28
Table 6.2: Length of surplus with 45° elbows
FITTING AIR/FLUE DUCT EXTENSIONS BETWEEN TWO 45° ELBOWS
Length of Air duct
• Cut the length of the air duct as
follows:
Length of air duct as per table.
Length of Flue duct
• Cut the length of the flue duct as
follows:
Length of flue duct = Length of air
duct + 40 mm
How to measure length
of air and flue ducts
Measure the distance between centres
of the two flue pipes to be connected.
Using the table below identify and
note the air duct length to be cut
(Length of air duct).
80
0
194
85
0
199
90
0
204
95
0
209
> 95 -
not
< 155 mm
possible
155
85
269
160
92
274
165
99
279
170
106
284
175
113
289
180
121
294
185
128
299
190
135
304
195
142
309
200
149
314
205
156
319
210
163
324
215
170
329
220
177
334
225
184
339
230
191
344
235
198
349
240
205
354
245
212
359
250
220
364
255
227
369
260
234
374
265
241
379
270
248
384
275
255
389
280
262
394
285
269
399
290
276
404
295
283
409
300
290
414
305
297
419
310
304
424
Distance Length
of-
Height
between centres
air duct
[in mm]
[in mm]
[in mm]
Distance Length
of-
Height
between centres
air duct
[in mm]
[in mm]
[in mm]
Distance Length
of-
Height
between centres
air duct
[in mm]
[in mm]
[in mm]
315
311
429
320
319
434
325
326
439
330
333
444
335
340
449
340
347
454
345
354
459
350
361
464
355
368
469
360
375
474
365
382
479
370
389
484
375
396
489
380
403
494
385
410
499
390
418
504
395
425
509
400
432
514
405
439
519
410
446
524
415
453
529
420
460
534
425
467
539
430
474
544
435
481
549
440
488
554
445
495
559
450
502
564
455
509
569
460
517
574
465
524
579
470
531
584
475
538
589
480
545
594
485
552
599
490
559
604
495
566
609
500
573
614
505
580
619
510
587
624
515
594
629
520
601
634
525
608
639
530
616
644
535
623
649
540
630
654
545
637
659
550
644
664
555
651
669
560
658
674
565
665
679
570
672
684
575
679
689
580
686
694
585
693
699
590
700
704
595
707
709
600
715
714
605
722
719
610
729
724
615
736
729
620
743
734
625
750
739
630
757
744
635
764
749
640
771
754
645
778
759
650
785
764