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Flue Systems,

Installation Requirements,

System Certification

Certification Information No. 3 01/99

C er tif ica t ion B od y


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1997 DVG W, B onn, 2. Edition, J a nuary 1999

DVG W Deutsc her Verein d es G a s- und Wa ss erfac hes e.V.

G erman Ass ociation of the G as a nd Water Industry

Tec hnica l and sc ientific a ss oc ia tion

Certification Body

PO box 14 03 62

D-53058 Bonn

Telephone : + 49 (228) 91 88 807

Telefax : + 49 (228) 91 88 993

E-Ma il: zg w@d vg w.d e

Internet: http ://www.dvgw.de

Any reprint or photomechanical reproduction in full or in part is only permitted with the

a pproval of DVG W Deutsc her Verein des G a s- und Wa ss erfac hes e.V., B onn.

Distributed by: Wirtsc hafts- und Verla gs ges ellsc haft G a s und Wa ss er mbH,

PO box 14 01 51, 53056 Bonn


3/22

Essentially, the innovations in the updated

D VG W -TR G I 86/96 can be described as fol-

low s:

Sim plified requirem ents for the installation

room , particularly w ith respect to ventilation

and exhaustion.

The general requirem ent for a chim ney hasbeen dropped and is replaced by a re-

quirem ent for a flue system in general as

standard approach for flue gas discharge

from gas appliances.

R educed distances betw een flue system s

and inflam m able building m aterials.

R educed height of flue system outlets a-

bove roof.

Sim plified requirem ents of shafts for flue

ducts and connection ducts.

Adoption of the E uropean classification of

types of appliance according to C EN .

Summary

Cert i fica t ion Bod y

C ER T - IN FO N o. 3 01/99 1

Flue Systems,Installation Requirements,

System Certification

The updated D VG W -TR G I 86/96 include a num ber of significant concessions on the

installation and approval of gas appliances, including flue gas discharge and com bustion

air supply. B oth the sim plified requirem ents of the new Specim en Firing O rdinance of Fe-

bruary 1995 and the harm onisation objectives of European D irectives and standards

have been taken into account here. The latter provide for uniform classification and de-

signation of the various types of appliance w ith respect to com bustion air supply and flue

gas discharge, w hich are also taken into consideration as part of the com m on system

certification of appliances and flue system s under the EC G as A ppliances D irective. This

system certification helps to achieve significant sim plification and reduce costs and istherefore explicitly recom m ended by the D VG W C ertification B ody.

Appliance installationrequirements

A m ajor change is the requirem ent for on-

ly one ventilation opening (instead of tw o) of

150 cm 2 clear section, w hich m eans sim pler

installation of gas appliances w ith a residualfeed pressure at the flue outlet, such as con-

densing appliances. The flue duct of such

appliances can now be directly routed in the

installation room , independent of its m aterial

and w ithout additional protective tubes or

jackets, provided that there is at least one

ventilation opening of 150 cm 2. In the case of

increased tightness of the duct system , as

expressed for type C appliances by the addi-

tional m arking x, no ventilation opening is

now necessary and appliances w ith 50 kW

m axim um output can be installed in room s for

hum an occupation. Although the increased

tightnessrequirem ent has been left open in-


4/22

,

2 C ER T - IN FO N o. 3 01/99

tentionally in the TR G I in order to arrive at a

harm onised European definition, this require-m ent is likely to be guided today by the cur-

rent tightness definition in D VG W VP 113

System certification of appliances and flue

system s, i.e. to result in 0.05 m 3/h m 2 inter-

nal surface at1000 Pa test pressure.

Table 1 show s the various installation

room requirem ents for type B and C gas ap-

pliances w ith respect to the ventilation situ-

ation. It can be seen that a com bustion air

com pound system is still possible w ith type B

appliances up to 35 kW as an alternative to

the ventilation opening m entioned above, and

that opening sections > 150 cm 2 are only re-

quired for ap pliance output greater than

50 kW , i.e. another 2 cm 2/kW for outputs

> 50 kW . If flue gases are discharged under

pressure the version w ith increased tightness

(as w ith type Cxappliances) is also possible

w ith outputs < 35 kW as an alternative to a

ventilation opening, irrespective of the room

dim ensions and ventilation m easures. Ade-

quate ventilation (or a com bustion air com -

pound system for < 35 kW ) is only required

w ith respect to com bustion air supply. Appli-

ances > 50 kW m ust be installed in separate

room s w hich do not serve any other pur-

poses, i.e. they m ust not be room s for hum an

occupation. H ow ever, a boiler room is gen-

erally no longer required.

