launderess
Well-known member
140F
While doing a better job of sanitation than say 120F for automatic dishwashing historically the two main purposes of using temps of at least 140F were at least two.
One, to ensure powdered automatic dishwasher detergents fully dissolved. The second is that soils, fats, and oils commonly found on dishware are not easily shifted, kept suspended and or dissolved in cooler water.
Anyone who has washed a sink full of dishes using warm or *gasp* cool water will notice greasy scum forming in the water and or clinging to surfaces. Way around this is to add more product but that will get you but so far.
Older dishwashers required 140F minimum incoming hot water temps also because only a few had temperature hold features. That is the timer would not advance until the proper water temp in the wash and or rinse was reached. Standard for years was that the heater simply came on during the cycle and went off at the end or after the assigned heating period was over. Well it takes about one minute to raise water inside the DW about one degree. With the short cycles of older dishwashers starting at say 120F after about five or six minutes of heating you only ended up with 130F (if that) water temps.
Of course today modern enzyme dishwasher detergents have replaced the highly caustic stuff of old. Enzymes can be designed to work in 120F or even lower temps, but will require longer contact times to "eat" off the gunk that formerly was blasted off with scalding water containing caustic chemicals.
In order for a DW to shorten cycles it must have some sort of temperature feedback via thermometer to tell the machine water has reached the desired temp. Without such measuring ability don't see how the machine could "tell" what was going on inside the tub. As previously stated many early dishwashers fired up the heater regardless of what the water temp was and kept it on for whatever was set via the timer. A quick check of the electrical schematic should tell the tale.
While doing a better job of sanitation than say 120F for automatic dishwashing historically the two main purposes of using temps of at least 140F were at least two.
One, to ensure powdered automatic dishwasher detergents fully dissolved. The second is that soils, fats, and oils commonly found on dishware are not easily shifted, kept suspended and or dissolved in cooler water.
Anyone who has washed a sink full of dishes using warm or *gasp* cool water will notice greasy scum forming in the water and or clinging to surfaces. Way around this is to add more product but that will get you but so far.
Older dishwashers required 140F minimum incoming hot water temps also because only a few had temperature hold features. That is the timer would not advance until the proper water temp in the wash and or rinse was reached. Standard for years was that the heater simply came on during the cycle and went off at the end or after the assigned heating period was over. Well it takes about one minute to raise water inside the DW about one degree. With the short cycles of older dishwashers starting at say 120F after about five or six minutes of heating you only ended up with 130F (if that) water temps.
Of course today modern enzyme dishwasher detergents have replaced the highly caustic stuff of old. Enzymes can be designed to work in 120F or even lower temps, but will require longer contact times to "eat" off the gunk that formerly was blasted off with scalding water containing caustic chemicals.
In order for a DW to shorten cycles it must have some sort of temperature feedback via thermometer to tell the machine water has reached the desired temp. Without such measuring ability don't see how the machine could "tell" what was going on inside the tub. As previously stated many early dishwashers fired up the heater regardless of what the water temp was and kept it on for whatever was set via the timer. A quick check of the electrical schematic should tell the tale.
