Honeywell T874R - Operation and Installation Basics; System Operation Details; Important Safety Precautions; Thermostat Location Guidelines

T874R THERMOSTATS AND Q674L SUBBASES
OPERATION
O n a 2 -h e a t th e rm o s ta t, th e tw o s ta g e s o f h e a t make
s e q u e n tia lly a s th e te m p e ra tu re d ro p s . M ake re fe rs to th e
m e rc u ry s w itc h in itia tin g a c a ll fo r h e a t o r c o o l.
T h e re is a b o u t 1° F (0 .6 ° C ) b e tw e e n s ta g e s s o th e s e c 
o n d s ta g e m a k e s o n ly w h e n th e firs t s ta g e c a n n o t h a n d le
th e lo a d . T h e 1 ° F (0 .6° C ) is re fe r re d to a s th e interstage
differential
T h e lig h t e m ittin g d io d e s (L E D ) o n th e s u b b a s e lig h t w h e n
s o m e th in g s p e c ific h a p p e n s w ith in th e s y s te m . W h e n a n
L E D lig hts , re fe r to th is lis t fo r th e m e a nin g :
E M . H T .: E m e rg e n c y h e a t is o p e ra tin g . T h e c o m p re s 
s o r h a s fa ile d , a n d th e h e a t p u m p is n o t o p e ra tin g .
L E D lig h ts w h e n s y s te m s w itc h is p la c e d in th e
E M .H T . p o s itio n b y th e h o m e o w n e r.
A U X .H T .: A u x ilia r y h e a t is o p e ra tin g , w h ic h m e a n s th e
w e a th e r is s o c o ld th a t th e h e a t p u m p c a n n o t h a n d le
th e lo a d .
C H E C K : S y s te m n e e d s to b e c h e c k e d . S e e h e a tin g
s y s -te m in s tru c tio n s fo r s p e c ific m e a n in g .
N O T E : L E D s a re n ot fie ld re p la c e a b le o r a dd a b le .
®) RECYCLING NOTICE
T h is c o n tro l c o n ta in s m e rc u ry in a s e a le d tu b e . D o no t
p la c e c o ntro l in th e tra s h a t th e e n d o f its u s e fu l life.
If th is c o n tro l is re p la c in g a c o n tro l th a t c o n ta in s
m e r- c u ry in a s e a le d tu b e , d o n o tp la c e y o u r o ld
c o n tro l in th e tra sh .
C o n ta c t y o u r lo c a l w a s te m a n a g e m e n t a u th o rity fo r
in s tr u c tio n s r e g a rd in g r e c y clin g a n d th e p ro p e r
d is p o s a l o f th is c o n tro l, o r o f a n o ld c o n tro l
c o n ta in in g m e rc u r y in a s e a le d tu b e .
INSTALLATION
When Installing this Product...
1. R e a d th e s e in s tru c tio n s c a re fu lly . F a ilu re to fo llo w
th e m c o u ld d a m a g e th e p ro d u c t o r c a u s e a h a z a rd 
o u s c o n d itio n .
2 . C h e c k th e ra tin g s g iv e n in th e in s tru c tio n s a n d o n
th e p ro d u c t to m a k e s u re th e p ro d u c t is s u ita b le fo r
y o u r a p p lic a tio n .
3 . In s ta lle r m u s t b e a tra in e d , e x p e rie n c e d s e rv ic e
te c h n ic ia n .
4 . A fte r in s ta lla tio n is c o m p le te , c h e c k o u t p ro d u c t
o p e ra tio n a s p ro v id e d in th e s e in s tru c tio n s.
A CAUTION
1. D is c o n n e c t p o w e r s u p p ly to p re v e n t e le c tric a l
s h o c k o r e q u ip m e n t d a m a g e .
2. T o p r e v e n t in te rfe re n c e w ith th e th e rm o s ta t
lin k a g e , k e ep w ire le n g th to a m in im u m a n d
ru n w ire s a s c lo s e a s p o s s ib le to th e s u b b a s e .
3. P u s h e x c e s s w ir e b a c k in to th e h o le a n d p lu g
h o le to p re v e n t d ra fts fro m a ffe c tin g th e rm o 
s ta t o p e ra tio n .
4. D o n o t o v e rtig h te n th e rm o s ta t c a p tiv e
m o u n tin g s c re w s b e c a u s e d a m a g e to
s u b b a s e th re a d s c a n re s u lt.
5. D o n o t s h o rt a c ro s s c o il te rm in a ls o n h e a tin g
re la y o r g a s v a lv e . T h is c a n b u rn o u t th e
th e rm o s ta t h e a t a n tic ip a to r.
6. N e v e r in s ta ll m o re th a n o n e w ir e p e r te rm in a l
u n le s s fa c to ry -s u p p lie d ju m p e r w ith s p a d e
te rm in a ls is us e d .
IMPORTANT
Thermostats are calibrated at the factory using
subbase mounted at true level Inaccurate
subbase leveling causes the actual temperature
to deviate from the setpoint temperature.
Location
In s ta ll th e th e r m o s ta t a b o u t 5 ft (1 .5 m ) a b o v e th e flo o r in
a n a re a w ith g o o d a ir c irc u la tio n a t a v e ra g e te m p e ra tu re .
D o n o t in s ta ll th e th e rm o s ta t w h e r e it c a n b e a ffe c te d b y:
— d ra fts o r d e a d s p o ts b e h in d d o o rs a n d in c o rn e rs .
— h o t o r c o ld a ir fro m d u c ts .
— ra d ia n t h e a t fr o m s u n o r a p p lia n c e s .
— c o n c e a le d p ip e s a n d c h im n e y s .
— u n h e a te d (u n c o o le d ) a re a s s u c h a s a n o u ts id e w a ll
b e h in d th e th e rm o s ta t.
Mounting The Subbase
T h e th e rm o s ta t s u b b a s e c a n b e m o u n te d o n a v e rtic a l
o u tle t b o x , h o riz o n ta l o u tle t b o x o r d ir e c tly o n th e w a ll.
1. If y o u m u st m o u n t th e s u b b a s e o n a v e rtic a l o u tle t
b o x, o rd e r H o n e y w e ll 1 9 3 1 2 1 A A d a p te r A s s e m b ly .
S e e F ig . 1. T h e a s s e m b ly in c lu d e s a n a d a p te r ring ,
tw o s c re w s a n d a c o v e r p la te to c o v e r m a rk s o n th e
w a ll. In sta ll th e rin g a n d c o v e r p la te on th e v e rtic a l
o u tle t b ox .
F o r a w a ll in sta lla tio n , h o ld s u b b a s e in p o s itio n a n d
m a r k h o le s fo r a n c h o rs . S e e F ig . 2. O b ta in w a ll
a n c h o rs lo c a lly . B e c a re fu l th a t th e w ir e s d o n ot fa ll
b a c k in to th e w a ll o p e n in g . S e t a s id e s u b b a s e . D rill
tw o 3 /1 6 in. (5 m m ) h o le s a n d g e n tly ta p a n c h o rs
in to th e h o le s u n til flu sh w ith th e w a ll.
69-0392—9
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