Install Instructions
CG
i
GAS-FIRED
wATER
BOILER-
sERIEs
a-
Boiler
Manual
4d
28
Piping - low
temperature
systems
SYSTEM-bypass
piping
me
thod
This
piping method
is
called a
system-bypass
because
pa
rt
of
th
e circulator
fl
ow
bypasses the system (
thr
ough
valve
7a). This bypassed
hot
water
fro
m the boiler outlet
mixes wi
th
cool
er
system
return
water
temperature in
order
to
provide minimum
130°F
return
water
to
the
boiler.
Valve
7b
will m
ost
often be full open,
but
may
need to
be
slightly
dosed
on
some low pressure drop sys-
tems
in
o
rd
er
to cause enough
fl
ow
through
va
lve 7a.
Figure
24
is an alternative piping
method
that provides
return water temperature control for boilers installed
on
converted
gravity
systems
(large water content
or
steam systems).
Do
not
apply
the
piping
of
Figure
24
on
radiant
heat
-
ing
systems
. It provides no method regulating the water
temperature provided to the system
and
could result
in
excessi
ve
water
temperature
in
the
radiant
tubing.
System-bypass piping as shown
in
Figure
24
can be used
with either zone
va
l
ve
or
circulator zonin
g.
When used
with
circ
u
lator
zon
in
g
however,
the boiler
circulator
(item 3
),
mu
st
be piped as shown.
It
cannot be used as
one
of
the zoning circulators.
Do
not apply system-bypass pip
in
g
if
th
e reduced
fl
ow
in
the system could cause
poor
heat distribution.
That
is, system-bypass piping reduces
th
e
fl
ow
in
th
e system
and
increases the water tempera
tur
e supplied to
the
system.
This
can cause increased h
eat
from radiators
at
the
beginning
of
the
system and reduced heat from
radiators near the
end
of
the
system.
Val
ve
adju
st
ment
I.
Start
with val
ve
7a fully
dosed
and
7b
fully open.
2. Gradually
ope
n val
ve
7a while dosing valve
7b
until
the temperature
at
gauge 8 reads
at
least 1
30
°F
at
all
times.
3.
Valve
7a regulates the amountofboiler supply water
mixed wi
th
re
turn
water.
Valve
7b
causes a pressure
drop
in
the system needed to balance
fl
ow
through
valve 7a
and
the system.
4.
The
valve
adjustment
sho
uld be
do
ne with
the
system at the coldest expected temperature (600F
for converted gravity systems
or
high mass radiant
systems).
I&
WARNI
NG!
Failure to
prevent
low
return
water
tempe
r
ature
to
the
boiler could cause corrosion
of
the boiler sections or burners, resulting in severe personal injury, death or substantial
property damage.
Radiant heating system piping shou
ld
in d
ude
a means
of
r
egulating
the
boller r
eturn
water
temperature
and
the
system
supply
temperatu
re
(s
uch as provided by an InJec-
tion
pumping
cont
rol).
Boiler return water temperature will be adequately co
ntr
olled using the
meth
ods shovm
in this manual provided the
system
supply
tempe
r
ature
is relatively
cons
tent.
DO
NOT
apply the methods
of
this manual if the system is equipped with
an
outdoor
r
eset
cont
rol. Instead, provtde
controls
and
piping
which
can
r
egulate
the
boller
re-
turn
water
tempe
r
ature
at
no
less
than
130'F
regardless
of
system supply temperature.
Contact your
Weil
-Mclain representative
fo
r suggested piping
and
control methods.
Failure to
prevent
cold
r
eturn
water
temperatu
re
to
the
bo
il
er could cause corrosion
damage to
the
sections or burners, resulting in possible severe personal inju
ry,
death or
substantial property dan1age.
Part
Number
550
-
142-780/07
12