up air if necessary.

Observe the following instructions concerning combustion air.

Appliances located in unconfined spaces:

a)An unconfined space is one whose volume is greater than 50 cubic feet per 1000 Btu per hour of the combined rating of all appliances installed in the space. That would be 5850 cubic feet for the AquaStar 125B “S” alone.

b)In unconfined spaces in buildings of conventional frame, masonry, or metal construction, infiltration is normally adequate to provide air for combustion, ventilation, and dilution of flue gasses.

Appliances located in confined spaces:

The confined space must be provided with two permanent openings, one commencing within 12 inches of the top and one commencing within 12 inches of the bottom of the enclosure. Each opening must have a minimum free area of one square inch per:

-1000 Btu/hr if all air is taken from inside the building.

-2000 Btu/hr if all air is taken from the outside by horizontal ducts.

-4000 Btu/hr if all air is taken from the outside by direct openings or vertical ducts.

Or the confined space must be provided with one permanent opening or duct that is within 12 inches of the ceiling of the enclosure. This opening must have a minimum free area of one square inch per:

-3000 Btu/hr if all air is taken from the outside by a direct opening or vertical duct.

Air Vents

(10 ¾ X 10 ¾ in. each) 125BS

125BS	Air Vents
	(5 ½ X 5 ½ in. each)

Louvers, grills and screens have a blocking effect. If the effective free area is not known, increase the sizes of your openings by 75% if your louvers are wood and by 30% if your louvers are metal. Refer to the National Fuel Gas Code for complete information. In buildings of tight construction all air should be taken from outside.

CLEARANCES

The Aquastar 125 B “S” is design certified for installation on a combustible wall and for installation in an alcove or closet with the minimum clearances to combustible and non -combustible construction listed below

A.Top 12 inches (306 mm)

B.Front 4 inches (102 mm)

C.Back 0 inches

D.Sides 4 inches (102mm)

E.Bottom 12 inches (306 mm)

Clearance from vent is dependent upon the clearance rating of the venting material used. For example, type B-a vent is approved for 1 inch clearance.

Note: Typically, the minimum clearance to combustible materials should not be less than 6” for single wall flue pipe. Note that this clearance can be reduced if combustible materials are protected as per table VI of the National Fuel Gas Code or if Type B gas vent is used.

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