Baxi Potterton Condensing Combination Boiler 28/33, Determining Permissible Lengths, Example

	16												16
X	14											X	14
	10												10
(metres)												(metres)
	12				24								12				24
ExhaustØ	8			28/33								ExhaustØ	8			28/33
60	6										60		6
	4												4
	2												2
	0												0
	0	1	2	3	4	5	6	7	8	9			0	1	2	3	4	5	6	7	8	9
			Concentric 60/100 Flue (metres)Y												Concentric 60/100 Flue (metres)Y
		Example 1											Example 2
		Flue Lengths - Not Permissible											Flue Lengths - OK
					16
				X	14
					10
				(metres)
					12						24
				ExhaustØ	8					28/33
				60	6
					4
					2
					0
						0		1	2	3	4		5	6		7		8	9
									Concentric 60/100 Flue (metres)Y

Example 3

Flue Lengths - OK

60Ø Exhaust	Support
	Bracket

9.0Plume Displacement

9.2Determining Permissible Lengths

In the graph the solid line diagonal represents the relationship between the concentric flue assembly (and any extensions) and the 60Ø exhaust (and any extensions or additional bends).

Example 1 - Not Permissible

If, for instance, a concentric length of 5 metres was required and the 60Ø exhaust needed to be 6 metres the graph shows that this combination would NOT be permissible as the intersection point would be above the solid diagonal line.

Example 2 - Flue Lengths OK

Where both lengths have been determined they can be applied to the graph to check that the installation is permissible. For example, if it was known that 2 metres of concentric flue and 4 metres of 60Ø exhaust were required, the values could be applied to the graph as shown in Example 2.. As the point of intersection of the dotted lines is below the solid diagonal line, the combination of lengths is shown to be acceptable.

Example 3 - Flue Lengths OK

In the example shown in Fig. 4 assume that the concentric part of the flue needs to be 2.3 metres long. Find the position of ‘2.3’ on the horizontal axis of the graph and then project upwards to the solid diagonal line. This is represented by the vertical thick dotted line. Where this dotted line intersects with the solid diagonal line on the graph, project across to the vertical axis. As can be seen this corresponds with 6 metres. Therefore, the total equivalent length of the 60Ø exhaust can be up to 6 metres. Any bend equivalences must be accounted for i.e. 93° bends are equal to 1 metre, each 45° bend to 0.5 metres.

X

Y

45° Elbow

Flue Length - Worked Example Potterton Heatmax Combi 33HE

93° Elbow

Concentric 60/100 Flue

Fig. 26

Additional Accessories
A - 93° Elbow	5121369
B - 45° Elbow (Pair)	5121370
C - 1 metre 60Ø Extension	5121368

1 metre Extension

1 metre supplied in kit

Concentric Flue

Fig. 27

In Fig. 27 opposite an additional 93° bend and pair of 45° elbows have been included in the 60Ø exhaust.

Also 3 straight extension pieces have been used.

To calculate total length:-
Length of 60Ø supplied in kit =	1 metre
3 x 1 metre Extensions =	3 metres
1 x 93° Elbow =	1 metre
2 x 45° Elbow =	1 metre (0.5 metres each)
Total 60Ø =	6 metres

After consulting the table in Example 3 it can be determined that the concentric flue could be up to approximately 2.3 metres long.

26© Baxi Heating UK Ltd 2012