EN 13384-1:2002+A2:2008

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Chimneys - Thermal and fluid dynamic calculation methods - Part 1: Chimneys serving one applianceConduits de fumée - Méthodes de calcul thermo-aéraulique - Partie 1: Conduits de fumée ne desservant qu'un seul appareilAbgasanlagen - Wärme- und strömungstechnische Berechnungsverfahren - Teil 1: Abgasanlagen mit einer Feuerstätte91.060.40Dimniki, jaški, kanaliChimneys, shafts, ductsICS:SIST EN 13384-1:2003+A2:2008en,frTa slovenski standard je istoveten z:EN 13384-1:2002+A2:200801-junij-2008SIST EN 13384-1:2003+A2:2008SLOVENSKI
STANDARD
EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM
EN 13384-1:2002+A2
April 2008 ICS 91.060.40 Supersedes EN 13384-1:2002 English Version
Chimneys - Thermal and fluid dynamic calculation methods - Part 1: Chimneys serving one appliance
Conduits de fumée - Méthodes de calcul thermo-aéraulique - Partie 1: Conduits de fumée ne desservant qu'un seul appareil
Abgasanlagen - Wärme- und strömungstechnische Berechnungsverfahren - Teil 1: Abgasanlagen mit einer Feuerstätte This European Standard was approved by CEN on 23 October 2002 and includes Corrigendum 1 issued by CEN on 17 December 2003, Amendment 1 approved by CEN on 19 September 2005 and Amendment 2 approved by CEN on 24 February 2008.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN Management Centre or to any CEN member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36
B-1050 Brussels © 2008 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 13384-1:2002+A2:2008: E

Calculation of thermal resistance.83 Annex B (informative) Tables.84 Annex C (informative)
Chimney outlet with regard to adjacent buildings.100 Annex D (informative)
Limit curves of the classification for the draught regulator.101 Annex E.102 Bibliography.103

and # $. The modifications of the related CEN Corrigendum have been implemented at the appropriate places in the text and are indicated by the tags ˜ ™. This European Standard has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association and supports essential requirements of EU Directives. Annexes A, B, C and D are informative. This European Standard “Chimneys – Thermal and fluid dynamic calculation methods” consists of !three" Parts: - Part 1: Chimneys serving one heating appliance - Part 2: Chimneys with multiple inlets and one inlet with multiple appliances - !Part 3: Methods for the development of diagrams and tables for chimneys serving one heating appliance" According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

1 Scope This European Standard specifies methods for the calculation of the thermal and fluid dynamic characteristics of chimneys serving one appliance. The methods in this Part of this European Standard are applicable to negative or positive pressure chimneys with wet or dry operating conditions. It is valid for chimneys with heating appliances for fuels subject to the knowledge of the flue gas characteristics which are needed for the calculation. The methods in this Part of this European Standard are applicable to chimneys with one inlet connected with one appliance. The methods in Part 2 of this European Standard are applicable to chimneys with multiple inlets and one inlet with multiple appliances. !Part 3 describes methods for the development of diagrams and tables for chimneys serving one heating appliance."
2 Normative references This European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to, or revisions of, any of these publications apply to this European Standard only when incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies (including amendments). #EN 1443:2003$, Chimneys - General requirements !EN 1856-1", Chimneys – Requirements for metal chimneys – Part 1: System chimney products EN 1859, Chimneys - Metal chimneys - Test methods EN 13502, Chimneys - Requirements and test methods for clay/ceramic flue terminals #CEN/TR 1749, European scheme for the classification of gas appliances according to the method of evacuation of the combustion products (types)$ 3 Terms and definitions For the purposes of this European Standard, the terms and definitions given in #EN 1443:2003$ and the following apply. 3.1 heat output (Q) amount of heat produced by a heating appliance per unit of time 3.1.1 nominal heat output (QN) continuous heat output specified by the manufacturer of the heating appliance related to specified fuels

