(a) Expansion tanks.

1. (1)

   1. (A) If the system is equipped with an open expansion tank, an internal overflow from the upper portion of the expansion tank must be provided in addition to an open vent, the internal overflow to be carried within the building to a suitable plumbing fixture or to the basement.
   2. (B) If the system is of the closed type, an airtight tank or other suitable air cushion must be installed that will be consistent with the volume and capacity of the system.

2. (2)

   1. (A) If a system is equipped with a check valve or pressure-reducing valve in the cold water inlet line, consideration should be given to the installation of an airtight expansion tank or other suitable air cushion.
   2. (B) Otherwise, due to the thermal expansion of the water, the safety relief valve may lift periodically.
   3. (C) If an expansion tank is provided, it shall be constructed in accordance with Section VIII Division 1 for a maximum allowable working pressure equal to or greater than the water heater.
   4. (D) Except for prepressurized tanks, provisions shall be made for draining the tank without emptying the system. Recommended Expansion Tank Capacities for Gravity Hot Water Systems Based on two-pipe system with average operating water temperature 170° F, using cast iron column radiation with heat emission rate 150 Btu/hr sq ft equivalent direction radiation

      Installed Equivalent	Tank Capacity,
      Direct Radiation, sq ft	gal
      [Note (1)]
      Up to 350	18
      Up to 450	21
      Up to 650	24
      Up to 900	30
      Up to 1100	35
      Up to 1400	40
      Up to 1600	2-30
      Up to 1800	2-30
      Up to 2000	2-35
      Up to 2400	2-40

      NOTE: For systems with more than 2400 sq ft of installed equivalent direct water radiation, the required capacity of the cushion tank shall be increased on the basis of one gallon tank capacity per 33 sq ft of additional equivalent direct radiation. Recommended Expansion Tank Capacities for Forced Hot Water Systems Based on average operating water temperature 195° F, fill pressure 12 psig, and maximum operating pressure 30 psig

      	Tank Capacities, gal
      System Volume,	Prepressurized	Nonprepressurized
      gal	Diaphragm Type	Type
      100	9	15
      200	17	30
      300	25	45
      400	33	60
      500	42	75
      1,000	83	150
      2,000	165	300

      NOTE: System volume includes volume of water in boiler, radiation, and piping, not including the expansion tank. Expansion tank capacities are based on an acceptance factor of 0.4027 for prepressurized types and 0.222 for nonprepressurized types. A procedure for estimating system volume and determining expansion tank sizes for other design conditions may be found in Chapter 13 of the 1987 Systems and Applications Volume of the ASHRAE Handbook.

(b)

1. (1) The return water connections to all low-pressure steam heating boilers supplying a gravity return heating system shall be so arranged as to form a loop substantially as shown in Section 4 of the ASME Boiler Construction Code, the bottom of the return pipe close nipple where it enters the equalizing loop being at the same level as the top of the lower water gauge glass nut.
2. (2) Equalizing pipe sizes shall not be less than the following:

   GRATE AREA	EQUALIZING PIPE INCHES
   Under 4 sq. ft	1 ½
   4 to 15 sq. ft	2 ½
   15 sq. ft and over	4

(d)

1. (1) When a stop valve is used in the supply pipe connection of a single boiler, there shall be one (1) used in the return pipe connection.
2. (2) When stop valves over two inches (2”) in size are used, they shall be of the outside-screw-and-yoke-rising-spindle type or of such type as to indicate at a distance by the position of its spindle or other operating mechanism whether it is closed or open, and the wheel may be carried either on the yoke or attached to the spindle.
3. (3) If the valve is of the plug-cock type, it must be fitted with a slow-opening mechanism and an indicating device, and the plug must be held in place by a guard or gland.
4. (4) When stop valves are used, they shall be properly designated substantially as indicated by the following tags of metal or other durable material fastened to them:

   Supply Valve-Number ( )Do Not Close Without Also Closing Return Valve –Number ( )

   Return Valve-Number ( )Do Not Close Without AlsoClosing Return Valve –Number ( )

(j)

1. (1) Should a situation arise which is not covered by this part, the ASME code Section One (I) for Power Boilers and Section Four (IV) for Heating Boilers shall be consulted.
2. (2) Should Section Four (IV) for Heating Boilers not cover the situation, Section One (I) shall be consulted, even though the object may come under Section Four (IV).