There is also far-reaching sim plification for

installation of type C appliances. In accord-

ance w ith the state of appliance developm ent

in Europe, the sim plified installation condi-

tions w ithout special ventilation m easures are

now perm itted even for versions w ithout air

circulation in addition to the concentric de-

sign w ith com bustion air circulation of all

com ponents carrying flue gas under pres-

sure, provided that the above-m entioned in-

creased tightness requirem ents of the flue

gas carrying parts are m et. In both cases

(concentric com bustion air circulated or in-

creased tightness): this is expressed by the

xin the appliance type m arking schem e.

Another extension of current sim plified re-

quirem ents m akes possible type C3gas appli-

ances w ith integral air/flue ducts term inating

above roof. In addition to the fan-assisted ver-

sions C32

and C33

(previously C3.2), w hich m ay

only be installed in the attic or in room s directlybeneath the attic, joint testing and approval of

air/flue ducts and appliance is now possible

even for duct lengths greater than 4 m ac-

cording to the EC G as A ppliances D irective.

This also applies to type C5appliances w ith

appliance type pressure of fluegas installation room requirements section

and size carrying compo- (ventilation) TRGInents relative to

installation room

type B < 35 kW negative pressure combustion air compound system or opening to 5.5.2

atmosphere (1 x 150 cm or 2 x 75 cm )2

type B > 35 kW negative pressure opening to atmosphere (1 x 150 cm or2 5.5.3

< 50 kW positive pressure 2 x 75 cm2 )

type B > 50 kW negative pressure separate room, opening to atmosphere 5.5.4

positive pressure (150 cm2 + 2 cm2 / kW above 50 kW)

type B < 35 kW positive pressure opening to atmosphere (1 x 150 cm or2 5.5.2.8

2 x 75 cm2 ) or special tightness

type C < 50 kW negative pressure independent of room volume and 5.6.1

ventilation

type C < 50 kW positive pressure opening to atmosphere (1 x 150 cm or 2 5.6.1

2 x 75 cm2 )

type Cx< 50 kW positive pressure independent of room volume and 5.6.1ventilation

type C/Cx > 50 kW negative pressure separate room, with ventilation facility 5.6.8

positive pressure

2

Table 1: installation room requirements (ventilation) for type B and C gas appliances

Cert i f ica t ion Body


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C ER T - IN FO N o. 3 01/99 3

air/flue ducts term inating in areas of different

pressures. W hile installation in the attic re-quires a protective tube m ade of non-inflam -

m able m aterials (w hich only has to prevent

m echanical dam age), and installation beneath

the attic requires a protective tube w ith the

sam e fire-resistance rating as that of the ceil-

ing being penetrated, a ventilation shaft w ith a

fire-resistance rating of F 90 (F 30 for low er

buildings such as one or tw o-fam ily houses) is

required w here several floors are passed. For

type C3and C

5appliances and the associated

com bustion air and flue ducts this results not

only in a significantly sim plified approval proce-

dure and increased reliability of operation but

also in installation and fitting requirem ents that

can be m ore easily m et. The fact that gas ap-

pliances and their connecting com po-

nents/com bustion air and flue ducts belong

together and should be certified together is ex-

plicitly noted for type C1, C

3, C

4, C

5and C

8ap-

pliances. For type C6appliances, involving the

connection of air/flue ducts approved by the

building inspectorate, reference is m ade to the

m anufacturers installation instructions or thebuilding inspectorates approval of the air/flue

system s to be connected.

Another m ajor sim plification is for flue sys-

tem outlet levels above roof. The m inim um dis-

tance of 40 cm betw een flue outlet and roof

surface perm itted in the past only for type C32

and C33appliances up to 30 kW output is now

explicitly extended to cover all room air inde-

pendent type C appliances w ith fan up to

50 kW output. It therefore applies to types C32,

C 33, C 52, C 53, C 62 and C 63. This m eans a signi-ficant sim plification and cost reduction for the

installation and flue gas discharge of room air

independent appliance types, w hich are in-

creasingly becom ing the standard appliance.

As an alternative to the previously prescribed

40 cm exit level above ridge, a distance of 1 m

betw een exit and roof surface is also required

for all room air independent and room air de-

pendent appliance types connected to chim -

neys or air/flue ducts (a practice already found

in som e Federal Laender).

