Weil-McLain 550-110-260/0508 manual SYSTEM-bypass piping method

GOLD CGs Gas-Fired Water Boiler — Boiler Manual

3d Piping — low temp systems (continued)

SYSTEM-bypass piping method

This piping method (Figure 12, page 23) is called a sys- tem-bypassbecause part of the circulator flow 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 flow 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 flow in the system could cause poor heat distribution. That is, system-bypass piping reduces the flow 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 flow 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).

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.

22 Part number 550-110-260/0508