Patterson-Kelley MOD-04 Modu-FireGas-Fired Boiler Gas Supply Piping by Installer, Piping Design

Modu-Fire®Gas-Fired Boiler

3.7.1 Gas Supply Piping by Installer

The boiler and all gas piping connections should be pressure-tested and must be checked for leaks be- fore being placed into service. Test with com- pressed air or inert gas if possible.

The boiler must be disconnected at the boiler man- ual shut-off valve (located at the end of the supplied gas train) from the gas supply piping system during any pressure testing of the system at pressures in excess of 1/2 psig (14 inch w.c.).

During any pressure testing of the gas supply piping system at pressures equal to or less than 1/2 psig (14 inch w.c.), the boiler should be isolated from the gas supply piping system by closing the manual shut- off.

Some leak test solutions, including soap and water, may cause corrosion. These solutions should be rinsed-off with water after testing.

3.7.2 Gas Bleeds and Vents by Installer

If your unit is equipped with a diaphragm gas valve, the bleed vents on the diaphragm gas valves have been factory-piped to terminate at the burner, as re- quired by ANSI Z21.13. This feature provides com- bustion of any gas which leaks past a ruptured dia- phragm during operation. Gas vents to outdoor air must be provided for the main pressure regulator. The pilot regulator is equipped with a vent limiting device and does not require external venting!

•When installing per ASME CSD-1, discon- nect factory piped bleed vents and vent the diaphragm gas valves to outdoor air (field piping.)

If a N.O. (normally open) vent valve is provided, it must be vented independently of any other bleeds and vents. Discharge of vent lines should be pro- tected by an insect screen.

The air gas ratio control valve is equipped with a “reference chamber vent filter” which does not re- quire any additional venting. This connection is labeled COMBUSTION / ATMOSPHERE.

If local conditions require venting to outdoors, the vent line connection must be piped by the installer

Installation

in accordance with the National Fuel Gas Code (NFPA 54), ANSI Z223.1, which states:

“In the case of vents leading outdoors, means shall be employed to prevent water from entering this piping and also to prevent blockage of vents by in- sects and foreign matter.”

The National Fuel Gas Code Handbook goes on to say that “Insects, insect nests, ice, or freezing rain can block outdoor vents....”

The pilot regulator is equipped with a vent limiting device and does not require external venting!

Gas Vents by Installer

Note: Provide a drip leg in all vent/bleed lines. All vent lines should be pitched up at all times to prevent building a trap into the vent line.

“Vent limiters” are NOT to be installed on this boiler.

The air gas ratio control valve is equipped with a “reference chamber vent filter” which does not re- quire any additional venting.

3.8BOILER WATER PIPING

3.8.1 Piping Design

Water Flow in System

Ideal operation of the P-K MODU-FIRE®Boiler would consist of a 20º F temperature differential across the heat exchanger at High fire. Insufficient flow may result in excessive short cycling of the boiler and eventual damage or premature failure of the equipment.

Minimum Return Water Temperature should be greater than 130º F to avoid problems of condensa- tion on the outside of the heat exchanger or in the flue passages.

Proper flow rates and return water temperature may be achieved through a combination of primary and secondary flow loops. Multiple zones and pumps may result in different flow rates at different times.

11