Any research done on efficiency of wiring techniques for wall receptacles?

Everyone on here probably knows the three ways a standard wall outlet receptacle can be wired: rear insert, or, "back stab", side screw, or
"pressure plate"(where you insert the wire in the rear and tighten it with sidescrews.
What I would like to know is if the resistance and efficiency of each method has been tested and documented under various load levels.
I am asking this only because in spring of '05 I rewired most of the outlets in my apartment, built in 1969. They were of the spring- loaded backstab method, so I cut down to clean wire and wrapped the conductors around the sidescrews in each case.
I did this for three kitchen outlets on the same branch, controlling a toaster, microwave, and refrigerator. I also replaced most of the outlets in the living and bedroom areas.
Kid you not - my electric bills for April-Sept 2006 were lower than those for the same period in 2005 - albeit lower in terms of average kWh per day than in actual dollars on the bill. Our utility rates have gone up 26% since '05 so the savings in dollars is not proportionate to the decrease in kWh used.
This year the avg. kW hours per day were even lower from April - Sept, though the actual dollar amount of the bills have been about the same. Again, part of that rate increase that was imposed over a long time period.
I sincerely believe that switching all those receptacles from back- stab to side-screw, and one of them(which I broke!) to back pressure plate, played at least a *small* part in increasing the efficiency of our electrical consumption.
I know there is more contact area between the receptacle and the conductor using side screw VS using back-stab(single point grab), so it would seem to make sense that my electricity is going more efficiently to where it is needed, rather than wasted as excess heat.
Opinions? Conclusions?
-ChrisCoaster
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ChrisCoaster wrote:

That is correct, but the watts used by a resistive load is voltage squared divided by the load's resistance. In this case the only thing changed is the load resistance, increased a small amount by the "stab" connection resistance. At the same line voltage, the watts used will actually decrease. True, there is loss at the connection which results in lower load efficiency, but the power drawn is less.
You'll have to look elsewhere for your lower power bills.
There can be a fire danger due to poor connections, so you did well!
--
Virg Wall, P.E.

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VWWall wrote:

I'll agree that the loss in the higher resistance contacts is small. But for some appliances, the energy consumption will be constant. For appliances with thermostatically controlled heating elements, the voltage drop may cause lower power consumption by the heater, but the t'stat will cause the element to run longer to achieve the same temperature.
For appliances with motors, such as a refrigerator, lower voltage will result in increased current draws, so excessive voltage drops will in fact result in greater power dissipation both in the motor's windings (I^2R loss) plus in the poor connection.
--
Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com
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Paul Hovnanian P.E. wrote:

I don't know of anything that will draw more power if you put a small resistance in series with it. For a fixed mechanical workload, certain appliances might possibly consume slightly more watt-hours. There are few of these in an average household, not enough to see a greater electric bill due to the resistance of a wiring connection.
-- VWW
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VWWall wrote:

IIUC, the post that you responded merely presented possibilities as to how an electricity bill could theoretically increase due to added series resistance. It wasn't intended to argue that such increases would or could ever happen in practice.
Take boiling a kettle: If the added series resistance equalled the value of the kettle element, then to produce each cuppa would actually cost the equivalent of producing two (or more) on the bill...
But this ignores the main practical effect of a significant power loss in a connection, hinted at by a pp. Those extra kWHr on the bill have actually had to go somewhere - which basically means dissipated as heat. There isn't all that much possibility of conducting or convecting that heat energy out of the back of a socket buried in a wall - which just leaves good old radiation....
--
Sue




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Palindrome wrote:

The OP said: (Prompting my original response.)
"Kid you not - my electric bills for April-Sept 2006 were lower than those for the same period in 2005 - albeit lower in terms of average kWh per day than in actual dollars on the bill..."

I should have said for a fixed mechanical/thermal function, which would have included your kettle! In a normal household, there are probably more loads which will draw less power with a series resistance, than those doing a fixed amount of work, (mechanical or thermal), which require more power for the same job.

The largest example of this was in the use of aluminum, (aluminium?), conductors. Fires were started by the resistance of improper wire connectors.
In my reply to the OP, who had changed stab connections to screw, I said:
"There can be a fire danger due to poor connections, so you did well!"
Perhaps I should have emphasized that part more!
--
Virg Wall, P.E.


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VWWall wrote:

It was that very comment that I was thinking of when writing," ...main practical effect of a significant power loss in a connection, hinted at by a pp". Sorry, just being lazy and not going back to see who had written it.
Just a little tale to amuse:
There *can* be very severe power loss due to bad connections - without fire risk...
I'm thinking of when I was working in PAP and one day noticed that our neighbours lights went off when I tripped our inverter. Investigation revealed that the builder of our house had done a deal with the neighbours during construction - and made a "bad" connection to the wiring and run it through and under the slab to next door.
Whilst that cut their bills during the years that PAP had a reliable mains supply - it saved them buying a genny/inverter after 2 hours a day mains supply became the norm.. They just ran off ours.
We never found the "Bad" connection. Which is presumably still buried under the slab somewhere. It was between the meter and distribution board - so we replaced that cable.
--
Sue











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Palindrome wrote:

Trimming excess and still leaving it obvious who posted what is difficult. Your using Thunderbird makes it easier than some! :-)

I was in the US Army in Rome during WWII. I helped several Italian friends with "bad connections" around their power meters.
The wartime Italian power sometimes got as low as 42 cycles at around 190 V. We had to use our diesel generators quite often. Most equipment was rated 50/60 cycles, but 42 was a bit much!
I did some work, as system engineer, installing US made test equipment in the RAF Oakhanger satellite tracking station in late 1960. It made an interesting mating of the UK power distribution system with American equipment. Not just the voltage, but the sockets, switches, etc. were different.
--
Virg Wall, P.E.

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equipment
According to the Thomas Hughes book "Networks of Power", 40 and 42 cycles were standard frequencies in some parts of the world. There was an extensive 40 cycle network in north-east England prior to the national Grid coming in the latter 1920's, and 42 cycles was used in Italy and some other parts of the world. So, this wasn't just a case of overloaded power plants but just a different standard frequency.
Bill
( who's been spending a lot of time researching standard utility frequencies)
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Bill Shymanski wrote:

Not in this case. When the Germans retreated they were very good at disabling generators. They exploded a grenade in the exciters. When the remaining generators became overloaded, the system was allowed to "slow down" from the normal 50 Hz to whatever it took to "stabilize". Maybe this was because much of the system could operate at that frequency because of earlier standards.
This was not normal, and our equipment worked normally at 50 Hz with just 240/120 volt inputs set to 240 V. The 240 V often went as low as 190 V. This was in Rome--I don't know about other parts of Italy at that time.
It is interesting to look at power transmission standards. There are still some DC networks in New York City.
The plugs and sockets have more variation than even the voltage and frequency. My son just returned from working in China. It's easy to find adapters to use US equipment in China, but finding one for his laptop computer, bought there, to fit US outlets is difficult.
--
Virg Wall, P.E.

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----------------------------

Paul did not say that a motor load would draw more power (in fact it may draw a bit less) - He said it would draw more current (for a given power) at the lower voltage and this would result in a higher I^2R loss as he indicated. As he said, it is small compared to the household load.
The problem with the situation described by the originator of the thread is that he is comparing '05 to '06 and such things as weather and usage patterns will differ.
--

Don Kelly snipped-for-privacy@shawcross.ca
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