selection of relay for driving an immersion rod

Discussion in 'The Projects Forum' started by issac newton, Dec 17, 2012.

  1. issac newton

    Thread Starter New Member

    Jan 25, 2011
    i am designing a heating element control system. i am looking for a relay(with 5V input voltage if possible or 12V) which can control an immersion rod with specification 16-A & 250 V AC. The following are my questions.

    1. the heater has to be driven with power sockets(type M sockets -16A). can i use normal sockets of "type D"(which produces max current of 15A). what will happen if i use this. will the heating process be slow because of lower current driving capacity of the socket or the effect will create some problems ?

    2. to control this heating element i am using MSP 430G2231. is there any switching device instead of relays like mosfets which work out cheaper for controlling the heater with specified ratings.

    3. which relay might suit my requirements. cheap and best ones.

    4. i am using LM35 as my temperature sensor. please suggest me with some other best,cheap and user friendly sensors with resolution upto 0.5 degree.

    thank you all.
  2. jwd217

    New Member

    Jun 19, 2012
    If your load draws 16a and you run it through a relay socket that is rated for 15a, the load will still draw 16a. However the socket will become too hot and eventually fail. One way to overcome this is if the relay has more than one set of contacts, then run the load through two or three contacts. The 15a rating would be per contact so by connecting the contacts in parallel, then each contact would have 1/2 or 1/3 of the current. Make sure the relay contacts have a high enough rating as well.
  3. wayneh


    Sep 9, 2010
    This is definitely not a good idea. As noted, the load will draw more current than the socket is rated for. Find a better one.
    There is such a thing as a solid state relay (SSR), but it's tough to beat a conventional relay for what you're doing with it.
    I'd start at one of the big suppliers like Mouser, DigiKey or Newark and see what you find. Be sure you look for relays rated for switching AC to 20A or more (for safety margin) and 220V.
    I use the LM35 and usually recommend it.