HOUSING                                                  PIH-110


                Electrical Wiring for Swine Buildings

Eldridge R. Collins, Jr., Virginia Polytechnic
  Institute and State University
Gerald R. Bodman, University of Nebraska
LaVerne E. Stetson, USDA-ARS, Lincoln, Nebraska

R.F. Espenschied, University of Illinois
Larry D. Jacobson, University of Minnesota
Vernon M. Meyer, Iowa State University

     Proper design and installation of swine facility  electrical
systems  is  crucial  to using electricity efficiently, providing
safety for workers and animals,  and  minimizing  potential  fire
loss.  A majority of all farm fire losses are related to electri-
cal system failure (Figure 1). Many  wiring  practices  that  are
acceptable for use in our homes are unsafe when used in livestock
housing because of exposure to dust, moisture,  corrosive  gases,
and  physical damage. Inferior wiring causes hazardous conditions
for livestock and humans,  expense  of  early  rewiring  of  many
buildings,  and possible fires. The losses from burning of even a
fully insured building can be disastrous; there may be months  of
production  loss  before  new  buildings  can  be constructed and
animals phased back into production, and years  of  genetic  herd
improvement  can  be  forever lost. Even when fires do not occur,
poor wiring may contribute to higher maintenance costs because of
overheated   motors  and  equipment  and  can  result  in  costly
failures. The mere fact that a system ``works'' doesn't speak for
its  safety. Special wiring methods and components are needed for
swine structures.

     The guidelines given in this fact  sheet  will  aid  you  in
evaluating  potential wiring problems in an existing swine build-
ing, or in ensuring that a new building is wired to reduce danger
of  wiring  failure  and fire loss. This leaflet does not provide
all information necessary  to  properly  design  and  install  an
electrical wiring system, nor does it describe all specialty dev-
ices, mechanical protection, and special  requirements  for  feed
handling  and grain storage facilities with severe dust problems.
For these you should consult with a qualified electrician  having
training,  experience,  and  knowledge of the National Electrical
CodeO (NEC) as well as understanding of importance  of  following
accepted  proper  wiring practices. Assistance is often available
from your power supplier in planning and installing the distribu-
tion  system to your building. By being familiar with some of the
special problems and requirements of  swine  buildings,  you  can
better  advise your electrician how you want your building wired;
and, you will be able to assure that the job is done so  that  it
will  stand up to the harsh swine building environment. Some com-
panies will not insure buildings  wired  by  older  commonly-used
methods.  Check with your insurance company before beginning con-
struction to determine their requirements.


     The standard for electrical work in the United States is the
National  Electrical CodeO published by the National Fire Protec-
tion Association.  The NEC is a guide to selection and safe  ins-
tallation  of  proper  materials.  The NEC has become law in many
states, but there is often limited inspection or  enforcement  in
rural   areas.  In  other  states,  agricultural  structures  are
exempted from national, state, or local codes, so  NEC  practices
are  often not followed. Nevertheless, the NEC provides a minimum
standard (Article 547) for wiring swine buildings or  other  damp
corrosive  environments.  Good practices often go beyond the bare
minimum of the NEC to minimize fire  hazards  and  reduce  future
maintenance problems. Because of the potential impact a fire loss
can have on your total swine  enterprise,  it  is  in  your  best
interest  to  see  that  all  wiring meets or exceeds the minimum
standard. The lowest priced electrical system is seldom the  most


     Dry farm buildings generally do not require  special  wiring
materials   or   procedures.   Such  structures  include  garages
(detached from houses), machine sheds, shops, and similar  build-
ings. These buildings may normally be wired with the same materi-
als commonly used in residences and in accordance  with  standard
procedures and practices of the NEC.

     Dust-ignition-proof  wiring  systems  should  be   used   in
extremely  dusty feed processing areas. However, most small feed-
grain handling centers are  not  classified  as  areas  requiring
dust-ignition-proof  wiring and should be wired like swine struc-
tures described below.

     Open and enclosed swine housing structures and other  build-
ings  that  are washed periodically should be considered damp and
corrosive atmospheres.  Ammonia, hydrogen sulfide, and other cor-
rosive  gases,  in  combination  with  moisture  and dust, hasten
deterioration  of  electrical  components.  Many  existing  swine
buildings have been wired using practices and materials that can-
not withstand these conditions. Many older  buildings,  including
those  constructed  since 1960, have electrical systems that have
deteriorated to the point of  danger.  The  following  discussion
will  focus on practices that reduce electrical system deteriora-
tion and its associated fire hazard,  and  foster  efficient  and
safe use of electricity.


