Air conditioning power svings

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SNIP
There's no single answer that's best for every homeowner.
Bingo... homeowner must do the eval for their situation.
cheers Bob
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On Wednesday, January 23, 2013 8:59:25 PM UTC-8, Wes Groleau wrote:

What you should really be asking is: If your A/C suddenly stops working one hot day, how will you know if it just broke down or if the electric company turned it off.
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On Jan 24, 12:32 pm, snipped-for-privacy@gmail.com wrote:

On the unit I had, the controller that was mounted on the condenser had a couple of LEDs. I would think they all would have similar indicators.
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On 1/24/13 12:23 PM, snipped-for-privacy@optonline.net wrote:

The rural power companies here in Nebraska use controllers on irrigation wells. The LEDs are red and green. Green means the controller is on and the power is off to the well. Red means the controller is off and the power is on to the well. It's a bit confusing. The labels on the controllers are illegible after a few years.
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A large part of the male population is red green color blind.
Christopher A. Young Learn more about Jesus www.lds.org .
The rural power companies here in Nebraska use controllers on irrigation wells. The LEDs are red and green. Green means the controller is on and the power is off to the well. Red means the controller is off and the power is on to the well. It's a bit confusing. The labels on the controllers are illegible after a few years.
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If the house warms up, you have to go out and take the panel off, and look at the LEDs on the box? Not sure that idea sounds good.
Christopher A. Young Learn more about Jesus www.lds.org .

On the unit I had, the controller that was mounted on the condenser had a couple of LEDs. I would think they all would have similar indicators.
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On 1/24/13 4:15 PM, Stormin Mormon wrote:

The lights are on the exterior of the controller units I've seen. I think they're usually on the bottom but I can't remember for sure. They're easy to see for people who can distinguish red and green.

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I live in Maryland near DC. I have A/C on the first floor and basement and a heat pump for the upper level. I get $50/month discount for the four months of May - August by allowing the utility to be able to shut off the A/C.
Two years ago during a heat wave, they shut it off from 11:30 AM - 7:00 PM. By that time, my upstairs thermostat read 91 F. That's not a typo. It got back to a sleepable temp by about 1:00 AM.
You just need to decide what's more important, saving a few bucks or having ensured comfort.
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On 1/24/2013 4:55 PM, Dimitrios Paskoudniakis wrote:

Yep, that's the issue. To do any good, they have to turn it off when you most need it.
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On 01-24-2013 23:19, mike wrote:

I never need it. But sometimes I want it.
--
Wes Groleau

A pessimist says the glass is half empty.
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But they are not supposed to turn it off for eight hours straight. The idea is to turn them off in groups for maybe 20 mins at a time, if necessary. Either something exceptional was happening or something screwed up. As I said before, I had one on mine here in NJ for over 10 years and never noticed any difference. It's going to depend a lot on the shape of the electric system in the area. But still, turning it off for 8 hours doesn't seem right. Wonder if he complained to the utility and what they said? You would think if they did that to people, most of them would say come take this thing off, end of story....
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On 1/25/2013 6:18 AM, snipped-for-privacy@optonline.net wrote:

Do the math. If the power isn't off longer than the thermal time-constant of your house, it does zero good. There's a very strong correlation between how much you suffer and the goodness of decreasing peak load for the utility. And that happens at the peak load time when you most want the air conditioning.
If you turned mine off for 20minutes, I'd never notice, because it doesn't run that often. And the utility would have gained nothing because mine wouldn't have run anyway.
Take the energy saved while it's off. Subtract the energy used when it comes back on to bring the temperature back to where you want it. Unless the number is positive, or the recovery time is outside the peak load window, the utility gained nothing.
The way to solve the problem is to store heat (cold) locally. Cool a tank of water during off peak and use it to reduce the peak load. That trades efficiency loss for load leveling.
There is no free lunch...
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That's not true. There are a lot of AC's that during peak demand days, ie when it's 100F out, could be running almost constantly for hours. Take folks that have setback thermostats for example. They have it set to come on at say 3 or 4PM so that the house will be cooled down by the time they come home. If the utility cycles say 1/3 or half of them to be off at a time, they have reduced their load. It clearly doesn't require turning off the AC for 8 hours straight to be effective.

The point is that I think it's very unusual for a utility to shut off your AC for 8 hours straight.

That's true if it doesn't run that often. But I'd say there are enough AC's running a lot so that cutting them back so they can only run say 20 mins or half the time will indeed make a difference. There's a big difference between that and cutting you off for 8 hours, which is nuts.