There are also im portant sim plifications in

specifications for appliance type C11(balanced

flue appliances w ithout fan). A lateral and ver-

tical distance of 2.5 m from one flue gas ter-m inal to another and a lateral one to ventilation

openings as w ell as a vertical distance of 5 m

to ventilation openings is applicable to this

appliance type, w hich is im portant for existing

installations and m odernisation of old build-

ings. The sam e applies to the distances to

w indow s and opening facade doors. A special

regulation expiring on 31 D ecem ber2004 w as

adopted specifically for balanced flue room

heaters w ithout fan. N o lateral clearance is

specified and a vertical distance of 0.3 m to

opening w indow s is held sufficient if the N Ox

concentration in the flue gas does not exceed

50 m g/kW h and the C O concentration does

not exceed 100 m g/kW h. R eference is m ade

to D IN 3364, Part1 A 2, D raft June 1994 (gas

appliances, room heaters; term s, require-

m ents, m arking, testing; am endm ent 2) for fur-

ther details. To prevent a concentration of flue

gas term inals on one facade, the m ean facade

area per term inal m ust not be sm aller than

16 m 2 and a m axim um of four is specified for

flue gas term inals arranged vertically.

Flue gas dischargerequirements

In addition to the above-m entioned speci-

fic provisions for room air independent appli-

ances of type C , the general requirem ents for

the flue gas discharge of gas appliances have

also been substantially revised.

This includes the follow ing item s:

G eneral dem and for a flue system instead

of a chim ney as a standard approach.

U se of an L 90 installation duct for flue sys-

tem s, or L 30 in the case of low er buildings

(one/tw o-fam ily houses) for fire protection

reasons.

O ption of com bining m ultiple flue tubes in

one duct if flue tubes m ade of non-in-

flam m able building m aterials are used and

if appliances are installed in the sam e sto-

rey or otherw ise perm itted by the building

inspectorate.



6/22


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C ER T - IN FO N o. 3 01/99 5

or a non-inflam m able 5 cm thick jacket

w hen passing ceilings or other com po-nents m ade of inflam m able m aterials.

These distances also apply to com po-

nents m ade of or containing inflam m able

m aterials.

Flue ducts, m atching pieces or duct pas-

sages w ith surface tem peratures show n tobe < 85C at nom inal conditions are not

subject to any special distance require-

m ents.

type of flue system distance requirement section TRGI

matching piece for flue systems 40 cm 6.5 para 2

shared by solid fuel burning

furnaces, without jacket

matching piece for flue systems 10 cm 6.5 para 2

shared by solid fuel burning

furnaces, with non-inflammable

2 cm thick jacket

matching piece or flue 20 cm 6.5 para 1

duct with T > 160C without

jacket

matching piece or flue duct 5 cm 6.5 para 1

with T > 160C, with non-in-

flammable 2 cm thick jacket or

with T < 160C

duct passage for appliance 20 cm in non-inflammable 6.5 para 3

without downdraught diverter protective tube orwith non-in-

and T < 160C flammable 20 cm thick jacket

duct passage for appliance with 5 cm in non-inflammable 6.5 para 3

downdraught diverter (B1) or protective tube orwith non-in-

with T < 160C flammable 5 cm thick jacket

flue duct on buildings, distance 20 cm 6.5 para 4

to windows

flue duct distance or passage, 5 cm in non-inflammable 5.6.3

circulated by combustion air protective tube orwith non-in-

with T > 85C flammable 5 cm thick jacket

flue duct, matching piece or no distances required 5.6.3 and 6.5passage with T shown to be para 5

< 85C

Table 2: requirements o f distance to inflammable building materials



8/22

6 C ER T - IN FO N o. 3 01/99

Flue ducts on buildings m ust be at least

20 cm from w indow s.

C learance requirem ents significantly low er

than those usually applicable in the past now

exist for m ost m odern gas appliances w ith

flue gas tem peratures < 160 C or < 85 C .

This enables flue ducts to be installed in attics

or on facades under sim plified conditions.

Since m ost of the condensing appliances do

not exceed flue gas tem peratures of 80 C ,

the fact that any distance requirem ents have

been om itted for this tem perature range is

particularly helpful in practice.

European gasappliance typeclassification scheme

Abbreviations used to designate appli-

ances w hich have already appeared in the pre-

ceding text and have not been usual for us in

the past, such as designs designated C 5 or C 8.These abbreviations represent a new denom i-

nation system based on a European harm o-

nisation docum ent. W ithin the European

standardisation organisation C EN a classifica-

tion schem e has been developed for gas ap-

pliance types w ith respect to their air/flue duc-

ting w hich serves as a basis for the individual

standardisation com m ittees that are required

to use these designations in draw ing up the

various appliance-specific standards. This

schem e continues to follow the coarse

classification usual in our country in the past intype A appliances (appliances w ithout flue gas

discharge), type B (room air dependent appli-

ances w ith flue gas discharge) and type C

(room air independent appliances w ith flue gas

discharge). A suffixed tw o-digit code indicates

how the flue gas is discharged and the com -bustion air is supplied or how specific air/flue

system s are connected. The first digit stands

for the design of the air/flue system w hile the

second digit indicates the existence and the

location of a fan. N um ber 1 m eans an ap-

pliance design w ithout fan, num ber 2 the loca-

tion of a fan in the flue, and num ber 3 the lo-

cation of a fan on the com bustion air side.

