§ 27-770 Noise control of mechanical equipment.

   (a)   Minimum airborne noise insulation requirements.

      (1)   BOILER ROOMS. Boiler rooms adjoining dwelling spaces, either vertically or horizontally, shall be separated therefrom by floor-ceiling or partition constructions having a minimum STC rating of fifty.

      (2)   MECHANICAL EQUIPMENT SPACES. Spaces or shafts containing air conditioning, refrigeration, or ventilating equipment, elevator machinery, or other mechanical equipment shall be separated both vertically and horizontally from dwelling units by constructions that will provide a minimum STC rating of fifty. Spaces or shafts containing equipment totaling more than seventy-five rated h.p. shall not be located vertically or horizontally adjacent to dwelling units unless the total sound power level output of all the equipment in the space or shaft is certified not to exceed the maximum sound power levels of table 12-3 in any octave band. Such sound power level ratings shall be obtained by tests conducted in accordance with the procedures of reference standard RS 12-5.

   a.   Ventilating openings into mechanical equipment spaces. Ventilating openings into boiler rooms and other mechanical equipment spaces shall not be located in yards or courts where there are windows opening from living quarters, unless such ventilating openings are provided with sound attenuating devices if needed to limit noise transmission to NC-40 (noise criterion) levels in the exposed dwelling units. For permits issued after January first, nineteen hundred seventy-two, the permissible noise levels shall not exceed NC-35.

   b.   Noise criteria requirements. Noise criteria requirements prescribed in this subchapter shall be in accordance with reference standard RS 12-4.

TABLE 12-3
Maximum Sound Power Levels Permitted in Mechanical
Spaces or Shafts Adjoining Dwelling Spaces

Octave Bands, c.p.s. Mid- Frequency	Max. Sound Power Level db a
	db re 10 -13 Watts	db re 10 -12 Watts
63	101	91
125	101	91
250	103	93
500	105	95
1,000	102	92
2,000	101	91
4,000	98	88
8,000	96	86

 

Notes for Table 12-3:

a The maximum sound power levels shall be reduced five db in any octave band where the equipment data indicate pure tone generation. The presence of pure tones may be determined by means of one-third octave band analysis. The criterion for a significant pure-tone component shall be an audible pure-tone sound together with an increase of the sound pressure level in the corresponding one-third octave band above the mean of the two adjacent one-third of at least:  

 

Center frequency of one-third octave band	40/125	160/250	215/19500	630/1,000	1,000/ 10,000
Increase in sound pressure level (db)	6	4	3	2	1 1/2

 

b For permits issued after January first, nineteen hundred seventy-two, the maximum sound power levels shall be changed as follows:

Octave Bands, c.p.s. Mid-Frequency	db re 10-13 Watts	db re 10-12 Watts
63	98	88
125	97	87
250	100	90
1,000	97	87
2,000	96	86
4,000	93	83
8,000	91	81

 

      (3)   DUCTWORK. Ducts serving dwelling units shall be lined with duct lining for at least twenty feet from the fan discharge or intake; otherwise, an approved sound attenuating device shall be installed therein. All toilet exhaust ducts shall be lined with duct lining for at least twenty feet upstream of the exhaust fan intake, otherwise, an approved sound attenuating device shall be installed therein. Duct lining shall conform to the requirements of subchapter thirteen of this chapter. (4) EXTERIOR MECHANICAL EQUIPMENT. Mechanical equipment in a building in any occupancy group, when located outside of the building in a yard or court or on a roof, or where the equipment opens to the exterior of the building, shall be subject to the noise output limitations given in table 12-4 where one or more windows of a dwelling unit in any building in occupancy groups J-1, J-2, or J-3 is located within a sphere of one hundred foot radius whose center is any part of the equipment or its housing, unless it can be shown that the sound pressure levels, in octave bands, of the exterior mechanical equipment as measured within the dwelling unit do not exceed the levels given in table 12-5.

   (b)   Minimum structure-borne noise and vibration isolation requirements. All isolators used in accordance with the following requirements shall be approved.

Table 12-4
Maximum Sound Power Levels Permitted for Exterior
Mechanical Equipment Adjoining Buildings b

Minimum Distance from Equipment to Exterior Window (ft.) a	Maximum Sound Power Levels in Octave Bands-db re 10-13 Watts a
	Octave Bands c.p.s. Mid Frequency
	63	125	250	500	1,000	2,000	4,000	8,000
12	99	92	88	84	82	82	82	82
25	103	96	92	88	86	86	86	86
50	107	100	96	92	90	90	90	90
100	110	103	99	95	93	93	93	93
	in Octave Bands-db re 10-12 Watts
12	89	82	78	74	72	72	72	72
25	93	86	82	78	76	76	76	76
50	97	90	86	82	80	80	80	80
100	100	93	89	85	83	83	83	83

 

Notes for Table 12-4:

a The minimum distance shall be measured in a straight line regardless of obstructions. Interpolated levels may be used for distances between those given in this table. See note a. at end of table 12-3.

   1.   In the event sound power level data for the exterior mechanical equipment is not available, the sound pressure levels in octave bands, of the exterior mechanical equipment shall be measured.