     Equipment and methods necessary to meet the special require-
ments  of  swine  housing  are different from residential wiring.
Therefore, you will need to plan ahead. Many of the materials may
be  available  only  from wholesale electrical supply houses. Use
materials of at least 20 ampere (A)  rating.  All  materials  and
equipment should bear a seal indicating they are listed by Under-
writers' Laboratories (UL), or by some other  recognized  testing

Cable and Conduit

     Either type UF cable or conduit (Figure 2) can be  used  for
wiring circuits in swine buildings. All wiring should be attached
to interior surfaces of the building  and  not  concealed  within
wall cavities, ceilings, or attic spaces.  Surface mounting elim-
inates the need to make holes in the  continuous  vapor  barrier,
thus  reducing  the risk of warm, moist room air moving into wall
or ceiling cavities and attics with resulting condensation.  Sur-
face  mounting  also reduces the risk of rodent damage and allows
periodic inspection and repair.

     Damage more serious than simple  wet  insulation  may  occur
when  electrical wiring is involved. Electrical boxes recessed in
walls or ceilings will  be  cold  during  winter,  thus  becoming
``condensation  boxes.''  As  a result, switches, wire junctions,
duplex outlets, and circuit breakers will corrode  rapidly  which
may  result  in  a  short-circuit.  When  cables  or conduits are
extended into cold wall cavities or  ceiling  and  attic  spaces,
condensation  follows  the cable or conduit (by draining or wick-
ing) into electrical fixtures and boxes. When this occurs, corro-
sion  and circuit resistancewith associated overheating of wiring
or equipmentare greatly increased.  Cables  and  conductors  with
nonwaterproof  covering  can also lead to current leakage through
the insulation, which may cause problems with stray  voltage  and
increased potential for electric shock.

     Surface wiring with cable is relatively easy, saves  materi-
als  and  labor,  and  is  generally preferable to conduit except
where subject to physical damage.  Type UF cable  is  recommended
because  it  is moisture resistant and allows use of weatherproof
connectors and fittings at box connections. Do not use Type NM or
NM-B cable in swine buildings.

     Install cable where it will be protected from physical  dam-
age.  Normally  it  should be installed on flat surfaces of walls
and ceilings. Use nylon or plastic coated staples,  or  stainless
steel nails and nonmetallic straps at a maximum of 4.5-ft. inter-
vals and within 8 in. of each junction or fixture  box.   If  the
building  has  exposed joists, beams, or trusses, run cable along
the joist, beam, or truss chord. If it must run perpendicular  to
joists  or ribs of metal ceiling or wall liners, install cable on
a 1- x 2-in. running  board.   Sharp  bends  should  be  avoided;
minimum bend radius is five times the cable diameter.

     Conduit offers an alternative to Type UF  cable,  especially
where  wiring  is subject to physical damage or where conduit may
facilitate use of multiconductor control circuits. Otherwise, its
use is discouraged because inadequate sealing will allow entry of
vapor which may condense and contribute to system  deterioration.
Rigid Schedule 40 PVC conduit is recommended.  Provide extra pro-
tection in areas subject to physical abuse by animals  or  equip-
ment.  PVC  conduit is available in 10- and 20-ft. lengths and in
commonly used diameters of 1/2, 3/4, and 1 in. Larger conduit for
large  motors  or  service  entrances  are also available. Single
strand wire rather than cable is used in  conduit.  Select  wires
with  a  Type W designation (RHW, THW, THWN, or XHHW). Use a bare
or green insulated copper wire of the same size as  line  voltage
wires for grounding. All equipment MUST be grounded.

     Mount conduit on the surface of interior walls  or  ceiling.
Conduit  (1/2-  to 3/4-in. diameter) should be supported at 3-ft.
(maximum)  intervals  with  nonmetallic  fasteners.  PVC  conduit
elbows and offsets are available, or straight conduit can be bent
using a ``hot box'' or hot air blower,  but  never  use  an  open
flame.   Maintain   a   circular  cross-section  of  the  conduit
throughout the bend. No more than the equivalent of four  quarter
bends (360 degrees total) may be installed between junction boxes
and/or fittings.

     PVC conduit can be cut with a fine-tooth saw  or  a  special
cutter.  Ream  or  file  the ends smooth after cutting. Permanent
joints can be made using PVC connectors and solvent weld  cement,
or  temporary  joints  can  be  made using threaded adapters with
rubber washers or O-rings.

     Allow for thermal expansion and contraction in each  conduit
circuit.  Expansion joints are available, but normal expansion is
compensated for by leaving bends unrestrained within 1 ft. of the
radius center.

