Amanda, this is a great story. The solution saves money on energy and the solutions used to keep costs down are really innovative. I worked with an electrical contractor once who, when show a Zigbee based building controll system said, wait a minute now. He was seeing his business going away, since wiring is a major cost and very labor intensive.
The other aspect of this solution that many people overlook is the need (or lack thereof) to get a PC to run the system. The whole premise of clould computing is that businesses have to purchase computer equipment that meets peak needs, while they end up spending a lot of time running at less than a quarter of their capacity. This is even more true of PCs in offices. Hats off to the Building Maintenance Supervisor.
This was a very interesting use of a PLC and interfacing to cycle block heaters. One thing that sort of irritated me was the initiative to save money was only driven when taxpayer funds became short. Why is it government entities only come up with good solutions when the taxpayer is fed up with feeding the behemoth?
Kudos to the bus guy! I now have at least one example of government doing something right.
Now if the spendaholics in DC could find ways to save money???
20 years ago whilst working for Idiot Blinking Management I realised running the cooling compressors on a walk in thermal chamber that was designed to be able to reach -80 and +150 C when it was only ever run at +75 to condition Hard-Drive casings was just plain stupid. I discussed it with my line manager, and his manager, was given a small budget and designed some really simple timer relay circuits, a PLC would have been nice, but back then simplicity and low cost was required.
We installed it on several different chambers and over several months cut power costs significantly. So we converted the whole plant, and not just power but wear saving soon mounted up. When my idea was put forward for the I'm Bloody Marvelous employee idea's scheme the plant managements answer was it wasn't worth it, and I was 'only a fu*king contractor'. 6 months later one of the plant managers put it in under his name and 5% of the savings made by modifying every thermal chamber world wide owned by Incredibly Badly Managed was his...
I hope the supervisor gets at least some credit for this work, beyond those in the technical field, and it's uptake by others, but somehow I doubt those in charge will care.
This is indeed an interesting application of PLCs, but I am puzzled as to why it had to be that complex. That may be due to having the heating outlets tied to the lighting circuits, I suppose, which may have been cheaper when the lot was first built. Otherwise, a simple system to switch on the power only when the ambient temperature demanded it and only at the times needed would probably have been much less expensive. But possibly there are a few details not mentioned that would have mandated the PLC choice.
William K. I agree that the PLC may have been a little overkill, but that there may be other requirements or functionality not detailed in the article. I wonder if a simpler timer circuit, and possibly a temperature switch in the circuit with each block heater could give similar savings.
Certainly a temperature switch that was fairly accurate could avoid unneeded heater operation, no question about that, and a time switch could also eliminate heating until it was needed. BUT all of those operations require a bit of attention and some intelligence, and those are sadly lacking in maany organiizations these days.
I too didn't get some of the details. Each PLC has one 20A relay, but the details made it sound like there were more than one outlet in each junction box. Were multiple block heaters controlled a single PLC? Were all outlets on that box switched on/off at the same time by that one single relay?
Jim, it has occurred to me that the solution using PLCs was done by an outside contractor. It is entirely possible that nobody in the organization had the required skills to implement an X10 solution, or to wire up anything, much less design it. The problem I have is realizing that so many people have no concept of anything that is technical. They lack the expertise to put oil in their cars engine or even air in the tires. They don't realize that things need to connect to a power source if not using batteries. It would seem that our public schools need to alter what they teach so as to provide everybody with a better chance of being able to help themselves in real life. Of course I am sure that the educators will claim that they already do that, or that the standardized testing does not allow time for that.
William K; Everyone can't know everything, but some gaps seem surprising. I had a disagreement with a mechanical engineer over whether nitrogen was heavier than air - from my memory of the periodic table, nitrogen is 7, while oxygen is 8. Thus nitrogen is lighter than oxygen, and since air is 80% nitrogen and 20% oxygen, nitrogen cannot be heavier than air. The engineer was sure that I was wrong and instructed me to do some research and then come back and apologize. I was surprised that an engineer didn't know the periodic table.
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