3.5 effective height of the chimney (H) difference in height between the axis of the flue gas inlet into the chimney and the outlet of the chimney
3.6 effective height of the connecting flue pipe (HV) difference in height between the axis of the flue gas chimney outlet of the heating appliance and the axis of the flue gas inlet into the chimney
In the case of open fire chimneys, HV is the difference in height between the height of the upper frame of the furnace and the axis of the flue gas inlet into the chimney.
3.7 draught positive value of the negative pressure in the flue 3.8 theoretical draught available due to chimney effect (PH) pressure difference caused by the difference in weight between the column of air equal to the effective height outside a chimney and the column of flue gas equal to the effective height inside the chimney
3.9 pressure resistance of the chimney (PR) pressure which is necessary to overcome the resistance of the flue gas mass flow which exists when carrying the flue gases through the chimney 3.10 wind velocity pressure (PL) pressure generated on the chimney due to wind 3.11 ####minimum$$$$ draught at the flue gas inlet into the chimney (PZ) #difference between the minimum theoretical draught and the sum of the maximum pressure resistance of the chimney and the wind velocity pressure$

3.13 minimum draught for the heating appliance (PW) difference between the static air pressure of the room of installation of the heating appliance and the static pressure of the flue gas at the chimney outlet of the appliance which is necessary to maintain the correct operation of the heating appliance ####3.14 maximum draught for the heating appliance (PWmax) difference between the static air pressure of the room of installation of the heating appliance and the static pressure of the flue gas at the outlet of the appliance which is the maximum allowed to maintain the correct operation of the heating appliance$
3.15 effective pressure resistance of the connecting flue pipe (PFV) static pressure difference between the axis of the inlet of the connecting flue pipe and the axis of the chimney outlet due to the theoretical draught and pressure resistance
3.16 effective pressure resistance of the air supply (PB) difference between the static pressure in the open air and the static air pressure in the room of installation of the heating appliance at the same height
3.17 ####minimum$$$$ draught required at the flue gas inlet into the chimney (PZe) sum of the minimum draught required for the heating appliance and the draught required to overcome the effective pressure resistance of the connecting flue pipe and the effective pressure resistance of the air supply
####3.18 maximum allowed draught at the flue gas inlet into the chimney (PZemax) sum of the maximum draught allowed for the heating appliance and the draught required to overcome the effective pressure resistance of the connecting flue pipe and the effective pressure resistance of the air supply$
3.19 ####maximum$$$$ positive pressure at the flue gas inlet into the chimney (PZO) #sum of the difference of the maximum pressure resistance and the minimum theoretical draught of the chimney and the wind velocity pressure$

3.21 maximum differential pressure of the heating appliance (PWO) maximum difference between the static pressure of the flue gas at the chimney outlet of the appliance and the static pressure of the air at the inlet to the heating appliance specified for its correct operation
####3.22 minimum differential pressure of the heating appliance (PWOmin) minimum difference between the static pressure of the flue gas at the outlet of the appliance and the static pressure of the air at the inlet to the heating appliance specified for its correct operation. This can be a negative value.$
3.23 maximum differential pressure at the flue gas inlet into the chimney (PZOe) difference between the maximum differential pressure of the heating appliance and the sum of the effective pressure resistance of the connecting flue pipe and the effective pressure resistance of the air supply 3.24 secondary air ambient air added to the flue gas in addition to the nominal flue gas mass flow
####3.25 minimum differential pressure at the flue gas inlet into the chimney (PZOemin) difference between the minimum differential pressure of the heating appliance and the sum of the effective pressure resistance of the connecting flue pipe and the effective pressure resistance of the air supply$
3.26 secondary air device draught regulator or a draught diverter 3.27 draught regulator component which automatically supplies ambient air to the chimney, the connecting flue pipe or the heating appliance 3.28 draught diverter device, placed in the combustion products passage of the heating appliance, that is intended to maintain the quality of combustion within certain limits and to keep the combustion stable under certain conditions of updraught and downdraught 3.29 temperature limit of the inner wall (Tg) allowed minimum temperature of the inner wall of the chimney outlet