     Install conduit to prevent entry of dust, water, and  vapor.
If  the conduit must be exposed to widely differing temperatures,
such as where it passes through the  outside  wall  of  a  heated
building  or  between two different rooms, the inside of the con-
duit must be sealed where it passes from a warm to a  cool  area,
using  electrician's  duct  sealer.  In this way, moisture in the
warm conduit will be prevented from entering the cold conduit and

     Use flexible wiring methods for fans  and  other  equipment.
Liquidtight,  flexible, nonmetallic conduit with stranded conduc-
tors is one option. The maximum length of  liquidtight,  flexible
conduit permitted is 6 ft.; thus, careful planning of the overall
electrical system is required. Ordinary bare metal flexible  con-
duit is NOT permitted in livestock buildings. Flexible cords with
water and dust proof strain-relief fittings  can  also  be  used.
Select cords with a Type S outer covering.

Boxes and Fixtures

     Corroded metallic boxes and fixtures often lead to  electri-
cal  system  failure.  Despite  the higher cost and lack of ready
supply in some areas, molded plastic boxes and  other  components
are  required. Gasketed covers are necessary on all boxes to seal
wire splices, switches, and  other  electrical  contact  surfaces
from  exposure to dust, moisture, and corrosive gases.  Moisture-
proof receptacle boxes with spring-loaded  covers  are  required.
Standard metal boxes with screwed-in-place face plates (Figure 3)
are not permitted. Switches should also be moisture-proof, either
by  means  of  spring-loaded covers, moisture-tight switch levers
(Figure  4),  or  moisture-tight  covers  with   flexible   press
switches.  General  use switches and controls are cheaper but are
prone to corrosion and early failure.  Moisture-  and  explosion-
proof controls last longer and are safer. Do not use brown Bakel-
iteO fixtures in livestock buildings!

     All connections should be moisture-  and  dust-tight.  Where
surface  wiring is used, totally nonmetallic cable-to-box connec-
tors are available with  tapered  hub  threads  and  a  neoprene,
rubber,  or  plastic  bushing  sized and shaped to fit the cable.
When connected to a box, the bushing  is  compressed  to  form  a
seal.   Select boxes that are made to fit the tapered hub connec-
tors. Moisture- and dust-tight connectors should also be used  to
connect conduit to boxes and fixtures.

     All cable or conduit should enter electrical boxes from  the
side  or  bottom  (Figure  5)  if possible. Then, if condensation
occurs in or on the cable or conduit, or water accumulates during
washdown,  it  will not drain onto electrical contact surfaces or
leak into the box and corrode or  short-circuit  electrical  com-

     Mount receptacles and light switches where they will be pro-
tected  from animals and water. A rule of thumb is to place boxes
at least twice animal height, or at least 4 ft. above  the  floor
unless  extra protection is provided.  Provide 6 to 8 in. of wire
at each box to allow easy connections, plus  a  little  extra  in
case  switches,  outlets,  or  fixtures are later replaced. Avoid
placing boxes, cable, conduit, or fixtures on the ceiling  within
6  ft. of ventilation air inlets that direct air across the ceil-
ing; otherwise the devices might deflect  cold,  fresh  air  onto
young pigs and chill them.


     Incandescent and fluorescent are the two types  of  lighting
most  common  in  swine  buildings. Each type of fixture has dif-
ferent properties of light output, color, and  maintenance  which
might  make it more suitable for special tasks. However, for most
swine structures the decision between the two types will be based
on cost and service.

     Incandescent fixtures have a low initial  cost  and  operate
well  in  most conditions including low temperatures. Their light
efficiency is low, so it  takes  more  fixtures  to  provide  the
desired  lighting  level,  and  they  are relatively expensive to
operate. Bulb life is also short, usually about 750  to  800  hr.
for  100  to  150 watt (W) bulbs. Porcelain sockets are mandatory
for heat lamps. Fixtures should be dust-  and  moisture-resistant
with  a  heat-resistant globe to cover the light bulb (Figure 2).
Fixture boxes can become quite hot when  used  with  globed  fix-
tures. Since the conductors in Type UF cable do not meet the tem-
perature limits  for  many  fixtures,  UF  cable  should  not  be
extended  directly  into  globed  fixture  boxes. The safe way to
avoid wire insulation failure from heat buildup is to  install  a
junction  box  near the fixture and extend conduit and type SFF-1
conductors into the fixture box.

