19
60mm inner flue of the concentric terminal connects to the pipe bridge, this point must be adequately sealed with silicone
sealant to avoid condense leakage at this point.
NOTE: Vertical twin flue installations must have a trap on the exhaust. MTS supply a suitable condense trap Part No. 705774
and recommend that this be used in the event that the flue may not form condense.
When siting the twin flue pipe, the air intake and exhaust terminals must terminate on the same wall, the centres of the
terminals
must be a minimum of 280 mm apart and the air intake must not be sited above the exhaust terminal (refer to Fig.
25). 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 24
metres (24kW) and 30 metres (30kW), 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 45 metres (24kW)
and 60 metres (30kW).
The maximum length is reached by combining the total lengths of both the air intake and exhaust pipes. Therefore a
maximum length of 45 metres for example, will allow a flue run of 22.5 metres for the air intake and 22.5 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 page 21.
For further information relating to flue runs not illustrated, please contact the Technical Department on 01494 539579.
12
Connecting the Flue (continued)
WARNING!!
Consult the table on Page 20, to see if a restrictor is
required for the type of flue system being used.
Should it be necessary to fit the restrictor, it must be
fitted as illustrated in Fig. 23.
Twin flue
In the event that twin flue pipes are used, and the
boiler has a side clearance of less than 60mm from
the wall, it is necessary to cut a larger diameter
hole for the flue pipe, this should be ø10 cm, this
will then allow for easier assembly of the air intake
elbow and the tube outside the wall (see Fig. 24).
Fig. 23
Fig. 24
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