Keston C36 Installation Manual download pdf (Page 21)

3.8 FLUE SYSTEM

NB: When installing a replacement boiler a new flue system must be used. Do

not re-use the existing boiler flue installation.

3.8.1 Design

Individual air supply and flue outlet pipes are used. The material used for flue outlet &/or

air inlet must be muPVC to BS 5255 and/or BSEN1566-1 and BSEN1329 of an internal

diameter of 51 mm. (i.e. nominal 50 mm diameter muPVC solvent weld waste pipe).

Marley muPVC Solvent Weld Waste System (50mm) and Polypipe System 2000 muPVC

Solvent Weld Waste (50mm) are recommended systems. DO NOT USE ABS PIPE OR

FITTINGS.

Alternatively, where flue or air intake lengths of up to 60m are require, Keston Composite

75mm flue and air pipe can be used (contact your KESTON Heating stockist for details).

Keston Composite 75mm pipe MUST be painted where exposed to UV light.

Both 50mm flue outlet terminal and 50mm air inlet terminal are supplied and are illustrated

in Figure 3.8.1. Both terminals are identical. If 75mm terminals are required these can be

obtained from your KESTON Heating stockist. Request part numbers C.17.2.26.00.0

(terminals) and C.17.2.00.60.0 (50 to 75 adapters).

3.8.2 Maximum Lengths

The maximum lengths of both air inlet pipe and flue outlet pipe, when no bends are used,

are as detailed below.

However, each bend used has an equivalent length that must be deducted from the

maximum straight length stated above. Knuckle bends must not be used.

A 92.5

sweep elbow is equivalent to 1.0m straight length. A 45

bend is equivalent to

0.5m straight length

50mm 75mm

Maximum Air Inlet Length : 39.0m 117.0m

Maximum Flue Outlet Length: 20.0m* 60m**

Maximum Total Flue and Air Intake Length : 40.0m 120.0m

* A flue length of between 16 and 20m in 50mm pipe will reduce the DHW output by 1%

** A flue length of between 48 and 60m in 75mm pipe will reduce the DHW output by 1%

Example (assuming

50mm muPVC flue

and air pipework)

Air inlet uses two 92.5

sweep elbows.

Hence, maximum length permissible

(i.e. a+b in figure 3.8.2) = 39.0m - 1.0m -

1.0m = 37.0m

Flue outlet uses one 92.5

sweep elbow.

Hence, maximum length permissible (i.e.

c+d in figure 3.8.2 = 20.0m - 1.0 m =

19.0m

3.8.3 Slope

‘Horizontal' flue outlet pipework MUST

slope at least 2 degrees (35 mm per

metre run) downwards towards the boiler.

Pipework can be vertical. Only swept

elbows can be used.

Air inlet pipework can be truly horizontal or vertical, or sloping in a downward direction

towards the boiler but in this case rain, etc., must

be prevented from entering the pipe.

WD388/0/2004 Chapter 3 - Boiler Location The Keston C36 Combi & C36P Combi Boilers

Installation & Servicing Instructions Page : 16

$,5

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Figure 3.8.2 : Flue Air Maximum Length Example

KESTON COMBI

(COMBI P)

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Keston C36 Installation Manual Page 21

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