Bradford-White Corp BJVS Water Connections, Water Piping, Adjusting the bypass, By-pass Piping

Page 12 BRADFORD WHITE CORP.

SECTION 5.

Water Connections

5.1 Water Piping

Figure 6 shows ‘typical’ plumbing installations. Be sure to provide unions and isolation valves at the boiler inlet and outlet so it can be isolated for service. Check local codes for specific plumbing requirements before beginning the installation.

An ASME pressure relief valve is supplied on all BJV boilers, and is pre-set at 30 PSI. The valve outlet piping must discharge to a drain. Under no circumstances should the relief valve piping be a closed circuit.

A pressure reducing valve (automatic feed) must be used to maintain system at constant proper pressure (see Figure 6). Supply properly installed purge valves to eliminate air from each circuit.

A drain valve is supplied with the boiler, and can be found in the plastic bag shipped with each boiler. This valve is to be installed on the lower right side of the boiler, see Figure 1, and is used for draining the unit. To drain the boiler completely, open the drain valve and remove the two drain plugs located on the lower left side of the boiler.

Be sure to include air vent devices located at the highest point in the system to eliminate trapped air, and an air elimination device near the outlet side of the BJV boiler. Manual vent valves are recommended.

Hot water piping should be supported by suitable hangers or floor stands, NOT by the boiler. Due to expansion and contraction of copper pipe, consideration should be given to the type of hangers used. Rigid hangers could transmit noise through the system caused by the piping sliding in the hangers. It is recommended that padding be used when rigid hangers are installed.

Gas piping should also be supported by suitable hangers or floor stands, not the boiler.

A properly sized expansion tank must be included in the system. offers an aircharged diaphragm-type expansion tank, with an automatic feed valve, which includes a pressure regulator set at

12 psig. The part numbers are:

Less Than 20 Gallons in System	A0066800
20 to 45 Gallons in System	A0066900

5.1.1 By-pass Piping

The following information and suggestions are made on by-pass piping as it affects the temperature rise at the boiler. A boiler temperature rise must be taken on all BJV boiler installations. If the temperature rise exceeds 30°F (17°C) at full rate, it is an indication that the boiler is not receiving adequate water flow. Check the pump for any obstruction, replace the pump with a larger size where necessary, or install a system by-pass as indicated in Figures 6 and 7.

A full sized, 1¼" bypass with balancing valves is strongly recommended for all systems, and required when: 1) the boiler is installed without primary- secondary piping in a multiple zone system; 2) when the return water temperature can be expected to be lower than 120°F (44°C); or 3) whenever the system piping on the outlet side of the boiler may allow reduced flow through the heat exchanger, causing excessive temperature rise (see Section 5.2).

Note: Bradford White strongly recommends a primary/secondary piping system for all installations, especially sizes 125, 160 and 225. In this system, a circulator is dedicated to pumping the boiler only. This circulator should be sized for the boiler head loss and flow rate.

All precautions must be taken by the installer to insure that a maximum temperature rise through the boiler does not exceed 30°F (17°C). The temperature rise on boilers installed in multi-zone systems using zone valves must be taken when the zone of the longest length and/or the zone of the highest head loss is open.

Afull size, 1¼" diameter by-pass with balancing valve must be installed if a return water temperature below 120°F (44°C) is expected under operating conditions regardless of boiler size. This may be expected in many systems, including in- floor radiant and snow melt systems.

Adjusting the bypass:

Refer to figure 7. Provide a means of measuring temperature on the inlet pipe to the boiler such as using a strap on or infrared themometer. Starting with both balancing valves fully open, start the boiler. Adjust the balancing valve on the return to the system slowly to provide 120°F (44°C) water at the inlet to the boiler, leaving the bypass balancing valve fully open. As the system warms up, this valve may need to be adjusted open. In rare cases, this valve will have to be kept fully open, and the bypass balancing valve adjusted toward closed to prevent heated bypass water from satisfying the call for heat when the system is up to temperature.

5.2 Alternate Auto-Bypass Operation

Use of the themostatic union, p/n 2400-030, can provide automatic bypass operation in primary - secondary piped systems (but cannot be used when primary - secondary piping is not used). The thermostatic union is installed on the outlet piping, after the bypass assembly. It can be used in place of a balancing valve. It opens fully at 140°F (see Figure 6). Contact the factory for more information.