WIRE GAUGE TABLES

WIRE GAUGE TABLES

American Wire Gauge (AWG) sizes may be determined by measuring the diameter of the conductor (the bare wire) with the insulation removed. Refer to the Wire gauge Diameter Table for dimensions. When choosing wire gauge, the distance the wire must run and the amperage it will be expected to carry must be determined first. Refer to the Wire gauge Selection Table. Note that you can always use thicker wire (lower gauge number) than is recommended.

METRIC-TO-AWG CONVERSION TABLE
Metric Size mm2	AWG Size
0.5	20
0.8	18
1.0	16
2.0	14
3.0	12
5.0	10
8.0	8
13.0	6
19.0	4
32.0	2
52.0	0

WIRE GAUGE DIAMETER TABLE
American Wire gauge	Wire Diameter in inches
20	0.03196118
18	0.040303
16	0.0508214
14	0.064084
12	0.08080810
10	0.10189
8	0.128496
6	0.16202
5	0.18194
4	0.20431
3	0.22942
2	0.25763
1	0.2893
0	0.32486
00	0.3648

WIRE GAUGE SELECTION TABLE
Circuit Amperes		Circuit Watts		Wire gauge (for length in feet)
6V	12V	6V	12V	3'	5'	7'	10'	15'	20'	25'
0 to 2.5	0 to 5	15	30	18	18	18	18	18	18	18
3.0	6	18	36	18	18	18	18	18	18	16
3.5	7	21	42	18	18	18	18	18	18	16
4.0	8	24	48	18	18	18	18	18	16	16
5.0	10	30	60	18	18	18	18	16	16	16
5.5	11	33	66	18	18	18	18	16	16	14
6.0	12	36	72	18	18	18	18	16	16	14
7.5	15	45	90	18	18	18	18	14	14	12
9.0	18	54	108	18	18	16	16	14	14	12
10	20	60	120	18	18	16	16	14	12	10
11	22	66	132	18	18	16	16	12	12	10
12	24	72	144	18	18	16	16	12	12	10
15	30	90	180	18	16	16	14	10	10	10
20	40	120	240	18	16	14	12	10	10	8
25	50	150	300	16	14	12	12	10	10	8
50	100	300	600	12	12	10	10	6	6	4
75	150	450	900	10	10	8	8	4	4	2
100	200	600	1200	10	8	8	6	4	4	2

IEC 61439 - The New Switchgear Standard

The new standard IEC 61439 replaces the old 60439.  After a first reading my initial impressions are that it is a more clearly defined standard.  Some key differences are that the distinction between type tested assemblies (TTA) and partially type tested (PTTA) is gone, verifying the performance is addressed in new ways and the specification of current ratings is updated.   What I found particularly interesting is the clarifications on the specification of current ratings.

Current Ratings

• The standard defines the overall rated current of the assembly (I_na) as the smaller of the sum of  rated currents of incoming circuits or the total current the main busbar is capable of distributing.
• The rated current of a circuit (I_nc) is the rating of a circuit taking in to account the installed devices, disposition and application (and may be lower than the rated current of the devices used).
• A rated diversity factor (RDF) is assigned by the manufacturer to groups of outgoing circuits which can be simultaneously loaded and takes into account the mutual thermal influence between the circuits.  This can be applied to the whole assembly or a group of circuits.

This clarification of ratings ties the consideration and specification of a switchboard more closely into the manufactured product.  Personally I think is a good thing.  It does put more emphasis on specifiers to understand how the assembly will perform and what they want out of it. 

Typical RDF

The RDF is a figure to be given by manufacturers.  Some typical values I found on the Schneider website are:

Number of main outgoing circuits	Diversity factor
2 and 3	0.9
4 and 5	0.8
6 to 9 inclusive	0.7
10 and more	0.6

Specification of Switchboards

The standard will change how specifiers state their requirements.  Currently specification is often carried out based around devices (i.e. circuit breakers from a particular manufacturer for example), with the device ratings being applied to switchboards.  This is not the case any longer.  There is now a clear need to consider the effect of the enclosure and surrounding components in addition to those of the protective devices and trip units. 

