15
F
IG
2.18
IMPORTANT!!!
W
HERE CONDENSE WILL FORM WITHIN THE FLUE SYSTEM
,
ENSURE THERE IS A FALL BACK TO THE BOILER OF
3
O
AND A
SUITABLE TRAP IS FITTED AS CLOSE TO THE BOILER AS
POSSIBLE
. MTS
SUPPLY A SUITABLE COLLECTOR
P
ART
N
O
.
705798
OR A CONDENSATE DISCHARGE
T
WITH BUILT IN TRAP
P
ART
N
O
. 705774.
F
IG
2.17
F
IG
2.19
and the air intake
must not be sited above the exhaust
terminal
(refer to F
IG
. 2.21). The air intake pipe can be
run horizontally, however, the terminal and the final 1
metre of flue must be installed with a fall away from the
boiler to avoid rain ingress.
It is also strongly recommended that the air intake pipe
run be constructed of insulated pipe to prevent condense
forming on the outside of the tube.
The maximum permissible flue length for twin flue is
dependent on the type of run used.
For flue runs with the intake and exhaust pipes under the
same atmospheric conditions (T
YPE
4) the maximum
length is 60 metres (28kW), 46 metres (28kW) and 47
metres (31kW). For runs with the terminals under
different atmospheric conditions (T
YPE
5) the exhaust
terminal
must extend 0.5 metres above the ridge of the
roof (this is not obligatory if the exhaust and air intake
pipes are located on the same side of the building). For
T
YPE
5 also, the maximum permissible combined length is
59 metres (24kW), 48 metres (28kW) and 42 metres
(31kW). Flue types are shown on Page 16 (
F
IG
. 2.20).
The maximum length is reached by combining the total
lengths of both the air intake and exhaust pipes.
Therefore a maximum length of 40 metres for example,
will allow a flue run of 20 metres for the air intake and 20
metres for the exhaust pipes, also for each 90
o
elbow 1.3
metres must be subtracted from the total length and for
each 45
o
elbow 1 metre must be subtracted from the total
flue length.
Some of the acceptable flue configurations are detailed
on page 16
(F
IG
. 2.20).
For further information relating to flue runs not illustrated,
please contact the Technical Depar tment on 01494
539579.