Table 1 - Symbols, terminology and units Symbol Terminology Unit ------------------------------------------------------------------------------------------------------------------------------------- A cross section area
m2 c
specific heat capacity
J/(kg·K) cp specific heat capacity of flue gas J/(kg·K) d thickness of the section
m D diameter
m Dh hydraulic diameter
m H effective height of the chimney
m k coefficient for heat transmission
W/(m2.K) K coefficient of cooling --
L length
m
&m flue gas mass flow
kg/s Nu Nusselt number
-- p static pressure
Pa pL external air pressure
Pa PB pressure resistance of the air supply for a flue gas mass flow Pa PE pressure resistance due to friction and form resistance
of the chimney
Pa PFV effective pressure resistance of the connecting flue pipe Pa PG difference in pressure caused by change of
velocity of flue gas in the chimney
Pa PH theoretical draught available due to chimney effect Pa PHV theoretical draught available due to chimney effect of
the connecting flue pipe Pa PL wind velocity pressure Pa
PNL draught required for secondary air devices Pa PR pressure resistance of the chimney
Pa PRV pressure resistance of the connecting flue pipe Pa PW minimum draught for the heating appliance
Pa #PWmax maximum draught for the heating appliance Pa$ PWO maximum differential pressure of the heating appliance Pa #PWOmin minimum differential pressure of the heating appliance Pa$ PZ #minimum$ draught at the flue gas inlet into the chimney Pa #PZmax maximum draught at the flue gas inlet into the chimney Pa$ PZe #minimum$ draught required at the flue gas inlet into the chimney Pa #PZemax maximum allowed draught at the flue gas inlet into the chimney Pa$ PZO #maximum$ positive pressure at the flue gas inlet into the chimney
Pa #PZOmin minimum positive pressure at the flue gas inlet into the chimney Pa$

PZOe maximum differential pressure at the flue gas inlet into the chimney Pa #PZOemin minimum differential pressure at the flue gas inlet into the chimney Pa$ Pr Prandtl number
-- Q heat output
kW !qC
heat transfer from the flue to the outer surface
K" QF heat input
kW QN nominal heat output
kW r mean value of roughness of the inner wall m R gas constant of the flue gas J/(kg·K) RL gas constant of the air J/(kg·K) Re Reynolds number
-- s cross section
m SE flow safety coefficient
-- SH correction factor for temperature instability -- t temperature
°C
T temperature, absolute
K Tg temperature limit K Tio inner wall temperature at chimney outlet K Tiob inner wall temperature at the chimney outlet at temperature
equilibrium K TL external air temperature K Tm mean temperature of the flue gas K Tp water dew point K Tsp condensing temperature K Tu ambient air temperature K Tub ambient air temperature of the boiler room K Tuh ambient air temperature for heated areas K Tuo ambient air temperature at the chimney outlet K Tul ambient air temperature for areas external to the building K Tuu ambient air temperature for unheated areas inside the house K TW flue gas temperature of the appliance K TWN flue gas temperature of the appliance at nominal heat output K TWmin flue gas temperature of the appliance at the lowest possible heat output
K U
internal chimney segment parameter m w mean velocity within a cross section m/s wm mean velocity over a defined length m/s y form value
-- z height above sea level m α coefficient of heat transfer W/(m2·K) β ratio of the combustion air mass flow to the
flue gas mass flow
-- γ angle between flow directions
° δ wall thickness m
Table 1 (concluded) Symbol Terminology Unit ----------------------------------------------------------------------------------------------------------------------------
ζ coefficient of flow resistance due to a directional and/or
cross sectional and/or mass flow change in the flue - η dynamic viscosity
N⋅s/m2 ηW efficiency of the heating appliance
-- ηWN efficiency of the heating appliance at nominal heat output -- λ coefficient of thermal conductivity
W/(m·K) ρ density
kg/m3 ρL density of the external air ρm mean density of flue gas averaged over a defined length and over the cross kg/m3
section σ (CO2) volume-concentration of CO2
% σ (H2O) volume-concentration of H2O (vapour)
% !1Rad
black body radiation number W/(m2·K4)" ψ coefficient of flow resistance due to friction of the flue -- 1Λ thermal resistance
m2·K/W
Table 2 - Additional subscripts Subscript Terminology
Unit ---------------------------------------------------------------------------------------------------------------------------------- a outside
-- A flue gas
-- b equilibrium temperature condition
-- B combustion air
-- e entrance
-- G change in velocity
-- i inside
-- L open air (outside)
-- m mean value
-- M mixture
-- n counting index
-- N nominal value -- NL secondary air
-- o chimney outlet
-- O positive pressure
-- tot totalized over all sections (segments) -- u ambient air
-- V connecting flue pipe -- W heating appliance
-- _____________________________________________________________________________