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Maximum Demand for Buildings

Estimating maximum demand is a topic frequently discussed. Working out how much power to allow for a building in my experience a very subjective . Allowing too much power results in additional equipment, increased space requirements, greater system losses and extra cost. On the other side, not enough power results in operational problems. Trying to find the right amount of power is like gazing into a crystal ball and everyone will see something different. Early in a project power demand is estimated on a w/m2 basis. Each building needs to be considered on it merits and appropriate allowances worked out (for example a office designed for high end banking clients will require more power than a general purpose office). While there are no fixed guidelines it is good to have some sort of starting point. The table below is something I have put together as an initial set of demand figures to start playing with. Hopefully it may help someone or at least give some food for thought. In putting the table together I used the area descriptions and maximum lighting power densities from ASHRAE 90.1-2007 (Energy Standard for Buildings). For the power densities I sought guidance and extrapolated from Siemens Application Manual - Basic Data and Preliminary Planning, 2006.  Major plant and equipment such as chillers, fire pumps, etc. should be estimated separately.

	Lighting		Power
Space	(W/m2)	SF	(W/m2)	SF2
Atrium - First Three Floors	6	0.85	9	0.3
Atrium - Floors (above first 3)	2	0.85	9	0.3
Audience/Seating Area - Convention Centre	8	0.85	5	0.3
Audience/Seating Area - Exercise Centre	3	0.85	5	0.3
Audience/Seating Area - General	10	0.85	5	0.3
Audience/Seating Area - Gymnasium	4	0.85	5	0.3
Audience/Seating Area - Motion Picture Theatre	13	0.85	5	0.3
Audience/Seating Area - Penitentiary	8	0.85	5	0.3
Audience/Seating Area - Performing Arts Theatre	28	0.85	5	0.3
Audience/Seating Area - Religious Buildings	18	0.85	5	0.3
Audience/Seating Area - Sports Arena	4	0.85	5	0.3
Audience/Seating Area - Transportation	5	0.85	5	0.3
Automotive-Service/Repair	8	0.85	72	0.6
Bank/Office-Banking Activity Area	16	0.85	54	0.6
Classroom/Lecture/Training - General	15	0.85	15	0.6
Classroom/Lecture/Training - Penitentiary	14	0.85	15	0.6
Conference/Meeting/Multipurpose	14	0.85	26	0.8
Convention Centre-Exhibit Space	14	0.85	26	0.8
Corridor/Transition - General	5	0.85	10	0.3
Corridor/Transition - Hospital	11	0.85	10	0.3
Corridor/Transition - Manufacturing Facility	5	0.85	10	0.3
Courthouse - Confinement Cells	10	0.85	0	0
Courthouse - Courtroom	20	0.85	20	0.8
Courthouse - Judges' Chambers	14	0.85	20	0.8
Dining Area - Bar Lounge/Leisure Dining	15	0.85	10	0.3
Dining Area - Family Dining	23	0.85	10	0.3
Dining Area - General	10	0.85	10	0.3
Dining Area - Hotel	14	0.85	10	0.3
Dining Area - Motel	13	0.85	10	0.3
Dining Area - Penitentiary	14	0.85	10	0.3
Dormitory-Living Quarters	12	0.85	18	0.6
Dressing/Locker/Fitting Room	6	0.85	10	0.3
Electrical/Mechanical	16	0.85	15	0.3
Exterior -  Stairways	10.8	0.85	0	0
