Bosch 520-PN-L Specifications download pdf (Page 13)

6 720 644 942 (2014/11)520 HN

Installation instructions | 13

Fig. 8 Secure heater to wall

4.4 Combustion air requirements

The Protankless 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 structure

are not being supplied with sufficient combustion air. A wood

stove or furnace can pull it's combustion air from the

Protankless vent pipe. This allows the cold infiltrating air to

potentially freeze the cold water in the water heater. Damage

from freezing is not covered under the manufacturer's

warranty. Supplying more combustion air for all combustion

appliances is the solution. Follow the instructions on venting

and checking adequacy of combustion air. A HVAC specialist

should be consulted 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 Protankless 520 HN alone.

b) Installations in structures that have been tightly constructed

(air infiltration rate of 0.40 ACH or less) must be provided with

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.

4.5 Venting

▶ Minimum vent pipe diameter: 5inches

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

▶ 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.

DANGER:

▶ Do not reduce the vent pipe size. Do not

put an elbow directly on top of heater.

Failure to follow venting requirements

may cause dangerous exhaust gases to

enter living space.

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Bosch 520-PN-L Specifications Page 13

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