Draft failure of domestic chimneys at Amherstburg, Ontario

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Draft failure of domestic chimneys at Amherstburg, Ontario

NATIONAL RESEARCH COUNCIL CANADA

DIVISION OF BUILDING RESEARCH

DRAFT FAILURE OF DOMESTIC CHIMNEYS AT AMHERSTBURG, ONTARIO

by

C . Wachmann and A . Grant Wilson

ANALYZED

( p r e p a r e d f a r t h e C e n t r a l Mortgage and Housing C o r p o r a t i o n )

Report No. 92 of t h e

D i v i s i o n of E u i l d i ng Research

Ottawa

PREFACE

This r e p o r t was prepared i n t h e f i r s t i n s t a n c e f o r C e n t r a l Mortgage and Housing Corporation following a r e q u e s t f o r a s s i s t a n c e w i t h t h e problem of chimney d r a f t f a i l u r e s i n a group of houses a t Amherstburg, Ontario. Study of t h i s problem has shown t h a t t h e d i f f i c u l t i e s were n o t due t o any s p e c i a l c o n d i t i o n s but t o t h e use of o u t -

s i d e chimneys i n combination w i t h o t h e r f a c t o r s . The

a n a l y s i s of t h e f a c t o r s a f f e c t i n g chimney d r a f t i n houses, which was made i n t h i s c a s e , i s a p p l i c a b l e t h e r e f o r e , t o

o t h e r a r e a s and may be found u s e f u l i n o t h e r s i t u a t i o n s I n which chimney d r a f t i s involved.

Ottawa

A U ~ U S ~

1956

N.B.

Hutcheon, A s s i s t a n t D i r e c t o r .

TABLE OF CONTENTS

Page

...

Description of Houses and Heating Systems 1

...

Field Observations 2

...

Suggested Mechanism of Draft Failure

3

...

Discussion of Factors Influencing Draft Failure

8

1

.

Flue Dimensions

...

8

2

.

Furnace Operation

...

9

3

.

Climate

...

11

...

DRAFT FAILURE OF DOMESTIC CHIMNEYS AT AMHERSTBURG, O N T A R I O ... by C . Waehrnann and A . Grant Wilson

S i n c e t h e b e g i n n i n g of t h e 1954 h e a t i n g s e a s o n , d r a f t f'ail- u r e had been e x p e r i e n c e d i n s e v e r a l 1 3 - s t o r e y houses w i t h basements and o u t s i d e chimneys ( i . e . chimneys on t h e o u t s i d e walls of h o u s e s and exposed t o w e a t h e r on t h r e e s i d e s ) s i t e d on t h e C e n t r a l Mortgage and Housing C o r p o r a t i o n housing p r o j e c t a t Amherstburg, O n t a r i o . Fumes escaped from t h e s o l i d - f u e l h a n d - f i r e d f u r n a c e s i n t o t h e

h o u s e s d u r i n g s p e l l s of r e l a t i v e l y m i l d w e a t h e r , ( a s o c c u r s o f t e n a t t h e b e g i n n i n g and end of t h e h e a t i n g s e a s o n ) , and t e n a n t s complained a t t h e

C.M.H.C.

o f f i c e i n Windsor. Some r e p o r t e d t h a t t h e y had

s u f f e r e d fume p o i s o n i n g .

The D i v i s i o n of B u i l d i n g R e s e a r c h w a s n o t i f i e d and, i n co- o p e r a t i o n w i t h C.M.H.C. e n g i n e e r s , a f i e l d t r i p was made t o Arnherst- b u r g on t h e 1 s t and 2nd December, 1954 t o s t u d y t h e problem a n d , i f p o s s i b l e , recommend a remedy. Measurements of chimney d r a f t , f l u e g a s t e m p e r a t u r e , and f l u e g a s c o m p o s i t i o n were t a k e n . The h e a t i n g u n i t s and chimneys were examined and t e n a n t s were q u e s t i o n e d . Draft f a i l u r e was observed i n one house w h i l e measurements were b e i n g t a k e n .

T h i s r e p o r t s u g g e s t s a mechanism of d r a f t f a i l u r e and g i v e s g e n e r a l recommendations t o a l l e v i a t e t h e f a u l t . Only f u r n a c e and chimney thermodynamics a r e d e a l t w i t h and h e a l t h o r o t h e r haz- a r d s a r i s i n g from d r a f t f a i l u r e a r e n o t c o n s i d e r e d .

D e s c r i p t i o n of Houses and H e a t i n g Systems

The h o u s i n g p r o j e c t c o n s i s t e d of 25 houses b u i l t t o C.M.H.C. d e s i g n : twenty l $ - s t o r e y one-family d w e l l i n g s w i t h basements and o u t - a i d e chimneys; and f i v e one-family bungalows w i t h basements and i n s i d e chimneys.

A i l houses were h e a t e d by g r a v i t y warm a i r systems w i t h s e l i d - f u e l h a n d - f i r e d f u r n a c e s l o c a t e d c e n t r a l l y i n t h e basements. I n one house t h e f u r n a c e had been moved c l o s e r t o t h e chimney a f t e r i n s t a l l a t i o n . Combustion was c o n t r o l l e d by v a r y i n g t h e a i r s u p p l y t o t h e f u e l bed t h r o u g h openfng and c l o s i n g p l a t e dampers i n t h e a s k p i t d o o r and smokepipe. The damper s e t t i n g was ~ e g u l a t e d by means of c h a i n s from t h e l i v i n g s p a c e above. I n a d d i t i o n , a i r c o u l d be admitted i n t o t h e combustion chamber above t h e g r a t e t h r o u g h a manual s l i d e i n t h e f i r i n g d o o r .

The chimneys, b u i l t of a s i n g l e t h i c k n e s s of s o l i d b r i c k g e n e r a l l y t o C.M.H.C. s t a n d a r d s , were f i t t e d w i t h s t a n d a r d v i t r i f i e d c l a y l i n e r s 7-1/8 by 7-1/8 i n c h e s , ( a c t u a l i n t e r n a l d i m e n s i o n s ) , extendl-ng from c i e a n o u t t o chimney

6 0 ~ .

No o t h e r h e a t i n g d e v i c e s v e n t e d i n t o t h e s i n g l e f l u e s . The chimney h e i g h t was a p p r o x i m a t e l y 2 5 f e e t above smokepipe t h l m b l e s .

The u n i n s u l a t e d smokepipes were of s t a n d a r d s h e e t metal c o n s t r u c t i o n ,

8

inches i n diameter and 12 t o

13

f e e t long,

(73

f e e t lorLg w i t h t h e y e l o c a t e d f u r n a c e ) , When i n s t a l l e d t h e chimney thimbles bad a diameter of

6+

i n q h e s , l a t e r i n c r e a s e d t o

8

i n c h e s .

F i e l d Observations

S i x

13

s t o r e y houses w i t h bassments and o u t s i d e chimneys and one bungalow w i t h basement. and i n s i d e s:;ximr!ey were v i s i t e d .

Wednesday mo.as.taLng, 1st; Dsoem:3es,, was w3.nd!-es8 and o v e r c a s t w i t h o c c a s i o n a l snow, T.3.e ternpez;.at;irr.,? wa.3 .z%,-~lS;

3 & " ~ , ,

The weather

began t o c l e a r wikh l i g h t wind and d . ~ ( s p ? . n g temperature, d u r i n g t h e a f t e r n o o n . Thursday was c l e a r w i t h l i g h t . wind and a temperature about 25OF.

