SIST EN 834:2013

SLOVENSKI STANDARD
01-november-2013
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SIST EN 834:2002
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Heat cost allocators for the determination of the consumption of room heating radiators -
Appliances with electrical energy supply
Heizkostenverteiler für die Verbrauchserfassung von Raumheizflächen - Geräte mit
elektrischer Energieversorgung
Répartiteurs de frais de chauffage pour enregistrer les valeurs de consommation de
surfaces de corps de chauffe - Appareils avec une alimentation en énergie électrique
Ta slovenski standard je istoveten z: EN 834:2013
ICS:
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 834
NORME EUROPÉENNE
EUROPÄISCHE NORM
August 2013
ICS 91.140.10 Supersedes EN 834:1994
English Version
Heat cost allocators for the determination of the consumption of
room heating radiators - Appliances with electrical energy supply
Répartiteurs de frais de chauffage pour déterminer la Heizkostenverteiler für die Verbrauchserfassung von
consommation des corps de chauffe - Appareils dotés Raumheizflächen - Geräte mit elektrischer
d'une alimentation en énergie électrique Energieversorgung
This European Standard was approved by CEN on 28 December 2012.

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-CENELEC 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-CENELEC Management Centre has the same
status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United
Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2013 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 834:2013: E
worldwide for CEN national Members.

Contents Page
Foreword .4
Introduction .5
1 Scope .5
2 Normative references .6
3 Terms and definitions .6
4 Functional principle and measurement methods . 11
5 General specifications . 12
5.1 Base condition . 12
5.2 c-value . 13
5.3 Rating factors . 13
5.4 Calendar function . 14
6 Requirements for heat cost allocators . 15
6.1 Requirements concerning temperature stress . 15
6.2 Storage temperature . 15
6.3 Start of counting . 15
6.4 Idle counting rate . 15
6.5 Temperature sensors . 15
6.6 Calculator/central processing unit . 16
6.7 Auxiliary power supply . 16
6.8 Overflow of the display . 16
6.9 Display resolution . 16
6.10 Functional check. 16
6.11 Limits of relative display deviation . 17
6.12 Ageing . 17
6.13 Electrical, electrostatic and magnetic influences . 17
6.14 Thermal impact on heat cost allocators operating in accordance with the single-sensor
measurement method . 17
6.15 Thermal impact on heat cost allocators operating in accordance with the two-sensor
measurement method . 17
6.16 Thermal impact on other devices or components . 18
6.17 Impact on transmission systems . 18
6.18 Sealing . 18
6.19 Calendar function . 18
6.20 Taking into account operating conditions . 18
7 Requirements for use and installation . 19
7.1 Temperature limits . 19
7.2 Attachment of the sensors . 19
7.3 Attachment position of the sensors . 20
7.4 Connecting cable installation . 20
7.5 Uniformity of heat cost allocators . 20
8 Rating requirements . 21
8.1 Rating factor K . 21
Q
8.2 Rating factor K . 21
C
8.3 Rating factor K . 21
T
8.4 Resulting rating factor K . 21
8.5 c-value . 21
9 Requirements for maintenance and reading . 22
9.1 Visual reading . 22
9.2 Close-range reading . 22
9.3 Remote reading . 22
10 Testing . 22
10.1 General . 22
10.2 Test documents . 23
10.3 Test report . 23
10.4 Test protocols . 23
11 Test procedures . 23
11.1 Construction test . 23
11.2 Sealing test . 23
11.3 Temperature durability test . 23
11.4 Test for compliance with the limits of the relative display deviation . 24
11.5 Ageing resistance test . 24
11.6 Test of the start of counting at normal operation and also, for heat cost allocators with
room temperature sensors, at operation with thermal impact . 24
11.7 Test of the idle counting rate . 25
11.8 Test of the counting rate in the case of thermal impact . 25
11.9 Test for external influences . 26
11.10 Test of c-values, procedure . 26
11.11 Test of c-values, scope of testing . 26
11.12 Test of rating factor K . 26
Q
11.13 Test of rating factor K . 27
C
12 Marking . 27
Annex A (informative) Information and recommendations . 28
A.1 General . 28
A.2 Heating systems . 28
A.3 Recommended field of application . 28
A.4 Heat emission not controllable by the consumer . 29
A.5 Additional corrections . 29
A.6 Documentation of the relationship between the counting rate and the thermal output . 30
Bibliography . 32

Foreword
This document (EN 834:2013) has been prepared by Technical Committee CEN/TC 171 “Heat cost
allocation”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an identical
text or by endorsement, at the latest by February 2014, and conflicting national standards shall be withdrawn at
the latest by February 2014.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 834:1994
Amendments
Compared to EN 834:1994, the following changes were made:
a) Definitions, requirements and test procedures have been refined and expanded,
b) Introduction of new values for the lower temperature limit,
c) Uniform definition for the mounting location of heat cost allocators on the radiator.