W ithin type B1appliances there is a special

variant, i.e. type B14, w here a fan is located

dow nstream of the dow ndraught diverter. In

G erm any a special feature w ith type C appli-

ances is to suffix the low er case xto the ap-

pliance code if the com ponents of the applian-

ce and the flue system under pressure are

com pletely circulated by com bustion air or in-

creased tightness of the flue system is en-

sured. This results in a logically designed

structured denom ination schem e w hich classi-

fies the various types of appliance w ith respect

to com bustion air supply and flue gas dis-

charge and thus serves as a reference to the

various nationally different installation require-m ents. The m ost im portant basic types of ap-

pliance are explained in the follow ing by

m eans of typical applications w hich reflect the

optional variants perm itted in G erm any. It

should be noted that the schem atic diagram s

show n do not alw ays reproduce all optional

and perm issible features. They should be un-

derstood as exam ples reflecting the flexibility

and versatility of the E uropean classification

schem e. A synoptic table (3) classifies and ex-

plains the various types of appliance according

to their im portance. The form er nationalnam es and the G erm an installation require-

m ents of the individual types have also been

included w here possible.



9/22

C ER T - IN FO N o. 3 01/99 7

gas app- flue combustion down- type of air supply and fan combustion CO2- former national

liance system air supply draught flue gas discharge location air circulation stop = national installation requirements

type diverter or increased AS designation according to DVGW Codes

tightness1) FGS2) of Practice

yes = x = BS

1

2

3

1

2

3

4

1

2

3

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

2

A1

A2

A3

B11

B12

B13

B14

B21

B22

B23

B32

B33

C11

C12

C13

C21

C22

C23

C31

C32

C33

C41

C42

C43

C51

C52

C53

C61

C62

C63

C71

C72

C73

C82

no

flue gas discharge and

combustion air supply via

installation room

without

downstream

of burn./h.e.

upstream

of burner

without

downstream

of h.e.

upstreamof burner

downstream

of ddr. div.

without

downstream

of h.e.

upstream

of burner

downstream

of h.e.

upstream

of burner

without

downstream

of h.e.

upstream

of burner

without

downstream

of h.e.

upstream

of burner

without

downstream

of h.e.

upstream

of burner

without

downstream

of h.e.

upstream

of burner

without

downstream

of h.e.

upstream

of burner

without

downstream

of h.e.

upstream

of burner

without

downstream

of h.e.

upstream

of burner

downstream

of h.e.

upstream

of burner

AS

AS

BS

BS

BS

B with burnerwithout fan

cf. TRGI '86/96, para 5.4:gas appliances with "AS"

additional marking(CO2stop device) do not meetthe installation requirements

for Germany

A

A

B

room air

dependent

1 yes

connection to flue system,

shared flue system (negative

pressure), combustion air supply

via installation room

connection to flue system, shared

flue system (negative / positive

pressure), combustion air supply

via installation room

cf. TRGI '86 / 96

at present not covered by Germaninstallation rules

possible with "fan-assistedburner" like B11

not specifically covered by Germaninstallation rules (ggf. G 626, G 660)


B

B with burnerwith fan

cf. TRGI '86 / 96,

special ventilation conditions with

flue outlet under pressure

3

1

2

3

4

5

6

7

connection to flue system, shared

flue system (negative pressure),

combustion air supply in external

tube via installation room

air supply and flue gas

discharge through external

wall in an area of equal

pressure

circulated

circulated

D3.1

D3.1

cf. G 637 / I and

TRGI '86 / 96

x

x

C1

C3.3

C3.3

cf. TRGI '86 / 96

cf. TRGI '86 / 96

yes

room air

independent

no

no

yes

(in the

attic)

connection to AFS3),

(single flue),shared flue system

connection to AFS,

(twin flue),

shared flue system


discharge above roof in an

area of equal pressure


discharge from / to

atmosphere in areas of

different pressure

air/ flue connection to

separately tested and supp-

lied air/ flue tubes

flue gas discharge above

roof, combustion air

supply via attic

connection to flue system,

shared flue system,

combustion air supply through

separate air duct

x

x

x

x

x

x

x

x

x

x

x

x

x

x

C2only existing appliances

according to G 627

not permitted under building

regulations


C3.2

C3.2cf. TRGI '86 / 96


C3.1

C3.1cf. TRGI '86 / 96


only in combination with a

jointly approved flue system

at present not covered by German

installation rulesonly possible with clearly defined

interface and e.g. flue system

approved by the building

inspectorate

at present not covered byGerman installation rules

D3.2

D3.2

cf. G 637 / I and

TRGI '86 / 96

1) appliances without "x" require special installation room ventilation2) FGS = flue gas sensor3) AFS = combined air flue system