     Fluorescent fixtures cost more than incandescents  but  pro-
duce 3 to 4 times more light per watt of electricity. If fluores-
cents are turned on and off frequently  (less  than  a  10-minute
burn  cycle), lamp life will be reduced; incandescents would be a
better choice for such use. But if light will be on  for  a  long
time  between  switching, fluorescents provide higher efficiency.
Lamp life ranges from 7,500 hr. for short use  cycles  to  20,000
hr.  for  long  use  cycles.  Fluorescents are best used indoors,
since standard units do not perform well below 50o F without  spe-
cial  ballasts. They are also more sensitive to relative humidity
higher than 65%. Because of the damp, corrosive conditions normal
in  swine  housing,  fixtures should be nonmetallic with gasketed
enclosures over bulbs. Units designed and listed for mildly  cor-
rosive  industrial  environments  do  well in swine housing. Heat
buildup is less of a problem in  fluorescent  lighting  fixtures.
While not acceptable for incandescent lighting, type UF cable can
be extended directly into fluorescent fixtures if the  conductors
are kept away from the ballast.

     Provide enough light so inspection  and  work  can  be  done
efficiently.  Each  room  should  have at least two lighting cir-
cuits; two rows of lights on separate switches will  provide  two
levels  of  lighting  intensity. If ceiling and wall surfaces are
light, no reflectors are needed. However, if surfaces  are  dark,
provide  reflectors.  A  guideline  for  light placement in swine
housing is to provide one row of lights over each row of pens  or
stalls,  and  one  row  along  the feed alley. At least one light
should be installed over  every  other  pen  partition.  Table  1
recommends  the amount of lighting for various building purposes.
For example, a 24-ft. wide nursery could  be  illuminated  to  10
foot-candles with (0.28 x 24 x 1) = 6.72 watts (W) of fluorescent
lighting/ft. of room length, or (1.00 x 24 x 1) = 24 W of  150  W
incandescent lighting/ft. of room length. For a 25-ft. long room,
this would mean at least one double-tube  40-W  fluorescent  fix-
ture,  or  two  single-tube  fixtures  (6.72 W/ft. of room length
times 25 ft. of length) on each side of the room,  or  two  150-W
incandescent  fixtures  (24  W/ft. of room length times 25 ft. of
length) on each side. For wider buildings, you may want  to  con-
sider additional rows of lighting. Observe wattage limitations on
incandescent bulb fixtures. Many of them have 60- or 75-watt lim-

Table 1. Light level for swine buildings.*
                          Foot-candle  cool white      Standard
                          illumination fluorescent   incandescent
Building                     level        40 W      100 W   150 W
                                      Watt/sq. ft. of building area
Farrowing                      15         0.42       1.72    1.50
Nursery                        10         0.28       1.15    1.00
Growing/finishing              5          0.14       0.58    0.50
Breeding/gestation             15         0.42       1.72    1.50
Animal inspection/handling     20         0.55       2.29    2.00
Office                         50         1.38       5.72    5.00
Feed storage/processing        10         0.28       1.15    1.00
* Space lighting uniformly.
Values assume monthly bulb cleaning and regular bulb replacement.
For infrequent cleaning, increase table values 40%.
Assumed 8-ft. ceiling height and 50% wall and 70% ceiling reflec-
Values based on ASAE Farm Lighting Design Guide, SP-0175.


     Have an electrician or other knowledgeable person  calculate
circuit sizes because of the special heavy uses of electricity in
hog buildings (heat lamps, portable motors, and other equipment).
Circuits  should include both those for general purpose and those
for special equipment. General purpose  circuits  include  lights
and  duplex convenience outlets (DCO). Equipment circuits include
those for ventilation fans, heaters, fixed equipment,  appliances
over  1,500  W,  motors  exceeding  1/3  hp., and special purpose
outlets (SPO) for uses such as high pressure washers.

     As a guide, a general purpose  circuit  should  be  computed
allowing 1.5 A per light fixture or DCO if not used for motors or
heat lamps. Use the actual load value for DCOs and SPOs that sup-
ply  motors, heat lamps, floodlights, or other large power users.
Use #12 AWG copper wire (Table 2) and a 20-A circuit breaker  for
each  20  A  of electrical load. Circuits may not be continuously
loaded to more than 80% of their designed  capacity.  Where  cir-
cuits  serve  heating lamps, ventilation equipment, or other con-
tinuous or  extended  use  equipment,  the  80%  load  factor  is
required  by the NEC, so plan the number of circuits accordingly.
If each DCO will be used with heat lamps or  other  large  resis-
tance loads, circuit load should be calculated as follows:
|Table 2. Maximum current  capa-      |
|city of copper wire.                 |
|                                     |
|____________________________________ |
|                   Ampacity          |
|          __________________________ |
|                         Type THW,   |
|Wire size               THWN, RHW,   |
|AWG copperType UF cableand XHHW wire |
|____________________________________ |
|    12         20           20       |
|    10         30           30       |
|    8          40           50       |
|    6          55           65       |
|    4          70           85       |
|    3          85           100      |
|    2          95           115      |
|    1          110          130      |
|   1/0         125          150      |
|   2/0         145          175      |
|   3/0         165          200      |
|   4/0         195          230      |
|____________________________________ |

     Amps (A)   =   Watts (W) : Volts (V),
            A   =   current flowing through the conductor
            W   =   total power to be in service on circuit
            V   =   120 V or 240 V service

Remember, if the circuit will be  continuously  loaded,  such  as
with  heat  lamps, a 20-A circuit should be planned to carry only
16 A (80% of its actual rated load).