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, Croatia, Cyprus, Czech
Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

Introduction
This document deals with heat cost allocators with electrical power supply used for establishing the
consumption value of room heating surfaces. It specifies the minimum requirements for the construction,
materials, production, installation, function and evaluation of the displayed readings established by these
measuring devices.
This document describes test procedures to establish compliance with the stated requirements and specifies
instructions for their nature and scope.
1 Scope
NOTE See Clause 3 for a definition of the terms used below.
This European standard applies to heat cost allocators which are used to capture the proportionate thermal
output of radiators in consumer units.
If an account unit comprises consumer units of different types (e.g. technically different types of heating
systems or differences due to the consumer behaviour, e.g. industrial plants as opposed to private
apartments), it could be necessary to divide this account unit into groups of users.
Heat cost allocators enable the determination of the heat consumption only of each radiator in a consumer
unit as a share of the total heat consumption of the account unit or user group (see Clause 4); it is therefore
necessary to determine this total heat consumption either by measuring the consumed fuel quantity or the
amount of heat delivered (the latter by means of a heat meter, for example).
For the appropriate use of the heat cost allocators in accordance with this standard, the heating system needs
to:
 correspond to the state of the art at the time of installation of the heat cost allocators;
 be operated in accordance with the state of the art (see A.2).
This standard specifies that heat cost allocators shall not be used for heating systems where the temperature
of the heating system falls below or exceeds the temperature limits of the heat cost allocators, where the
rating factor for the thermal output, K , cannot be clearly specified or where the heating surface is
Q
inaccessible. This applies usually to the following heating systems:
 floor heating;
 radiant ceiling heating;
 flap-controlled radiators;
 radiators with ventilators;
 fan-assisted air heaters;
 heating systems with steam-operated radiators.
2 Normative references
Not applicable.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
heat cost allocator
instrument for registration of the proportionate thermal output of radiators in consumer units
3.2
heat cost allocation system
overall system, as verified by an inspection authority, consisting of a heat cost allocator, installation
equipment, installation instructions, rating system, existing rating factors, maintenance and reading
instructions
3.3
measurement method
physical principle of measurement in combination with fundamental properties of the appliance type
Note 1 to the term: For heat cost allocators in accordance with this standard, the fundamental property of the appliance
type characterizing the method is the number of measuring sensors for registering the relevant temperatures. The physical
principle of measurement which is applied preferably is the temperature dependency of electrical components.