C

a1 a2 b c d e f g h i j

Table 3: European gas app liance type classification sc heme including air supp ly and flue gas discharge

according to CEN CR-17.4.9



10/22

8 C ER T - IN FO N o. 3 01/99

Type A appliances are only classified into the

three fan-specific variants A1, A

2and A

3(Fig-

ure 1). These gas appliances have no flue gas

discharge and include gas cookers, stool

cookers, laboratory burners, baking ovens

etc.

,,,,,

,

,

,

,

,,,,,

,,,,,

,

,

,

,

,,,,,,

,

,

,

,

,,,,,,,,,

,,,,,,,,,

,,,,,,,,,

,,,,,,,,,

,,,,,,

A1without fan

A2with fan downstream of the

burner / heat exchanger

A3with fan upstream of the

burner

The installation of this appliance type is sub-

ject to very different regulations in the indi-

vidual European countries and requires that

m ainly the various ventilation conditions w ith

respect to flue gas dilution and com bustion

air supply are observed.

Figure 1: Type A: gas app liance w ithout flue system. The comb ustion air is withdraw n from the installation room

(e.g. gas coo ker, stoo l cooker, laboratory burner, built-in baking oven)



11/22

C ER T - IN FO N o. 3 01/99 9

,,,,,

,

,

,

,

,,,,,,

,

,

,

,

,,,,,,,,,

flue duct suitable for

negative pressure(at least F90)

B11without fan

B12withfan downstreamof the heat exchanger

B13with

fan upstream

of the

burner

B14with

fan down-

stream of

the down-

draught

diverter

flue gas

40 cm min.

types B12and B14are only

permitted if the type of

construction ensures that

the residual feed pressure

is reduced right to the down-

draught diverter or flue en-

trance and if it is also en-

sured that flue gas cannotenter the installation room

Figure 2: Type B: gas appliance with flue system withdraw ing the combustion air from the installation room

(room air dependent gas app liance)Type B

1: Gas app liance with d owndraught diverter

Add itional marking BS for flue gas sensor

The type B1is defined as an open appliance

w ith a draft diverter to be connected to a m ul-

ti connection natural draft chim ney (Figure 2).

In addition to appliances B11, B

12and B

13there

is the special variant B14

w ith fan dow nstream

of the dow ndraught diverter. For installation in

G erm any it m ust be observed that B 12 and B 14

designs on a shared chim ney are only perm it-

ted if the type of construction ensures that the

residual feed pressure is reduced right to the

dow ndraught diverter (B12) or flue entrance

and if it is also ensured that flue gas cannot

enter the installation room .



12/22

10 C ER T - IN FO N o. 3 01/99

Type B2gas appliances w ill be a very im por-

tant group in the future since they represent a

m ajor part of the condensing appliances (Fig-

ure 3). This type com prises room air de-

pendent gas appliances w ithout dow ndraught

diverter designed for connection to chim ney,

but m ainly for operation w ith their ow n flue

ducts. Type B21

appliances are ruled out for

practical considerations since operation w ith-out fan and w ithout dow ndraught diverter on

a flue system w ould result in problem s of

com bustion stability. This approach is also in-

,,,,,

,

,

,

,

,,,,,,,

,

,

,,,,,,,,,,

,,,,,,,,,

,,,,,,,,,

,,

,,,

,

,,

flue duct fornegative pressure (F90 min.)

B22with fandownstream of the

heat exchanger

B23 with fan

upstream ofthe burner

B21 without fan

at present not covered

by German installation

rules

fire-resistant

Jacket

where T>85C

flue

1m

min

.

flueflue

40 cm min.

ventilation

opening

1 x 150 cm2

or

2 x 75 cm2

20 cm min.

shaftF90/F30

flueduct



2: gas app liance without downdraught d iverter

teresting as the flue gas can be discharged

both at negative and positive pressure (see left

and right parts of figure). This is not, how ever,

reflected by the designation key. In this exam -

ple, the above-m entioned distance require-

m ents of 40 cm above ridge or 1 m from the

roof area apply for ducts ending above roof.

The relevant provisions for com bustion air

supply or installation room ventilation m ustalso be observed (also applicable to type B

1

appliances).