Table I g i v e s r e a d i n g s of f l u e gas temperature, f l u e gas composition and chimney d r a f t Eos dampep s e t t i n g s found on a r r i v a l and f o r a l t e r n a t e settings. Equilib?lun c o n d i t i o n s can be assumed f o r measurements obtained on arr2;ial, but not a f t e r khe smoke- pipe dampers were r e s e t .

The f l u e gas t e m p e r a t i ~ r e d r o p in t h e 1 2 - t o 13-foot l ~ n g smokepipes i n d i c a t e s a l a r g e h e a t l c s s . This l o s s v a r i e d w i t h t h e f l u e g a s temperature a t f u ~ w a c e exLt. When o p e r a t i n g wi$h t h e smokepipe damper c l o s e d , t e m p e r a 5 u ~ e drops of ~ o " F , , 9 0 " ~ ~ and 140°F. were observed w i t h gas t e m p e r a T u ~ e s at srnckepipe e n t r y of L ~ o " F , , 2 5 0 " ~ . and 3 5 0 " ~ . , ~ e s p s c t i v e l y .

In

a 7$--raot long smoke- p i p e , t h e temperature d ~ o p waa approximately h a l f t h a t f o r l o n g e r smokepfpes a t t h e same f l u e gas temperature.

With d i l u e n t ~ P F entering tksough 8n open ~rlaokepfpe damper, t h e temperature drops were almost do2hled, being ~ Q O F , , 1 5 0 ~ ~ . and

2 2 0 ' ~ . w i t > h t h e same f l u e gss tenperat.uL?2s a t Furnace e x l t as mentioned abi3ve , I n t,ni,s c a s e , .,?etJ1u:l:~~g t h e smhakspipa l e n g t h had much Less ina'l.uerace oa?. tr.Sae snokep:i2,? z x . i t t . e ~ i p a ~ ~ a t ~ u _ r e s .

The s a l a t l . o n w h i p between d r a f t ,3nd f l ~ . . : ? gas temperature a t smokepipe e x i t i s give.n 1x1 Fig. 1. :!'a,lT~ea E a L l wit.hin the c r o s s -

hatched a r e a ; some a p ~ e a d 1.s expacked a s meas;rrernsnts were taken under d i f f e r i n g cos,ciitiona o f f l ~ ~ e gas v o l : m e , The 1owez-n end of t h e graph shows typYcal cond.FtYo.rAa of i i m l , ~ a e ~ t . d r a f t f a i l u r e .

A 11 houses used Penrr.sy1vard.a a~?,r,:h:.;~ac 2 , t t . 9 P.as Tenant s claimed s t r i c t adhe~en:;?.e to nan:,rfa!:t?.l!??.,?!s < . ; n i : : ; f u ~ ~ x . ~ ~ ~ " . i 3 3 ~ .In. i?tll.r>ing

1',,3 + ; i 7 , . . .

t h e f u r n a c e s , $ . e . on a side-to-side b a ~ ' , ; 3 ~ ...- .,.,~~:.s,nt s t a t e d

t h a t he obtained b e t t e r F e a ~ - . j $:s when

['%:r.:/l;:is

': r..7'-.-zo-.Sack0 Tne t e n a n t s Aotl.;eci tkaht tL1er.a w.i31 nc:2 a2g.z I>F d,raf t

f a i l u r e i n c o l d weather wken heat%ng .wqu-era&,","fifis ~ 5 hfgh; ~ 2 b u t ,

f u r n a c e s sometLmes d i d yen? .:.nto bzass!jzi?nta lc ~ , . ; . l , d , ? ~ weather when

No d r a f t f a i l u r e w a s r e p o r t e d by t e n a n t s of t h e bungalows. T h e i r chimneys were t h e same a s t h o s e i n t h e

13

s t o r e y houses, but were lower and l o c a t e d i n s i d e t h e b u i l d i n g s .

Sungested Mechanism of D r a f t F a i l u r e

D r a f t i s t h e p r e s s u r e d i f f e r e n c e between some p o i n t i n a v e n t i n g system and t h e s u r r o u n d i n g a i r a t t h e same l e v e l , S i n c e t h e a b s o l u t e p r e s s u r e s d i f f e r a t v a r i o u s p o i n t s i n t h e v e n t i n g system and t h e s u r r o u n d i n g s , when c o n s i d e r i n g d r a f t v a l u e s t h e p o i n t s must be c l e a r l y s t a t e d between which p r e s s u r e d i f f e r e n c e i s measured. I n t h i s r e p o r t , d r a f t i s d e f i n e d a s t h e p r e s s u r e d i f f e r e n c e between a chimney and basement of a house a t t h e same l e v e l , and t h e o r e t i c a l d r a f t as t h e p r e s s u r e d i f f e r e n c e between a chimney and t h e o u t s i d e a i r o r a heated s t r u c t u r e and t h e o u t - s i d e a i r a t t h e same l e v e l . To understand f u l l y t h e mechanism of v e n t i n g f a i l u r e , it i s important t o a p p r e c i a t e t h e f a c t o r s t h a t determine t h e s e p r e s s u r e s and t h u s t h e p r e s s u r e d i f f e r e n c e s . B a s i c a l l y , any d r a f t i s t h e r e s u l t of t e m p e r a t u r e d i f f e r e n c e

between columns of g a s . F i g . 2a r e p r e s e n t s a v e r t i c a l column o f h e i g h t H enclosed a t both ends and provided w i t h a s i n g l e opening i n i t s s i d e a t e l e v a t i o n h l above t h e base. Suppose t h e temperature Tc of t h e a i r i n t h e e n c l o s e d column i s uniform and h i g h e r t h a n t h a t of' t h e s u r r o u n d i n g a i r To. A t t h e

e l e v a t i o n h l , i . e . a t t h e opening, s t a t i c p r e s s u r e i n s i d e and o u t s i d e t h e column w i l l be t h e same. The p r e s s u r e a t t h i s e l e v a t i o n i s d e s i g n a t e d as pl.

A t h e i g h t H t h e p r e s s u r e o u t s i d e t h e column w i l l be

p 1 l e s s t h e weight of t h e column of o u t s i d e a i r above t h e opening:

and i n s i d e t h e column t h e p r e s s u r e w i l l be p l l e s s t h e weight of t h e column of i n s i d e a i r above t h e opening:

where w, and wc a r e t h e mean weight p e r c u b i c f o o t of a i r and f l u e g a s i n house and chimney, r e s p e c t i v e l y . S i n c e Tc i s g r e a t e r t h a n To, o u t s i d e a i r i s d e n s e r t h a n i n s i d e a i r , 1.e. wo i s g r e a t e r t h a n w c , and p r e s s u r e i n s i d e t h e column w i l l be g r e a t e r t h a n o u t - s i d e by

S i m i l a r l y , a t t h e base, p r e s s u r e i n s i d e t h e column. i s l e s s t h a n p r e s s u r e o u t s i d e by

Regardless of t h e p o s i t i o n of t h e opening, i t f o l l o w s t h a t p r e s s u r e i n s i d e t h e column above t h e opening w i l l exceed t h a t o u t - s i d e a t t h e same l e v e l , and p r e s s u r e i n s i d e t h e column below t h e opening w i l l be l e s s t h a n t h a t o u t s i d e a t t h e same l e v e l .