   2.   The measurements shall be obtained with the microphone of the measuring equipment located at the interior of the dwelling unit affected in a line with the window nearest the exterior mechanical equipment. The window shall be fully open and the microphone shall be located three ft. away from the open portion of the window.

   3.   Measurements shall be obtained during times when the ambient sound pressure levels, in octave bands, are at least six db lower at all octave bands than the sound pressure levels measured with the exterior equipment operating. By ambient sound pressure levels is meant the measured sound pressure levels, at the above described measuring location, with the exterior equipment not in operation.

b For permits issued after January first, nineteen hundred seventy-two, the permitted maximum sound power levels for exterior mechanical equipment adjoining buildings shall be changed as follows:

Maximum Sound Power Levels in

Feet	Octave Bands-db re 10-13 Watts
	63	125	250	500	1,000	2,000	4,000	8,000
12	97	90	83	78	75	73	72	71
25	104	96	89	84	81	79	78	77
50	110	102	95	90	87	85	84	83
100	116	108	101	96	93	91	90	89
	in Octave Bands-db re 10-12 Watts
12	87	80	73	68	65	63	62	61
25	94	86	79	74	71	69	68	67
50	100	92	85	80	77	75	74	73
100	106	98	91	86	83	81	80	79

 

Table 12-5
Noise Output Limitations for Exterior Mechanical Equipment
Maximum Sound Pressure Level a, b
(Not to be exceeded in any octave bands)

Octave Bands Center Frequencies (cps)	Decibels re .0002 Microbar
63	64
125	57
250	51
500	45
1,000	41
2,000	39
4,000	38
8,000	37

 

Notes for Table 12-5:

a Measurements shall be obtained with a sound level meter and octave band analyzer, calibrated both electronically and acoustically before and after the measurements are made. The equipment used shall meet the requirements of reference standards RS 12-6.

b For permits issued after January first, nineteen hundred seventy-two, the maximum sound pressure levels shall be changed as follows:

Octave Bands Center Frequencies (cps)	Decibels re .0002 Microbar
63	61
125	53
250	46
500	40
1,000	36
2,000	34
4,000	33
8,000	32

 

   (b)   Minimum structure-borne noise and vibration isolation requirements. All isolators used in accordance with the following requirements shall be approved.

      (1)   BOILER ROOMS.

         a.   Boilers. All boilers supported on floors above a story having dwelling units shall be supported on resilient isolators having a minimum static deflection of one inch. The isolators shall be installed directly under the structural frame of the boiler.

         b.   Boiler breeching and piping. When boilers are equipped with mechanical draft fans, the boiler breeching and piping that is supported from or on slabs, floors, or walls that are contiguous to the dwelling unit shall be supported for a distance of fifty pipe diameters on or from resilient isolators. Each isolator shall have a minimum static deflection of one inch.

      (2)   INCINERATOR CHARGING CHUTES.

         a.   Metal chutes. Metal chutes, metal chute supports, and/or metal chute bracing, shall be free of direct contact with the shaft enclosure and the openings provided in the floor construction. Metal chutes shall be resiliently supported at each structural support location. Isolators shall provide a minimum static deflection of 0.30 in. All chutes shall be plumb.

         b.   Masonry chutes. The interior chute wall shall be plumb and without obstructions for the full height of the shaft and shall have a smooth interior finish.

      (3)   PIPING.

         a.   Metal piping connected to power driven equipment shall be resiliently supported from or on the building structure for a distance of fifty pipe diameters from the power driven equipment. The resilient isolators shall have a minimum static deflection of one inch for all piping with a four inch or larger actual outside diameter and one-half inch for piping with less than four inches in actual outside diameter. Piping connected to fluid pressure-reducing valves, shall be resiliently isolated for a distance of fifty pipe diameters from pressure reducing valves and isolators shall provide a minimum static deflection of one-half inch.

         b.   Equipment such as heat exchangers, absorption refrigeration machines, etc., that is located on any floor or roof other than a floor on grade, and that is not power driven but is connected by metal piping to power driven equipment, shall be resiliently supported from or on the building structure, for a distance of fifty pipe diameters from the power driven equipment. The resilient supports shall be vibration isolators having a minimum static deflection of one inch and shall incorporate approved resilient pads having a minimum thickness of one-quarter inch.

      (4)   Fans. Except for fans installed in compliance with section 27-353 of article five of subchapter five of this chapter all fan equipment located on any roof or floor other than a floor on grade shall be mounted on or from vibration isolators. Fan equipment with motor drives separated from the fan equipment shall be supported on an isolated integral rigid structural base supporting both the fan and motor. Fan equipment with motor drives supported from the fan equipment shall be mounted directly on vibration isolators. Each isolator shall have provision for leveling. Isolators shall incorporate resilient pads having a minimum thickness of one-quarter inch. The vibration isolators shall provide a minimum isolator efficiency of ninety percent at fan rotor rpm with a maximum deflection of two inches. Fans and compressors of three h.p. or less assembled in unitary containers may meet this requirement with isolators internal to the container providing the isolators meet the above minimum isolator efficiencies.