How practical is that?
So, did you call them up to find out if they actually intended to cut your AC off for 8 hours? Or if something went wrong? I had the same kind of system for over 10 years and never had any experience like that. Never had a single occasion where I could tell it was even activated. And if I did, and they told me that's how it's supposed to work, I'd call them up and tell them to remove it. Did you?
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On 1/25/2013 2:42 PM, snipped-for-privacy@optonline.net wrote:

spoiler alert...math below.

About the only choice we have is to pay a monthly fee so that we can pay slightly less for off-peak and more for peak consumption. If I signed up and moved 80% of my consumption to the 3AM time frame, I'd save just about enough to pay the fee.
There seems to be a math aversion in this thread.
Here's a simple calculation with numbers pulled out of my ass. You can publish the results with your assumptions...
If the utility has a peak capacity of 1000. And if the demand is 1100 And if air conditioning represents 500 of that load, you need to shed 20% of the air conditioning load. If 20% of the air conditioning load signed up for the shutoff option You need to turn ALL of them off for the duration. Note, I said 20% of the A/C load, not customers. Altruistic customers are disproportionately punished...and paid handsomely for the privilege. The utility paid you an insurance premium. It's time to pay the claim.
The person who quoted the 8 hour duration got exactly what he contracted to get.
Bottom line is that the grid can't support peak load in some areas. We either get more efficient and reduce the peak, or we suffer loss of power, incrementally or catastrophically.
If I weatherize to reduce my load, I'd still get hit with blackouts. If my tiny load signs up for a shutoff option, it provides proportionately less help for the utility. Ironically, the most frugal can help the least.
There is no free lunch!!!
This problem is more political than technical. If the anti-nuke people and the anti-wind farm people and the no power lines in my back yard people and the no hydro dams people would just get out of the way the situation would improve.
We need to have a vote on issues like nukes, wind, transmission lines, hydro, etc. Every time you vote no on one of them, your "number" gets incremented. You get to share in the shortfall proportional to your "number". That'd fix it real quick! My mom used to call it, "put your money where your mouth is."
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That makes a bunch of assumptions designed to prove that it doesn't work. For example, just change the peak capacity overage from 1100 to 1050. Then the utility no longer needs to turn off all the AC's for the duration. What basis do you have that those numbers to run your "math" reflect reality?
More fundamentally, there is going to be a distribution of AC duty cycles out there. On peak days which are typicallly VERY hot days, a significant number are probably going to be running constantly, or close to constantly. If they throttle all AC's back to 50% duty cycle, the power usage by those units that were running 100% has been cut 50%. The AC's that were running 75% of the time are now running 50%, saving 33% there. The ones that were running 66% of the time are now running 50%, saving 24% there. If your AC was only running 50% of the time or less, then there is no power saving there. Taken together it all adds up enough to make a difference, without shutting everyone down for long periods or making them suffer. I'll bet there are plenty of houses out there with the AC running 66% to 100% of the time with it 72F inside. So, they wind up drifting up to 76F and the utility sheds some load. That is how it typically works, not by cutting folks off with no AC for 8 hours straight. And cumulatively it works, is significant enough, which is why utilities do it.

And from my experience, that is an exceptional case and *not* how the system is typically implemented. It's *not* how the system here in NJ worked for the 10 plus years I had it. It's just plain dumb, because very few customers are going to tolerate it. I would bet 99% of them don't understand that their AC will be off for 8 hours. And once they have it happen once, they are gonna call the utility up to come remove it. No benefit to the utility for the cost of install, removal, etc and getting a black eye. Just because ONE utility is dumb, doesn't mean that's how it works everywhere.
Have you ever had actual experience with such a system yourself?

No you wouldn't, unless you had an extreme nut case utility. Per my example above, if you're running your AC only 30% and the utility throttles everyone on the plan back to 30% to 50% duty cycle, you would see no effect. And again, that is how it typically works, not cutting folks off for 8 hours straight. Why do you insist on using the most pathological case?

Apparently there is, because in the case you just cited you would be getting paid for participating in the program the same amount as everyone else. But if you you're frugal with AC usage, it doesn't impact you.

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On 1/26/2013 5:10 AM, snipped-for-privacy@optonline.net wrote:

You should read more carefully. I said they were pulled out of my ass. Telling me they're wrong is not helpful. Publish better numbers.