It i s apparent t h a t no i n t e r c h a n g e of a i r t a k e s p l a c e between t h e o u t s i d e and i n s i d e of t h e column, and t h a t f o r flow t o occur, a t l e a s t two openings a t d i f f e r e n t l e v e l s a r e n e c e s s a r y . This c o n d i t i o n i s i l l u s t r a t e d i n F i g . 2b where t h e upper opening

i s l a r g e enough t o o f f e r no r e s i s t a n c e t o flow and t h e lower opening i s s u f f i c i e n t l y small t o o f f e r a n a p p r e c i a b l e r e s i s t a n c e t o flow. I n t h i s c a s e , s t a t i c p r e s s u r e i n s i d e and o u t s i d e t h e opening a t e l e v a t i o n h2 i s t h e same. A t t h e small opening a t e l e v a t i o n h l p r e s s u r e o u t s i d e i s e q u a l t o

A t e l e v a t i o n h l s t a t i c p r e s s u r e i n s i d e t h e column, i f t h e e f f e c t of f r i c t i o n p r e s s u r e l o s s due t o f l u i d flow i n t h e column i s n e g l e c t e d , i s e q u a l t o

The d i f f e r e n c e between p r e s s u r e i n s i d e and o u t s i d e t h e column, o r t h e t h e o r e t i c a l d r a f t , i s

Pressure i n s i d e t h e column a t e l e v a t i o n hl a c t u a l l y w i l l

be h i g h e r t h a n t h a t j u s t c a l c u l a t e d because of t h e amount needed t o overcome t h e f l u i d flow r e s i s t a n c e of t h e column, and t h e

d i f f e r e n c e i n p r e s s u r e i n s i d e and o u t s i d e t h e column a t e l e v a t i o n hl w i l l be reduced correspondingly.

I f t h e s i z e s of t h e openings i n t h e column a r e r e v e r s e d , F i g . 2 c , p r e s s u r e i n s i d e and o u t s i d e t h e column w i l l be t h e same a t e l e v a t i o n hl. SimLlarly, p r e s s u r e i n s i d e t h e column a t e l e v a t i o n

h2 w i l l be g r e a t e r t h a n p r e a s u r e o u t s i d e by

i f p r e s s u r e l o s s e s due t o f l u i d f r i c t i o n i n t h e column a r e

n e g l e c t e d . Pressure i n s i d e t h e column a t e l e v a t i o n h2 a c t u a l l y w i l l be lower than t h a t j u s t c a l c u l a t e d because of t h e amount needed t o overcome t h e f l u i d flow r e g i s t a n c e of t h e column, and t h e d i f f e r e n c e i n p r e s s u r e i n s i d e and o u t s i d e t h e column a t e l e v a t i o n h2 w i l l be reduced correspondingly.

I f t h e s i z e of both openings i s small enough t o c r e a t e a p p r e c i a b l e r e s i s t a n c e t o a i r flow, F i g . 2d, t h e n $LevatLon h3, a t which p r e s s u r e o u t s i d e i s e q u a l t o p r e s s u r e i n s i d e t h e column, w i l l

depend on f l o w r e s i s t a n c e of t h e two openings and always w i l l be n e a r e r t h e opening having l e s s e r r e s i s t a n c e ,

These c o n s i d e r a t i o n s apply t o any heated s t r u c t u r e i n c l u d i n g both chimneys and houses. Pressure d i s t r i b u t i o n s i n F i g . 2 b a r e f o r chimneys and t h o s e i n F i g . 2d a r e f o r houses o r s i m i l a r heated s t r u c t u r e s .

F i g . 3 i s a s i m p l i f i e d diagram of t h e

13

s t o r e y houses a t Amherstburg. D r a f t f a i l u r e o c c u r s when f l u e gases escape from t h e smokepipe p l a t e damper, 1 . e . when p r e s s u r e ps i n t h e smoke- pipe a t t h e smokepipe p l a t e damper i s g r e a t e r t h a n p r e s s u r e pb a t e l e v a t i o n hl i n t h e basement. Pressure p i s determined by t h e d i f f e r e n c e between t h e mean temperature of fyue gas i n t h e

chimney Tc and t h e o u t s i d e temperature To, t h e d i f f e r e n c e i n e l e v a t i o n between t h e smokepipe p l a t e damper and t h e t o p of t h e chimney, and t h e r e s i s t a n c e t o flow i n t h e f u r n a c e , smokepipe, dampers and chimney.. Pressure ( p c , e ) , i n s i d e t h e chimney a t e l e v a t i o n h2, i s t h e same as p r e s s u r e po.2, o u t s i d e a t t h e same e l e v a t i o n . Pressure ps i s t h e n

where we i s t h e mean weight p e r cubic f o o t of f l u e gas a t chimney temperature T c , and

Fc

a r e t h e f r i c t i o n l o s s e s due t o flow r e s i s t a n c e i n t h e chimney. Thus, p r e s s u r e p o . l i s

where w i s t h e mean weight p e r c u b i c f o o t of o u t s i d e a i r a t t e m p e r a R r e To. The d i f f e r e n c e between p r e s s u r e i n s i d e and out

-

s i d e t h e chimney a t e l e v a t i o n hl i s

P o

-

Ps = Po.2 + w0 (ha

-

hl)

-

Po.a

-

W c ( h p

-

h l )

-

Fc

-

_-

_{W o ( h 2 - h l )}

_-

_{wc (ha}

_-

_hl)

_-

_F,.

Pressure i n t h e basement ( p b ) a t e l e v a t i o n h depends on e l e v a t i o n h

,

(when p r e s s u r e i n s i d e and qut s i d e t h e

8

~ o ~ l s a is e q u a l ) and t h e dif.?erence between t h e mean temperature over h e i g h t ( h 3

-

h l )

i n s i d e t h e house Th and o u t s i d e To. The d i s c u s s i o n of F i g . 2d" showed t h a t e l e v a t i o n h3 would depend on t h e l o c a t i o n of openings i n t o t h e house, t h e i r r e l a t i v e r e s i s t a n c e t o flow, and t h e r e s i s t a n c e t o flow w i t h i n t h e house. A t e l e v a t i o n hl t h e d i f f e r e n c e between p r e s s u r e i n s i d e and o u t s i d e t h e house i s

where w i s t h e weight p e r c u b i c f o o t of a i r i n t h e house at.

