GOLD CGs 
3d Piping — low temp systems
Primary/secondary (preferred) bypass piping method
Primary/secondary bypass piping is preferred because the flow rate and temperature drop in the heating circuit(s) is determined only by the heating circuit circulator(s). So adjustment of the bypass valves in the boiler circuit will not cause a change in the heating circuit rate and temperature distribution.
Figures 8 and 9, page 19, show suggested bypass ar- rangements using primary/secondary bypass piping (preferred) for low temperature systems such as radiant heating systems or converted gravity systems. For alternatives, see pages 20 through 23.
The bypass valves in Figures 8 and 9 (items 7a and 7b) provide mixing of hot boiler outlet water with cooler system return water — set to assure a minimum return water temperature (at least 130°F) to the boiler. Set the valves as explained below.
Temperature gauges
Gauge 4a is suggested, but optional on any system.
Gauge 4b is optional on converted gravity systems, but required on radiant heating systems — to display
the water temperature being supplied to the radiant tubing.
Gauge 8 is required on all systems to assure the return water temperature is accurately set for a minimum of 130°F. If this gauge is not available however, adjust the valves such that the
Valve adjustment (Figures 8 and 9 only)
1.Set the valves while the system is cool, setting for the coldest expected water temperature (usually 60°F since the system will often drop to room tempera- ture between cycles).
2.Start with valve 7a fully closed and 7b fully open.
3.Gradually open valve 7a while closing valve 7b until the temperature at gauge 8 reads 130°F when gauge 4a reads 60°F.
4.Note that valve 7a regulates the amount of hot wa- ter from the boiler supply which mixes with return water.Valve 7b regulates the amount of system water flowing through the boiler secondary loop.
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
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.
18
Part number