Testing Challenging Assumptions
I recently posted this little bit about whether dishwashers or hand washing is more resource/energy efficient. I've made some measurements which by no means answers the question, but which does add to info to the debate.
Years ago, I bought one of these meters from Brand Electronics. Sadly, neither I nor they anticipated the growth of USB connections in computers. As a result, the data logger I have connects through a standard phone plug to a proprietary PC interface, currently installed on a machine too obsolete to even fire up.
This forced me to simply read the peak power and cumulative consumption of my dishwasher as it did a load. To measure water consumption, I collected the waste water, measuring both the volume and temperature. Here are the results.
Initial Water Temp = 110∘F (all temps F)
Initial Bowl Temp = 64∘
Waste water discharge temperatures
1st = 73∘
2nd = 87∘
3rd = 118∘
4th = 115∘
5th = 122∘
(All discharge volumes 1.5 gallons)
Sharp eyes will spot where my assumptions in the previous post went horribly wrong. I had stated that the heating element remained cool if I set the washer to NO HEAT DRY. Wrong. I had felt the element after the first wash; it turns out the element does kick on after the second discharge, in order to heat the water hot enough to sterilize the dishes after the last soap has been rinsed. This makes sense. Hot water rinses more thoroughly thus avoiding the Dehn Syndrome mentioned previously.
It is also verified by the power meter. In the first two washes, the meter held at a steady three hundred watts or so; after the second discharge it spiked to over a thousand. This reflects the heating element and the pumps combined. Total wash power = 1.8Kw.
In order to determine whether or not this is power efficient, I would need to calculate how much power it takes to warm the cold water to the temperatures needed for sterilization; determine the heat loss from the water heater to the sink; factor in how much more/less water at what temperature each used.
I won't be doing that. I will, though, be shopping for a replacement for the old washer, paying close attention on models that in general use less water and electricity. Why? Whether or not we (er, I) wash by hand or by machine is not my decision to make. The wife likes the dirties tucked away, and I don't feel the burning desire to wash whenever a dish becomes sullied. A newer machine is the best power/resource compromise we can expect to reach.
Years ago, I bought one of these meters from Brand Electronics. Sadly, neither I nor they anticipated the growth of USB connections in computers. As a result, the data logger I have connects through a standard phone plug to a proprietary PC interface, currently installed on a machine too obsolete to even fire up.
This forced me to simply read the peak power and cumulative consumption of my dishwasher as it did a load. To measure water consumption, I collected the waste water, measuring both the volume and temperature. Here are the results.
Initial Water Temp = 110∘F (all temps F)
Initial Bowl Temp = 64∘
Waste water discharge temperatures
(All discharge volumes 1.5 gallons)
Sharp eyes will spot where my assumptions in the previous post went horribly wrong. I had stated that the heating element remained cool if I set the washer to NO HEAT DRY. Wrong. I had felt the element after the first wash; it turns out the element does kick on after the second discharge, in order to heat the water hot enough to sterilize the dishes after the last soap has been rinsed. This makes sense. Hot water rinses more thoroughly thus avoiding the Dehn Syndrome mentioned previously.
It is also verified by the power meter. In the first two washes, the meter held at a steady three hundred watts or so; after the second discharge it spiked to over a thousand. This reflects the heating element and the pumps combined. Total wash power = 1.8Kw.
In order to determine whether or not this is power efficient, I would need to calculate how much power it takes to warm the cold water to the temperatures needed for sterilization; determine the heat loss from the water heater to the sink; factor in how much more/less water at what temperature each used.
I won't be doing that. I will, though, be shopping for a replacement for the old washer, paying close attention on models that in general use less water and electricity. Why? Whether or not we (er, I) wash by hand or by machine is not my decision to make. The wife likes the dirties tucked away, and I don't feel the burning desire to wash whenever a dish becomes sullied. A newer machine is the best power/resource compromise we can expect to reach.