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Part number 550-110-260/0508
22
GOLD CGs Gas-Fired Water Boiler — Boiler Manual
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 regulating the boiler return
water temperature
and the system supply temperature (such as provided by an injec-
tion pumping control
).
Boiler return water temperature will be adequately controlled using the methods shown
in this manual provided the system supply temperature is relatively constant.
DO NOT apply the methods of this manual if the system is equipped with an outdoor
reset control.
Instead, provide controls and piping which can regulate the boiler re-
turn water temperature
at no less than 130°F regardless of system supply temperature.
Contact your Weil-McLain representative for suggested piping and control methods.
Failure to
prevent cold return water temperature to the boiler could cause corrosion
damage to the sections or burners, resulting in possible severe personal injury, death or
substantial property damage.
3d Piping — low temp systems (continued)
SYSTEM-bypass piping
method
This piping method (Figure 12, page 23) is called a sys-
tem-bypass
because part of the circulator fl ow bypasses
the system (through valve 7a). This bypassed hot water
from the boiler outlet mixes with cooler system return
water temperature in order to provide minimum 130°F
return water to the boiler. Valve 7b will most often be
full open, but may need to be slightly closed on some
low pressure drop systems in order to cause enough
fl ow through valve 7a.
Figure 12 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 12 on radiant heat-
ing systems
. It provides no method regulating the water
temperature provided to the system and could result in
excessive water temperature in the radiant tubing.
System-bypass piping as shown in
Figure 12 can be used
with either zone valve or circulator zoning. When used
with circulator zoning however, the boiler circulator
(item
3), must be piped as shown. It cannot be used as
one of the zoning circulators.
Do not apply system-bypass piping if the reduced fl ow
in the system could cause poor heat distribution. That
is, system-bypass piping reduces the fl ow in the system
and increases the water temperature supplied to the
system. This can cause increased heat from radiators
at the beginning of the system and reduced heat from
radiators near the end of the system.
Valve adjustment
1. Start with valve 7a fully closed and 7b fully open.
2. Gradually open valve
7a while closing valve 7b until
the temperature at gauge 8 reads at least 130°F at all
times.
3. Valve
7a regulates the amount of boiler supply water
mixed with return 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 should be done with the
system at the coldest expected temperature (60°F
for converted gravity systems or high mass radiant
systems).