5'

tempera u r e Th and Fh a r e f r i c t i o n l o s s e s due t o flow r e s i s t a n c e i n t h e house. T h e p r e s s u r e d i f f e r e n c e ( p b

-

p ) a c r o s s t h e smoke- p i p e p l a t e damper w i l l determine whether o r no& f l u e gas s p i l l s

i n t o t h e basement. S p i l l a g e w i l l n o t t a k e p l a c e i f pb i s g r e a t e r t h a n ps, or i f

i s g r e a t e r t h a n zero. This equation can be r e w r i t t e n

If Fc and Fh a r e n e g l e c t e d d r a f t f a i l u r e w i l l occur when

The above e q u a t i o n s show t h a t t h e l o c a t i o n of e l e v a t i o n h3 h a s a n e f f e c t on d r a f t a c r o s s t h e smokepipe p l a t e damper and t h u s , i s r e l a t e d t o d r a f t f a i l u r e . If e l e v a t i o n h3 Y= hl, t h e d r a f t a c r o s s

t h e ' smokepipe p l a t e damper w i l l be z e r o when t h e mean temperature of f l u e gas i n t h e chimney T, i s equal t o t h e o u t s i d e temperature To, i g n o r i n g f r i c t i o n e f f e c t s . S i m i l a r l y , i f h3 = h2, t h e d r a f t a c r o s s t h e smokepipe p l a t e damper w i l l be z e r o when t h e mean temperature of f l u e gas i n t h e chimney T, i s e q u a l t o t h e mean temperature i n t h e house Th. If t h e r e i s f l u e g a s flow i n t h e v e n t i n g system, f r i c t i o n l o s s e s i n t h e f u r n a c e , smokepipe, smoke- p i p e p l a t e damper and chimney must be overcome. An i n c r e a s e of approximately lo°F. i n t h e mean temperature of f l u e gas Tc would overcome t h e s e f r i c t i o n l o s s e s f o r t h e small f l u e g a s volumes

involved when d r a t k f a i l u r e i s imminent. Thus, t h e lower l i m i t of mean chimney f l u e gas tempefature necessary t o prevent d r a f t

f a i l u r e i s approximately 10 F. above o u t s i d e temperature when h3 = hl and 1 0 O ~ . above room temperature when h3 = h2.

I n p r a o t i c e , h w i l l be a t some e l e v a t i o n between hl and

2

h2 and w i l l depend on he l o c a t i o n and c h a r a c t e r i s t i c s of openings i n t o t h e house from o u t s i d e . It f o l l o w s t h a t opening upper windows i n t h e house w i l l a f f e c t t h e f u r n a c e v e n t i n g a d v e r s e l y , whereas opening basement windows w i l l have a b e n e f i c i a l e f f e c t . C l e a r l y , t o ensure proper furnace venzing under a l l c o n d i t i o n s of house

o p e r a t i o n t h e mean f l u e gas temperature i n chimney Tc must not f a l l below mean house temperature Th. This i s e s p e c i a l l y t r u e w i t h a r e l a t i v e l y h i g h o u t s i d e temperature To.

The e f f e c t on d r a f t of i n c r e a s i n chimney h e i g h t can be p r e d i c t e d from t h e equation f o r ( p

-

p

f

.

I f , f o r example, t h e f l u e gas temperature a t chimney e x t t i s assumed t o be 1 0

'I?.

above

o u t s i d e temperature T and i f t h e mean d e n s i t y of f l u e gau wc i s assumed c o n s t a n t , an Pncrease i n chimney h e i g h t of 5 f e e t w i l l i n c r e a s e t h e d r a f t (pb

-

p s ) by approximately 0.004 inches water gauge. T h i s n e g l e c t s any i n c r e a s e i n f r i c t i o n l o s s e s

Fc

due t o added h e i g h t . The

5

f e e t of added h e i g h t have n e a r l y t h e same e f f e c t on d r a f t as has an i n c r e a s e of 5OF. i n t h e

m a n

r l u e gas temperature i n t h e chimney Tc. Such a n i n c r e a s e i n d r a f t can o f f s e t only t o a l i m i t e d e x t e n t t h e c o n d i t i o n s l e a d i n g t o d r a f t f a i l u r e .

The n!2c:car_ism of d r a f t f a i l u r e d e s c r i b e d a p p l i e s d i r e c t l y t o t h e c o n d i t i o n s found a t Amherstburg. Presumably, t h e mean f l u e g a s t e m p e r a t u r e i n t h e chimney Tc sometimes f e l l below t h e c r i t i c s 1 v a l u e d e f i n e d by t h e p r e v i o u s e q u a t i o n s . Measured c o n d i t i o n s ,

under which d r a f t f a i l u r e was imminent, a r e r e c o r d e d i n c o l m 5 of T a b l e I .

Furnaces were o p e r a t e d a t low f i r i n g r a t e s because of m i l d w e a t h e r and consequent low h e a t i n g r e q u i r e m e n t s , r e s u l t i n g

i n r e l a t i v e l y s m a l l q u a n t i t i e s of f l u e g a s and low f l u e gas

temperattk*~ z t f u r n a c e o u t l e t s . There w a s a s u b s t a n t i a l d r ~ p i n f l u e gas t e m p e r a t u r e i n t h e l o n g u n i n s u l a t e d smokepipes ( T a b l e I).

Th2s d r o p , combined w i t h t h e e f f e c t of d i l u t i o n of f l u e g a s e s

by basement a i r e n t e r i n g t h r o u g h t h e open smokepipe damper, r e s u l t e d i n r e l a t i v e l y low f l u e g a s t e m p e r a t u r e s a t e n t r y t o c h i m r y . A t

a l l t i m e s , however, t h e s e were h i g h e r t h a n t h e mean house t e m p e r a t u r e T h . Cooling of f l u e g a s i n c o l d o u t s i d e chimneys caused a f u r t h e r l a r g e t e m p e r a t u r e d r o p . The r e s u l t was mean f l u e g a s t e m p e ~ a t u r e s

T, which sometimes were lower t h a n t h e c r i t i c a l v a l u e .

Although t h e r e a r e s e v e r a l c o n t r i b u t i n g f a c t o r s t o 1 ~ w f l u e g a s t e m p e r a t u r e s , t h e e f f e c t of c o o l i n g t h e f l u e g a s l n exposed

o u t s i d e chimneys must be c o n s i d e r e d t h e u l t l m a t e cause o f d r a f t

f a i l u r e . I n comparison, t h e t e m p e r a t u r e of f l u e gas p a s s i a g t h r o u g h a chimney w i t h i n t h e house and exposed t o house t e m p e r a t u r e s on a l l f o u r s i d e s , cannot d r o p below t h e mean house t e m p e r a t u r e Th. I n t h i s c a s e , t h e p o s s i b i l i t y of d r a f t f a i l u r e r e s u l t i n g from a mean f l u e g a s t e m p e r a t u r e i n t h e chimney l e s s t h a n t h e c r i t i c a l v a l u e i s e l i m i n a t e d .

With a n i n s i d e chimney no d i f f i c u l t y i s expected i n

p r o v i d i n g a d e q u a t e d r a f t a t low f i r e o r f u s n a c e s t a r t up. I n a d e q u a t e d r a f t , however, can be e x p e c t e d w i t h a n o u t s i d e chimney o p e r a t i n g under t h e s e s o n d i t i o n s . A t Amherstburg i t w a s r e p o r t e d t h a t i f

t h e f i r e burned down d u r i n g t h i s p e r i o d of low f u r n a c e l o a d arL3

i n c r e a s e d h e a t i n g was r e q u i r e d , c l o s i n g t h e smokepipe dampek had no e f f e c t on i n c r e a s i n g t h e d r a f t , I n f a c t , small wood f i r e s

were

l i t f n t h e chimney c l e a n o u t s i n a n a t t e m p t t o r e s t o r e normal d r a f t .