13/22

C ER T - IN FO N o. 3 01/99 11

, ,,, ,,, ,

, ,

,

,

, ,

, ,,, ,, ,,, ,

, ,

,

,

, ,

, ,,, ,, ,,, ,, ,,, ,

, ,,, ,, ,,, ,, ,,, ,

, ,,, ,, ,,, ,, ,,, ,

, ,,, ,, ,,, ,, ,,, ,

, ,,, ,, ,,, ,

flue duct for negative

pressure (F90 min.)

B33 with

fan upstreamof the burner

B32 with

fan down-stream ofthe heat

exchanger

B31without fan

this appliance type is not in use

flue

40 cm min.



3: gas appliance without downd raught diverter, where all component s of the flue system under pres-

sure are circulated by com bustion air

Appliance type B3, form aly called D

3.1so far,

is a design brought into the European classi-

fication schem e by G erm any alone (Figure 4).

There are only the tw o fan-assisted types B32

and B33

(type B31

w ithout fan is not in use).

W ith this type of appliance the flue gas is

discharged m echanically before entering a

shared chim ney, all com ponents of the appli-

ance and its m atching piece carrying fluegas under pressure being circulated by com -

bustion air (analogously to version xof type

C appliances). This allow s installation of the

appliance in room s for hum an occupation

w ithout ventilation. C om bustion air supply

using a com pound system is possible even

under difficult conditions thanks to fan as-

sistance. The installation requirem ents for

com bustion air supply are specified in TR G I

Section 5.5 and for chim ney sharing and de-sign in D VG W W ork Sheet G 637/I.



14/22

12 C ER T - IN FO N o. 3 01/99

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,

,

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,

,

,

,

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,

,

,

,

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,

,

,

,

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,,,,,,,,,

,,,,,,,,,,

C11without fan

C12 with fan

downstream

of the heat

exchanger

C12

C13x

C13 withfan upstream

of the burner

C12x

C13

ventilation

opening

1 x 150 cm2

or

2 x 75 cm2

Figure 5: Type C: gas appliance with flue system withdrawing the combustion air from the atmosphere through a closed

system (room sealed gas appliance)Type C

1: gas app liance w ith horizontal combustion air supp ly and flue gas discharge through the exterior wall.

They terminate close to each other in an area of equal pressure.

Type C appliances show the greatest variety

w ithin the individual types of appliance and also

the m ost flexible installation and configuration

options. The so-called exterior w all approach

(Figure 5 )is the first and oldest variant of this

type, w hich is still w idespread throughout the

other European countries. C om bustion air and

flue connections are fitted w ith short tube

lengths running either in parallel or concentri-cally through the exterior w all to the atm os-

phere. Appropriate ventilation (150 cm 2 open-

ing) m ust be provided unless the com ponents

of the flue system under pressure are circulated

by com bustion air or m eet higher tightness re-

quirem ents (xdesign). Appliance type C11

now is only of practical im portance for gas-fired

room heaters in G erm any. In our country, the

exterior w all approach is subject to strong re-

strictions by the building inspectorate for envi-

ronm ental protection reasons. N evertheless, in

exceptional cases this type of appliance is per-m issible under the m arginal provisions of TR G I

Section 5.6.4.



15/22

C ER T - IN FO N o. 3 01/99 13

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,,,

C22

C21

C23

,

cleaning door

air/flue duct

according to

DVGW G 627

flue combustion air

40 cm min.

ventilation

opening

1 x 150 cm2

or

2 x 75 cm2

Figure 6: Type C: gas appliance with flue system w ithdrawing the com bustion air from the atmosphere through a closed


2: gas appliance with combustion air supp ly and flue gas discharge for connect ion to a common air and

flue duct; this gas appliance is not perm issible under building regulations in Germany.

Only type C21gas app liances already installed are perm issible in Germany under DVGW Work Sheet G 627 (pro-

tection of existing installations).

Type C2gas appliances, w hich can still be found

in other countries and in the new Federal

Laender, represent an installation approach

(Figure 6)w here the appliances are connected

to a so-called tw o-legged air/flue ductor

U -duct. Fresh com bustion air is led via the

first duct to the base of the second duct from

w hich the appliance both w ithdraw s its com -

bustion air and discharges its flue gas. The

com bustion air available to the appliances at

higher levels is in this w ay enriched w ith flue

gas. H ow ever, m odern gas burners fail to

operate stably w hen the C O2content in the

com bustion air varies w idely, so that this ap-

proach has long since lost its im portance. It

is only perm issible in G erm any to protect

existing installations under DVG W W ork

Sheet G 627.



