Install Instructions

CG i GAS-FIRED wATER BOILER- sERIEs a- Boiler Manual
4d
26
Piping - low temperature systems
BOILER-bypass piping
method
Th is piping method (Figure 22 or 23) is called a boiler-
bypass be ca use part of the circulat or flow is bypassed
around the boiler (through val ve 7a ). This m ethod
reduces th e fl ow ra te thro ugh o ut the boiler, in order to
raise the average water temperature in the boiler en oug h
to prevent flue
gas condensation. Boiler-bypass piping
is effective for some boilers - including the
CGi -
pro vided the fl ow rat es are adjusted according to the
instructions following.
Figures 22
and 23 are alternative piping suggestions
for converted gravity (large water content
or steam
systems)
or radiant heating system - for use when
primary/secondary piping
can't be applied (Figure 24
is another alternative, using system bypass in place
of
boiler-bypass piping. Figure 24 however, is not suitable
for radiant heating
app lications because it does n ot
protect the radiant system fro m possible high water
temperature.)
Boiler
-b ypass piping ke e ps system fl ow rate as high as
possible and temperature drop as low as possib
le, help-
ing to equalize the building heat distribution.
Temperature gauges
Gau ge 4a is optional if the bypass valves w ill be ad -
justed using cold (o r room temperature) return water
to the boiler. (When setting the valves without gauge
4a installed - using cold or room temperature water
- assmne the
re turn wa t er temperature to be 6Q•F. Set
the valves so gauge 8 reads at least t 20"F.
Gauge 4b is optional on converted gravity systems,
but required on radiant heating systems - to display
the water tempera
tur e being supplied to the radiant
tubin
g.
Gau ge 8 is required on all systems to assure reliable
adjustm
ent of the bypass valves. The bo il er -mounted
temperature/pressure
gauge can be used if a separate
temperature
gauge is n ot installed
Valve adjustment
t. Start with val ve 7a fully dosed and 7b fully open.
2. Gradually
open val ve 7a while dosing valve 7b
until the temperature at gau ge 8 reads 60 °F higher
than gauge
48 . A minimum 60°F temperature rise
through the boiler assures a low eno
ugh fl ow rate
and high eno ugh average temperature to prevent
condensation even with low system
return water
temperature.
3. Valve 7a regulates th e system fl ow rate, wllile valve
7b regulates th e boiler fl ow rate.
4. The boiler-mounted tempera tur e/pressure gauge
may
be used in place of a separate gau ge 8.
I& WARNING !
Failure to prevent low return water temperature 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 should include a means
of r egulating the boiler r eturn
water temperature and the system supply temperature (s uch as provided by an InJec-
tion pumping cont rol ).
Boiler return water temperature will be adequately co ntr olled using th e methods shovm
in this manual provi ded the system supply temperature is relatively cons tent.
DO NOT apply the methods of this manual if the sys tem is equipped with an outdoor
r eset cont rol . Inste ad , provtde controls and piping which can r egulate the boiler re-
turn water temperature at no less than 130 °F regardless of sys tem supply temperature.
Contact your We il-Mcl.ain representat ive for suggested piping and control methods.
Failure to
prevent cold r eturn water temperature to the bo il er co uld cause corrosion
damage to
the sections or burners, resulting in possible severe personal injury, death or
substantial
pr operty damage.
Part Number 550-142-780/0712