Exterior - Building Facades (illuminated)	2.2	0.85	0	0
Exterior - Building Facades (non-illuminated)	0	0.85	0	0
Exterior - Canopies/Overhangs	13.5	0.85	0	0
Exterior - Entrances/Inspection Station	13.5	0.85	0	0
Exterior - Loading Areas	5.4	0.85	0	0
Exterior - Sales Areas	5.4	0.85	0	0
Exterior - Uncovered Parking Area	1.6	0.85	0	0
Exterior - Walkways (< 3m wide)	9.9	0.85	0	0
Exterior - Walkways (≥3 m wide)	2.2	0.85	0	0
Fire Stations - Engine Room	9	0.85	15	0.3
Fire Stations - Sleeping Quarters	3	0.85	18	0.6
Food Preparation	13	0.85	387	0.8
Gymnasium/Exercise Centre - Exercise Area	10	0.85	20	0.6
Gymnasium/Exercise Centre - Playing Area	15	0.85	15	0.6
Hospital - Emergency	29	0.85	360	0.6
Hospital - Exam/Treatment	16	0.85	360	0.6
Hospital - Laundry-Washing	6	0.85	360	0.6
Hospital - Medical Supply	15	0.85	360	0.6
Hospital - Nursery	6	0.85	360	0.6
Hospital - Nurses' Station	11	0.85	360	0.6
Hospital - Operating Room	24	0.85	360	0.6
Hospital - Patient Room	8	0.85	360	0.6
Hospital - Pharmacy	13	0.85	360	0.6
Hospital - Physical Therapy	10	0.85	360	0.6
Hospital - Radiology	4	0.85	360	0.6
Hospital - Recovery	9	0.85	360	0.6
Hotel/Motel Guest Rooms	12	0.85	18	0.6
Laboratory	15	0.85	360	0.6
Library - Card File and Cataloguing	12	0.85	38	0.6
Library - Reading Area	13	0.85	32	0.6
Library - Stacks	18	0.85	32	0.6
Lobby - General	14	0.85	1	0.3
Lobby - Hotel	12	0.85	18	1
Lobby - Motion Picture Theatre	12	0.85	18	1
Lobby - Performing Arts Theatre	36	0.85	18	1
Lounge/Recreation - General	13	0.85	2	0.3
Lounge/Recreation - Hospital	9	0.85	6	0.3
Manufacturing - Control Room	5	0.85	72	0.6
Manufacturing - Detailed Manufacturing	23	0.85	72	0.6
Manufacturing - Equipment Room	13	0.85	72	0.6
Manufacturing - High Bay (≥7.6 m)	18	0.85	72	0.6
Manufacturing - Low Bay (<7.6 m)	13	0.85	72	0.6
Museum - General Exhibition	11	0.85	69	0.6
Museum - Restoration	18	0.85	62	0.6
Office -Enclosed	12	0.85	28	0.8
Office -Open Plan	12	0.85	28	0.8
Parking Garage-Garage Area	2	0.85	8	0.6
Penitentiary - Confinement Cells	10	0.85	0	0
Penitentiary - Courtroom	20	0.85	20	0.8
Penitentiary - Judges' Chambers	14	0.85	20	0.8
Police Station - Confinement Cells	10	0.85	0	0
Police Station - Courtroom	20	0.85	20	0.8
Police Station - Judges' Chambers	14	0.85	20	0.8
Post Office-Sorting Area	13	0.85	72	0.6
Religious Buildings - Fellowship Hall	10	0.85	5	0.3
Religious Buildings - Worship Pulpit, Choir	26	0.85	5	0.3
Restrooms/Toilets	10	0.85	5	1
Retail Mall Concourse	18	0.85	42	0.6
Sales Area (for accent lighting)	18	0.85	0	0
Sports Arena - Court Sports Area	25	0.85	5	0.6
Sports Arena - Indoor Playing Field Area	15	0.85	5	0.6
Stairs	6	0.85	9	0.3
Storage Active - General	9	0.6	6	0.3
Storage Active - Hospital	10	0.6	6	0.3
Storage Inactive - General	3	0.4	6	0.3
Storage Inactive - Museum	9	0.4	6	0.3
Transportation - Air/Train/Bus Baggage Area	11	0.85	19	1
Transportation - Airport Concourse	6	0.85	24	1
Transportation - Terminal Ticket Counter	16	0.85	14	1
Warehouse - Fine Material Storage	15	0.85	5	0.6
Warehouse - Medium/Bulky Material Storage	10	0.85	5	0.6
Workshop	20	0.85	72	0.6

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