I don't know much about electricity, calling all experienced electricians out there!

My goal is to merge the max 6V small water pump to my air conditioner. I'm trying to connect a small submarine pump with my air standard 115V window conditioner. I need a solution on how to properly and safely get this to work.

Essentially I want to power on the air conditioner and also have the small water pump power on automatically. I don't want to damage anything or cause a fire, so please let me know what I can do to get this to work.

P.S. If there are important steps required, please list them in laymen's terms.

Thank you!

Below here are links to the small water pump and air conditioner:



  • There's no need to call all experienced electricians. One will do. Have you got a 115 V power supply for your pump? Are you hoping that you can get the pump to run only when the AC unit is running? – Transistor May 16 at 19:09
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    @JimStewart Yes Jim, I'm trying to prevent it because the Air conditioner unit is spilling water and getting go to the walls and damaging the walls. Do you have another solution for this problem? Thanks – Val May 16 at 21:18
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    The back bottom of the AC unit needs to be lower than the front bottom, so that condensate drains away from the wall. All you need are some shims; cardboard, wood scraps, styrofoam blocks, etc. – dandavis May 16 at 21:28
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    A correctly-operating window air conditioner won't drip water. Either something is awry within the unit, or (as dandavis notes in Comments) the unit is mounted improperly. I'll urge you to find out what's wrong with the air conditioner or its mount (the problem), rather than treating the excessive dripping (only a symptom). – DavidSupportsMonica May 16 at 21:53
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    A window or wall mounted A/C should be installed slightly tilted downwards to the outside so that water collected in the A/C's pan will drain away from the house. Using a pump to collect water that is collecting and dripping down the wall of your house might only partially solve the problem. It's the wrong approach. Install the unit properly. Some A/Cs allow you to plug the drain hole so water gets evaporated outside ... but those ones can still overflow and need proper drainage. Some A/Cs allow you to connect a drain line to the pan. Have a look. – jay613 May 16 at 23:42

Mixing AC mains and low voltage involves some very complicated rules, and it may be prohibitive to do this as an electronics design exercise, especially if (as you say) you don't really have the chops.

One option is don't even detect the air conditioner running. Detect water rising above a certain level in a reservoir. Then, the project becomes a simple "float switch": if water present, run pump. Doing this allows you to build your entire project using 5 volt power only, and therefore the harsh rules on mixing AC power with low voltage will not come into play.

Note that having your common everyday "wall wart" convert AC power into 5 volts is perfectly legit, since the vast majority of such wall-warts are UL-Listed as safe in that application.

Another that comes to mind is a "smart power strip" used for controlling "dust collectors" in wood shops. (when they see current flowing to the table saw, they turn on the dust collector socket). You plug the air conditioner into the "table saw" socket, and the 5V wall-wart power supply into the "dust collector" socket.

They make the same kind of thing for PCs (when the PC turns on, turn on the monitor, USB hub, printer, etc.) However, the "wood shop" units are actually rated for the heavy current of an air conditioner.

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    "Then, the project becomes a simple "float switch": if water present, run pump." - another benefit is that it becomes something you can simply buy instead of something you build. OP: search for condensate pumps. – whatsisname May 17 at 0:24
  • From experience, if building a float switch-activated pump you very likely need a relay to activate the pump, and both the switch contacts and the relay contacts need a flyback diode each to avoid damage to the contacts. – Andrew Morton May 17 at 14:16

You could install a paper towel or cloth wick in the back to drip water out of the tray in a controlled fashion. https://youtu.be/weRHRXbhAk4

But some creators of these videos on improving drainage of the window a/c don't seem to understand that having a tray of water in contact with the coil improves cooling efficiency and is intended by the designers and manufacturers. It would be very risky to drill a hole in the back as some suggest doing.

I am sure that these units must be designed to drip excess water at the back and the assumption is that the back will protrude past the window sill. If the unit does not protrude that far, then the best solution would be to attach a drain tray to the bottom.


Examine the back of the unit in operation and see if the condensed water is visible at the bottom back. Perhaps the tube or trough through which the water is supposed to flow away from the cooling coil is plugged.

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