Heating element wiring confused

Discussion in 'General Electronics Chat' started by Imzautomation, Feb 26, 2014.

  1. Imzautomation

    Thread Starter New Member

    Feb 15, 2013
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    Hi as the title suggests I am confused ... I am building a oven for which I need a fan and heating element to recirculate hot air so I planed of using this setup
    One hairdryer with 800 watts element and another 2000 watt element from fan heater salvaged I have also bought rex c100 temperture controller with 40amp SSR

    WHAT I WOULD LIKE TO DO

    I have disassembled the hairdryer and kept fan+heating element intact now I want to connect the leads of this setup to the other heating element so that I can get a total of 2800 watts and control the whole setup with ssr

    My question
    How do I connect the salvaged 2000 watt heater element to hairdryer fan/element .
    Do I need to seperste the heting element of hair dryer and separately connect heating elements in series or can I just connect the already existing hairdryer fan heat element combo to the leads of heater please help
     
  2. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    380
    hi,
    To get 2800W from a 2000W and 800W elements they should be connected in parallel across the mains supply, NOT series.

    To enable switching 2000W or 800W , connect one end of the 2000W element to one end of the 800W element, this pair of wires will go to the Neutral Mains connection.

    You can then switch as required the 'other' ends of the 2000W or 800W to the Line Mains connection. It MUST be fused at 13 Amp.

    Do you follow OK.?

    E
     
  3. Imzautomation

    Thread Starter New Member

    Feb 15, 2013
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    Hi Eric I understand what you are saying but my problem is I have hairdryer unit which I disassembled it has heating element connected to dc motor via diodes I want to keep this setup as it is and want to connect another 2000 watt heating element to the leads of the hairdryer setup the hairdryer setup has a button which slides up for switching on I would like wire 2000 watt element to this existing setup so that when I switch on the power I should be able to switch both hairdryer setup as well as the other 2000 wat element at the same time I don't want want to seperate the element from hairdryer and connect the other heater element in parallel I am trying to find a way to connect as described above
     
  4. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    The easiest way would be to have a double switched, wall mounted pair of sockets.

    Plug the existing hair dryer into one switched socket.

    Connect the 2000W to the second wall mounted socket, via a 13 Amp cable and mains plug into the second socket.

    You could switch On the 800W fan/heater and when required the 2000W element..

    Thats the way I would do it, using readily available mains rated plugs/sockets.

    E
     
  5. Imzautomation

    Thread Starter New Member

    Feb 15, 2013
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    Thanks Eric but in my first post I mentioned that this setup is for using in oven where I can circulate hot air in convection process I need to control temperature using pid so I have already purchased a pid controller with ssr your idea is good but my requirement Is to have 2800 watts of heat produced and blown by fan inside oven and a thermocouple monitors the temp and switches on off ssr as I said I just removed the plastic parts of hairdryer and want to join the external 2000 watt heater which I salvaged to the wires of hairdryer which plugs into wall socket
     
  6. t06afre

    AAC Fanatic!

    May 11, 2009
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    The heating element from the hairdryer and the other oven have very different characteristics. The hair dryer element need a constant flow of cold air in order to not overheat and burn out. And it is also not made for long term operations I am not sure what you are building. But to me it sounds like a very big fire hazard. I do not hope you plan to leave this construction of yours unattended for even a second
     
  7. Imzautomation

    Thread Starter New Member

    Feb 15, 2013
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    Hi I am building a oven where I need to maintain chamber temperature around 100degrees I will be controlling it with a pid and it is not always on it cycles through on off to maintain the desired temperature I am using the hairdryer fan to blow across the heating elements the hairdryer I am using is rated 800 watts but I need around 2500 watts so that my chamber heats up quickly can u explain why can't hairdryer element be used for this ?
     
  8. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    hi,
    How many watts are required to maintain the oven at 100Cdeg.?

    If its more than 800W, you could leave the fan and 800W [ hair dryer] on constantly and just PID control the 2000W element.

    E
     
    Imzautomation likes this.
  9. GopherT

    AAC Fanatic!