16/22

14 C ER T - IN FO N o. 3 01/99

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C32x

C33

C33x C32

,

C32 with fan

downstream ofthe heat exchanger

40cm

min

.combustion air

C33 with fan up-stream of the burner

flue40cm m

in.

flue

combustion air

flue combustion air

fire-resistant

jacket

where T>85C

C33 with fan

upstream of

the burner

protective

tube or

shaft

F90/F30

C32 with fandownstream of

the heat exchangerat present not covered by

German installation rules

C31 without fan

ventilations-

opening

1 x 150 cm2

oder

2 x 75 cm2

Figure 7: Type C: gas appliance with flue system withd rawing the combustion air from the atmosp here through a closed

system (room sealed gas appliance)

Type C3: gas app liance with combustion air supply and flue gas d ischarge system extending vertically above

roof. They terminate close to each other in an area of equal pressure.

Type C3appliances (Figure 7 )represent an in-

stallation variant w hich is now becom ing alm ost

a standard solution, m ainly in low -cost new one

or tw o-fam ily houses and in m any m oderniza-

tion projects. The special feature of this type is

that com bustion air supply and flue gas dis-

charge are above roof by m eans of air/flue tubes

w hich are tested and approved together w ith

the appliance. In contrast to the previous C3ap-

proach w hich also involved flue gas discharge

above roof, duct lengths of m ore than 4 m are

also perm itted. This how ever requires the use of

a duct or protective tube depending on the type

of floor passed. The above details on the venti-

lation of room s w here appliances w ithout an ad-

ditional xm ark are installed and the m inim um

distance of 40 cm betw een duct end and roof

surface or ridge apply accordingly.



17/22

C ER T - IN FO N o. 3 01/99 15

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C42x C42

C43x

C43

cleaning door

fluecombustion air

C41 without fan

at present not covered by


C42 with fan


AFS according

approval of the building

inspectorate

40 cm min.

ventilations-

opening

1 x 150 cm2

or

2 x 75 cm2

ventilation

opening

1 x 150 cm2

or

2 x 75 cm2

Figure 8: Type C: gas appliance with flue system w ithdrawing the com bustion air from the atmosphere through a closed


Type C4: gas appliance with combustion air supply and flue gas discharge designed for connec tion to an air/fluesystem (AFS)

Another installation configuration increasingly

found in our country uses type C4appliances

for connection to air/flue ducts (Figure 8). Spe-

cial air/flue tubes for connection to air/flue sys-

tem s (AFS) are supplied w ith the appliance. In

contrast to the tw o-legged air/flue duct in the

case of type C2appliances, separate ducts are

used here for com bustion air supply and flue

gas discharge, ensuring that every appliance issupplied w ith fresh com bustion air. Air/flue

system s of this type are on the m arket w ith

both parallel and concentric duct configura-

tions. Appliances w ith either concentric or par-

allel air/flue system can be connected to both

configurations. Som e of the air/flue system s

perm it connection of m ore than 10 appliances

over several floors, thus offering an outstand-

ing option of installing room sealed appliances

in m ultiple dw elling units. Appliances w ith the

suffix xare used for preference in our coun-

try because of the less severe installation re-quirem ents in room s for hum an occupation.

D etails on installation requirem ents are given in

TR G I Sections 5.6 and 6.



18/22

16 C ER T - IN FO N o. 3 01/99

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,,,

C53

C52,

C53x

C51 without fan



flue40cm

min.

C52 with fandownstream

of the heat

exchanger

combustion air

protective tube

C53 with fan

upstream of the

burner

40cm

min

.

flue

ventilation

opening

1 x 150 cm2

or

2 x 75 cm2

ventilationopening

1 x 150 cm2

or

2 x 75 cm2

constructive

isolation40cm

min.

flue

Figure 9: Type C: gas appliance with flue system withdrawing the combustion air from the atmosphere through a closed


Type C5: gas appliance with separate combustion air supply and flue gas discharge systems; these term inate

in areas of different pressure.

In contrast to type C3

appliances, the

com bustion air of C5, w hich also features a

flue duct term inating above roof as an integral

part of the appliance, is supplied from an area

of different pressure, e.g. through a com -

bustion air duct term inating at the exteriorw all(Figure 9 ). B ecause of the greater effect

of pressure differences due to w ind betw een

airduct and flue ends, such appliances m ust

have high com bustion system stability

against external pressure effects on the com -

bustion air or flue gas side. This can be

achieved for instance by a fan w ith steep

characteristic or pneum atic gas/air com -

pound control. O f the type C 5 appliances theC51

design w ithout fan is not practicable and

is therefore not covered by G erm an installa-

tion rules.