#The calculation of inside dimensions (cross section) of negative pressure chimneys is based on the following four criteria:  the minimum draught at the flue gas inlet into the chimney shall be equal to or greater than the minimum draught required at the flue gas inlet into the chimney;  the minimum draught at the flue gas inlet to the chimney shall be equal to or greater than the effective pressure resistance of the air supply;  the maximum draught at the flue gas inlet into the chimney shall be equal to or less than the maximum allowed draught at the flue gas inlet into the chimney;  the temperature of the inner wall at the outlet of the chimney shall be equal to or greater than the temperature limit. The calculation of inside dimensions (cross section) of positive pressure is based on the following four criteria:
 the maximum positive pressure at the flue gas inlet into the chimney shall be equal or less than the maximum differential pressure at the flue gas inlet into the chimney;  the maximum positive pressure in the connecting flue pipe and in the chimney shall not be higher than the excess pressure for which both are designated;  the minimum positive pressure at the flue gas inlet into the chimney shall be equal or greater than the minimum differential pressure at the flue gas inlet into the chimney;  the temperature of the inner wall at the chimney outlet of the chimney shall be equal to greater than the temperature limit. NOTE The pressure requirements for maximum draught or minimum positive pressure are only required if there is a limit for the maximum draught for the negative pressure heating appliance or a minimum differential pressure of the positive pressure heating appliance.
In order to verify the criteria two sets of external conditions are used:  the calculation of the minimum draught and maximum positive pressure is made with conditions for which the capacity of the chimney is minimal (i.e. high outside temperature); and also
 the calculation of the maximum draught and minimum positive pressure and of the inner wall temperature with conditions for which the inside temperature of the chimney is minimal (i.e. low outside temperature.$
5.2 Pressure requirements 5.2.1 Negative pressure chimneys The following relationships shall be verified:
PZ = PH - PR - PL ≥ PW + PFV + PB
= PZe in Pa
(1)
PZ ≥ PB in Pa (2) #PZmax = PH - PR ≤ PWmax + PFV + PB
= PZemax
in Pa
(2a)$
Where PB
is the effective pressure resistance of air supply (see 5.11.3), in Pa; PFV
is the effective pressure resistance of the connecting flue pipe, in Pa; PH
is the theoretical draught available due to chimney effect, in Pa; PL
is the wind velocity pressure, in Pa; PR
is the pressure resistance of the chimney, in Pa; PW
is the minimum draught for the heating appliance, in Pa; #PWmax is the maximum draught for the heating appliance, in Pa; PZ is the minimum draught at the flue gas inlet into the chimney, in Pa; PZmax is the maximum draught at the flue gas inlet into the chimney, in Pa; PZe
is the minimum draught required at the flue gas inlet into the chimney, in Pa; PZemax is the maximum allowed draught at the flue gas inlet into the chimney, in Pa.$ #NOTE The values of PH and PR in Equations (1) and (2a) are normally different because the conditions are different.$
5.2.2 Positive pressure chimneys The following relationships shall be verified:
PZO = PR - PH + PL ≤ PWO - PB - PFV = PZOe in Pa (3)
PZO ≤ PZ excess in Pa (4)
PZO + PFV ≤ PZV excess in Pa (5) #PZOmin = PR - PH
≥ PWOmin - PB - PFV = PZoemin
in Pa
(5a)$
Where #PB is the effective pressure resistance of air supply, in Pa; PFV is the effective pressure resistance of the connecting flue pipe, in Pa; PH
is the theoretical draught available due to chimney effect, in Pa;