(k) Feedwater connections.

1. (1)

   1. (A) Feedwater connections shall be independent of any water gauge connections and it is recommended that the connection be made to the condensate return pipe or reservoir of the condensate return pump.
   2. (B) There should be a stop valve and a check valve in the feedwater line of the boiler.
2. (2) Feed or make-up water shall not be discharged directly into any part of the boiler exposed to the direct radiant heat of the fire.
3. (3) A bypass shall be provided around any pump or trap.
4. (4) Feedwater shall not be introduced through the openings or connections used for the water column, the water gauge, or the gauge cocks.
5. (5) The boiler-feed line shall be adequate to take care of the maximum demand of the boiler.
6. (6) A manual bypass shall be provided around any feedwater pressure-reducing regulator on all hot water heating boilers.
7. (7) Each boiler equipped with a condensate return pump, where practicable, shall be provided with a water level control arranged to automatically maintain the water level in the boiler within the range of the gauge glass.

8. (8)

   1. (A) Hot water heating and hot water supply boilers shall have a flow switch installed to detect loss of water flow through the boiler.
   2. (B) It shall be so located in the line that it cannot be isolated from the boiler through valve manipulation.

(l) Bottom blowoff.

1. (1) Each boiler shall have one (1) or more blowoff pipe connections fitted with straightaway valve or cocks of not less than three-fourths-inch pipe size connected directly with the lowest water space and so located that the discharge shall not constitute a hazard.
2. (2) All washout plugs and handhole openings shall be accessible and shall not be obstructed in any way.
3. (3) All hot water heating systems shall be so installed that there will be no opportunity for the fluid-relief column to freeze or to be accidentally shut off.

(m) Safety valves.

1. (1)

   1. (A) Each steam boiler shall have one (1) or more safety valves of the spring-pop type adjusted and sealed to discharge at a pressure not to exceed fifteen pounds per square inch (15 psi).
   2. (B) Seals shall be attached in a manner to prevent the valve from being taken apart without breaking the seal.
   3. (C) The safety valves shall be arranged so that they cannot be reset to relieve at a higher pressure than the maximum allowable working pressure of the boiler.

2. (2)

   1. (A) Each safety valve three-fourths inch (3/4”) or over, used on a steam heating boiler, shall have a substantial device which will positively lift the disk from its seat at least one-sixteenth inch (1/16”) when there is no pressure on the boiler.
   2. (B) The seats and disks shall be of suitable material to resist corrosion.

3. (3)

   1. (A) No safety valve for a steam boiler shall be smaller than three-fourths inch (3/4”) except in case the boiler and radiating surfaces are a self-contained unit.
   2. (B) No safety valve shall be larger than four and one-half inches (4 1/2").
   3. (C) The inlet opening shall have an inside diameter approximately equal to, or greater than, the seat diameter.

(n) Relief valves.

1. (1)

   1. (A) Each hot water heating or hot water supply boiler shall have one (1) or more relief valves of the spring-loaded type, without disk guides on the pressure side of the valve.
   2. (B) The valves shall be set to relieve at a pressure at or below the maximum allowable working pressure of the boiler and so arranged that they cannot be reset to relieve at a higher pressure than the maximum allowable working pressure of the boiler.
2. (2) Each relief valve shall have a substantial device which will positively lift the disk from its seat at least one-sixteenth inch (1/16”) when there is no pressure on the boiler.

3. (3)

   1. (A) The seats and disks shall be of material suitable to resist corrosion.
   2. (B) No materials liable to fail due to deterioration of vulcanization when subjected to any temperature not exceeding two hundred fifty degrees Fahrenheit (250° F) shall be used for any part.

4. (4)

   1. (A) No relief valve shall be smaller than three-fourths inch (3/4”) nor larger than two-inch standard pipe size.
   2. (B) The inlet opening shall have an inside diameter approximately equal to, or greater than, the seat diameter.

(o) Installation of safety and relief valves.