    Nov 23, 2012
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    An insulated box 2 feet on each side takes about 150 to 200 watts to maintain 100 C.

    It depends on the size and insulation of his chamber, but both will need to be onPID or he could just live with one heater if he has enough time to let it heat up.
     
    Imzautomation likes this.
  10. Imzautomation

    Thread Starter New Member

    Feb 15, 2013
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    Thanks for the replies guys Eric I can try your suggestion of just controlling the 2000 watt but then I have some issues I am building this box for 3d printer cum small pc oven it's inside dimension are 2.5x2.5x3.5' as gopher suggested I can just use the 800 watts but since it's a forced convection process it takes a lot of time I am thinking of removing the 800 watts element from the diode connection and attach the dc motor with diodes to 2000 watt element but not sure if it works the motor is a 12vdc any ideas
     
  11. ericgibbs

    AAC Fanatic!

    Jan 29, 2010
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    Hi Im'
    IIRC the fan in a hair dryer is not designed to work as a recirculating fan inside a hot oven.?
    It normally blows ambient temperature air thru the heated coils.

    Have you considered getting an oven fan from a scrapped fan assisted oven and dropping the hair dryer idea.?

    Just use the PID to control the 2000W element, from your description of the oven, it should be more than enough to rapidly heat the oven and maintain its 100Cdeg.

    E
     
  12. t06afre

    AAC Fanatic!

    May 11, 2009
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    First the hairdryer is design to suck in room temperature air and blow this over heating element. The fan blades are most often made of plastic. If you somehow restrict the airflow. The heating element will very quickly get into thermal runaway. Inside the hairdryer heating element you will find a thermal switch. That will very quickly shut down the element to prevent a total meltdown of the hair dryer if the airflow happened to be restricted. In your setup in using the heating element without blowing cool air past it. The thermal switch will engage very quickly. This will of course confuse the PID controller. And your setup will not work anyway.
     
  13. Little Ghostman

    Member

    Jan 1, 2014
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    at that size 1000W will heat it quickly! we make incubators, 50w heats and maintains a fridge size Cabinet pretty quickly to 37C, 2800W is overkill. We also tried hair dryer elements and hair straighteners, even just heating to around 37C they didnt last long in extended use.
    You might do better with a cooker ring?
     
  14. Electric Al

    Member

    Nov 6, 2013
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    Strip Heaters





    Strip heaters, often considered component heaters, are a simple way of using surface area to transfer heat effectively. Steel strip heaters are an excellent heat transfer product and can be easily controlled by using either mechanical thermostat not cost effective bimetal thermostats that can be installed on the surface you are heating. Mounting holes are useful to mount the heaters securely on almost any surface with terminal extending from the sheath for easy electrical connections. Many users also request lead wires that extend from one end that make the installation more flexible as the temperature controller is easily adaptable to this configuration.

    Temperatures reach as high as 500 degrees F and use the high quality magnesium oxide that is used in tubular elements that allow for effective heat transfer. A fairly inexpensive way of heating surfaces or small areas, strip heaters are an excellent solution to meet any budget.

    Strip heaters are composed of a heating element, a protective sleeve or sheath, and mounting hardware. If strip heaters are used as a radiant heater, they have can have fins to maximize surface area and heat transfer to the air. Strip heaters can be clamped or bolted onto objects or solid surface contact heating over large areas and are primarily used in indoor applications.



    We used to use this type of heater for many uses when I was working in a mining facility .

    They were available in assorted wattages , sizes , shapes .
     
  15. Imzautomation

    Thread Starter New Member

    Feb 15, 2013
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    Thanks a lot guys for your replies I will follow your suggestions the reason I am using hairdryer is because the size of the fan sits perfectly inside the round duct I am using for Blowing air . It a continuous loop open at end of the oven and collects warm air at the other end and follows the convection process I have detached the heting element from the hairdryer so that I can only use the 12v fan for sir circulation as suggested I only pid control only the heating element and power fan from external dc source so that it is always on I have seen some ricirculating fans which are used in PC ovens but the size is a bit of concern for me I hope this setup will work for the time being fingers crossed
     
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