      (5)   PUMPS. All pumps of three h. p. or more located on any floor other than a floor on grade shall be supported on vibration isolators having a minimum isolation efficiency of eighty-five per cent at the lowest disturbing frequency. Each isolator shall incorporate a leveling device and a resilient pad having a minimum thickness of one-quarter inch.

      (6)   COMPRESSORS. Compressors and drives located on a floor other than a floor on grade shall be mounted on vibration isolators having a minimum isolation efficiency of eighty-five per cent at the lowest disturbing frequency. Each isolator shall incorporate a leveling device and a resilient pad having a minimum thickness of one-quarter inch.

      (7)   COOLING TOWERS. All moving parts of cooling towers located on a roof or floor other than a floor on grade shall be installed on vibration isolators providing a minimum isolation efficiency of eighty-five per cent at fan rotor rpm with a maximum static deflection of four inches. Each isolator shall incorporate a leveling device and a resilient pad having a minimum thickness of one-quarter inch.

      (8)   EVAPORATIVE CONDENSERS. Evaporative and air cooled condensers located on a roof or floor other than a floor on grade shall be mounted on vibration isolators providing a minimum isolation efficiency of eighty-five per cent at fan rotor rpm with a maximum static deflection of four inches. Each isolator shall incorporate a leveling device and a resilient pad having a minimum thickness of one-quarter inch.

      (9)   DUCT CONNECTIONS TO FAN EQUIPMENT. Flexible connections shall be installed between fan equipment and connecting ductwork.

      (10)   ELEVATOR MACHINERY. Gear-driven machinery, gearless machinery, motor generators, and controllers located in an elevator machinery room or shaft on a roof, or on a floor other than a floor on grade, shall be supported on vibration isolator pads having a minimum thickness of one-half inch.

   (c)   Maximum permissible air velocities in ducts.

      (1)   DUCTS LOCATED OVER CEILINGS OF DWELLING SPACES. The maximum permissible air velocity in ductwork located over the ceilings of dwelling spaces or in masonry shafts adjoining dwelling spaces shall not exceed the velocities prescribed in table 12-6.

TABLE 12-6
Maximum Permissible Air Velocities in Ducts

 

Type of System	Branch Ducts	Sub-Main Ducts	Main Ducts
Low Velocity	750 fpm	1,000 fpm	1,500 fpm
High Velocity	1,000 fpm	2,000 fpm	3,000 fpm

In the application of table 12-6 the following shall apply:

   a.   Any duct that connects directly to any terminal device (grille, diffuser, etc.) shall be classified as a branch duct for a distance of at least four feet from the terminal device.

   b.   Any duct that connects a branch duct to a main duct or to the fan shall be classified as a sub-main duct. No duct may be classified as a sub-main duct if it connects to a terminal device by means of a connection less than four feet in length.

   c.   When a duct is connected to the fan and to two or more sub-main ducts it shall be classified as a main duct.

   d.   The maximum velocities shown in table 12-6 for low velocity ductwork shall apply in all cases except where a system of round ductwork is used and an acoustic air control device with self-contained attenuation components is located in the duct work prior to each air terminal device. Branch ducts, if any, connecting the acoustic air control devices to the terminals shall not have air velocities exceeding seven hundred fifty fpm. Maximum power level ratings for the acoustic air control devices shall be three db less than the values shown in table 12-7.

   (d)   Maximum permissible sound power levels of fan coil units, grilles, registers, diffusers and induction units. Sound power level data, in octave bands, shall be certified in accordance with the provisions of section 27-131 of article seven of subchapter one of this chapter, for grilles, registers, diffusers and induction units at design operating conditions and for coil units when operating at specified cfm. The sound power levels shall not exceed the levels listed in table 12-7 when measured in accordance with the provisions of reference standard RS 12-5.

TABLE 12-7
Maximum Permissible Sound Power Levels for Terminal Units1

Octave Bands, c.p.s. Mid-Frequency	Sound Power Levels, db
	db re 10-13	db re 10-12 Watts
63	79	69
125	73	63
250	67	57
500	62	52
1,000	59	49
2,000	57	47
4,000	54	44
8,000	53	43

 

Notes for Table 12-7:

1 For permits issued after January first, nineteen hundred seventy-two, the Maximum Permissible Sound Power Level for terminal units shall be changed as follows:

Octave Bands, c.p.s. Mid Frequencies	Sound Power Levels
	dB re 10-13	db re 10-12 Watts
63	76	66
125	69	59
250	62	52
500	57	47
1,000	54	44
2,000	52	42
4,000	49	39
8,000	48	38

 

Subchapter 13: Mechanical Ventilation, Air Conditioning, and Refrigeration Systems

Article 1: General

§ 27-771 Scope.

This subchapter shall establish the minimum safety requirements for, and control the design, construction, installation, alteration and use of, systems for providing mechanical ventilation, air conditioning, air cooling, air heating and refrigeration. In addition, within special flood hazard areas, and below the regulatory flood datum, as described in article ten of subchapter four of this chapter, mechanical ventilation, air conditioning and refrigeration systems and related equipment shall meet the requirements of the applicable provisions of reference standard RS 4-5.