3.4
consumer unit
dwellings, office, business or industrial premises in which the heat is supplied by a common central heating
system or by a common district heating connection
3.5
account unit
total of all consumer units
3.6
user group
group of consumer units within one account unit, each with a uniform heating system and comparable type of
use
3.7
mean heating medium temperature
t
m
mean value of the flow and return temperatures of the heating medium
Note 1 to the term: In this standard, t is determined by adding up the logarithmic heating medium excess temperature,
m
Δt , (formula (2), see 5.2) and the reference air temperature, t .
ln L
3.8
heating medium excess temperature
Δt
temperature difference between the mean heating medium temperature and the reference air temperature
Note 1 to the term: In this standard, the heating medium excess temperature (abbreviated as "excess temperature") is
determined as the logarithmic excess temperature Δt in accordance with formula (2) (see 5.2).
ln
3.9
design flow temperature
t
V,A
value of the flow temperature of the radiators required in order to reach the design indoor temperature in the
heated rooms under steady state conditions at a heat load corresponding to a geographically determined
design reference outside temperature
3.10
design return temperature
t
R,A
value of the return temperature of the radiators required in order to reach the design indoor temperature in the
heated rooms under steady state conditions at a heat load corresponding to a geographically determined
design reference outside temperature
3.11
mean design heating medium temperature
t
m,A
mean value of the design flow temperature and the design return temperature
Note 1 to the term: In this standard, t is determined by adding up the logarithmic mean value of the design excess
m,A
temperature and the basic reference air temperature of 20 °C in accordance with formula (2) (see 5.2).
3.12
base condition
radiator operating condition which is freely selectable within predefined limits and which is used for specifying
the rating factors and for determining the c-values
3.13
basic reference air temperature
t
L,B
value of the air temperature at base condition
Note 1 to the term: For t the specified target value is 20 °C, see 5.1.
L,B
3.14
reference air temperature
t
L
actual value of the air temperature while requirements are specified and measurements are carried out
3.15
heating medium base flow
medium flow through the radiator at base condition
3.16
temperature sensors
sensors consisting of a sensor element and a sensor casing, which generate a temperature-dependent signal
Note 1 to the term: The sensor casing serves both to transfer heat and to protect the sensor element from mechanical
influences.
3.17
measuring range of temperature sensors
temperature range within which temperature sensors can be used
Note 1 to the term: For pairs of temperature sensors which are used for the determination of temperature differences, in
addition to the measuring range, there is also a temperature difference range.
3.18
upper temperature limit
t
max
maximum mean design heating medium temperature t of the heating system heating surfaces equipped
m,A
with heat cost allocators at which the heat cost allocator can be used
Note 1 to the term: t is a property of the heat cost allocator which is determined by the temperature resistance of the
max
components used.
3.19
lower temperature limit
t
min
minimum mean design heating medium temperature t of the heating system at which the heat cost
m,A
allocator can be used
Note 1 to the term: t is a property of the heat cost allocator, which is determined by the measurement method. This
min
definition applies to double-pipe systems directly. For single-pipe systems, the mean design heating medium
temperature t of the heating system is replaced by the mean design heating medium temperature t of the last
m,A m,A
radiator in the string or, as a substitute, the design return temperature t of the string.
R,A
3.20
start temperature
t
Z
mean heating medium temperature of the radiator, t = t , at partial load, with the mass flow corresponding to
Z m
the base condition, at which the heat cost allocators start counting, in accordance with the single-sensor
measurement method without a room temperature start sensor
3.21
start excess temperature
Δt
Z
mean heating medium excess temperature Δt = t - t of the radiator at partial load, with the mass flow
Z m L
corresponding to the base condition, at which the heat cost allocators start counting, in accordance with the
two-sensor measurement method or single-sensor measurement method with a room temperature start
sensor
3.22
c-value
measure for the degree of thermal coupling between the temperature sensors and the temperatures to be
registered
Note 1 to the term: The c-value is defined as a temperature difference ratio, see 5.2, formula 1.
3.23
displayed reading value
measuring value produced by the heat cost allocator which can be read off as a numerical value at the display
device
Note 1 to the term: If this value does not equal zero at the beginning of the measuring period, the displayed reading
relevant for the heat cost calculation is determined from the difference between the numerical values at the end and the
beginning of the measuring period. The reading may be a non-rated value or the consumption value (see 3.24).
