Simple float switch design with electrical diagram

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Dec 17, 2004
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In this design the switch sits a top of the mash via an adjustable plastic tube that also protects the wiring. The wiring or most of the switch for that matter is never in the mash water. The 'float' part of the switch simply goes up and down. When it goes down all the way it turns on the pump, filling the mash tun until the mash tun is filled with enough sparge water to return the float part of the switch all the way back up--then the switch turns off the pump again... This repeats until all the mash water is gone.

The float switch sold by,, doesn't look like much different of a design then mine.

One electrical box from MoreBeer v.s. mine has two boxes (you easily could use one if you want), very similar float switch judging by the picture, if not the same, and it's 90 smacks... I would say just about the right mark up for a retailer. Mine will cost under $25. MoreBeer's is also rated the same: Any pump of 1/3 horse power or less, as that is the limit using standard household current of 15 amps and 14 guage wire.

NOTE: You are working with 120 volt household current so make sure you install all ground wires. Make sure the wiring is adequately protected from moisture. That is common sense when working with anything electrical.

The float switch is designed to be in water and is already sealed by the manufacturer with silicone. It will not cause a problem. But yes if you damage a wire and water crosses the circuit you may have a short and blow a fuse. Just like any electrical device. If the wires inside the mash tun cross due to moisture and a crack in the wire, you may have a short or the pump may flicker on and off... They are the same switchable wire-- so it's not as dramatic, even at 110 volts, as crossing wires with opposite polarities. If you did suspect a short or the pump turned on and off randomly--- don't do anything stupid-- like sticking your hand in the mash tun, simply unplug the power supply and inspect and fix before using again.,del:s,1:f,0

This is where i got the float switch:
9 smacks...
Definitely a much cheaper way to go on the float switch.

However, I am more interested in the rest of your system's design. Nice incorporation of a coil in the mash tun. I assume from your diagram that you pump hot water from your hot liquor tank through this coil to maintain/raise mash temperatures. Nice going, this is an idea I hadn't thought of. A benefit of this design might be that it would give a more even dispersion of heat through the grain bed compared to a more traditional HERMS design.

Keep the good ideas coming.
I have read about many recirculating mash systems. From RIMS to HERMS. Some heating electrically and some using propane or natural gas.
When i designed and built my sculpture i wanted to be able to do step infusion and be able to recirculate my mash.
I did things a little differently but--- from what i read, no body does everything the same way... And everyone make great beer!

TO HEAT the mash tun i use the burners to heat water up strike temperature for the first mash rest. After that i pump hot water from the hot liquor tank through 50 feet of copper coil wrapped around the inside of the mash tun, then the water goes back to the hot water tank in a continous cycle. The hot water tank is heated to 180-190 degrees and held there by the propane burner. The water recirculated in the mash tun through the copper coils is about 20 degrees less then that. The pump is regulated by a Ranco temperature control with the probe inside the mash tun. Once set mash temperature is reached the Ranco device shuts the pump off. If the mash temperature falls too low the Ranco device automatically turns the pump back on until the set temperature is reached again. An electric mash agitator is set inside the mash tun and ensures even heating. Once the final rest is complete the Ranco device is set for mash out temperature. Hot water is cycled until the mash out temperature is reached.

TO RECIRCULATE the wort for several minutes and create clear runnings after mash out i simply pump mash water from the bottom of the mash tun to the top of the mash tun.
*Hot wort never runs through copper coiling, when it is recirculated it goes directly from the bottom of the mash tun to the top of the mash tun. The copper coils are by-passed.

TO SPARGE i simply pump the hot liquor tank water over the mash with a sparge arm and simotaniously drain wort into the boil vessel at a SLOWER rate. The slower rate allows me to automate the sparging process by a float switch connected to the pump (water always comes into the mash faster then is leaves until all sparge water/water from hot liquor tank is emptied). The calculated amount of water is already in the hot liquor tank and when pump runs dry, sparging is done. When the runnings into the boil vessel is complete, boiling begins.

