Page No 18 of 56 Reznor, RHC21 4000 Installation EN May 2021 D301334 Issue 0
Table 9 : Flue Diameter and Flue Pipe Lengths
RHC21 Model
4024-05 4036-08 4050-06 4060-07 4075-09 4100-12 4125M15 4150M18
Heater socket and flue diameter
mm
100
130
Maximum straight length two pipes (combustion air
inlet and flue outlet pipe) with wall or roof terminal
(Type C appliance
m
9.0
Maximum straight length single pipe (flue outlet pipe)
with wall or roof terminal
m
9.0
Equivalent length of 45° elbow
m
0.75
Equivalent length of 90° elbow
m
1.5
Minimum flue length
m
1.0
Single wall flue pipe exposed to
cold air or run through unheated
areas must be insulated. Where
condensation is unavoidable,
provision must be made for the
condensation to flow freely to a
point to which it can be released,
i.e. a drain or gully.
The condensation drain from the
flue must be constructed from non-
corrodible material not less than
20 mm diameter. Copper or copper-
based alloys must not be used for
condensation drains.
Flue gas properties are given in table 2 : Nominal
combustion values and flue gas properties on
page 9 of this manual.
Table 10 below shows flue pipe sizes and
maximum vent lengths. The minimum flue
length is 0.5 metres.
4.8 Type B appliances
If the heater is to be installed internally as a
Type B appliance, air for combustion will be
taken from within the space where the heater is
installed.
Single wall seamless aluminium or stainless
steel flue pipes are required. All joints must be
sealed to prevent the products of combustion
from leaking into the building. If the flue passes
through a combustible element of the building it
must be enclosed in a sleeve of non-combustible
material and separated from the sleeve by a
minimum of 25 mm air break. The temperature
of any combustible material near to the flue
must not exceed 65°C when the heater is in
operation. The flue must be at least 150 mm
away from any combustible material.
Single wall flue pipe exposed to cold air or run
through unheated areas should be insulated.
Where condensation is unavoidable, provision
must be made for the condensation to flow
freely to a point to which it can be released,
i.e. a drain or gully. The condensation drain
from the flue must be constructed from non-
corrodible material not less than 20 mm
diameter. Copper or copper based alloys must
not be used for condensation drains.
Vertical flue runs greater than 3m long will
require a condensate drain fitting between the
flue outlet of the heater and the vertical flue
pipe. Alternatively, insulated flue pipe should be
considered.
Horizontal flue runs should be installed with a
slight gradient of approximately 5° towards the
terminal. Due consideration should be given to
the possibility of condensation from the flue
freezing on any footpaths that pass below the
terminal.
It is important to ensure that there is an
adequate air supply at all times for both
combustion and heating requirements.
Ensure that the air combustion inlet opening at
the heater cannot be obstructed.
4.9 Type C appliances
If the heater is to be used internally in a Type C
balanced flue application, it must be fitted with
a combustion air inlet duct that obtains outdoor
air and a flue pipe that exhausts flue products to
outdoors.