3.24
consumption value
displayed reading value rated by rating factors
3.25
counting rate
R
progression of the displayed reading or the consumption value per unit of time
Note 1 to the term: When determining the relative display deviation (3.28), the value measured at the temperatures of the
operating state is referred to as the actual counting rate.
3.26
counting rate characteristic
relationship between the counting rate and, according to measurement method, the temperature or the
temperature difference
Note 1 to the term: A distinction is made between the scheduled counting rate characteristic intended during the
construction of the heat cost allocator and the actual counting rate characteristic in the appliance type. When determining
the relative display deviation (3.28), the value of the counting rate determined from the scheduled counting rate
characteristic at the temperatures of the operating state is referred to as the scheduled counting rate.
3.27
basic counting rate
R
B
value of the counting rate resulting from the scheduled counting rate characteristic at the temperature or
temperature difference of the base condition and a c-value of zero
Note 1 to the term: It serves to determine the rating factor K (see 5.3.2).
C
3.28
relative display deviation
difference between the actual counting rate and the scheduled counting rate related to the scheduled counting
rate
3.29
idle counting rate
counting rate at room temperature without thermal output from the radiator
3.30
reading
making available the displayed reading or the consumption values of the heat cost allocators for the purpose
of heat cost calculation
3.31
visual reading
reading by means of visually reading off values at the display device of the heat cost allocator
3.32
close-range reading
reading by means of data transfer, via an interface, to a reader device which is arranged within sighting
distance of the heat cost allocator
3.33
remote reading
reading by means of data transfer to a receiver
Note 1 to the term: Usually, the receiver is arranged outside the consumer unit.
3.34
reference output
thermal output of the radiator under prescribed operating conditions
3.35
reference system
Q(60 K), Q(50 K)
prescribed operating conditions of the radiator during the determination of the reference output
3.36
rating factors
factors by which the non-rated displayed reading values of the individual heat cost allocators are multiplied so
as to be able to be used as consumption values directly for the consumer-based billing of heat costs
3.37
rating factor for the thermal output of the radiator
K
Q
non-dimensional numerical value of the reference output of the radiator expressed in watts or kilowatts
3.38
rating factor for the thermal coupling of the sensors
K
C
factor taking into account the different thermal coupling of the temperature sensors to the temperatures to be
registered for different types of heating surfaces
Note 1 to the term: See also 5.3.2, formula 5.
3.39
rating factor for rooms with low design indoor temperatures
K
T
factor taking into account the change of the thermal output and the change of the temperature of the sensors
where heat cost allocators according to the single-sensor measurement method are used at design indoor
temperatures less than the basic reference air temperature
3.40
resulting rating factor
K
product of the individual rating factors
Note 1 to the term: See also 5.3.3, formula 6.
3.41
calendar function
control of specific processes of the heat cost allocator as a function of the specific point in time within the
calendar year
3.42
transfer systems
any type of arrangement transferring signals between separately located assemblies of the heat cost allocator
3.43
manufacturer
person or organization responsible for the heat cost allocator system and the proper delivery and installation
of the heat cost allocator
3.44
thermal impact
influence of heat supply or heat accumulation on the heat cost allocator, acting in addition to the uninfluenced
heating operation
Note 1 to the term: Thermal impact can lead to incorrect displayed reading values.
4 Functional principle and measurement methods
Heat cost allocators in accordance with this standard are measuring devices for the registration of the
temperature integral with respect to time. The temperature is the basis for the determination of the heat
emission of the room heating surfaces on which the heat cost allocators or their sensors are installed. Heat
cost allocators with electrical supply as covered by this standard (in the following referred to as heat cost
allocators) depending on the measurement method register all or only a part of the characteristic temperatures
relevant for the heat emission of the room heating surface. The non-rated displayed reading value is the
approximate value of the time integral of the measured characteristic temperature of the room heating surface
or the time integral of the temperature difference between the room heating surface and the room.
