Need help with variable high powered heating element using SSR

Discussion in 'The Projects Forum' started by spdjnky_42, Dec 30, 2013.

  1. spdjnky_42

    Thread Starter New Member

    Dec 30, 2013
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    Hey guys I have been trying to build a controller to vary a heating element for boiling my beer mash tun. I keep running into issues. 1st issue was finding something that had no Rf interference. So I decided to go with a burst fire SSR. Second was I wanted ease of use so instead of PID I went with a resistive style SSR and a potentiometer. Heres where I am at. I got the unit working but kept wasting SSR's I used a 25A heat sink on a 40A SSR pulling 22A/5500w element. I used thermal paste and a fan. Then I ran into an issue with the fan. I had been grounding the fan to the heat sink. I realize this is a neutral not a ground coming from the fan, so I am not sure if that was an issue.

    But heres where I am now. To wire in the heating element I basically have two 120v hots and a ground (USA) SO for a 120v fan that leaves me no where to hook the neutral in. I have the ground wire hooked to the boiler so hooking in the fan neutral would be a bad idea. I have decided to use a 240v fan, but now I am wondering if the sine wave from the SSR is going to effect the fan? I can wire it in before the relay so it has no on/off issue that the relay does. But will it being wired into a leg the SSR is on have an issue? [​IMG][​IMG][​IMG]
     
  2. spdjnky_42

    Thread Starter New Member

    Dec 30, 2013
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    I will post a diagram as soon as I can figure out how to do it. Unless someone can fill me in. This forum is different than any other I have been on [​IMG][/URL][/IMG]
     
  3. inwo

    Well-Known Member

    Nov 7, 2013
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    Seems to be a hot topic.
    ie. ssr failures.

    I don't see a problem tapping the line side for fan.
    Should be separately fused or protected.

    Correct, don't use the ground for any load.

    Is your pot rated properly? Don't believe input is isolated from output.

    You may just have to go big.
    A manufacturer that I know of is up to 400% over-sizing heater ssrs.

    Why not on=off PID? Not that it would help your issues.
    So you have no temperature sensing?
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    I am confused about the "two hots" in conjuction with USA 120V power feed. You should have a black wire (Line, 120Vac), a white wire (Neutral, 0Vac) and a green wire (Safety Ground). The load is wired between black and white, never to green. Green connects only to the metal enclosure.
     
  5. inwo

    Well-Known Member

    Nov 7, 2013
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    My take is two hots mean, two phases for 240vac.
    He then tapped 120 from one hot to ground. Thought better of it and got a 240 fan.
     
  6. #12

    Expert

    Nov 30, 2010
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    The usual wire colors are red and black for the (2) 120 volt, out of phase by 180 degrees lines, green for bond and white for neutral.
     
  7. spdjnky_42

    Thread Starter New Member

    Dec 30, 2013
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    That is correct inwo! Sometimes customers want a 220v 3 wire setup. I have it all figured out for wiring with 4 wire ;) I guess a 240v fan would do if it wont fry from the sine wave using the variable resistance ssr?

    Can you guys point me in the direction of a cheap $$ low amperage inline fuse?

    And 400%!!!! 120A SSR??? Ive had better luck with the 40A than the 60A. I only have a 8 x 8 box would I be able to get by on a 40A heat sink with paste and a 200cfm fan? I dont think I can fit any bigger heat sink in the box.

    Any ideas where to get quality relays without paying the crazy prices of Crydom?

    I do use PID's and dc controlled SSR's but some people want cheap AND simple.

    Thanks for the help!

    If someone can tell me how to load a picture from photobucket, I can show you the setup
     
  8. inwo

    Well-Known Member

    Nov 7, 2013
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    This ap was only 16 amps.

    I have no idea why the high failure rate.

    Do you have specs on the resistor type?
    Are they scr/triac output?

    A 2 fuse block for NON type fuses may fit. It would be about the size of ssr.

    Or 2 of these.
     
  9. #12

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    Relays I use:
     
  10. inwo

    Well-Known Member

    Nov 7, 2013
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    I sometimes wonder if old school is better.
    From what I'm seeing of these ssrs.
     