You've demonstrated your ability to examine part of the problem. Back off and look at the big picture. Air conditioning load has so many contributors that the utility can view it as a load that varies very slowly over the day. There's a load that is the sum of the averages of all the A/C units over some time period. Exactly which unit is on for how long affects the average not at all.
There probably is some step increase in the afternoon when all the home units turn on before the owners get home and run at 100% for the rest of the day. It would be interesting to see what the numbers would look like if people just let their A/C run all day to eliminate that step.
When capacity is exceeded, the utility has to shed load. If everybody has the shutoff option, everybody suffers equally and not much. If only a few people representing a small portion of that average load have signed up, they bear the brunt of the load shedding.
They are willing to take the money, but bitch when the utility cuts them off. We're a greedy, bitchy bunch.
If you've got better numbers than mine, publish them. There has to be an analysis online somewhere.

I'm not insisting on anything. The specific case quoted here (not by me) was a rare incident where the utility used the insurance they had bought from the customer and turned off his A/C 100% per their contract.

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You said:
"There seems to be a math aversion in this thread. " "Do the math", as if we all just can't do the simple math required to analyze the problem. Then you came up with a set of numbers that as you say were pulled out of your ass. So, what exactly is your point? If you don't have realistic numbers, then what good is "doing the math"? 1 + 1 = 2. That math is as relevant to the issue at hand as anything you've posted.

Yes it is helpful, because it shows that contrary to your claim of "do the math", you're basicly clueless because doing math with garbage proves nothing. Yet it apparently gives you comfort. Go figure.

Which is more than I can say for you....

It doesn't matter which unit is on for how long. But it does matter how many of them are on at the same time. The example I just gave you shows how the utility can shed load. And it's not an unrealistic model. There is going to be a distribution of cycle times on hot, peak demand days. Everything from some AC's running 100% of the time to some that are not on at all. If the utility can lower the duty cycle, they can lower demand.

Again, per the clear example I gave you, that isn't true. The person who has his AC setback and it's not running at all, doesn't "suffer" at all. The person who has his AC running less than the duty cycle the utility is going to allow them, doesn't "suffer". If you system was running 15 mins an hour and the utility throttles all the AC they have control over back to 15 mins an hour, you don't see any difference. If you system was running 20 mins an hour and they throttle it back to 15, then you will see some temp rise. Is that really suffering? And if it was running constantly and they throttle it back to 20 mins, then yeah, the temp is going to rise somewhat. Is that "suffering" if the temp goes from 72 to 76?


Well, duh.... The utility can only shed load of those that have signed up.

So, I ask again. Do you have any actual experience with these load management systems? I had it for over 10 years. And there is no bitching here. The only bitching I've seen is from one poster where they cut him off for 8 hours straight. That has never happened here and I don't believe it's representative of how most of these systems are used.

Maybe you should find that before telling us all to "do the math...."

Non answer to perhaps the most relevant question noted.
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On 01-25-2013 17:06, mike wrote:

Are they just turning it off for a while? The letter made me think that they were altering the waveform into the motor
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Wes Groleau

β€œBeware the barrenness of a busy life.”
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The system here in NJ turns it off. They all have to do it that way for some key reasons. One is it has to have significant effect. Even if you operated the AC with your "altered waveform", you could only reduce the power going in slightly. Second, it has to be cheap. A relay is cheap, power control electronics for 50 amps isn't. And finally, turning it on and off, there is no risk to burning up the motor. When you try to run all kinds of AC units on some kind of reduced power, no telling what would happen.
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But they are not supposed to turn it off for eight hours straight. The idea is to turn them off in groups for maybe 20 mins at a time, if necessary. Either something exceptional was happening or something screwed up. As I said before, I had one on mine here in NJ for over 10 years and never noticed any difference. It's going to depend a lot on the shape of the electric system in the area. But still, turning it off for 8 hours doesn't seem right. Wonder if he complained to the utility and what they said? You would think if they did that to people, most of them would say come take this thing off, end of story....
+++++++++++++++++++++++++++++++
My utility has three duty-cycle options if you choose to sign up:
100% - Get 100% of the $12.50 discount per unit (I have two units) if you allow them to turn it off for 100% of the time they have an emergency.
75% - 75/75
50% - 50/50
I had chosen the 100% option.
Now as for the question why off for eight hours, it was an exceptional emergency event. After the utility received complaints, they sent a letter of apology, and also thanked those who had the switch units. They claimed if nobody had them, there would have been rolling brownouts, it was that much demand, and those of us who had the units saved their day. I think the temp that day reached 104 F.
As to another thread, even when there is no cycling off, when it is hot enough outside, my upstairs heat pump can't keep up when running constantly, and the temperature rises above the set point while running continuously, until the outside temp lowers and/or the sun gets lower in the sky. And that unit is required only for my upstairs. I have drapes/shades. The thermostat is in the master BR, which has a cathedral ceiling with its own roof. The room (and rooms below) are on a side section of the house with a lower roof above the master BR, ie not under the attic.
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