The rated displayed reading value referred to as the consumption value (see 3.24) is obtained (see 5.3) from
the non-rated displayed reading value (see 3.23) by multiplication by rating factors, particularly by those for
the reference thermal output of the room heating surface (K , see 3.37) and for the thermal contact between
Q
the sensors and the temperatures to be registered (K , see 3.38).
C
The consumption value is an approximate value for the heat emitted by the heating surface during the
measurement period and the heat consumed by the user. The consumption value is either read off directly at
the heat cost allocator or determined later by converting the non-rated displayed reading value.
The consumption value thus is a measuring result containing properties of the measuring device, room
heating surface, other boundary conditions and, in addition, uncertainties of the rating factors and the
installation. Measuring deviations (measuring errors) of the registered heat therefore do not depend on the
measuring device only. This means that heat cost allocators cannot be calibrated in the same manner as heat
meters.
Due to the properties described, the measuring result will not be allocated any physical energy units. The
consumption value is non-dimensional. It is used only as a relative value relating to the sum of the
consumption values of the account unit or group of users. A relative value of a measured consumption value
determined in this manner can be interpreted as a share of the heat consumption of the account unit or user
group. This quantity is determined after the measurement period has ended for each individual radiator. From
the sum of the consumption values for the radiators of a consumer unit, the described relative value can be
determined as the share of the heat consumption of the relevant consumption unit in the total consumption of
the account unit or user group.
Heat cost allocators usually consist of a casing, measuring sensors, a calculator unit, a display device, the
energy supply, fixing elements and the seal. The seal serves to protect the heat cost allocator against
unauthorized manipulation. The components of the heat cost allocator are manufactured in compliance with
certain tolerances. Thus, each individual one of a particular kind of heat cost allocator (type, make) functions
the same when used in an identical way.
Each heat cost allocator in accordance with this standard is a functional unit. It fulfils its intended task only as
a whole, with all its components and properties acting in systematic cooperation and together with all other
heat cost allocators within the same account unit or group of users. Tests of heat cost allocators in
accordance with this standard are therefore always system tests, the results of which are only valid for the
tested heat cost allocation system as a whole.
Heat cost allocators in accordance with this standard work according to one of the following measurement
methods.
The single-sensor measurement method utilizes one temperature sensor. The sensor registers the
temperature of the room heating surface or heating medium. Appliances with room temperature start sensors
fall under the single-sensor measurement method.
The two-sensor measurement method utilizes two temperature sensors. One sensor registers the temperature
of the room heating surface or heating medium, the second sensor registers the room temperature or a
temperature in a defined relation to it.
Multiple-sensor measurement methods register a measure of the mean heating medium temperature using at
least two radiator sensors and the room temperature using one other sensor. The measured values are used
for determining the heating medium excess temperature applying a suitable algorithm.
5 General specifications
5.1 Base condition
The following applies for the base condition of the radiator:
 upper flow inlet;
 mean heating medium temperature t = 40 °C to 60 °C;
m
 basic reference air temperature t = 20 °C, to be measured in a thermally stable test booth at a height of
L,B
0,75 m above the floor and a distance of 1,5 m in front of the heating surface; the acceptable deviation
from the scheduled value is ± 2 K;
 heating medium base flow which occurs at t = 20 °C and values of t /t in accordance with Figure 1.
L,B V R
The acceptable tolerance is ± 5 %;
where
t is the flow temperature in °C;
V
t is the return temperature in °C.
R
Figure 1 — Flow and return temperatures at heating medium base flow and t = 20 °C
L,B
NOTE Within the acceptable scheduled value deviation for t (see above), the flow and return temperatures t /t are
L,B
V R
each adjusted such that the excess temperature values of the radiator and the temperature drop t - t as given by
V R
Figure 1 remain unaltered.
