Kitfox Aircraft Stick and Rudder Stein Air Grove Aircraft TCW Technologies Dynon Avionics AeroLED MGL Avionics Leading Edge Airfoils Desser EarthX Batteries Garmin G3X Touch
Results 1 to 10 of 12

Thread: Shortening thermocouple wire

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1
    Senior Member
    Join Date
    Jun 2008
    Location
    wales,ny
    Posts
    710

    Default Shortening thermocouple wire

    I am replacing my westach quad gauge with a MGL EMS-2 engine monitor that allows 4 cylinder monitoring which the westach does not provide. Instead of looping up excess thermocouple wire (CHT and EGT) like I have done in the past, I would like to cut off the excess for custom lengths. Any problem with doing this? Bruce N199CL

  2. #2
    Senior Member Dave S's Avatar
    Join Date
    Oct 2008
    Location
    St Paul, MN
    Posts
    1,833

    Default Re: Shortening thermocouple wire

    Bruce,

    I'd recommend against cutting the lead because in the process a person may end up creating a "cold junction" which may alter the resistance value of the assembly, or introduce another bimetallic junction, of the manufactured part. In other words - it might not read predictably with the design value.

    I'd stay with a loop for the excess and cleverly call it a "Service Loop"

    There are a lot thermocouple references out there and it is similar to voodoo. Cut to the chase would be to contact Westach.

    DS
    Dave S
    Kitfox 7 Trigear (Flying since 2009)
    912ULS Warp Drive

    St Paul, MN

  3. #3
    Administrator DesertFox4's Avatar
    Join Date
    Aug 2008
    Location
    Arizona
    Posts
    3,562

    Default Re: Shortening thermocouple wire

    This may be of some help. MGL carries a splice kit for cht wires.

    http://www.mglavionics.com/CHT_Parallel_Splice.pdf


    DesertFox4
    Admin.
    7 Super Sport
    912 ULS Tri-gear


  4. #4
    Senior Member
    Join Date
    Jun 2008
    Location
    wales,ny
    Posts
    710

    Default Re: Shortening thermocouple wire

    Thanks for the responses Dave and Steve. Before I placed my order with MGL (the unit is on backorder so haven't received it yet) I took measurements from each cylinder(CHT) and exhaust stack(EGT) to where the RDAC (the smart box everything connects to on the firewall). Then called MGL and they told me their thermocouples come with 3 foot tails. Some of my runs are less than 3 feet some a bit longer (Steve I did order the splice kit for the longer runs). When the EMS-2 arrives I will check everything out and give the MGL tech support a call to see what they say. There was a discussion on the RV forum , and the consensus was it is OK to cut to length but I will see what MGL says. Looking forward to installing this neat little feature rich engine monitor (the post OSH spending continues!) Thanks guys Bruce N199CL

  5. #5
    Senior Member jmodguy's Avatar
    Join Date
    Jul 2014
    Location
    Carmel, IN
    Posts
    744

    Default Re: Shortening thermocouple wire

    The measurements we use on our engines are not that critical. If they were, manufacturers would be requiring cold junctions and/or chrome and alumel contacts in the connectors. You can shorten the leads without any major effect.
    I work on an experimental 747-200 that has a LOT of this wire installed on a couple hundred thermocouples. We do not leave excess wire on any harness. Our measurements are much more critical so we use both chromel and alumel contacts and cold junctions.
    Jeff
    KF 5
    340KF

  6. #6
    Senior Member
    Join Date
    Jun 2008
    Location
    wales,ny
    Posts
    710

    Default Re: Shortening thermocouple wire

    Thanks Jeff good to know that this can be done , as Dave mentioned above from what i've read , this is like voodoo science and its tough to get a definitive answer. Hopefully my MGL stuff arrives this week and I will talk to their tech support after seeing what the thermocouples look like. Can't wait to see your monster Kitfox fly. Looking pretty cool and have enjoyed following your build . Bruce N199CL

  7. #7
    Senior Member jmodguy's Avatar
    Join Date
    Jul 2014
    Location
    Carmel, IN
    Posts
    744

    Default Re: Shortening thermocouple wire

    Thanks Bruce! Final push is under way...
    For what it’s worth, I was reviewing my documentation to ensure I understand how all of this is supposed to work and re-read my GRT EIS manual and it also mentioned it was ok to trim the wire lengths.
    Jeff
    KF 5
    340KF

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •