Section 7.03 - Installation of Burners and Controls(1)Main Burners. (a) Each burner assembly and its component parts shall be installed according to the manufacturer's instructions and shall be properly and firmly secured in place to maintain correct alignment in normal use.(b) The burner assembly shall be installed so that sufficient accessibility is afforded for cleaning, inspection, repair, and replacement of all burners, controls and safety devices.(c) Burner assembly parts, when adjustable, shall be provided with suitable locking devices to prevent accidental shifting.(d) Provision shall be made to permit ready observation of each pilot and main burner flame during adjustment and under operating conditions.(e) A burner assembly, when adjusted according to the manufacturer's instruction, shall maintain satisfactory operating characteristics as specified in 248 CMR 7.04(5) at all firing rates called for by input and air-gas ratio controls applied to the installation.(2)Control Application. (a) Each control shall be supported in such a manner that it and its sensing element will remain in proper position. It shall be possible to determine by observation or test that each control is in its proper location and capable of functioning as intended.(b) Nothing shall be provided for the purpose of permitting any safety control to be rendered ineffective or allowing firing of the burner assembly without the protection of all of the specified safety controls except as permitted by 248 CMR 7.03(2)(c).(c) A low-water cutoff may be bypassed for blow-down purposes only. Such a bypass shall be of a type which must be manually held in the bypass portion and which is self-restoring when released.(d) A burner assembly not equipped to provide safe automatic restarting shall be arranged to require manual restart after any control functions to cause the fuel supply to be shut off and the following restoration of an interrupted power supply.(e) The safety-control circuit shall be two-wire, one side grounded, having a nominal voltage of 150 volts or less. The circuit shall be connected to a branch circuit that can be protected against over current at not more than the value appropriate for the rating of the electrical components included in the circuit.(f) A safety control or protective device switch shall interrupt the ungrounded conductor(s).(g) Safety controls shall not depend on electricity to attain the off position.(3)Control of Combustion Air. (a) An air shutter shall be capable of being readily adjusted to any desired setting and securely locked to prevent accidental change in setting.(b) The air inlet(s) shall supply an adequate amount of air for combustion under the specified draft conditions and at the maximum firing rate of the burner assembly as installed. All air required for combustion shall be introduced in a manner so as to provide thorough mixing of the gas and air. If a burner is intended for installation with an air or wind box(es), it shall be supplied by the burner manufacturer or be built in accordance with the burner manufacturer's instructions.(c) Linkage for controlling air and gas input rates shall be designed to reliably maintain the correct gas-air ratio and to resist accidental damage and disengagement.(d) Equipment having forced or induced draft fans or both, shall be provided with means to automatically continue safe combustion or to shut off the gas supply upon failure of the equipment supplying the air.(e) If air under pressure is mixed with the gas supply in a mixer, effective means shall be provided to prevent air from passing back into the gas line or gas into the air supply. The gas and air supply shall be controlled to prevent gas from entering burners until the air supply is available and, in the event of air failure, to shut off the gas supply.(4)Primary Safety Control (Flame Safeguard). (a) Unless a flame safeguard control is provided by the manufacturer, each burner assembly shall be provided with a non-recycling primary safety control that will de-energize the main gas safety shutoff valve(s) upon loss of flame at point of supervision.(b) Safety control timings shall not exceed the values given in 248 CMR 7.03: Table 1.(c) Gas to pilots shall be automatically shut off if the pilot is not proved, and safety shutdown established.(d) Pilot supervision by the primary safety control shall be only at the point where the pilot flame will effectively ignite the gas at the main burner or burner group with the pilot burning at any flame that will actuate the safety control.(e) Supervision of the main burner flame only shall begin at the end of the main burner flame-establishing period for: 1.Power burners having a firing rate per combustion chamber of 2,500,000 Btu per hour and over. TABLE 1 Maximum Safety Control Timings Maximum Firing Rate Per Combustion Chamber in Million Btu Per Hour |
2.5 or less | Over 2.5 to 12.5 | Over 12.5 |
Pilot Flame Establishing Period | 15 Seconds | 10 Seconds | 10 Seconds |
Main Burner Flame Establishing Period (If Required) | 15 Seconds * | 10 Seconds | 10 Seconds * |
Flame Failure Response Time | 4 seconds | 4 Seconds | 4 Seconds |
Valve Closing Time | 5 Seconds | 1 Second | 1 Second |
* Main burner flame-establishing period may be 30 seconds for burner other than power burners equipped with a safety shutoff valve having a full opening time of not less than 25 seconds.