19/22

C ER T - IN FO N o. 3 01/99 17

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C62

C63x

C62x

C63

,

,

C62 with fan downstreamof the heat exchanger

C63 with fan upstream

of the burner

C61 without fan


German installation rulesC62 with fan


flue

flue

combustion

air

40cm

min

.

40 cm min.

flue ducts approved

by building

inspectorate

shaft

F90/F30

ventilation

opening

1 x 150 cm2

or

2 x 75 cm2

20 cm min.

combustion air

Figure 10: Type C: gas appliance with flue system w ithdrawing the combustion air from the atmosphere through a closed

system (room sealed gas app liance).Type C

6: gas appliance designed for connec tion to a combustion air supply and flue gas discharge not tested

together with the appliance

In contrast to all other variants of type C appli-

ances, type C6appliances are tested, ap-

proved and delivered w ithout com bustion air

and flue ducts (Figure 10). H ow ever, the

installation options for separately approved

flue system s are virtually unlim ited. Virtually allcondensing appliances fall in this category

w hich have not been approved w ith their ow n

air/flue ducts and are operated w ith separate

flue system s (usually approved by the germ an

building inspectorate). Such flue system s can

be installed both along exterior w alls and in-

side ducts. Versions w ith air-cooled flue duct

or higher tightness as w ell as w ith separate air

and flue ducts also exist w ithin this appliancetype. A design w ithout fan (C61) is not practi-

cable and is therefore not covered by G erm an

installation rules.



20/22

18 C ER T - IN FO N o. 3 01/99

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C71

C72

C72 with fan


combustion air

protective tube or

fire-resistant

jacketwhere T>85C

flue flue

combustion air

C71without fan

C71/72/73 : at present not covered by


Figure 11: Type C: gas appliance with flue system withd rawing the combustion air from the atmosphere through a closed


7: gas appliance with vertical combust ion air supply and flue gas discharge system; the combustion

air is drawn from the loft and the flue gases discharged ab ove the roof; a downdraught d iverter is located in

the loft.

Type C7appliances are a special solution only

com m on in England, w here the flue gases are

discharged above the roof and the com -

bustion air is supplied through a special dow n-

draught diverter located in the loft (Figure 11).

Although operation of the appliance in the in-

stallation room is independent of the room air,the com bustion air is not directly supplied from

the atm osphere but through ventilation of the

loft. Such appliances are at present not covered

by G erm an installation rules since they are not

yet on the G erm an m arket. Installation of such

appliances in our country w ould currently re-

quire special approval by the building inspec-

torate.



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C ER T - IN FO N o. 3 01/99 19

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C82x

C83x C83

C82

flue duct suitable fornegative pressure

(min. F90)

C82 with fan downstream

of the heat exchanger

C83 with fanupstream of

the burner

C82 with fan downstreamof the heat exchanger

flue

C81 without fan

this type of applianceis not in use

40 cm min.

ventilation

opening

1 x 150 cm2

or2 x 75 cm2

Figure 12: Type C: gas appliance with flue system w ithdrawing the combustion air from the atmosphere through a closed


8: gas appliance with connect ion to a shared flue system (negative pressure operation) and separate

comb ustion air supply from the atmosphere

Another G erm an speciality is appliance type

C8w hich is identical w ith the form er D

3.2de-

sign (Figure 12). Like w ith type B3appliances,

its special feature is the m echanical com -

bustion air supply and flue gas discharge using

a fan and the flue gas discharge through a

shared chim ney. The m echanical dischargepressure is com pletely released before en-

tering the flue so that the flue gas is exclusive-

ly discharged using negative pressure. In con-

trast to type B3appliances, the com bustion air

is supplied from the atm osphere (independent

of room air), usually through a com bustion air

duct from the exterior w all. This solution also

represents an interesting approach in the

m odernization of old buildings since appliance

design xallow s installation in dw ellings. Adesign w ithout fan is im practicable w ith this

type of appliance and has therefore been

om itted from the classification schem e.



22/22

This com pletes the description of the m ost

im portant installation variants of the individualtypes of appliance. A m ultitude of different so-

lutions m eeting virtually all conceivable installa-

tion requirem ents are possible by com bining

the various types of appliance, installation op-

tions and com bustion air and flue duct con-

figurations. Thanks to the great variety of ap-

pliances offered on an European level and to

the ever grow ing practice of system certificati-

on com prising appliances and their air/flue

com ponents supplied by the sam e m anufac-turer, new appliance solutions are now availa-

ble to designers and tradesm en, m any of

w hich w ere not previously possible. The ever

increasing range of appliances on sale in the

European Single M arket w ill also result in price

reductions m aking such solutions increasingly

attractive.


dwgv boiler clasifications

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