T h i s d i s c u s s i o n of f a c t o r s a f f e c t i n g d r a f t h a s excli.idsd

any c o n s i d e r a t i o n of wind. When wind o c c u r s i t h a s a def.inSi;e e f f e c t on p r e s s u r e s w i t h i n t h e house a t a l l l e v e l s ; t h e ~ f f e c t , depends on t h e r e l a t i v e r e s i s t a n c e t o a i r flow between xhe i n s i d e and o u t s i d e of t h e house on t h e windward and leeward s l . d s s , hi',

f o r example, t h e r e i s l i t t l e r e s i s t a n c e t o a i r f l o w on t h e ~ l n d w s r C t s i d e cornpared t o t h a t on t h e leeward s i d e a n I.mcrease % P psLzsshire

o c c u r s w i t h i n t h e house, which i s r e l a t e d t o t h e ingaci; f-)aaessi eat:

of t h e wind, and d r a f t a t t h e base of t h e chimzey f n z r e a a e s p~opo::.+io~; a t e l y . Conversely, i f t h e r e i s l i t t l e r e s i s t a n c e cn t,he I.lie.wa:rc'L

a i d e r e l a t i v e t o t h a t on t h e windward s i d e , a g e n e r a l r e d a e t . i ~ n cf p r e s s u r e i n s i d e t h e house o c c u r s and t h e p o s s i b i l i t y of ;7e1%ti:::g

f a i l u r e i n c r e a s e s . The p o s s i b l e e f f e c t of wind on p r e s s u r e a t

t h e chimney o u t l e t has not been considered i n t h e foregoing d i s c u s s i o n , s i n c e d r a f t f a i l u r e a t Amherstburg was observed on windless days.

Discussion of F a c t o r s I n f l u e n c i n g D r a f t F a i l u r e

While t h i s problem was under c o n s i d e r a t i o n , t h e agencies and i n d i v i d u a l s involved i n t h e i n v e s t i g a t i o n advanced t h e o r i e s t o e x p l a i n t h e cause of d r a f t f a i l u r e and suggested v a r i o u s remedial measures. These a r e d i s c u s s e d i n d e t a i l i n t h e f o l l o w i n g paragraphs.

1. Flue Dimensions

The C.M.H.C. Building S t a n d a r d s , May 1955, require t h e

following f l u e dimensions i n chimneys b u i l t f o r one-or two-family dwellings as d e t a i l e d i n S e c t i o n 26 on Chimneys and F l u e s , ( b ) 1, page

66:

"Flues

...

s h a l l be n o t l e s s t h a n

8

by

8

inches o u t - s i d e , 7 by 7 inches i n s i d e , o r 7 inches i n s i d e diameter i f round". T h i s , however, d i f f e r s from p r o v i s i o n s f o r Gravity W a r m A i r Systems quoted i n S e c t i o n 49 on Heating, ( c ) Equipment and I n s t a l l a t i o n ,

4 ,

page 107, of t h e same Standards which r e q u i r e t h a t t h e "Design and i n s t a l l a t i o n of g r a v i t y and f o r c e d warm a i r systems s h a l l a t l e a s t 'conform t o t h e published b u l l e t i n s of t h e National Warm A i r

Heating and A i r Conditioning A s s o c i a t i o n " . S p e c i f i c a l l y , i n t h e Gravity Code and Manual No. 5 , 1954, 5 t h e d i t i o n , Appendix B,

A r t i c l e 7 on Chimneys, ( f ) i t i s r e q u i r e d t h a t : "The narrowest i n t e r n a l dimensions s h a l l be not l e s s than

8

inches and no f l u e s m a l l e r than

8

by

8

inches r e c t a n g u l a r o r 8-inch diameter round w i l l be considered s u i t a b l e when hard c o a l i s t o be burned, o r

8

by 12 inches r e c t a n g u l a r o r 10-inch round f o r s o f t c o a l o r wood. It i s s t r o n g l y recommended t h a t nothing l e s s t h a n

8

by 12 inches i n t e r n a l dimension be used i n any c a s e . "

The National Building Code 1953, P a r t 6

-

General

S e r v i c e s , r e q u i r e s under 6.2.3.9.5. F l u e s , on page 2 5 , t h a t "The minimum e f f e c t i v e c r o s s - s e c t i o n a l a r e a of every f l u e i n any chimney

o r smokestack s e r v i n g h e a t i n g a p p l i a n c e s r e g u l a t e d by Subsection

6 . 2 . 3 .

"

( c o v e r i n g Heating Systems and Equipment), s h a l l be ,;a follows: "Small s p e c i a l s t o v e s and h e a t e r s 28 squars tnches

Cooking s t o v e s , r a n g e s , room h e a t e r s 40 square inches Open f i r e p l a c e s ( a t l e a s t 1/12

t h e f i r e p l a c e opening) 50 square ic.ches

B o i l e r and f u r n a c e s , f o r hot water;

steam, o r w a r m a i r h e a t i n g 70 squzre i n c h e s . " The a c t u a l f l u e c r o s s - s e c t i o n s of t h e c h i m e y s i n s p e c t e d

inches conforms, t h e r e f o r e , w i t h t h e C.M.H.C. Building Standards but i s l e s s t h a n t h a t r e q u i r e d f o r t h i s type of h e a t i n g appliance ~y t h e N.W.A.H. and A . C . A . Standards and t h e National Building Code.

According t o t h e 1955 A.S.H.A.E. Guide, under Draft

R e q u i r e u n t s of Appliances on page 430, h a n d - f i r e d w a r m a i r

f u r n a c e s k r e q u i r e a d r a f t of

0.06

inches of w a t e r gauge when

o p e r a t i n g a t r a t e d output and u s i n g chestnut- s i z e d a n t h r a c i t e as f u e l . Measurements os*chimneys a t Amherstburg i n d i c a t e t h a t a d r a f t of 0.06 inches of w a t e r could be obtained w i t h f l u e gas

temperatures a t chimney e n t r y between 1 6 0 " ~ . and 2 5 0 ' ~ . ( ~ i g . 1 ) . These temperatures occurred a t r e l a t i v e l y low f i r i n g r a t e s .

D i l l , Achenbach and Duck i n t h e i r paper "Observed

Performance of Some Experimental Chimneys " published i n Heat fng,

Piping and A i r Conditioning, v o l . 14, no.

4,

A p r i l 1942, ~ e p o r t on t e s t s c a r r i e d out a t t h e Nat i o n a l Bureau of Standards i n

Washington, D.C. on a chimney 22 f e e t h i g h above smokepipe thimble,

i d e n t i c a l i n c o n s t r u c t i o n t o t h e Amherstburg chimneys. This chimney gave a d r a f t of more t h a n 0.06 inches of w a t e r gau e when vent i l ~ g

f l u e gas a t r a t e s between 20 c.f,m. and

70

c.f.m.

?

s t a n d a r d a i r a t 70°F. and 29.92 inches of mercury) w i t h an e n t r y temperature of approximately 250°F'. and o u t s i d e temperature 32OF. The t e s t s a l s o i n d i c a t e d t h a t i n t h i s r a n e of f l u e gas volume a chan e of f l u e

₈

s i z e from 7 i by

76

inches T1.e. 53 square i n c h e s ) t o 65 by 11 inches (1.e. 72 square i n c h e s ) had no s i g n i f i c a n t i n f l u e n c e on d r a f t

.