  11. #12

    Expert

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    A lot of new stuff goes through necessary improvements over time. The pure math approach of some engineers seems to miss some of the real world considerations, as if they can't think of everything that can go wrong on the first design. Maybe some of them think the highest allowable silicon temperature is really a design criteria? We at AAC have seen a lot of brand new BSEE's that have no practical experience. Still, the manufacturers set them to making new designs and are rude to people with 20 or 30 years of experience if they don't have a 4 year college degree.
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    What is meant by variable resistance SSR??
    You mentioned you were burst firing which is good, but this should be full on - full off cycling, which you can only do with a normal SSR?
    Where does the V.R. come in?
    I suspect your failures may be something to do with your set up?
    Max.
     
    #12 likes this.
  13. #12

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    More information would be good, and a schematic. A barrel of beer does not change temperature very much in 1/60 of a second. My experience says there is no need to fire tiny bursts of energy into a vat of mostly water.
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    I think there might be a misunderstanding, Burst firing is not on a cycle by cycle basis.
    But instead of phase angle control the SSR is either full on or off for a period of time depending on the PID loop, as opposed to switching on part way through the cycle .
    Just as your stove element is often controlled.
    But phase angle control requires a custom made SSR circuit usually.
    Max.
     
  15. inwo

    Well-Known Member

    Nov 7, 2013
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    My research shows a ssr with internal timer to send batches of full cycles to load. Duty set by rheostat on input pins.
    Could be random.

    Also it's not isolated. So rheostat input needs special consideration.

    Found reference @ digikey but didn't save it.
     
  16. spdjnky_42

    Thread Starter New Member

    Dec 30, 2013
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    Where are you saying to use these? These look like a nice alternative to my $40 disconnect switch. If I supplied 30A 120v to two of these and connected a simple 12v switch but then I need a 12v transformer...

    The controllers I use NORMALLY are a PID and SSR. The PID sends a DC signal to a SSR which then controls the 120v connection to vary the heating elements power. They work great if you are tech savvy.

    A lot of people cannot use a PID. So they want a simple dial to turn up or down the power like your stove but boiling cannot be done with a thermostat and a stove does not cycle enough nor at a high enough wattage for large boilers. Most boilers need 5500w some need 11kw and I have even made a few 22kw controllers.

    Since the heater brings the wash to a boil, the element has to have enough bursts to keep the wash in a tight temp as these are sometimes used for distilling ethanol. These are the resistant style SSR that use a potentiometer to adj the voltage being applied.

    http://www.reachelectrical.com/images/product_pdf/ControlDevices/SimmerstatsEnergyRegulators/fotek%20adjustable%20solid%20sate%20relay%20ssr40.pdf

    Sorry if I am not supposed to link outside links but no one has told me how to post a picture yet. I have tried the normal way of copying the url in photobucket and pasting here in the image prompt, with no luck.
     
    Last edited: Jan 2, 2014
  17. MaxHeadRoom

    Expert

    Jul 18, 2013
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    So if I read you right, you scrapped the Burst fire and PID method in favour of a phase angle controller?
    There is no reason why a thermostatically controlled PID burst fire method would not work if designed right?
    Max.
     
  18. inwo

    Well-Known Member

    Nov 7, 2013
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    I don't get it either.

    When op first posted I found a pot controlled ssr on digikey.
    Can't find it now.:confused:
    Only variable voltage controlled which is similar.

    Here is a link to pot type. Not much info though.
    http://www.kyotto.com/eng_KR20.htm

    The digikey one was non-isolated and put out 0-100% from pot only.
    This one needs dc input.
    http://www.crydom.com/en/Products/Catalog/p_cv.pdf

    It would seem op just wants a variable output with no control feedback and no phase control.

    User adjusted while monitoring temps.
     
  19. t06afre

    AAC Fanatic!

    May 11, 2009
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    If PID is not an option. Then you will need some sort of a thermostat control setup. If you want some control of the temperature. You will also need to control the amount of energy delivered in the system. So your requirements are puzzling.
     
  20. #12

    Expert

    Nov 30, 2010
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    You are supposed to look them up online and find the part number for the voltage you have available to drive the coil.
     
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