is the maximum positive pressure at the flue gas inlet into the chimney, in Pa; PZOmin is the minimum positive pressure at the flue gas inlet into the chimney, in Pa;$ PZOe is the maximum differential pressure at the flue gas inlet into the chimney, in Pa; #PZOemin is the minimum differential pressure at the flue gas inlet into the chimney, in Pa;$ PZ excess is the maximum allowed pressure from the designation of the chimney, in Pa; #PZVexcess is the maximum allowed pressure from the designation of the connecting flue pipe, in Pa.$ #NOTE The values of PH and PR in Equations (3) and (5a) are normally different because the conditions are different $ 5.3 Temperature requirement The following relationship shall be verified:
iobTTg≥ in K
(6) Where Tiob is the inner wall temperature at the chimney outlet at temperature equilibrium, in K; Tg is the temperature limit, in K. If the chimney above the roof has additional insulation the following relationship shall also be verified:
gT T≥irb in K
(7) Where:
Tirb is the inner wall temperature immediately before the additional insulation, in K.
The temperature limit Tg of chimneys with dry operating conditions shall be taken as the condensing temperature Tsp of the flue gas (see 5.7.6). The temperature limits Tg of chimneys with wet operating conditions shall be taken as 273,15 K which prevents the formation of ice at the chimney outlet. NOTE The comparison of the inner wall temperature before the additional insulation Tirb with the admissible limit temperature of the flue gas Tg is not necessary, if the value of the thermal resistance of the additional insulation is not more than 0,1 (m2⋅K)/W.

In 5.7 the formulae provide the calculation of the basic data which are needed for further calculation. In !5.5.3" and 5.8 the formulae for the calculations of the relevant temperatures are compiled. The formulae for the density of the flue gas and its velocity are compiled in 5.9. The procedure in 5.10 and 5.11 shall be used to validate the pressure requirement. The procedure in 5.12 shall be used to validate the temperature requirement. The validation for pressure and temperature requirement shall be conducted twice:
- for the nominal heat output of the heating appliance; - for the lowest value of the heat output range which is indicated by the manufacturer of the heating appliance. #If the pressure requirement for maximum draught (2a) or the temperature requirements (6) and (7) of negative pressure chimneys are not fulfilled the validation of the pressure condition or temperature condition can occasionally be achieved by taking additional secondary air to the flue gas into account according to Clause 6.$ !NOTE The temperature requirement need not be met for the following conditions provided that it is accepted that in case the requirement for temperature is not fulfilled no guarantee can be given that no moisture appears. The conditions are: - where the heating appliance is replaced by an appliance that has an output of < 30 kW, and - that the flue gas loss of the heating appliance is at least 8 %, and - that the heating appliance has a draught diverter which provides adequate ventilation in the chimney during standby periods or periods of low output.
This may be achieved by over-sizing the heating appliance output."
5.5 Flue gas data characterising the heating appliance !!!!deleted text"""" 5.5.1 General For the calculation of temperatures and pressure values the relevant flue gas data which characterises the heating appliance, consisting of flue gas mass flow, flue gas temperature and the minimum draught required for the heating appliance or the maximum differential pressure of the heating appliance shall be obtained. Additionally the kind of the fuel supplied, the volume concentration of CO2 of the flue gas and the geometry of the connecting flue pipe shall be specified.

m& = fmf. AF
in kg/s
(8) Where
fmf is the mass flow factor of an open fire place, in kg/(s.m2);
AF is the cross section of the opening of the open fire place, in m2; For open fire places with an opening height less than or equal its width
fmf
= 0,139 kg/(s.m2). For open fire places with an opening height greater than its width
fmf
= 0,167 kg/(s.m2). The CO2- content of the flue gas for open fire places may be taken as 1(CO2) = 1 %.
5.5.2.2 Flue gas mass flow at the lowest permissible heat output If the heating appliance is designed to operate under modulating conditions an additional check shall be conducted for the pressure and temperature requirement of the flue gas mass flow at the lowest possible and permissible heat output of the heating appliance.
If the manufacturer does not provide flue gas data for the lowest heat output use a mass flow of one third of the flue gas mass flow at nominal heat output. 5.5.2.3 ####Flue gas mass flow at the maximum draught or minimum differential pressure of the heating appliances For the calculation of maximum draught or minimum positive pressure in a chimney the flue gas mass flow at maximum draught or minimum differential pressure of the heating appliance shall be obtained from the manufacturer of the heating appliance if appropriate.$

