Order this information in Print

Order this information on CD-ROM

Download in PDF Format

     

Click here to make tpub.com your Home Page

Page Title: Figure 6-3. Temperature control thermostat test points
Back | Up | Next

Click here for a printable version

Google


Web
www.tpub.com

Home


   
Information Categories
.... Administration
Advancement
Aerographer
Automotive
Aviation
Combat
Construction
Diving
Draftsman
Engineering
Electronics
Food and Cooking
Math
Medical
Music
Nuclear Fundamentals
Photography
Religion
USMC
   
Products
  Educational CD-ROM's
Printed Manuals
Downloadable Books
   

 

TM 5-4120-270-15 Figure 6-3.  Temperature control thermostat test points. Caution: Do not apply test potentials in excess of 230 volts (d)   Energize   control   coil   using   a   2428V   DC source   or   two   12   volt   batteries   connected   in   series. Using a multimeter on lowest OHMS range, test contact resistance across each pair of line and load terminals L,- T,, L2-T, and L,-T,.  Contact resistance in excess of 0.2 ohms indicates dirty or burnt contacts.  Clean contacts if possible, or replace contactor. (2)  25-ampere  contactors.    Proceed  as  instructed above, noting that line and load terminals are now Al-A2, B1-B2 and C1-C2.  Observe same cautions. e.    Reassembly.    Reassemble  any  parts  that  were removed for cleaning or dressing contacts. f.        Installation.        Refer    to    figure    6-4    and    install contactors in junction box. 6-6.  Time Delay Relay a.    General.    The  time  delay  relay  is  a  hermetically enclosed, single-pole, single-throw normally open thermal   delay   relay   which   keeps   the   hot   gas   bypass valve open and prevents operation of the compressor for 30    seconds    after    the    selector    switch    is    placed    on "COOL".    The  time  delay  relay  closes  at  the  end  of  the delay   period   and   remains   closed   as   long   as   the   air conditioner   is   on   "COOL"   mode.      Switching   to   other modes  of  operation  opens  the  relay.    It  remains  open until the air conditioner is again placed on "COOL" mode, at  which  time  it  delays  valve  and  compressor  operation as outlined above. b.  Removal.  Refer to figure 6-4 and remove the time delay relay assembly from the junction box. c.    Disassembly.    Do  not  disassemble  for  testing.    If replacement  is  indicated,  remove  time  delay  relay  from its mounting bracket and disconnect electrical leads. d.  Testing. (1)  Refer  to  figure  6-7  and  place  a  continuity indicator or multimeter on low OHMS range across leads A and B. (2) Apply 2-28V DC from a test source or two 12-volt batteries in series across leads A and C. (3) Begin timing the relay from the  instant  DC power     is     applied     until     the     continuity     indicator     or multimeter   indicates   the   relay   contacts   have   closed. Normal  delay  is  30  seconds  :8  seconds.    Replace  time delay relay if delay time is not according to specifications. e.      Reassembly.      Connect   electrical   leads   to   time delay relay and mount relay in its bracket. f.    Installation.    Refer  to  figure  64  and  install  time delay relay in the-junction box. 6-7.  Transformer a.      General.      The   control   circuit   transformer   is   a single-phase, shielded, potted stepdown transformer with a  208V  AC  primary  and  a  30V  AC  secondary.    After rectification,   the   resulting   24V   DC   output   is   used   to energize   the   magnetic   contactor   and   solenoid   valve control  coils  and  the  time  delay  relay.    The  transformer primary circuit is protected by the auxiliary circuit breaker contact and by a cartridge-type fuse in each line. b.      Removal.      Refer   to   figure   64   and   remove   the transformer from the junction box. c.      Disassembly.      Disconnect   electrical   leads   from primary  and  secondary  terminals.    Do  not  disassemble further. d.  Testing. (1)  Connect  a  continuity  tester  or  multimeter on   low   OHMS   range   across   the   transformer   primary winding.  If winding is open, replace transformer. (3)  Connect  a  continuity  tester  or  multimeter on  low  OHMS  range  across  the  transformer  secondary. If winding is open, replace transformer. (3)   Connect   an   insulation   tester,   megger   or multimeter  on  high  OHMS  range  between  one  primary terminal and transformer, case.  If resistance is less than 0.5 megohm,-replace transformer. (4)   Connect   an   insulation   tester,   megger   or multimeter  on  high  OHMS  range  between  one  primary terminal and one secondary terminal.  If resistance is 6-4

Privacy Statement - Press Release - Copyright Information. - Contact Us - Support Integrated Publishing

Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business