stepping down power

thank you guys very much for this... i have an inkbird itc-708t. it it a PID controller that is only rated for 1850 watts ac max. unfortunately i have a 2000 watt heating i want to limit the draw from the element to say 1800 watts. what can i do to accomplish this without using a dimmer switch? is there an in line resister or perhaps a diode i can use? anyone with a solution gets a quart of my finest!!

by chrissnowboarder
December 12, 2020

Can you use a PWM based solution? since it is a heater, I assume that the "ripples" are not really a problem. Using a 90% duty sycle (90% of the time on, 10% of the time off) would, simply, do the trick, with a frequency as high as required to be un-noticeable (but highet the frequency, higher is the energy lost by the switch)..

by vanderghast
December 13, 2020

I tried to look up "inkbird itc708t and could only find 308 so there may be a discrepancy here. In any case the 1850 watts ac will be a rating for maximum rated ambient temperature and you are probably not there (see if the nameplate gives a max ambient). Your 2000W is only is only 8% too high so if I were doing it I would try it out, ramp the temperature reference slowly up, and check for controller overheating. Do you have instructions for setting the P, I, and D? If so I can only say follow them and good luck. I've built a couple of ovens (furnaces?) from scratch and it's not particularly difficult to get a good regulator. The "PID" is a sexy term which is supposedly intuitive but I call it deceptively intuitive. I doubt very much that you will need the D so you would best keep it at 0 unless a good reason shows up to use it.

by Foxx
December 14, 2020

i am really sorry the model is this actually... Inkbird Tem. Controller Thermostats Heat Cool Timer ITC-608T

by chrissnowboarder
December 14, 2020

guys i was thinking a PWM too with an amp meter there and adjusting until its until just under 15A. 15A is my max rating. I don't want to burn up the inkbird because I am going to use it on a smaller still after my flow test. I am going to make a PID for this one using the inkbird 100vh with 25A SSR. just ran outa funds! thanks guys like I said there is a pint in it for all of you!!! thank you so much!

by chrissnowboarder
December 14, 2020

1 Answer

Answer by Foxx

Your thought on using an ammeter is probably the most logical in the circumstance if done right. I would put in a low temperature set point, sit back and wait for the temperature to stabilize then read the ammeter. If below 15 amps increase the temperature SP and repeat. When the current gets to 15A. note the temperature and forever after keep the set point below this level. Should work for the test anyway. I note the 100vh uses .5sec "sampling time" and I might guess this means pulse rate also. I used 10 sec but that's probably not very significant. I also used the 40A SSR and it works fine, $10 US from Sparkfun.

+1 vote
by Foxx
December 15, 2020

Your Answer

You must log in or create an account (free!) to answer a question.

Log in Create an account

Go Ad-Free. Activate your CircuitLab membership. No more ads. Save unlimited circuits. Run unlimited simulations.

Search Questions & Answers

Ask a Question

Anyone can ask a question.

Did you already search (see above) to see if a similar question has already been answered? If you can't find the answer, you may ask a question.

About This Site

CircuitLab's Q&A site is a FREE questions and answers forum for electronics and electrical engineering students, hobbyists, and professionals.

We encourage you to use our built-in schematic & simulation software to add more detail to your questions and answers.

Acceptable Questions:

  • Concept or theory questions
  • Practical engineering questions
  • “Homework” questions
  • Software/hardware intersection
  • Best practices
  • Design choices & component selection
  • Troubleshooting

Unacceptable Questions:

  • Non-English language content
  • Non-question discussion
  • Non-electronics questions
  • Vendor-specific topics
  • Pure software questions
  • CircuitLab software support

Please respect that there are both seasoned experts and total newbies here: please be nice, be constructive, and be specific!

About CircuitLab

CircuitLab is an in-browser schematic capture and circuit simulation software tool to help you rapidly design and analyze analog and digital electronics systems.