2.All types of burners with modulating or high-low firing rate per combustion chamber of 2,500,000 Btu per hour and over.3.All types of burners with an interrupted pilot(s), and4.Atmospheric type burners having a firing rate per combustion chamber of 5,000,000 Btu per hour and over. If the main burner flame is not proved, safety shutdown shall be established.(f) A burner assembly shall be equipped so that no gas can flow to the main burner on burner group operating as a unit unless the pilot is proved.(g) If two or more burner assemblies are installed in a single piece of equipment, the primary safety control of each burner assembly shall operate independently of the other, or equivalent safety features shall be provided so that in no case can any one burner operate unsafely.(5)Limit Controls. (a)Limit Control. 1.A limit control shall be provided to prevent excessive steam pressure in a steam boiler or excessive pressure or temperature in a hot water boiler.2.Each steam and hot water boiler shall be equipped with a control which will prevent firing of the boiler in the event of insufficient water in the boiler.3.The limit control shall be in addition to operating controls. Manual restart shall be required after a pressure or temperature limit control functions.(b) A limit control which functions by opening a switch shall directly open the electrical circuit to the safety shutoff valve(s).(6)Combustion (Input) Control Systems. (a) The combustion (input) control system shall maintain predetermined air-fuel mixtures within the limits required by the burner for stable combustion throughout the entire operating range of the burner and during changes in the firing rate.(b) To accomplish changes in the firing rate, the fuel and air supplies shall be maintained at a pre-determined optimum air-fuel ratio, either manually or automatically.(c) Burners having a firing rate per combustion chamber of 1,000,000 Btu per hour and over shall be equipped with a proven low-fire start.(d) Burners having a firing rate per combustion chamber of 2,500,000 Btu per hour and over shall be provided with combustion control.(7)Pilots. (a) Main burners shall be equipped with a supervised pilot adequate to provide safe main burner ignition under all conditions of operation. Multiple burner heads operated as a single burner unit shall use a sufficient number of supervised pilots to accomplish safe ignition.(b) A pilot burner not automatically lighted shall be located so that it can be safely lighted manually.(c) Gas supply pressure to the pilot or group of pilots: 1.The gas supply pressure to the pilot or group of pilots shall be regulated.2.The regulator(s) shall be listed; and vented in accordance with 248 CMR 7.03(11)(c), unless constructed or equipped to limit the escape of gas from the vent opening in the event of diaphragm failure to not more that 2.5 cubic feet per hour.3.The pilot supply line shall be connected upstream of all main burner valves and the main gas pressure regulator.(d) Primary air openings and orifices shall be easily accessible for servicing.(e) An electric ignition system shall ignite only a pilot.(f) If means for ignition is cut off at the termination of either the main burner flame-establishing period, the ignition shall remain off for the duration of that firing cycle and for the specified purge period.(g) A pilot burner, electric igniter, and pilot flame sensing device shall be supported in such a manner that their position relative to each other and to the main burner port(s) will remain fixed.(8)Gas Valve Pressure Ratings. (a) Gas valves shall be capable of withstanding without damage a pressure of not less than 10% above the relieving pressure of the nearest upstream relief device.(b) In case no relief device is provided, the gas valves shall be capable of withstanding without damage a pressure of not less than the maximum inlet pressure of the nearest upstream gas pressure regulator or the maximum setting of the over-pressure protection device.(9)Manually Operated Gas Shutoff Valves. (See 248 CMR 7.03: Figures 1 and 2.) (a) A manually operated main burner shutoff valve shall be installed in the line supplying all main burners of each piece of equipment and upstream of all other main burner control valves.(b) A manually operated main pilot shutoff valve shall be located in the gas supply line to the pilot burner.(c) Manually operated main shutoff and pilot shutoff valves in sizes larger than two inches or for pressures greater than 1/2 psig shall be of the lubricated plug or ball type with stops. Manually operated valves shall have the handle securely attached parallel to the gas flow in the open position, shall be readily accessible, and shall clearly indicate the "on" and "off" positions.(d) A manually operated main burner test valve (checking gas cock) shall be provided downstream from the safety shutoff valve for each main burner. On manually lighted burners, the valves shall be interlocked with the safety control circuit and arranged so that the main burner safety shutoff valves must be opened against their associated closed test valves.(e) In multiple burner installations a manual valve shall be provided for each main and each pilot burner except those utilizing a single zero governor inspirator mixer for several burners in which case this valve shall be located at a point immediately upstream of the zero governor.(f) Provisions shall be made so that the gas supply to equipment may be shut off from a location outside the room where said equipment is located. FIGURE 1
Illustration of Manual Valving Arrangement for a Multiple Burner, Single Boiler Arrangement Click to view image
FIGURE 2
