How to automatically cut power to an induction cooktop?

I have successfully been working with an Auber PID, SSR,RTD probe, and a heat stick with a recirculating march pump to augment my propane brewing. So I’m not a noob, but I have a few questions.

I think I’d like to add one of those avantco 3500 watt 240V induction cooktops to the system to replace my propane burner. I want to know what it would take to make the 240 electical circuit cut off at a specific temperature set point. Essentially, I want to turn on the cooktop to heat water, but then I want to cut power to the cooktop entirely once a set temperature has been reached. What gear is best suited to doing that? Would a simple STC-1000 wired to a contactor be able to do that? Or maybe the existing auber output could be wired in parallel a contactor as well as the existing SSR?

I konw you can't easily adapt the Avantco to use with a PID. I just want it to turn off once at a set temp.

Basically – I want to use the heat stick and the cooktop to heat water. Once the water reaches a set point, I want the cooktop to cut off and allow the existing Auber PID to fire the heatstick as needed to maintain temp. How would you go about doing this?

stc and contactor sounds like a cheap solution to me.

Be careful. Some Induction Cook Tops default to a temperature set point of "off" when they are powered on. It is not always as easy as using a relay to cut the 110V from the Induction Cook Top. It depends on the model. There is information about this floating around HBT somewhere. I just don't remember which thread.

If you just want to switch it off at a setpoint, you could probably use the alarm output on the Auber to switch off a contactor.

As others have said, when it switches back on as the temperature drops below the alarm point, the likely result is that the cooktop will power up, but not turn the heat on. You'll probably also want to add a bypass switch to the alarm circuit, so you can later power up the induction cooktop with the Auber alarm output off for the boil.

dyqik said:

If you just want to switch it off at a setpoint, you could probably use the alarm output on the Auber to switch off a contactor.

As others have said, when it switches back on as the temperature drops below the alarm point, the likely result is that the cooktop will power up, but not turn the heat on. You'll probably also want to add a bypass switch to the alarm circuit, so you can later power up the induction cooktop with the Auber alarm output off for the boil.

Click to expand...

After reading the manual for the PID, this is exactly the conclusion I had come to. And I would put in an override switch to use the cooktop during the boil phase.

I assume a dual pole 120v contactor would be the appropriate contactor to use - one pole for each hot lead?

Yep, that's the right thing. I just bought a 30A dual pole contactor on Amazon for $10. Seems to work on in my new kettle controller.

dyqik said:

As others have said, when it switches back on as the temperature drops below the alarm point, the likely result is that the cooktop will power up, but not turn the heat on.

Click to expand...

Correct. For safety reasons any high power device such as this shouldn't turn "on" when first plugged in. You need to figure out how to bypass this.

Kal

kal said:

Correct. For safety reasons any high power device such as this shouldn't turn "on" when first plugged in. You need to figure out how to bypass this.

Click to expand...

I don't think he necessarily needs to bypass it. As I understand his plans, this is just to bring water/wort up to temperature unattended, without overheating and/or boiling over, before manually turning on the heat when he gets back to the system. Basically acting like a big electric tea kettle rather than a temperature controller.

Ok - that certainly simplifies things!

Kal

But if one were to create a temp control version, a simple internal hack of the cook top could/should/would easily handle this. Just need the appropriate inline cutoff whilst keeping the logic alive. hehe... "whilst"!

dyqik said:

I don't think he necessarily needs to bypass it. ... Basically acting like a big electric tea kettle rather than a temperature controller.

Click to expand...

Yep, this is correct. Thanks for summarizing my needs. N_G

The induction cooktop I have can be set to a given temperature. In your situation, assuming a normal mash routine, I would set the cooktop to maintain 140 degrees and set the heatstick to what you want. In that manner, the induction cooktop helps bring the temp up appropriately and turns itself off at 140 while the heatstick manages the extra temp rise. Mine also has setpoints at 180 and 210 (simmer, just short of boiling). Those may not be perfect setpoints for what you are trying to do, but it would require absolutely no additional items.

The set temperatures on most, if not all, induction cooktops are *not* accurate. I wouldn't go by them at all.

The induction units have horrible internal temp control. It's so far off, it's actually insulting that the manufacturers include the function. I haven't opened mine up yet, but whatever relay keeps kicking on and off to apply power to the high frequency driver would be the spot to switch with an add-on contactor

I would do by finding the low voltage signal and interrupting that. Keep the internal temp at max and let your temp controller interrupt the low voltage signal via a NO relay. A small reed relay would do great.

tjr3000 said:

The induction cooktop I have can be set to a given temperature.

Click to expand...

Which cooktop do you have?

I forget the user on here, but someone modded the avantco ic3500 but they weren't impressed. Someone else modded a different cooktop for their rims and I asked which cooktop in their build thread and never got a response...now I need to go find those users/ threads

brettwasbtd said:

I forget the user on here, but someone modded the avantco ic3500 but they weren't impressed. Someone else modded a different cooktop for their rims and I asked which cooktop in their build thread and never got a response...now I need to go find those users/ threads

Click to expand...

Here is the build where the guy originally uses the Avantco. Looks like he then switches to an adcraft burner which has an 1800W and 3000W analog model

I know that this might be a little off topic, but here is a link to a tear down / hack to manually control an induction burner. I have not tried this.

http://openschemes.com/2011/04/28/manual-control-of-the-1-8kw-induction-cooktop/

After shutting down, the internal fan runs for a while to cool off and protect the electronics. Not a good idea to turn off by cutting power.

AnOldUR said:

After shutting down, the internal fan runs for a while to cool off and protect the electronics. Not a good idea to turn off by cutting power.

Click to expand...

I hadn't thought about that... that is something to consider.

The_Bishop said:

The set temperatures on most, if not all, induction cooktops are *not* accurate. I wouldn't go by them at all.

Click to expand...

Let me clarify.

I was not insinuating to use that temp control for anything other than an automatic shutoff. The true temp control would be provided by the heat stick and the control associated with that. If I set the induction top to 140 but am looking to mash at 152, the cooktop is never going to get me there consistently. Even if it is off by 8-10 degrees, its not going to matter because the heat stick is going to be controlling the temperature and firing at that point anyway.

In regards to the internal fan. If you cut the AC power and turn it back on, the unit would restart w the induction unit off but the cooling fan on. I'm not sure how to wire this, but a brief interrupt on the AC line might do the trick.

kwadric said:

In regards to the internal fan. If you cut the AC power and turn it back on, the unit would restart w the induction unit off but the cooling fan on. I'm not sure how to wire this, but a brief interrupt on the AC line might do the trick.

Click to expand...

I thought I'd just take control of that externally with an always-on fan sucking through the exhaust vent (assuming there is one vent).