The low f l u e gas flow r a t e of 20 c,f .m. can be compared w i t h t h e furnace o p e r a t i o n a t Amherstburg when h e a t i n g requirements were low. There i s , t h e r e f o r e , no i n d i c a t i o n t h a t an i n c r e a s e i n

t h e f l u e a r e a of t h e Amherstburg chimneys would improve d r a f t , under c o n d i t i o n s approaching f a i l u r e .

2. Furnace O ~ e r a t i o n

I n t h e s o l i d - f u e l hand-fired furnacea used' i n A w e s s f b u r g , combust i o n i s c o n t r o l l e d by damper ad j u s t w n t

.

Closing t h e smoke

-

pipe damper o r opening t h e a s h p i t door d m p e r i n c r e a s e s t h z a l p

flow through t h e f u e l bed and causes more r a p i d burning. Both dampers a r e a d j u s t e d t o t h e s e p o s i t i o n s p e r m i t t ing rnaxlrnum f u e l a e r a t i o n only when l i g h t i n g t h e f u r n a c e o r when r a p l d nouse h e a t i n g i s r e q u i r e d . Under most o p e r a t i n g c o n d i t i o n s :the ashpiT; door d m p e r i s c l o s e d s i n c e t h e r e q u i r e d a i r f o r c o m b u a t i & ~ i s provided Sy

leakage around t h i s damper and by flow through' t h e m a x ~ ~ a i s l i d e i n t h e f u e l door which i s always l e f t open i n accordance w i t h good p r a c t i c e . Thus, t h e r a t e of combustion i s c o n t r o l l e d onby 3$ manipulation of t h e smokepipe p l a t e damper.

Heat l o s s e s from t h e houses decrease w i t h I.ncreaa%ng o u t - s i d e temperature. To prevent house overheat i n g , t h e f u x ~ z c e ,heat

t h e saokepipe damper. The d i l u t i o n of f l u e g a s e s w i t h a i r e n t e r i n g t h e s ~ o k e p i p e r e s u l t s i n lower f l u e g a s t e m p e r a t u r e s a t chimney e n t r y , t h u s r e d u c i n g d r a f t and u l t i m a t e l y , as shown by f i e l d o b s e r v a t i o n s , c o n t r i b u t i n g t o d r a f t f a i l u r e .

The t e n a n t s a p p e a r e d t o have f o l l o w e d t h e method of f i r i n g recommended ~ y t h e m a n u f a c t u r e r . Some r e d u c t i o n i n Pumace h e a t

o u t p u t a t a g i v e n smokepipe p l a t e damper s e t t i n g could have been achLeved by a s l i g h t v a r i a t i o n of t h i s method f o r mild w e a t h e r

o p e r a t i o n . T h i s would i n v o l v e r e d u c i n g t h e e f f ' s c t i v e a r e a of t h e g r a t e by a l l ~ w i n g a deep l a y e r of a s h t o accumulate around t h e s i d e s of t h e g r a t e , l e a v i n g o n l y t h e c e n z r e f r e e and m a i n t a i n i n g a s m a l l but a c t i v e f i r e w i t h r e l a t i v e l y f r e q l ~ e n t a d d i t i o n s of' s m a l l q u a n t i t i e s of f u e l . T h i s f i r i n g psocedure would n o t o v e r - come d r a f t f a i l u r e , but would r a i s e t h e u p p e r l i m i z of o y t s i d e + e m p e r a t u r e s under which e f f e c t i v e draft c o u l d Se mafn3ained.

The i n s t a l l a t i o n of b a r o m e t r i z dampers f n p l a c e of t h e p r e s e n t c h a i n - o p e r a t e d p l a t e dampers i n t h e smokepipes would n o t n e c e s s a r i l y remedy d r a f t f a i l u r e . The p r i m a r y i n t e n t i o n of

b a r o m e t r i c dampers i s t o c o n t r o l t h e d r a f t a t a more o r l e s s

c o n s t a n t p r e d e t e r m i n e d v a l u e by v a r y l n g t h e amount of d L l u e n t a i r allowed t o e n t e r t h e v e n t i n g system. These dampers b e c ~ m e

e f f e c t i v e when t h e d r a f t exceeds t h e p r e d e t e r m i n e d v a l u e . Below t h i s v a l u e t h e y remain c l o s e d and e x e r t no c o n t r o l on e i t h e r d r a f t o r b u r n i n g r a t e . The q u a n t i t y of h 2 a t l i b e r a t e d i n t h e

f u r n a c e under t h e s e low d r a f t c o n d i t i o n s c o u l d exceed t h a t r e q u i r e d f o r house h e a t i n g i n mild w e a t h e r . F o r t h i s c o n d i t i o n of low

h e a t r e q u i r e m e n t f u r n a c e c o n t r o l i s l e s s f l e x i b l e w i t h a b a r o m e t r i c damper t h a n w i t h manual smokepipe damper opepat Lon, Thus, t e n a n t s might i n t e r f e r e w i t h t h e b a r o m e t r f z dampsr s e t K i n g when r e q u i r i n g low h e a t o u t p u t from t h e f u r n a c e . Some c o ~ t z o l of o v e r h e a t i n g c o u l d be e x e r c i s e d by t e n a n t s t h r o u y h t h s a ~ d i f i e d f i s i 2 g

p r f i c e d u ~ e p r e v i o u s l y d e s c r i b e d .

The i n s t a l l a t i o r a of a n induced d r a f t ?an in t h e smokepipe n e a r t h e chimney wou1.d i n s u r e a d e q u a t e d r a f t a % a?; tlanes, T h i s

i s a s e l a t i v e i y expens!_-i:: i;Lem, Ezowev%?, .~e<.,:~.i:r'.rag pe:;-.L13d.!-c

r a i n t e n a n c e , If i t 1 s to , . ~ h v f a t e d r a f t fa;Llj.>?i? r;dj.t,,h0;?.t e.r"~=.tS;c Ig trombustPon :pates I n excess of t h o s e soqul..r?d f;c h.?at. :T!-L? khollve

i n m i l d weather e L a b o r a t e c o n t r o l s wou.Ld S e nsl?,?ssarg, It would r e q u i r e a l s o some s a f e t y c o n t ~ o l f e a t u r e s 2.n t h e e ~ ~ 5 r . t o.f pc~wer"

f a i . l u r e

.

A f o r c e d d r a f t f a n for. d e l i v e r i n g a i r I n t o t h e ~ T L A X . ~ : ! ~ , : : 9

has t h e same d i s a d v a n t a g e s a s t h e induced dsa.f't f a n , mil .:I::

a d d i t i o n , r e q u i r e s a c o m p l e t e l y g a s - t i g h t f u r n a c e arid v ~l.ng ~ t system. Anything l e s s t h a n t h i s wolldd .~e,suj,f, Ire a? extx~eme'lg hazardous c o n d i t i o n .

3.