     Branch circuits with only one motor should be sized for 125%
of  the  motor full load current rating. For example: for one 8-A
motor on a circuit, 8 x 1.25 = 10 A. If more than one motor  will
be on a circuit, rate the largest motor at 125%, and add the oth-
ers at 100% of full load current  rating.   Additional  loads  on
this circuit should be added at 100% of their full load current.

     General purpose circuits wired  with  #12  AWG  copper  wire
should  have  no  more than a 20-A connected load; #14 AWG copper
wire circuits should have no more than a 15-A connected load. New
general  purpose  circuits  smaller  than  20-A (#12 AWG, copper)
capacity are not recommended except for specific loads.

     Size all conductors based on length of run as well  as  con-
nected  load.   Long  runs  of  undersized  wire result in wasted
energy and reduced performance of lights  and  electrical  equip-
ment.  Branch  and  feeder  circuits should not exceed 2% voltage
drop, and should never be smaller than #12 AWG (copper).  Maximum
combined  voltage  drop for service drops, feeder and branch cir-
cuits should not exceed 5% to the most distant DCO. The relation-
ships  between  current,  circuit  length, voltage drop, and wire
size are given in Tables 3 and 4.

Table 3. Minimum copper conductor size for branch circuits  using
Type  UF cable (based on maximum conductor capacity or 2% voltage
drop, whichever is limiting).

           Nominal 120 V service    |     Nominal 240 V service
AmpereConductor length, ft. (one way)Conductor length, ft. (one way)
 load 30 4050 6075 100125 150 175200|5060 75100125 150175200 225250
            American wire gauge     |      American wire gauge
  5   12 1212 1212 12  12  10 10  10|1212 1212  12 12 12  12 12  12
  7   12 1212 1212 12  10  10  8  8 |1212 1212  12 12 12  12 10  10
  10  12 1212 1210 10  8   8   8  6 |1212 1212  12 10 10  10 10  8
  15  12 1210 1010  8  6   6   6  4 |1212 1210  10 10  8  8   8  6
  20  12 1010 8  8  6  6   4   4  4 |1212 1010  8   8  8  6   6  6
  25  10 10 8 8  6  6  4   4   4  3 |1010 10 8  8   6  6  6   6  4
  30  10 8  8 8  6  4  4   4   3  2 |1010 10 8  6   6  6  4   4  4
  35   8 8  8 6  6  4  4   3   2  2 |8  8 8  8  6   6  4  4   4  4
  40   8 8  6 6  4  4  3   2   2  1 |8  8 8  6  6   4  4  4   4  3
  45   6 6  6 6  4  4  3   2   1  1 |6  6 6  6  6   4  4  4   3  3
  50   6 6  6 4  4  3  2   1   1 1/0|6  6 6  6  4   4  4  3   3  2
  60   4 4  4 4  4  2  1   1  1/02/0|4  4 4  4  4   4  3  2   2  1
  70   4 4  4 4  3  2  1  1/0 2/02/0|4  4 4  4  4   3  2  2   1  1
  80   3 3  3 3  2  1 1/0 2/0 2/03/0|3  3 3  3  3   2  2  1   1 1/0
  90   2 2  2 2  2  1 1/0 2/0 3/03/0|2  2 2  2  2   2  1  1  1/01/0
 100   1 1  1 1  1 1/02/0 3/0 3/04/0|1  1 1  1  1   1  1 1/0 1/02/0

Source: Adapted  from  Agricultural  Wiring  Handbook,  8th  Ed.,
National  Food  and Energy Council, Inc. 409 Vandiver West, Suite
202, Columbia, MO 65202.

Table 4. Minimum copper conductor size for branch circuits  using
Type  THW,  THWN,  RHW, and XHHW wire (based on maximum conductor
capacity or 2% voltage drop, whichever is limiting).