The heating, recirculating, and sparging run through the same hard copper plumbing with bypass valves and 1/2" inner diameter hot water tubing with quick disconnects on the ends of the hard copper plubing to control what pumps-what-where-when... (see diagram, involves turning valves)

To make the system even more versital (not shown in the diagram) i turned my boil vessel into a second mash tun and added a fourth vessel-- a 60 gallon copper riveted water tank converted into a boil vessel.
The two mash tuns allow me to brew one 30+ gallon batch of beer or two completely seperate 15+ gallon batches at nearly the same time (mash at the same time then boil one after the other).

All four vessels have 150,000 BTU burners under them.

Each mash tun has it's own seperate but identical pluming. Each uses its own pump-- although you could easily only use one pump and rotate it with disconnects. I use a two tier four vessel system. Two 15 gallon mash tuns, one 15 gallon sparge vessel, and a 60 gallon converted water heater (beautifully copper riveted). The system is automated to a degree with a Ranco temperature controller and float switch to automate sparging.

Honestly less complicated then most RIMS systems i have looked at on line. The benefit of this system is i avoid pumping hot mash water through copper coils or scortching electrical elements, have great control of temperature during step mashes, and utilize one pump per mash tun. The amount of plumbing is typical of other systems and probably easier to construct.
I have easy designs to follow for anyone, as it's the least i owe from all the knowledge gained from forums like this.
UPDATE: The float switch incorporates a rely and a transformer to use 15 volts DC instead of 115 volts AC to switch the float switch on and off. I will post a design using the 15 volts DC. This will cost a little more but is safer.

Here is a similar one that another homebrewer did:
I had a friend who had the More Beer float switch. I took his apart and bought all the parts separately and made my own. Much, much cheaper. I also incorporated a relay which is an Omron G2R-1A-T 120 VAC. You can get a similar one at: I have used these guys for years without any difficulties. I agree that the use of a relay is much safer. I have a diagram of the wiring I used here: I also used the float switch that is available at: It is very heavy duty and I have never had a problem with it.
I just noticed that Mouser doesn't seem to have this part anymore. Allied Electronics has it though and they are a very reliable company as well. They can be found at Allied Electronics. The one I got was the Omron G2R-1A-T-AC120. It works great. Page 841 of their catalog has the specifications for the relay.
Here is rough diagram of the float switch with a relay. It will cost more to build... maybe as much as the morebeer one... which does have relay i found out. But neat project. I will post a more specific diagram showing how it is mounted on a sculpture when i have time. As well as links to additional device. If any one has links or wants to look as well.

You need:
A relay capable of 120 volts and 15 amps and swichable with 12-24 volts DC current.

A Transitor dropping 120 AC volts (input) to 12 to 24 volts AC (output) (easy home depot device)

A Rectifier that changes 12 to 24 volt AC to 12 to 24 volts DC

(i say 12 to 24 volt generically but make sure all three match up as they are available between 12 to 24 volts)

New diagram:,del:s,1:f,0
if you cant read the print on the diagram cause its blurry...

The light switch is the master switch. No power runs past light switch unless it is on. When light switch is on 120 AC volts of power is sent to transitor and relay. Transistor turns 120 volts AC into 12 to 24 volts AC. The rectifier turns that 12 to 24 volt AC into 12 to 24 volts DC current.
When the float switch is on, it tells the relay to allow 120 volts AC to flow to the pump, turning the pump on. When the float switch is off it tells the relay NOT to allow 120 volts to flow to the pump. Not allowing the pump to turn on.
So basically when the light switch is on, the float switch regulates when the pump turns on and off.
Same as the other design, except now a safer 12 to 24 volts DC is running into the water filled mash tun.

*DC power is safer because your bodies muscles operate on DC current. DC current passing through your body will go straight to ground. While AC (alternating current) will change polarity and shock your muscles on and off. Which is dangerous and life threatening to muscles like the heart , especially at high voltage.

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