Just checking back in with some updated info to my situation: I discovered I was mistaken, and our dishwasher is connected to a hot water line. We also did some maintenance on our hot water heater. (FYI: We are in the US.) We did a full purge on the hot water tank and raised the setting on the two electrical elements. After giving the hot water heater a chance to reach equilibrium, the temperature at the hot water tap is now about 130 F. Then, we ran the dishwasher empty using a 1-hr wash on the basic setting to track the water temperature using a digital thermometer with a probe and an alarm set at 120 F. With 26 minutes left, the temp finally hit 120 F and rose as high as 136 F with 10 minutes remaining. But…
Two questions:
a) While we forgot to let the hot water run before initiating the test, the hot water line is a short run (maybe 12-ft total - sitting almost directly above the hot water heater). As such, it should not take over 30 minutes to hit 120 F. So, why should it take so long to reach 120 F? One reason, I wager, is the way my dishwasher does an initial assessment of how dirty the load is - by allowing water in to the dishwasher intermittently, perhaps? Other thoughts?
b) How does a dishwasher “sense” how dirty a load is? And, could running the dishwasher empty affect my results (when recording temps in various parts of the 1-hr cycle)? Your thoughts?
My apologies. I think I failed to mention this, but I did. The first thing the troubleshooting guide recommended was to clean both an outer filter and an inner filter on the dishwasher floor. …Although, this did not make sense to me. Isn’t the filter(s) protecting the drain from food particles that would clog the drain? Is the logic that some dishwashers sense backed-up water and then cut down on the intake to avoid a flood? In any case, it did not make any difference. However, I do have two clean filters now.
Three thoughts on the low temperature. A quick search suggests the average dishwasher uses 4-6 gallons per load, so even with a short run to the hot water heater, a sizable proportion of the water it uses may have been cold. Second where did you put the probe? The water at the top rack will be colder than the bottom near the heating element. Think of “top rack only” instructions on some plastic dishes. Finally, the air temperature inside will be lower than the water temperature. Perhaps if it can be done safely, and your probe can handle it, the best place to put it is on the very bottom of the dishwasher where it will be submerged.
I’m not sure of the method used to detect dirty water, but when the water is detected as clean, then the wash cycle will stop. So, running the dishwasher with dirty dishes in it will cause it to run longer, which is the intended behavior.
Where did you put the probe? For the test to accurately measure water temperature, it needs to be submersed in water. If it was on a rack, it’s going to measure a combination of air temperature and the temperature of any water that splashes on it.
The best place for it is going to be down on the bottom somewhere. Even better if you can get it near the drain/sump.
It uses an optical sensor that watches the water. I would assume there’s a sensor on one side and a light or reflector on the other. The dirtier the water going past it, the less light the sensor picks up. Again, I assume that it continues to drain and refill until the water cleanliness is above a certain threshold.
Yeah…in hindsight, placing on the bottom to keep submerged does seem the obvious choice for placement. I’ll have to rerun to collect better data. :smack:
It’s not dishwashers exactly, but part of my job is testing medical washer /disinfectors that clean instruments before sterilising, and they are basically dishwashers with better control. One of the things we test for is temperature achieved, and it has to be above a certain temp for a certain time, and the sensors need to record the temperature accurately to within a particular tolerance - I’m being a bit vague because the actual numbers vary on the model of machine.
Anyway, we put our probes up in the baskets, hanging in clear air (being sure to not block the spray arms with any wires). The machines have their probes down in the sump, and the temperature difference is less than 0.1C.