           Nominal 120 V service    |     Nominal 240 V service
AmpereConductor length, ft. (one way)Conductor length, ft. (one way)
 load 30 4050 6075 100125 150 175200|5060 75100125 150175200 225250
            American wire gauge     |      American wire gauge
  5   12 1212 1212 12  12  10 10  10|1212 1212  12 12 12  12 12  12
  7   12 1212 1212 12  10  10  8  8 |1212 1212  12 12 12  12 12  10
  10  12 1212 1210 10  8   8   8  6 |1212 1212  12 10 10  10 10  8
  15  12 1210 1010  8  6   6   6  4 |1212 1210  10 10  8  8   8  6
  20  12 1010 8  8  6  6   4   4  4 |1212 1010  10  8  8  6   6  6
  25  10 10 8 8  6  6  4   4   4  3 |1010 10 8  8   6  6  6   6  4
  30  10 8  8 8  6  4  4   4   3  2 |1010 10 8  6   6  6  4   4  4
  35   8 8  8 6  6  4  4   3   2  2 |8  8 8  8  6   6  4  4   4  4
  40   8 8  6 6  4  4  3   2   2  1 |8  8 8  6  6   4  4  4   4  3
  45   8 8  6 6  4  4  3   2   1  1 |8  8 8  6  6   4  4  4   3  3
  50   8 6  6 4  4  3  2   1   1 1/0|8  8 6  6  4   4  4  3   3  2
  60   6 6  4 4  4  2  1   1  1/02/0|6  6 6  4  4   4  3  2   2  1
  70   4 4  4 4  3  2  1  1/0 2/02/0|4  4 4  4  4   3  2  2   1  1
  80   4 4  4 3  2  1 1/0 2/0 2/03/0|4  4 4  4  3   2  2  1   1 1/0
  90   3 3  3 3  2  1 1/0 2/0 3/03/0|3  3 3  3  3   2  1  1  1/01/0
 100   3 3  3 2  1 1/02/0 3/0 3/04/0|3  3 3  3  2   1  1 1/0 1/02/0

Source: Adapted  from  Agricultural  Wiring  Handbook,  8th  Ed.,
National  Food  and Energy Council, Inc. 409 Vandiver West, Suite
202, Columbia, MO 65202.

     Stationary  equipment  should  be  permanently  wired   into
moisture-proof  boxes  as  described  earlier. This will minimize
problems  of  moisture  and  dust  entering  the  wiring  system.
Suspended  appliances,  lighting  fixtures, and heating equipment
should be provided with mechanical support such as chains and not
suspended  by  their  electrical supply wires, conduit, or cords.
Minimize the use of extension cords.

     Circuits servicing high pressure washers  must  be  equipped
with  a  ground  fault  interrupter  (GFI) device unless a GFI is
built into the washer.  Installing a ground rod at the receptacle
is  not an allowed practice by itself, though a ground rod may be
used to complement proper wiring techniques.


     The electrical supply system is the ``heart'' of the  build-
ing electrical system and consists of service conductors from the
power supply, the  main  disconnect,  one  or  more  distribution
panels  (DP), and associated equipment. Often the main disconnect
and DP will be in the same panel. Be sure that service conductors
and equipment are large enough to provide electrical capacity for
present and future needs. Minimum supply service for farm  build-
ings  is  60 A, but most modern buildings require at least 100 A;
your power supplier can help in determining  the  proper  service
supply.  An  undersized  service supply is unsafe and inefficient
and reduces the longevity of the system and equipment.

     Where building openings such as doors, hatches,  or  windows
are used for transfer of materials between the inside and outside
of the building, overhead  service  conductors  must  be  out  of
reach.  Portable  elevators and other equipment must be maneuver-
able into openings  with  minimal  risk  of  contacting  overhead
wires.  Therefore,  have the point of attachment of overhead ser-
vice conductors or other wiring no closer than 10 ft.  on  either
side  of  the  opening,  and  at least 3 ft. above. Under no cir-
cumstance should the point of attachment be below such  openings.
A minimum clearance of 18 ft. should be provided above all drive-
ways. Remember: clearance will decrease in warm weather as  ther-
mal  expansion  causes  conductors  to sag. Contact of conductors
with equipment can kill!

     Each circuit should be protected in the DP with its own fuse
or circuit breaker selected to correspond to the size of the con-
ductors used in the circuit. Do not load circuits  to  more  than
80% of their current-carrying capacity (Table 2). This limitation
is especially important for circuits loaded continually for  long
periods of time as with fans or heat lamps. Where fuses are used,
they should be of the Type S kind sized for the  current-carrying
capacity  of the circuit conductor. Type S fuses prevent the ins-
tallation of a larger capacity fuse when a properly selected fuse

     Location of the DP can affect  its  rate  of  deterioration.
Never  install  a  DP recessed into an outside wall. Lack of ade-
quate insulation behind the  panel  can  result  in  condensation
within  the box and rapid corrosion of electrical equipment. Even
surface mounted DPs, if possible, should not be  mounted  on  the
inner surface of an outside wall for the same reason.