1. (1) Safety valves shall be connected to boilers with the spindle vertical, if possible, either directly to a tapped or flanged opening in the boiler, to a fitting connected to the boiler by a close nipple, to a Y base, to a valveless steam pipe between adjacent boilers, or to a valveless header connecting steam outlets on the same boiler.
2. (2) Relief valves shall be connected to the top of boilers with a spindle vertical, if possible, either directly to a tapped or flanged opening in the boiler, to a fitting connected to boiler by a close nipple, to a Y base, to a valveless water pipe between adjacent boilers, or to a valveless header connecting water outlets on the same boiler.
3. (3) When a Y base is used, the inlet area shall be not less than the combined outlet areas.

4. (4)

   1. (A) When the size of the boiler requires a safety valve larger than four and one-half inches (4 1/2") in diameter or a relief valve larger than two inches (2”) in diameter, two (2) or more valves having the required combined capacity shall be used.
   2. (B) When two (2) or more valves are used on a boiler, they may be:

(i) Single;

1. (ii) Directly attached; or

   1. (iii) Mounted on a Y base.

2. (5)

   1. (A) No shutoff of any description shall be placed between the safety or relief valve and the boiler, or on discharge pipes between such valves and the atmosphere.
   2. (B) Safety and relief valves shall not be connected to an internal pipe in the boiler.

3. (6)

   1. (A) When a discharge pipe is used, its area shall be not less than the area of the valve or aggregate area based on the nominal diameters of the valves with which it connects, and the discharge pipe shall be fitted with an open drain to prevent water from lodging in the upper part of the valve or in the pipe.
   2. (B) When an elbow is placed on a safety or relief valve discharge pipe, it shall be located close to the valve outlet.
   3. (C) The pipe shall be supported so that no undue stress is placed on the valve body.
   4. (D) The discharge from safety or relief valves shall be so arranged that there will be no danger of scalding attendants.

(p) Steam gauges.

1. (1)

   1. (A) Each steam boiler shall have a steam gauge connected to its steam space, or to its water column, or to its steam connection by means of a siphon or equivalent device exterior to the boiler and of sufficient capacity to keep the gauge tube filled with water, and so arranged that the gauge cannot be shut off from the boiler except by a cock with tee or lever handle placed in the pipe near the gauge.
   2. (B) The handle of the cock shall be parallel to the pipe in which it is located when the cock is open.

2. (2)

   1. (A) The scale on the dial of a steam boiler gauge shall be graduated to not less than thirty pounds (30 lbs.).
   2. (B) The gauge shall be provided with effective stops for the indicating pointer at the zero (0) point and at the maximum pressure point.
   3. (C) The travel of the pointer from zero (0) to thirty (30) pounds pressure shall be at least three inches (3”).
3. (3) Connections to steam-gauge siphons shall be of nonferrous metal when smaller than one-inch pipe size and longer than five feet (5’) between the siphon and point of connection of pipe to boiler, and also when smaller than one-half-inch pipe size and shorter than five feet (5’) between the siphon and point of connection of pipe to boiler.
4. (4) On a compound gauge, effective stops shall be set at the limits of the gauge readings on both the pressure and vacuum sides.

(q) Pressure or altitude gauges.

1. (1)

   1. (A) Each hot water boiler shall have a pressure or altitude gauge connected to it or to its flow connection in such a manner that it cannot be shut off from the boiler except by a cock with tee or lever handle placed on the pipe near the gauge.
   2. (B) The handle of the cock shall be parallel to the pipe in which it is located when the cock is open.
   3. (C) It is recommended that this gauge be of the pressure type with its equivalent in altitude feet indicated.

2. (2)

   1. (A) The scale on the dial of the pressure or altitude gauge shall be graduated to not less than one and one-half (1 1/2) times the maximum allowable working pressure.
   2. (B) The gauge shall be provided with effective stops for the indicating pointer at the zero (0) point and at the maximum pressure point.
3. (3) Pressure or altitude-gauge connections shall be of nonferrous composition when smaller than one-inch pipe size and longer than five feet (5’) between the gauge and point of connection of pipe to boiler, and also when smaller than one-half-inch pipe size and shorter than five feet (5’) between the gauge and point of connection of pipe to boiler.

(r) Thermometers.