Illustration of Manual Valving Arrangement for a Multiple Burner, Single Boiler Arrangement Click to view image
(10)Control and Safety Shutoff Valves. (See 248 CMR 7.03: Figure 3.) (a) An automatic input control valve may be in combination with a safety shutoff valve.(b) A bypass to provide for minimum flame may be installed around a valve to control input only. A bypass shall not be installed around a safety shutoff valve or a combustion input control and safety shutoff valve.(c)Safety Valves: 1.Each main burner supply line and each pilot supply line shall be equipped with a safety shutoff valve(s) which will close independent of external force.2.The safety shutoff valve(s) shall close with sufficient force to provide tight shutoff under normal operating conditions and when closed by the safety control system or by an emergency device.3.If the maximum firing rate per combustion chamber exceeds 1,000,000 BTU/hour, the main burner supply line shall be equipped as indicated in 248 CMR 7.03(10)(c)3.a. and b.: a.Two safety shutoff valves, in series, or one safety shutoff valve of the type incorporating a valve seal overtravel interlock, when the maximum firing rate per combustion chamber exceeds 1,000,000 BTU/hour but less than 5,000,000 BTU/hour.b.Two safety shutoff valves, in series, one of which is of the type incorporating a valve seal overtravel interlock when the maximum firing rate per combustion chamber exceeds 5,000,000 BTU/hour. The Board may prescribe two safety shutoff valves in series, for combustion chambers with inputs less than 1,000,000 BTU/hour, in buildings of public assembly.
(d) Safety shutoff valves shall be suitable for the application and shall have a shutoff time not to exceed that specified in 248 CMR 7.03: Table 1. They shall be constructed so that they cannot be restrained or blocked in the open position. Such valves shall close upon being de-energized regardless of the positions of damper-operating levers or reset handles.(e) An electrically operated safety shutoff valve shall not depend on electricity to shut off the gas supply.(f) A pressure-operated safety shutoff valve shall close upon failure of its operating pressure.(g) Permanent and ready means for making easy, accurate, periodic tightness tests of the main burner gas safety shutoff valves shall be provided in the piping. FIGURE 3A.
Illustration of Gas Train 248 CMR 3.00 through 7.00 requirements 400,000 to Less Than 1,000,000 BTU/hour Input Click to view image
FIGURE 3B.
Illustration of Gas Train 248 CMR 3.00 through 7.00 1,000,000 to Less Than 2,500,000 BTU/hour Input Click to view image
FIGURE 3C.
Illustration of Gas Train 248 CMR 3.00 through 7.00 requirements for 2,500,000 to less than 5,000,000 BTU/hour Input Click to view image
FIGURE 3D
Illustration of Gas Train 248 CMR 3.00 through 7.00 requirements for 5,000,000 to less than 12,500,000 BTU/hour Input Click to view image
(11)Main Gas Pressure Regulators and Gas Pressure Interlocks. (a) Each burner assembly shall be equipped with a listed main gas pressure regulator that will regulate within plus or minus 10% of the operating pressure at all firing rates. (See 248 CMR 7.03: Figure 3 for location).(b) Spring or weight-loaded regulators shall have springs covered by a suitable housing. Under no circumstances shall a weight and lever type of regulator be used.(c)Main Gas Pressure Regulators: 1.Except where zero governors are used in connection with air-gas mixers, all main gas pressure regulators shall be independently vented to a safe outdoor location.2.Vent lines from main gas pressure regulators shall not be connected into a common line with the bleed line from gas operated diaphragm valves or from pressure relief valves.3.Vent lines shall be steel, wrought iron pipe or corrugated stainless steel tubing (CSST) with Product-approved devices provided at termination points to prevent stoppage of the lines by foreign material, water or insects and, shall extend no less than 18 inches above the roof surface.4.Vent lines shall be sized as specified in 248 CMR 7.03: Table 2.5.Vent lines shall be supported in accordance with 248 CMR 1.00 through 10.00.6.Vent lines shall be run to the outside using the shortest practical route and shall not be trapped or installed in a manner that restricts air-flow.7.Vent lines that penetrate roofs and sidewalls shall be run through metallic sleeves that are sealed from the weather and insects.8.CSST vent lines that penetrate roofs shall transition to steel pipe no less than one foot inside the building.9.Vent lines that terminate outside a building shall be located no less than four-feet away from any building opening or air intake and ten feet away from forced air intakes. Outside(d)Pressure Switches. 1.If the maximum firing rate per combustion chamber is 1,000,000 BTU/hour or over, gas pressure supervision shall be provided by listed pressure switches, or listed combination high-low switch, interlocked to accomplish a non-recycling safety shutdown in the event of either high or low gas pressure.2.Pressure setting shall be adjusted by the installer in accordance with the burner or equipment manufacturer's instructions.3.Pressure switches that require venting to the outside atmosphere shall be vented in accordance with 248 CMR 7.03(11)(c). Pressure switches only may be manifolded.(e) Accessible IPS plugged pressure tappings or connections shall be provided; one located upstream of the main gas pressure regulator and another located near the burner head to permit accurate measurement of gas pressure. (See 248 CMR 7.03: Figure 3.) TABLE 2
Minimum Pipe Size/CSST for Venting
Gas Train Components in 248 CMR 7.04 Figures 3a, 3b, 3c, and 3d.