If no values are available, the relevant values of the minimum draught for the heating appliance should be selected from relevant product standards for heating appliances. If no values for boilers are available see Table B.2. If the available value of the minimum draught is a negative number (implying a positive pressure operation) a value of PW = 0 shall be used in the calculations. If no valid data for the draught diverter from the manufacturer is available, for gas fired appliances designated as B1 according to #CEN/TR 1749$ use a value of 3 Pa for the minimum draught and use the value of 10 Pa for all other gas fired appliances equipped with a draught diverter. The minimum draught PW for the operation of fire places should be calculated with the flue gas mass flow and the cross section of the chimney outlet of the open fire place. The theoretical draught available due to chimney effect in the #open$ fire place and the flue gas collector should be neglected. The local resistance in the flue gas collector (gather) is taken into account by using a flow safety coefficient SE = 1,5.

5.5.5 #Maximum draught for the heating appliance (PWmax) for negative pressure chimney For the calculation of a negative pressure chimney the value of the maximum draught for the heating appliance PWmax shall be obtained from the manufacturer of the heating appliance if appropriate.$
5.5.6 Maximum differential pressure of the heating appliance (PWO) for positive pressure chimney For the calculation of a positive pressure chimney the value of the maximum differential pressure for the heating appliance PWO shall be obtained from the manufacturer of the heating appliance.
5.6 Characteristic data for the calculation 5.6.1 General In order to calculate the relevant pressure and temperature values the roughness of the inner wall and the thermal resistance of the connecting flue pipe and the chimney shall be determined. 5.6.2 Roughness value (r) The mean value for roughness of the inner liner shall be obtained from the product manufacturer. The mean values of roughness of inner liners of materials normally used are listed in Table B.4. 5.6.3 Thermal resistance (1/ΛΛΛΛ) The thermal resistance 1/Λ of the system chimney shall be obtained from the product manufacturer. The thermal resistance 1/Λ of the components shall be obtained from the product manufacturer and should include the effects of thermal bridges (e.g. joints). NOTE Calculations involving thermal resistance for system chimneys and/or components should normally be undertaken using values obtained at the mean operating temperature. The thermal resistance value obtained at the designation temperature may be used.
For multiwall custom built chimneys the thermal resistance shall be determined using the following formula:

1 1 1nnh,nh ∑Λ=ΛDD in m2·K/W (10) Where Dh is the internal hydraulic diameter, in m; Dh,n is the hydraulic diameter of the inside of each layer, in m; n1Λ is the thermal resistance of a pipe shell, referring to its internal surface, in m2·K/W. Where the specific data for individual components is not known the thermal resistance can be determined in accordance with Annex A. The thermal resistance of closed air gaps is given in Table B.6. 5.7 Basic values for the calculation 5.7.1 Air temperatures 5.7.1.1 General On chimneys which pass through heated areas, a differentiation shall be made between the external air temperature and the ambient air temperatures. 5.7.1.2 External air temperature (TL) The external air temperature TL shall be taken as the maximum temperature of external air at which the chimney is intended to be used. #The external air temperature TL for heating systems is normally calculated using LT = 288,15 K (Lt = 15 °C) for the calculation of minimum draught or maximum positive pressure at the flue gas inlet into the chimney;
LT = 258,15 K (Lt = -15 °C) for the calculation of maximum draught or minimum positive pressure at the flue gas inlet into the chimney.$ Other values for TL may be used based on national accepted data. 5.7.1.3 Ambient air temperature (Tu) #To check that the pressure requirement for the minimum draught or maximum positive pressure has been met the ambient air temperature uT = LT shall be used. To check that the pressure requirement for the maximum draught or minimum positive pressure and the temperature requirement have been met the following values for ambient air temperatures uT shall be used:$ - for chimneys without ventilated air gaps: uoT = 258,15 K (uot = -15 °C) for chimneys operating under wet conditions

EN 13384-1:
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