     Avoid problems by locating the DP outside the dusty,  humid,
and  corrosive environment of the animal housing. The environment
is less likely to be harsh in an entry hall, office,  or  utility
room, and the DP could be located there using a NEMA 3R enclosure
with corrosion-resistant finish. If the DP must be located  in  a
room  with animals, use a moisture-tight nonmetallic unit (NEMA 4
or 4X enclosure). For safety and convenience, be sure to  provide
at least 3 ft. of open, accessible work space in front of the DP.
The door or cover must be capable  of  being  opened  a  full  90

     Where possible, place DPs near the largest electrical loads.
This  will  minimize  requirements  for long runs of larger, more
expensive conductors and eliminate energy-wasting voltage drops.

     Surface mount DPs on a fire resistant surface such  as  con-
crete  or  26  gauge  (minimum thickness) galvanized steel over a
fire-resistant material. Use spacers to provide a gap of at least
1/4  in. between the DP and wall (Figure 6).  If overheating does
occur with this installation, the air space will help protect the
combustible  wall  of  the building. The spacing arrangement will
also help maintain the DP at room temperature, reducing the  pos-
sibility  of condensation, and will eliminate entrapment of mois-
ture, dust, manure, and other corrosive matter.

     As noted earlier, service conductors and branch circuit con-
duit  or  cable  should  enter  at or near the bottom of the main
disconnect or DP. In this way, draining of water  and  condensate
down  the  cable or conduit and into the panel can be more easily

     Where existing DPs have been installed so that  condensation
may develop during cold weather, a small amount of heat installed
around, on, or in the DP may help alleviate the problem. If  pos-
sible,  first install some insulation behind the panel. If the DP
is surface mounted, it may be possible to wrap the perimeter with
a  heat tape. Another alternative during cold weather is to mount
a heat lamp in a holder outside the panel directed  to  warm  the
DP.  Take care that the bulb is not close enough to wires, walls,
or other materials that it might cause damage or fire.

     Since some corrosion may develop on contact surfaces  of  DP
circuit  breakers,  a monthly schedule to switch circuit breakers
off and on should be established. This will help wear away  minor
amounts  of  corrosion  which  may develop at the breaker contact
surface, and which could contribute to electrical resistance  and
overheating.  Circuit breakers that are not switched off periodi-
cally are frequently found ``frozen'' into the  ``on''  position.
In  such cases, it is unlikely they would trip under high current
load, so the intended safety feature no longer exists.


     Safety requires two systems of grounding:

     1. System groundingthe connection of the ground service con-
ductor  through  an  acceptably sized (based on service capacity)
conductor  to  an  acceptably  sized  grounding  electrode.  This
grounding  electrode  conductor must be connected at the terminal
or bus bar to which  the  grounded  service  conductor  (commonly
called  the  ``neutral'')  is  terminated in the main disconnect.
Grounded conductors carry current during the normal operation  of
115-V  equipment  and must have white or gray insulation or mark-

     2. Equipment groundingthe grounding or bonding of noncurrent
carrying  equipment  such  as  motor  frames  back to the service
entrance panel grounding bar. Failure to provide proper equipment
grounding may contribute to stray voltage problems causing stress
and danger to animals and humans. The NEC requires that grounding
conductors  be  bare  or have a green or green with yellow stripe
insulation. This conductor is  designed  to  carry  current  ONLY
under  fault  conditions  and  is  commonly  referred  to  as the
``ground'' wire.

     Grounding electrodes are required at all service  entrances,
using  approved bonding (clamps) properly sized, based on service
capacity.  Rods of 8 ft. (minimum) are commonly used, but the NEC
does  allow  other methods. The grounding conductor from the ser-
vice entrance disconnect to the  grounding  electrode  should  be
protected  from  physical damage and should be continuously main-
tained. Resistance from the grounding  electrode  to  surrounding
soil  must be 25 ohms or less. If more than one electrode must be
used to get this resistance, rods should be spaced at least twice
the length of the ground rods and interconnected with a noncorro-
sive conductor and ground rod clamps approved for  that  purpose.
Use clamps designed and rated for direct burial.

     To minimize danger from electrical faults, the NEC  requires
all metallic equipment including building components within 8 ft.
of the floor or soil surface to be bonded to the system grounding
electrode through the branch circuit grounding or other appropri-
ate grounding conductors. Although separate grounding rods may be
used  in  these  cases, they must be in addition to and bonded to
the main system  electrode.  All  metallic  water  lines,  gates,
flooring  materials,  animal crates or pens and similar equipment
must be bonded together and to the  electrical  system  grounding

     All new wiring should include  equipment  grounding  conduc-
tors.  Equipment  such  as motors or electrically-heated waterers
should be grounded by means of an equipment  grounding  conductor
connected  to  the  grounding bus at the DP.  Installing a ground
rod at such equipment as a substitute for an equipment  grounding
conductor  is not permitted, but a ground rod may be installed as
a complement to the grounding conductor.


