Bosch 520-HN-N Specifications download pdf (Page 8)

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Installation instructions

3.5 Combustion air requirements

The AquaStar water heater holds cold water in its

copper heat exchanger and water valve when not in use.

Because of this, any cold air that comes down 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

makeup air in the AquaStar's vent pipe, leaving the cold

infiltrating air capable of freezing the cold water in the

AquaStar heat exchanger. Supplying more combustion

air for all combustion appliances 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 GWH

1600 H alone.

b) Installations in structures that have been tightly

constructed (air infiltration rate of 0.40 ACH or less)

must be provided for combustion air per the National

Fuel Gas Code. Consult a HVAC specialist if your air

infiltration rate is questionable.

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.

Louvers, grills and screens have a blocking effect. If the

effective free area is not known, increase the sizes of

your openings by 400% if your louvers are wood and by

135% 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.

3.6 Venting

B Minimum vent pipe diameter: 5 inches

B Minimum vertical vent height: 6 feet, with no elbows

B Establish 12 inch rise before any elbow

The heater must be vented to the outside following all

local ordinances and specifications for installing a gas

appliance vent or chimney. The heater must be located

as close as practicable to a vertically rising chimney or

vent that has a listed vent cap at its termination point.

The venting system must be designed and constructed

so as to develop a positive flow adequate to remove flue

gasses to the outdoors. Consult the National Fuel Gas

Code if the vent will have elbows or share venting with

another natural draft appliance.

3.6.1 Horizontal venting

A power vent, with a proof-of-draft safety interlock

device, is required and is available for sidewall venting.

Contact your dealer. In the Commonwealth of Massa-

chusetts power vented applications must utilize proof-

of-draft safety interlock device.

3.6.2 Vertical venting

B A 5 inch diameter gas vent constructed of double

wall Type B gas vent is recommended. A 6 inch vent

is required in elevations greater than 2000 feet, see

Fig. 4. Under no circumstances should the vent pipe

be reduced in size.

B An approved gas vent connector must be attached to

the top of the water heater and rise vertically at least

12" before entering into an approved gas vent

connector elbow.

B The minimum vertical gas vent height allowed is 6

feet; horizontal vent connectors and elbows are not

to be considered in the total gas vent height.

Danger: Do not reduce the vent pipe

size. Do not put an elbow directly on top

of heater. Failure to follow venting

requirements may result in dangerous

exhaust gases to enter living space.

Warning: Do not combination vent with

a mechanically vented appliance.

Warning: Horizontally venting to a

vertically constructed vent stack along

an outside wall of a building is not

permissible.

Warning: Horizontally venting to a

sidewall vent terminator (without power

vent) is not permissible.

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Bosch 520-HN-N Specifications Page 8

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