Climate

It

has been suggested that the draft problems experienced

at Amherstburg and Windsor were related to a climatic condition known as temperature inversion, sometimes referred to as air

inversion. According to the Meteorological Division of ths

Department of Transport the temperature of air in the t:ropusphere

(layer of atmosphere extending about

7

miles upwards f ~ o m earth's

surface) decreases with altitude, but occasionally the reverve occurs. This inversion of the temperature gradient occurs at

various altitudes, and usually does not extend over any great range

of height.

It

always involves thermal stability of the atmosphere

and the absence of wind at ground level. This phenomeno~ is not

unusual on clear windless nights in temperate climatesp when lower air layers cool faster than thost at hdgh altitudes.

With high atmospheric pressure in winter this condition may extend

to

a

considerable height and persist for several days. Consequently,

Cogs or smoke accumulation above cities develop.

-

Draft failure does not develop as a result of temperature inversion since draft is a thermodynamic effect pertaining to the furnace-chlmney combination, and the only way that climatic

conditions can affect draft, if there is no wind action, is

indirectly, through ambient temperature. In the ~elatively mild

weather at the beginning and end of the heating season, when heat loss from well insulated houses is low and furnaces are operated at low load, draft failure can develop.

Wind action can cause draft failure if it has

a

d~wnward

component impingeing on the chimney top. Draft faih~re through

this cause can be alleviated by the installation of a c o ~ s e c t ~ y

designed flue cap. Draft failure was observed at Atnhe,rstb~xsg,

however, on windless days when a chimney l l u e cap would have had

no beneficial effect.

Conclusions

An equst ion f oz3 draft defined as The pr;?cs;r~.re dKiYeren@e

betwem the house basement and the chimney at t h o sz5'-3 level., hae

been developed. This equation shows thht ara25 depends on house

condltions as well as chiml-cy 2nd outside condition.^ a.rd that

draft failure will occur if the mean flue gas temperature In the

chimney falls below a critical value. Disregarding the effect of

wind on pressures within the house or at the chlmey t c p y this

critical mean flue gas temperature deper~ds on me*i+: k.tc:~,re air

temperature, outside air tempesaturs, locatl~n has rLelght af

chimney and characteristics of openlngs :nto the :louse

r~

v r a <>lit -

side. Under the most unfavcurable coraciltxor~s, k~c3tkciing f,k;12

effect of wind, draft failure occurs when the mean i ? - i ~ c : gas

temperature in the chimney is less than the mean nouse air

D r a f t f a i l u r e i n C.M.H. C . houses a t Amherstburg car, be

a t t r i b u t e d p r i m a r i l y t o c o o l i n g of f l u e g a s i n exposed o u t s i d e c h l m e y s t o below t h e c r i t i c a l mean f l u e g a s temperatu.se.

T h i s o c c u r r e d d u r i n g m i l d w e a t h e r as a r e s u l t of f u r n a c e s h u t - down o r f u r n a c e o p e r a t i o n a t low h e a t o u t p u t . During o p e r a t i o c a t low h e a t o u t p u t , d i l u t i o n of f l u e g a s w i t h basement a % r t h r o u g h open smokepipe p l a t e dampers and h e a t l o s s from l o n g u n i n a u l a t e d smokepipea, c o n t r i b u t e d t o d r a f t f a i l u r e . Under c o n d i t i o n s of imminent d r a f t f a i l u r e a t Amherstburg f l ~ i w gas t e m p e r a t u r e s measured a t chimney e n t r y were s u b s t a n t 2 x l l;i

above mean house a i r t e m p e r a t u r e s . Tempesaturss a t r;!~imney e x i t were n o t measured, but it must be a s s - m e d t h a t m a n f l u e g a s t e m p e r a t u r e s i n t h e chimneys were below =he c s i t t c a ; v a l u e a s a r e s u l t of c o o l i n g i n t h e c o l d o u t s i d e c h i m e y s .

With a n i n s i d e chimney exposed t o house t e n p l ? ~ a t u r e e x c e p t above t h e roof l e v e l , t h e mean f l u e g m t e r n ~ e r a t a r e i n t h e chimney cannot -rop b e 1 . o ~ th e c r l t i c a l va'lae. T l " e a t ~ c ' c r e ,

d r a f t f a i l u r e c a u s e

!

by f l u e g a s c o o l i n g w i l l no? ~ c , c % ~ . r

d u r i n g f u r n a c e o p e r a t i o n a t low h e a t o u t p u t os even d u r i n g f u r n a c e s h u t -down.

The most e f f e c t i v e way t o - r e m e d y d r a f t f a i l u r e at Amherstburg i s t o r e p l a c e o u t s i d e chimneys w i t h i n s i d e chimneys o r t o i n s u l a t e t h e e x i s t i n g chimneys s o th2t t h e y

f u n c t i c n a s i n s i d e chimneys. I f replacement i s e c o a ~ ~ n i z a l l y f e a s i b l e t h e use of p r e f a b r i c a t e d chimneys might be c o n s i d e r e d ,

An i n c r e a s e i n chimney h e i g h t would improve t h e d r a f t i n t h e e x i s t i n g c o l d chimneys, b u t , improvement i s s m a l l even f o r s u b s t a n t i a l i n c r e a s e s i n h e i g h t . T h e r e f o r e , because of t h i s and s t r u c t u r a l and a e s t h e t i c c o n s i d e r a t i o n s it seems m6re p r a c t i c a l t o i n c r e a s e t h e mean f l u e g a s t e r n p ~ - ~ a , t ~ u - e t y l t h o

chimneys.

There i s no i n d i c a t i o n t h a t i . n s u f f i c i e n t f l u e &Tea in t h e chimneys h a s been a cause of d r a f t f a i l u r e . Simlia~

chimneys t e s t e d a t t h e N a t i o n a l Bureau of S t a n d a r d s ('.?,fi .A. ) performed s a t i s f a c t o r i l y . The d i s a g r e e m e n t between sectT.f,opl;~

i n the C.M.H.C, .Bu.il.ding S t a n d a r d s , May 1.955, c c n z e ~ r . $ ; ; ~ fl:- I-: u

a r e a s s h o u l d be r?medied f o r t h e sake of cl?c~aiste,asy. The installation of bar0metri.c dampers i n p l & r - 5 oZ

p l a t e dampers i n t h e smokepipe might a l l e v i a t e t.be d r , s f t prcblem t o some e x t e n t . Because t h e i r ~ p o r a t i o n i s cantrcpll.sd b y d m f t

and n o t by house t e m p e r a t u r e , some house over-heating m y

r e s u l t d u r i n g mild w e a t h e r . It might be a d v a n t s g e o u s , kc&- e v e r , t o i n s t a l l b a r o m e t r i c dampers 1.n p l s c e of t 9 e n.ari,,r.a1

. .

smokepipe p l a t e dampers i n some of t h e h o 1 . l . s ~ ~ t o i>.a?;.2:~i~,i.rie t h e i r e f f e c t i v e n e s s i n a l l e v i a t i n g d r a f t failure wkler! j,~,~,;:ilc~Ly i,.:ied,

7 fr , 2 d , ~ : 2 , - , ,;:;.L, tibe le:2gt;l? i3f' s ~ ~ o k e p i g e a be tween furnaces and chimneys would reduce t h e he3.t Ic,ss, 1 . e . tem~e;?z+.)re d s o p , and

would aaaist .in x.s.ts;.2g t.h!a me2.n k?.uc; gas; t~?mgera.t;~;r~a. in th; c h i r n n ~ y , 3ei.osat-Y,c;i.i c-C t"i,a:r+nace~, h o d e v e r , 3 . 7 . ~ ~ vtrL::._:3.,3 I.;?:J-::!,ve c o s t l y a i t e r s . t L ~ ; : , n a to the ducf ciystetn. C o n s l L I " L a : p isiigrt be: g i v e 3 tbiei?~:': Q P ~ tcr i~i.;:i.la.t, %zag J;?:aa aanohcep2p.2 ?*.3 ahn

alternst

i v e measus*e.