5.2 c-value
The c-value is calculated according to the following formula:
∆t
S
c= 1− (1)
∆t
where
Δt is the temperature difference of the sensors, e.g. t - t ;
s HS RS
Δt is the heating medium excess temperature t - t or Δt
m L ln
where
t is the temperature of the radiator sensor or radiator sensors;
HS
t is the temperature of the room temperature sensor (for heat cost allocators without room temperature
RS
sensors t = t );
RS L
t is the mean heating medium temperature;
m
t is the reference air temperature (measuring specification in accordance with 5.1);
L
t is the flow temperature of the radiator;
V
t is the return temperature of the radiator;
R
Δt is the logarithmic excess temperature of the heating medium with respect to t , calculated from the
L
In
measured values as follows:
t − t
V R
∆t = (2)
ln
t − t
V L
ln
t − t
R L
c-values are generally determined from measured temperatures. As an alternative, it is possible to determine
them by conversion of known c-values, but this usually requires verifying measurements. This applies to both
the conversion of c-values of known types of heat cost allocators and the derivation of c-values for radiators of
similar type.
5.3 Rating factors
5.3.1 Rating factor K for the thermal output of the radiator
Q
The thermal output of a radiator in a thermally stable test booth at flow, return and air temperatures of 90 °C,
70 °C and 20 °C, the air temperature being measured at a height of 0,75 m above the floor and a distance of
1,5 m in front of the heating surface, is the reference output relevant for the rating factor K (reference system
Q
Q(60 K)).
As an alternative, the standard thermal output given in EN 442-2 can be used as reference output, which is
determined at flow, return and air temperatures of 75 °C, 65 °C and 20 °C in a closed test booth cooled on all
sides (reference system Q(50 K)).
To ensure uniform ratings, 7.5 shall be taken into account.
If an output value is known in a reference system for the radiator to be rated, this value shall be applied
directly. If such a value is only available in the corresponding reference system, it shall be converted. For the
conversion of the reference outputs, the following formulae (3) and (4) shall be applied exclusively.
Conversion of a reference output Q(50 K) on the basis of 75 °C/65 °C/20 °C (excess temperature: 50 K) into
the reference output Q(60 K) at 90 °C/70 °C/20 °C (excess temperature: 60 K):
n
 
Q(60 K)= Q(50 K)⋅ (3)
 
 
Conversion of a reference output Q(60 K) on the basis of 90 °C/70 °C/20 °C (excess temperature: 60 K) into
the reference output Q(50 K) at 75 °C/65 °C/20 °C (excess temperature: 50 K):
n
 
Q(50 K)= Q(60 K)⋅ (4)
 
 
where
n is the radiator exponent determined during the radiator test.
If the true radiator exponent is not available, n = 1,3 may be used.
5.3.2 Rating factor K for the thermal coupling of the sensors
C
K is calculated as the quotient of the basic counting rate R and the counting rate R at the temperatures of
C B R
the sensors on the radiator to be rated operated at base condition:
R
B
= (5)
K
C
R
R
5.3.3 Resulting rating factor K
The resulting rating factor K is calculated as the product of the individual rating factors:
K= K ⋅ K ⋅ K
Q C T
(6)
Instead of the rating factors, corresponding proportional figures may be used.
5.4 Calendar function
The processes which are controlled by the calendar function can include the following:
 transmission of displayed reading values or consumption values or other stored values;
 recognition of operating states;
 recording of specific events (e.g. errors, thermal impact, appliance opening).
6 Requirements for heat cost allocators
6.1 Requirements concerning temperature stress
Brief occurrences of t of the mean heating medium temperature, t , shall cause no impairment of the
max m
proper function of a heat cost allocator or its components installed and ready for service on the radiator. This
similarly applies to heat cost allocators installed on other surfaces, e.g. on pipes.
For components not attached to the heating surfaces, ambient temperatures between 0 °C and 50 °C shall not
cause any malfunction.