Gas Train Components | Maximum lengths of iron pipe or corrugated stainless steel tubing (CSST) from components to outside the building |
0 - 40 feet | 0 - 100 feet | 0 - 200 Feet |
Main Gas Pressure Regulator - Steel Pipe Size - CSST Size (Low Pressure Gas only) | 3/4 inch IPS 30/31 EHD | 1 inch IPS 37 EHD | 11/4 inch IPS 46/48 EHD |
High & Low Gas Pressure Switches When Manifolded - Steel Pipe Size - CSST Size (Low Pressure Gas only | 3/4 inch IPS 30/31 EHD | 1 inch IPS 37 EHD | 11/2 inch IPS 60/62 EHD |
Block and Bleed Valves (when used) - Steel Pipe Size - CSST Size (Low Pressure Gas only | Full IPS Relief | Increase IPS/CSST one Size | Increase IPS/CSST two Sizes |
(12)Operating Sequencing. (See also 248 CMR 7.04, Initial Start-Up and Final Adjustments). Each installation shall be equipped to provide for sequencing in accordance with the following and in the order listed.
(a) Natural and mechanical draft systems with continuously burning pilot(s) capable of igniting any gas flowing from the main burner shall, upon demand for heat: 2.Prove combustion air flow for mechanical draft systems.3.Prove in light-off position, if either an automatically operated damper, or an automatically operated air shutter, or both, are employed.4.Prove combustion (input) control, if employed, in light-off position.6.Admit fuel to main burner.7.Prove main flame, if required, in accordance with 248 CMR 7.03(4)(e).8.Release combustion (input) control.9.Upon flame failure at point of supervision, shut off fuel by primary safety control.10.Shut off fuel to main burner on release from demand.(b) Natural draft systems with intermittent pilot or interrupted pilot shall, upon demand for heat: 2.Prove open for at least 90 seconds if either an automatically operated damper, an automatically operated air shutter, or both, are employed.3.Prove in the light-off position if either an automatically operated damper, and automatically operated air shutter, or both are employed.4.Prove combustion (input) control, if employed, in light-off position.6.Admit fuel to main burner.7.Prove main flame, if required, in accordance with 248 CMR 7.03(4)(e).8.Release combustion (input) control.9.Upon flame failure at point of supervision, shut off fuel by primary safety control.10.Shut off fuel on release from demand.11.If an automatically operated damper is employed, return to stand-by position.(c) Mechanical draft systems with intermittent pilot or interrupted pilot shall, on demand: 2.If an automatically operated damper is employed, prove in open position.3.Start fan(s) and prove air flow. Provide at least a four-air change purge of the combustion chamber and equipment passes. The four air changes must be accomplished in not more than 90 seconds with burners having maximum firing rate per combustion chamber of not more than 2,500,000 Btu per hour. With burners having maximum firing rates per combustion chamber in excess of 2,500,000 Btu per hour, the four air changes shall be accomplished without time limitation by an air flow rate not less than 60% of the air flow provided for the maximum firing rate.4.Prove combustion (input) control and automatically operated damper, if employed, in light-off position.6.Admit fuel to main burner.7.Prove main flame, if required, in accordance with 248 CMR 7.03(4)(e).8.Release combustion (input) control.9.Upon flame failure at point of supervision, shut off fuel by primary safety control.10.Shut off fuel on release from demand.11.If an automatically operated damper is employed, return to stand-by position.Amended by Mass Register Issue 1275, eff. 12/5/2014.