Find the Best Autofill Option for Your Business

Autofill Options: Floats vs. Continuity Switches

Autofill for kitchen equipment that uses water, such as steam tables and steamers, is a simple concept. Instead of manually filling a water reservoir, units with autofill detect when more water is required and use a water line connection to fill the unit as needed without user intervention. While an autofill option can drive up your initial purchase price, it will save time and money with its precise filling and saved labor.

There are two main types of designs used in autofill for kitchen equipment. Each uses a switch to complete an electrical circuit, but there are some major differences in how each type works, which has resulted in some debate over which style is superior. We will cover how each type of autofill switch works so you can make the best decision for your foodservice operation.

Continuity Switch/Sensor Probe Autofill

Continuity switch illustration

Autofill designs equipped with a continuity switch use water itself to conduct electricity. A sensor is placed in the bottom of the well, and another is placed on the side wall at the height that water should be filled to. In enclosed spaces like coffee maker tanks, this is sometimes seen as a sensor probe that looks like a wand. When the water reaches the top sensor, it conducts a small current to the sensor on the bottom, completing the circuit and sending the signal to shut off the incoming water. The biggest difficulty with this method is that it depends on the conductivity of water, which, despite what many believe, is not a good conductor of electricity on its own. Pure water is actually a very poor conductor, but the impurities dissolved in most water, such as salt ions, are excellent conductors of electricity. Because of this, if your business uses reverse osmosis filters on incoming water, your building's water is lacking in the impurities needed to conduct the necessary current between sensors. That can lead to failure of the system, which will not sense a current and may continually fill the unit until it overflows or malfunctions.

A common problem with a continuity switch autofill design is the top sensor becoming blocked by hard-water buildup. While it is simple to wipe it clean, the sensor can become completely blocked if cleaning isn't completed frequently enough, again leading to a messy water overflow. Water filter systems can help mitigate this risk, but removing too much from the water renders it unable to conduct the needed charge. Another problem occasionally experienced is units developing leaks around the sensors. However, this type of autofill, because it is always integral to the unit, is simple to install, and the easiest to reach when service is required. Some manufacturers that use sensors include Hatco, Cleveland, Bunn, Groen, and Vulcan-Hart.

Float Switch Autofill

Float switch illustration

Float switches use the principle that water seeks its own level, even in two separate vessels as long as they are connected. A float switch can be located in the main vessel containing the water, but in many applications it is located in a separate box that is connected to one or more steamers, steam tables, or hot wells with a pipe or hose. When the water reaches the switch, it causes it to float, creating a connection that completes a circuit to turn the incoming water off.

This type of autofill has the benefit of being able to fill several units with water at once, but on the flip side, that also means that if anything goes wrong, all of those units are down at the same time. Because the float switch has to be physically level with the desired water level, this type of system has a more complicated installation process than that of a sensor probe, but it does allow you to customize your water level as needed. Additionally, you may need more than one float switch system for vessels of different shapes, such as rectangular steam tables and round hot wells.

Like the continuity switch, the float switch can get gummed up with hard water deposits over time. This design has the benefit of being able to work with distilled water, so it is ideal for locations that use reverse osmosis or highly-effective filter systems. This type of autofill system, used by Vollrath, will usually require a separate power source than the unit it is being connected to.