     No more than two fans should be  wired  per  circuit  in  an
environmentally controlled swine room. With fractional horsepower
motors, or when more than one fan is included on  a  branch  cir-
cuit,  secondary  fusing  is  necessary to provide adequate over-
current protection of individual fan motors with a locked  rotor.
The  use  of automatic reset fans is not recommended because fans
often continue to restart until they finally burn out the  motor.
Also,  there  is  risk involved since a person who sees a fan not
operating could begin to check to determine why it is not running
and  the  automatic  restart  could  re-engage,  causing personal
injury. The manual reset is a much preferable and  safer  protec-
tive  measure  for  motors  that operate fans, feed, and material
handling systems.

     A fused switch installed in a corrosion resistant  box,  and
located  within  5  to  10 ft. of each fan is required for safety
during cleaning and maintenance. Fused switches are available  to
meet both individual fan fusing and switching requirements. Use a
time-delay fuse sized at 150% (125% for  motors  without  thermal
protection)  of  the motor full load current rating. At least two
fan branch circuits from opposite sides of  the  230  V  entrance
panel should be provided in each environmentally-controlled room.
Then, if one circuit fails, the room can still be ventilated.

     Because of dust and  corrosion,  use  only  totally-enclosed
motors  for  swine buildings. Open motors are more prone to early
failure and more apt to cause fire and  explosions  and  are  not
allowed in livestock buildings.


     Few states require the inspection of agricultural electrical
systems.   However,  some  power  suppliers require an inspection
before electrical service will be provided. Some  insurance  com-
panies  require  inspections,  while others offer reduced premium
rates for buildings that are inspected and  verified  as  meeting
NEC  requirements.  Consult your power supplier and and insurance
company, and use available  inspection  services  before  putting
newly wired facilities into use.


     Quality electrical wiring  practices  are  often  overlooked
when  remodeling  or  constructing new swine buildings. The moist
and corrosive conditions in these buildings necessitate  suitable
practices  and  materials  to increase the life of the electrical
system and to reduce the likelihood of loss of property, animals,
and income, or personal injury caused by electrical failure.

                      ADDITIONAL REFERENCES

Agricultural Wiring Handbook  (Eighth  Ed.).  National  Food  and
Energy Council, Columbia, MO 65202.

Electrical Wiring Systems for Livestock and  Poultry  Facilities.
National Food and Energy Council, Columbia, MO 65201.

Farm Buildings Wiring Handbook, MWPS-28.  Midwest  Plan  Service,
Iowa State University, Ames, IA 50011.

National Electrical CodeO. Published by and a  registered  trade-
mark  of  the  National  Fire  Protection Association, Quincy, MA


 Reference to products in this publication is not intended to be
 an endorsement to the exclusion of others which may be similar.
 Persons using such products assume responsibility for their use
   in accordance with current directions of the manufacturer.

NEW 6/87 (5M)


Figure 1. A majority of all farm fire losses are related to elec-
trical system failure.

Figure 2. Either conduit or Type UF cable wiring circuits may  be
used  in  swine  buildings. Wiring should be attached to interior
surfaces of buildingnot concealed in wall,  ceiling,  or  atticto
reduce  condensation  and  rodent  damage and facilitate periodic

Figure 3. Standard metal boxes are not suitable for swine housing
because  of susceptibility to corrosion and subsequent electrical
system failure. Boxes are required to be moisture-proof and  have
spring-loaded covers.

Figure 4. Switches should be moisture-proof, either by  means  of
moisture-tight  levers,  spring-loaded  covers, or moisture-tight
covers with flexible press switches.

Figure 5. All cable or conduit should enter electrical boxes  and
distribution panels from the side or bottom if possible.

Figure 6. A 1/4-in. gap is required between  distribution  panels
and  walls  to  reduce fire hazard if overheating occurs. Spacing
also helps to maintain panel at room temperature,  reducing  con-
densation, and reduces entrapment of dirt (Note: Normal operation
would assure that panel cover is in place).

% Figures are available in hard copy.

Cooperative Extension Work in  Agriculture  and  Home  Economics,
State  of Indiana, Purdue University and U.S. Department of Agri-
culture Cooperating. H.A. Wadsworth,  Director,  West  Lafayette,
IN. Issued in furtherance of the Acts of May 8 and June 30, 1914.
It is the policy of the Cooperative Extension Service  of  Purdue
University  that  all  persons  shall  have equal opportunity and
             access to our programs and facilities.