6.2 Storage temperature
The construction of all components shall ensure that storage temperatures of between - 25 °C and + 60 °C
shall not cause any functional disturbances.
6.3 Start of counting
During the thermally uninfluenced heating operation, the following applies:
Appliances operating according to the single-sensor measurement method without room temperature start
sensor shall, on a radiator with c ≤ 0,1 at a heating medium flow corresponding to the base condition (see 5.1)
in accordance with formulae (7)
and a reference air temperature of 20 °C, start counting at the temperature t
Z
and (8):
for t ≥ 60 °C: t ≤ 0,3 × (t - 20 °C) + 20 °C (7)
Z min
min
for 55 °C ≤ t < 60 °C: t ≤ 28 °C (8)
Z
min
For appliances with room temperature sensors, the criterion for the start of counting given as excess
temperature in formula (9) applies to all measurement methods (cf. Clause 4):
(9)
∆t = t − t ≤ z
z z L
For appliances operating according to the single-sensor measurement method having a room temperature
start sensor, z = 5 K applies. For appliances operating according to the two-sensor measurement method, the
values of z given in 7.1.3 apply as a function of t .
min
For different types of heating surfaces within one account unit, the start of counting of the individual
appliances may vary by 10 % (t —20 °C), but no more than 5 K.
min
6.4 Idle counting rate
At room temperatures of up to 27 °C, the idle counting rate shall not exceed 1 % of the scheduled counting
rate at a heating medium excess temperature of Δt = 60 K, with a heating medium flow corresponding to the
base condition.
6.5 Temperature sensors
The mechanical strength and thermal durability of the sensor coating shall be sufficient to prevent
deformations during installation, operation and dismantling for inspection purposes, which impair the intended
function of the sensor element.
For inspection purposes, the instruments or their components shall be capable of being dismantled in such a
way that it is possible to check the requirements as specified in 6.12.
The temperature sensors shall satisfy any classified environmental conditions which include a lower
temperature limit of + 5 °C, an upper temperature limit of at least t (see 3.18) and an annual mean value of
max
the relative humidity of ≤ 65 %.
6.6 Calculator/central processing unit
The mechanical design shall ensure protection against the penetration of solid foreign bodies and keep out
tools, wires and similar objects. Furthermore, it shall ensure that water dropping vertically onto it has no
damaging effect.
The requirement for the mechanical strength is an oscillating load at a frequency of (10 to 55 ) Hz, with an
acceleration of 20 m/s .
The calculator/central processing unit shall satisfy classified environmental conditions which include a lower
temperature limit of 0 °C, an upper temperature limit of 50 °C and an annual mean value of the relative
humidity of ≤ 65 %.
6.7 Auxiliary power supply
In the case of a battery power supply, the capacity of the battery shall be adequate to ensure trouble free
operation for at least three months longer than the period for changing the battery as specified by the
manufacturer; a minimum battery capacity of 15 months shall be ensured in any case. If the battery voltage
drops during this period, the display deviations in accordance with 6.11 shall not be exceeded.
6.8 Overflow of the display
Within two consecutive measuring periods (one measuring period usually comprises 12 months), no overflow
of the meter shall occur which would remain unnoticed. If counting at the beginning of a measuring period
starts at zero, verification for one measuring period is sufficient. A radiator operation of 1500 h per year at the
highest radiator output intended within the rating system of the heat cost allocator shall form the basis for this.
It shall be ensured that this requirement is also met in the case of higher design temperatures than
t /t = 90 °C/70 °C.
V R
6.9 Display resolution
After 24 hours of operation for a sectional radiator with a reference output of 1 kW (reference system Q(60 K),
see 5.3.1) at a partial-load thermal output corresponding to a logarithmic excess temperature of 35 K and a
heating medium flow corresponding to the base condition (see 5.1), the displayed reading value shall be at
least 10.
6.10 Functional check
A funct
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