Install Instructions

CG i GAS-FIRED wATER BOILER- sERIEs a- Boiler Manual
4d
24
Piping - low temperature systems
Primary/secondary (pre fer re d)
bypass piping method
Primar y/secondary bypass piping is preferred because
the flow rate and tem perature drop in the heating
circuit(s) is determined
on ly by the heating circuit
circulator(s).
So adjustment of th e bypass valves in
the boiler circuit w ill not cause a change in the heating
circuit
rate and temperature distribution.
Figures
20 and 21 show suggested bypass arrangements
using
prima r y/secondary bypass piping (p referred)
for l
ow temperature systems suc h as radiant heating
systems or converted gravity systems . For alte rn a-
tives, see pages 26 through 29.
Th e bypass valves (items 7a and 7b ) provide mixing of
hot boiler outlet water with cooler system return water
- set to assure a minimum return water temperature
(a t least 1 30' F) to the boiler. Set the valves as explained
below.
Tem perature ga u ges
Gau ge 4a is suggested, but option al on any system.
Gau
ge 4b is optional on converted gravity system s,
but required on radiant heating systems - to display
the water temperature being supp
li ed to the radiant
tubin
g.
Gau ge 8 is required on all systems to ass ur e the re turn
wate r temperature is accurately set for a mi nimum of
I 300F. If this gauge is not available however, adjust the
valves such
tha t the boiler-m ou n ted temperature/pres-
sure gau
ge reads at least I SO ' F when the system return
water
is cold (approximately 60'F water temperature).
Val ve adju st ment
(
Fi gu res 20 a nd 21 only)
I. Setthe valves while th e system is cool, setting for th e
coldest expected water temperature (usually
600F
since the system will often drop to room tempera-
ture between cycles).
2.
Start with val ve 7a fully dosed and 7b fully open.
3. Gradually open valve 7a while dosing val ve 7b until
the temperature
at gauge 8 reads I 30 ' F when gauge
4a reads 60 ' F.
4. Note that val ve 7a regulates the amo unt of h ot wa -
ter from the boiler supply which mixes with re turn
wa ter. Valve 7b regulates the am ount of syste m water
flowing through
th e boiler secondary loop.
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 include 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 constant.
DO NOT apply the methods of this manual if the system is equipped with an outdoor
r eset cont rol. Inste ad , 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 550-142-780/0712