Heat mats - best wired in series or parallel?

Discussion in 'Analog & Mixed-Signal Design' started by Martyn Lucas, Jul 11, 2016.

  1. Martyn Lucas

    Thread Starter New Member

    Jul 11, 2016
    3
    0
    Hi Guys

    I have a quick question, and I'd really appreciate a bit of advice if you wouldn't mind.

    I have an aluminium (die) mold which I'm looking to heat between 75-100 degrees C using silicone heat mats - (http://uk.rs-online.com/web/p/silicone-heater-mats/0245663/)

    I have an RCD, PID, TC and relay but I would like to control and power 4 identical heat mats in the same circuit (1.6kw total), but the question is whether to wire them in series or parallel? From what I can gather, if wired in series the v-drop would be spit over the 4 inductances. The mats are rated at 240v so would they work at 60v with a constant current of 6.6 A across each load to reach the 400w (ea) power rating?

    With parallel, it seems like the voltage be a constant 240v, with 1.6A across each load. Any ideas what would be the best way to go? I don't really have the money to replace burned out parts!

    Thanks
     
  2. #12

    Expert

    Nov 30, 2010
    16,248
    6,745
    That won't work because the mats will not reduce their resistance in order to draw 6.6 amps. They are 144 ohms each. They would go down to 25 watts each.
    They must be in parallel to get 400 watts.
     
  3. AlbertHall

    Well-Known Member

    Jun 4, 2014
    1,881
    373
    If you connect them in series then each one will provide only one sixteenth as much heat as a single mat at 240V.
    If you have four mats and just one temperature sensor and control circuit, can you be sure that the heat of each mat will be well enough matched to avoid any one mat overheating?
     
  4. Martyn Lucas

    Thread Starter New Member

    Jul 11, 2016
    3
    0
    Awesome, thanks #12 - much appreciated.
     
  5. Martyn Lucas

    Thread Starter New Member

    Jul 11, 2016
    3
    0
    Hi Albert hall. It'll just be a matter of 'suck it and see' I'm afraid as I'm still in the prototyping stage. The only thing that gives me comfort is that the mats are rated to 200 degrees, and I'm looking to heat the block up to 83. I'll also be in the room whenever the heaters are on so if one overheats and their wired in parallel, it wouldn't be a complete catastrophe
     
  6. wayneh

    Expert

    Sep 9, 2010
    12,087
    3,027
    I don't know anything about your mats but I'd be reluctant to just plug them in at full blast. It might quickly overheat and destroy itself. I'd be tempted to put a light bulb in series with it first, to see how it behaves. Or two mats in series. Just until you establish safe operating conditions.
     
Loading...