1. (1) Each hot water boiler shall have a thermometer so located and connected that it shall be easily readable when observing the water pressure or altitude.
2. (2) The thermometer shall be so located that it shall at all times indicate the temperature in degrees Fahrenheit of the water in the boiler at or near the outlet.

(s) Temperature-combustion regulators.

1. (1) A temperature-combustion regulator, which will control the rate of combustion to prevent the temperature of the water from rising above two hundred fifty degrees Fahrenheit (250° F) at or near the outlet, or a thermostatic device which will relieve the pressure on the boiler when the temperature exceeds two hundred fifty degrees Fahrenheit (250° F), shall be used on all hot water heating and hot water supply boilers.
2. (2) All hot water heating and hot water supply boilers automatically fired must be equipped with an automatic device to automatically control the rate of combustion.

(t) Pressure-combustion regulators.

1. (1) When a pressure-combustion regulator is used, it shall operate to prevent the steam pressure from rising above fifteen pounds (15 lbs.).
2. (2) All automatically fired boilers shall be equipped with an automatic pressure control.

(u) Water gauge glasses.

1. (1) Each steam boiler shall have one (1) or more water gauge glasses attached to the water column or boiler by means of valved fittings, with the lower fitting provided with a valve or pet cock to facilitate cleaning.
2. (2) Gauge glass replacement shall be possible under pressure.

3. (3) Transparent material other than glass may be used for the water gauge provided that material has proved suitable for the pressure, temperature, and corrosive condition met with in service.

   1. (v) Water-column pipes.

4. (1)

   1. (A) The minimum size of ferrous or nonferrous pipes connecting a water column to a steam boiler shall be one inch (1”).

   2. (B)

      1. (i) No outlet connections, except for damper regulator, feedwater regulator, steam gauges, or apparatus which does not permit the escape of any steam or water except for manually operated blowdowns, shall be attached to a water column or the piping connecting a water column to a boiler.
      2. (ii) See HG-705 of Section IV of the ASME code for introduction of feedwater into a boiler.
   3. (C) If the water column, gauge glass, low-water fuel cutoff, or other water level control device is connected to the boiler by pipe and fittings, no shutoff valves of any type shall be placed in such pipe, and a cross tee, or equivalent fitting, to which a drain valve and piping may be attached, shall be placed in the water piping connection at every right-angle turn to facilitate cleaning.
   4. (D) The water column drain pipe and valve shall not be less than three-fourths-inch pipe size.

5. (2)

   1. (A) The steam connections to the water column of a horizontal firetube wrought boiler shall be taken from the top of the shell or the upper part of the head, and the water connection shall be taken from a point not above the center line of the shell.
   2. (B) For a cast iron boiler, the steam connection to the water column shall be taken from the top of an end section or the top of the steam header, and the water connection shall be made on an end section not less than six inches (6”) below the bottom connection to the water gauge glass.

(w) Automatic low-water fuel cutoff and water feeding device.

1. (1)

   1. (A) All automatically fired steam or vapor-system boilers must be equipped with an automatic low-water fuel cutoff and automatic water feeding device so constructed that the water inlet valve cannot feed water into the boiler through the float chamber, and so located as to automatically cut off the fuel supply and supply requisite feedwater when the surface of the water falls to the lowest safe water line.
   2. (B) This point should be not lower than one inch (1”) above the bottom of the water glass.

2. (2)

   1. (A) Such a fuel cutoff or water feeding device may be attached directly to a boiler.
   2. (B) A fuel cutoff or water feeding device may also be installed in the tapped openings available for attaching a water glass directly to a boiler, provided the connections are made to the boiler with nonferrous tees or Ys not less than one-half-inch pipe size between the boiler and the water glass so that the water glass is attached directly and as close as possible to the boiler.
   3. (C) The run of the tee or Y shall take the water glass fittings, and the side outlet or branch of the tee or Y shall take the fuel cutoff or water feeding device.
   4. (D) The ends of all nipples shall be reamed to full-size diameter.
3. (3) Designs embodying a float and float bowl shall have a vertical straightway valved drain pipe at the lowest point in the water equalizing pipe connections by which the bowl and the equalizing pipe can be flushed and the device tested.