DIY plug and play trigger for AC heater dehu

Hello growers just completed building my first plug and play triggering device for ACs dehumidifier and heaters that draw high amperage. Very simple to use just plug and play. Considering building more if anyone is interested.



It’s looking great, I’m sure this will be helpful for everyone!

1 Like

Fancy. Nice job. I left my trigger out of a box because of heat. But I never seen this kind. Great job. I’m sure the community will appreciate it. Thank you for sharing.

Thanks! I see you used a solid state relay. They work great but unfortunately do produce heat and require heat sink. I used a contactor which you find in air conditioners to turn your compressor on and off. I used a contactor with a 120 volt coil. They are very reliable for many years, simple and inexpensive. Im an HVAC technician, so I also had one in my truck, no brainer for me. May your harvest be bountiful :v:


Its a very simple device I sourced all the materials at my local home Depot with the exception of the contactor. Contactor can be purchased on Amazon. But you do need to have to strip and crimp electrical terminals and drill holes. If you don’t already own some of the tools and materials needed, it can quickly add up an no longer be cost effective. Happy to help if its needed in future. Happy growing :v:

That’s really cool! Don’t need one at the moment but if that changes I’ll be in touch. Thanks for offering this to the community!

1 Like

Nice work! :metal:t2:

I’ve got a spare contactor on the shelf too…good idea, @420grower !

1 Like

KootMed made a great Youtube video on a DIY hack for power hungry devices. Check it out: Total Environmental Control - DIY NIWA Environmental Control Hack - YouTube


I went a different route but maybe it can give someone some ideas to create something better than what I threw together with my scraps.

For my dehumidifier I did it with phone charger, USB relay and a inkbird 1500w mechanical relay. Just the inkbirds sensor ran through the relay so it creates such a huge swing when triggered that it works. The sensor on a device could probably be directly tapped to it’s internal sensor and be used with no relay at all instead of using the inkbird.

Could you tell us more about how to make it? I found this relay on amazon is this that your talking about? How would we go about connecting the trigger plug, power plug and the outlet?

Sure. So that contactor would work just look up 2 pole instead of 3 pole. You also need two power cords. One is going to be plugged in to niwa and wired into coil on sides of contactor. The other cord is going to be wired on top of contactor. Its usually labled L1 and L2. Your receptacle is then wired to T1 and T2 on the bottom. Whenever niwa triggers you will have 120 at the receptacle allowing you to plug in any equipment youd like. Let me know if you atill have questions. I can send some diagrams if needed.

Thanks! I would appreciate any help with additional diagrams. There is clearly a gap in the market for commercial grade home accessories for items like the Niwa.

Sending diagram i made. Not the best but hope it helps. If youre interested i can also make you one for a small fee for labor to make it.


Thank you. What I struggled with until I listened to the YouTube trigger relay video is the path and connections of the ground wire. If I understand correctly, the ground wire runs from the wall plug directly socket ground. It bypasses the relay all together. Is this correct?

Thats correct. No problem.

Is there a benefit to using the low volt dc relay over the contactor? I read above about the heat production.

Either way will work but there is some heat using dc volts. Youre transforming 120 to volts dc so theres substantial heat created there. In my opinion theres also another possible failure point. With the contractor it uses the 120v that comes out the niwa. Contactors is what AC and heater manufacturer would use to turn off a heater or a compressor .

I have some clarification questions that will help in my electrical understanding.

My ac unit takes 11.3 amps and when the compressor turns on, it will pull over 15 amps. Should the power cord, hvac contactor, and appliance power plug be rated for 20 amps? The parts list from the YouTube video has a 20 amp relay with 15 amp power cord and appliance power plug.

Given this is a diy project that is a potential fire hazard, what is the safest way to build this relay?

Is there a particular brand of 2 pole hvac contactor that is preferred by electricians?

What size junction box would be required to house an additional 1 or 2 hvac contactors? Is this a bad idea as a failsafe prevention? If a contactor goes bad in a housing with others, could it cause damage or interference to the others?

Thanks for all your help and I look forward to sharing my parts list and customizations.