Weil-McLain 550-110-260/02002 manual 3e Water piping low temp systems

GOLD CGs Gas-Fired Water Boiler

3e Water piping — low temp systems

Boiler-bypass piping method

Temperature gauges

Valve adjustment

This piping method is called a boiler-bypassbecause part of the circulator flow is bypassed around the boiler (through valve 7a). This method reduces the flow rate throughout the boiler, in order to raise the average water temperature in the boiler enough to prevent flue gas condensation. Boiler-bypass piping is effective for some boilers — including the CGs — provided the flow rates are adjusted according to the instructions following.

Figures 10 and 11 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 12 is another alternative, using system bypass in place of boiler- bypass piping. Figure 12 however, is not suitable for radiant heating applications because it does not protect the radiant system from possible high water temperature.)

Boiler-bypass piping keeps system flow rate as high as possible and temperature drop as low as possible, helping to equalize the building heat distribution.

Gauge 4a is optional if the bypass valves will be adjusted using cold (or room temperature) return water to the boiler. (When setting the valves without gauge 4a installed — using cold or room temperature water — assume the return water temperature to be 60 °F. Set the valves so gauge 8 reads at least 120 °F.

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 reliable adjustment of the bypass valves. The boiler-mounted temperature/pressure gauge can be used if a separate temperature gauge is not installed.

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 60 °F higher than gauge 4a. A minimum 60 °F temperature rise through the boiler assures a low enough flow rate and high enough average temperature to prevent condensation even with low system return water temperature.

3.Valve 7a regulates the system flow rate, while valve 7b regulates the boiler flow rate.

4.The boiler-mounted temperature/pressure gauge may be used in place of a separate gauge 8.

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 injection 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 return 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.

20 Part number 550-110-260/0200