D r ~ f t f allure rsil.glat .- be a l l e v l a t , & l kc: ,501364 e:~C;efit 't~y

modifj7irg the firing p ~ o c e c ? . s e t o reduce t h e ef?e~tl,!rs-, area o f

t h e , The pate of ?;.i;ir!-iir~g W O : . L ~ ~ be ma$:.at;i7..j.:~ed 8.t a I; veL

snsuslnp p?o,pe4p lgr: :I t $ 3 ~ ~ and e%.t',ir f.erlt r,,>:x'b1a~s'!: d.i-t:? b.,?,f %he .cat* e

of

t.,-,?:~'. f 1 2 ~ r : a c e h e a t outpu'&, i , e n :p:.:';c ;?f P x e l r~;i~a,&~;>t~ri::~2,

, , . ,.. ' '- _{, -} . .." ,- 7

. , :.e!.i. 'Th1.s m e t h:.:d wo.t.ili: ?s 7.y ~rrml.i-i't;a 2.r~' p,g h i g h e r f l u e gaz t ~ e n t ~ e , ~ a i ; ~ ~ a ~ c s i ~ 3 t!?.e (;:rbL~li.i?;q j T f 2 r a & - ~ 9 , 3 Cce&t outlpl~t by

e 1imi.r.a'; fng d iluent a32 e:nterl.ng h'u t h e sr~.oice,~%pi3 p l a t e damper.

A t some h i g b e ~ outsi.de temperature, howevas, the hzat oratput of

t h e furnace &'ould exceed the h e a t re~.~u..L:~ern.mt .>C th.e Eaa't~se, and

if t h e r,:~!.o!-ceplpce p l a t e dar.pe.'-~ was op3r~2s?!, .v?ntLr;i; I"afl'::!rae sga.3.n w c w L d bezsme Inmineat,

I n m i l d windless weather t h e h e a t i n g requirements of t h e houses a r e low and f u r n a c e s a r e operated a t low h e a t output w i t h t h e f i r e s checked f o r long p e r i o d s . Consequently, t h e o u t s i d e chimneys t e n d t o be c o l d and d r a f t f a i l u r e i s t o be expected.

Draft f a i l u r e w i t h s o l i d - f u e l h a n d - f i r e d a p p l i a n c e s vented by c o l d o u t s i d e chimneys and long u n i n s u l a t e d amoke- p i p e s i s not r e s t r i c t e d t o t h e Amherstburg, Windsor and D e t r o i t r e g i o n a l o n e , but has been observed i n o t h e r p a r t s of t h e

~ o u n t r y . ~ I n one way o r a n o t h e r t h i s problem h a s e x i s t e d f o r a l o n g tiine. It may be e l i m i n a t e d t o a l a r g e e x t e n t by t a k i n g p r e c a u t i o n s i n t h e o r i g i n a l s e l e c t i o n and l a y o u t of t h e h e a t i n g equipment and t h e d e s i g n and l o c a t i o n of t h e chimney.

TABLE I

FIELD OBSERVATIONS AT AMHERSTBURG, ONTARIO.

Date Time of day Type of house Fue 1 Length of smokepipe Weather 1.12.54 1.12.54 am an

14

s t o r e y

13

s t o r e y Pa a n t h r a c i t e --- 7 ' - 6 " 12 I - 0" cloudy, cloudy, windless windless 1.12.54 2.12.54 Pm am

14

s t o r e y

1k

s t o r e y . - - - 121 - 0" 1 - 3 1 - o w c l e a r i n g , c l e a r , s l i g h t s l i g h t w ind wind 2.12.54 am 1+ s t o r e y ---- 1 2 1

-

8 " c l e a r , s l i g h t wind 2.12.54 Pm 1; s t o r e y --- 1 2 '

-

8" c l e a r , s l i g h t wind 2.12.54 2.12.54 Pm Pm 1; s t o r e y bungalow --- Pa a n t h r a c i t e 111

-

6 " c l e a r , c l e a r , s l i g h t s l i g h t w ind w i n d Ambient - OF Basement - OF Remarks no d r a f t f a l l u r e A s found on a r r i v a l

Ashplt door damper Smokepipe damper Fuel door s l i d e closed c l o s e d closed c l o s e d open open c l o s e d c l o s e d c l o s e d open open open c l o s e d open c l o s e d c l o s e d closed open open open n e a r l y c l o s e d 370 130 0.030 0.035 0.020 0 surge 0.045) 3 - 8 15.6 Flue gas a t smokepipe e n t r y - OF 310 140

Flue gas a t smokepipe e x i t - OF 250 102

Temp. drop i n smokepipe

-

O F 60

Draft-inches water gauge 0.02 38

0.060 210 123 150 0.055 surge 0.07 0.035 C02

-

$ by volume CO - $ by volume 02 - $ by volume A l t e r n a t e smokepipe damper s e t t i n g

Ashpit door damper cloeed c l o s e d c l o s e d

open open open open 118 200 90 100 2 8 100 0.005 0.015

closed closed c l o s e d closed

c l o s e d c l o s e d c l o s e d open

open open open open

260 350

170 255

90 95

0 055 0.04 0.11)

Smokepipe damper open

Fuel door s l i d e open

Flue g a s a t smokepipe e n t r y - O F 310

Flue gas a t smokepipe e x i t

-

O F 130

Temp. drop in smokepipe - OF 180

Draft -inches water gauge 0.02

0.15) surge 0.17 0.20 CO2 - $ by volume CO

-

$ by volume 02

-

$ by volume

F L U E GAS TEMPERATURE AT SMOKEPIPE E X l T (CHIMNEY E N T R Y ) IN O F

FIGURE 1

D R A F T

VS

F L U E

GAS

TEMPERATURE

AT

SMOKEPIPE E X l T (CHIMNEY

ENTRY)

D B R . R E P O R T 9 2

DAMPER POSITIONS INDICATED ON GRAPH

7

3

CLOSED OPEN CLOSED

2

CLOSED OPEN OPEN

-

CODE

NUMBER

ASHPIT DOOR DAMPER

SMOKEPIPE DAMPER

FUEL DOOR SLIDE

1

CLOSED CLOSED

FIGURE

3

0 W I N D O W S STAIRWELL L DOORS I WINDOWS a DOORS

SIMPLIFIED

DIAGRAM

OF

192

STOREY

HOUSES

h

AT

AMHERSTBURG,

ONTARIO.

DBR R E P O R T 92

L

AMBIENT HOUSE CHIMNEY AMelENT

To Th Tc To

- - -

[

STAIRWELL L DOORS DAMPER h 3 Po.1 ''1 t !' 1'