I need a furnace startup ladder program

I am new to ladder programming. Our church has eleven different furnace. I am asking for help in designing a ladder program that will allow spacing between the startup of the furnace. When they all start at the same time our electrical demand charge is extremely high. Can anyone e-mail me a simple ladder program that would have the furnaces start with a minimum of a 5 minutes delay between starts? I am using a Zen programmable relay.

Randalo

Apparently you need a PLC so that you can program a simple cascading timer setup. Automationdirect.com makes a Small PLC that has 6 outputs, and a option module that will provide 8 more. I would reccomend a DL05AR & D0-08TR. (about $150.00 U.S.) (8 ac inputs, and 14 relay outputs).

The 1st furnace would start off your start signal. The start signal would also provide a input to the PLC to start the other 10 furnaces. The 1st output would be timed to go on 5 or 10 seconds later; the 2nd output would go on 5 seconds after the 1st, and so on..

The PLC can be programmed to allow you to adjust your delay time, or time between starts, by holding an input on for the desired amount of time. etc. This would allow you to adjust your start time without the need for a programmer.

You should also program your project so that the furnaces also go off in sequence rather than all at once. This would help minimize the potentaial for a large voltage surge when all the motors all shutdown at one time, possabley causing damage to other equipment in the building.

Thanks for the quick response. The furnaces have independent thermostats so they can start anytime heat is required. However, we don't want any 2 or 3 furnace starting at the same time. Any help you can give with writing program would be appreciated


Randalo

I am only currently programming for PLCs from Automationdirect.com. So any program I write will only be for their PLCs.

If you are set on using your Zen programmable relay, I cant really help you with this as I am unfamillar with it.

Since all of the furnaces are on different thermostats, this may complicate the program a little, but not by much. You will have to run wires from each thermostat back to the PLC.

There are a few other issues involved with this also. Including the location of each thermostat, and furnas, and weather or not all or some of the furnases are running on a single controll system, or are they totally autonimous.

Question: What is your background, and level of expertise regarding setting up control systems? Can you provide a block diagram for the current system?

The answer is yes I could write the program but much more info is required. Feel free to email me with these details.

Your first time?

Originally posted by randalo I am new to ladder programming

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Well, you are going to have a time with this one. You can't just put a PLC or programmable relay into a church or any place and expect that a program written by you or anyone else is going to solve your problem. It just is not that simple.

Originally posted by elevmike The 1st furnace would start off your start signal. The start signal would also provide a input to the PLC to start the other 10 furnaces. The 1st output would be timed to go on 5 or 10 seconds later; the 2nd output would go on 5 seconds after the 1st, and so on..

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As elevmike put it, you have to do some major thinking about how you expect these 10 furnaces to operate.

Originally posted by randaloThe furnaces have independent thermostats so they can start anytime heat is required

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Now, I presueme you know that you will have to do some major rewiring here to make the system of these 10 units work the way you want. The T-stats will have to be inputs to the programmable device and the control of the furnace from there is an output from the programmable device. Are you and the other members of your church ready to re-wire the whole heating control system? This is a fair undertaking so be sure you understand the physical layout and wiring before you worry to much about a program. Also, it would be my recommendation that you not expect a solution to a problem you have not really considered very well. When you say,

Originally posted by randaloCan anyone e-mail me a simple ladder program that would have the furnaces start with a minimum of a 5 minutes delay between starts? I am using a Zen programmable relay

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you are placing the burden of your problem on someone else. That is not the way to do this. Asking for help is one thing, but expecting to be bailed out of a jam in this manner is quite another.

Figure out how you intend to make this system function by re-wiring the entire control to include a programmable device and then you may find that you have just about all the solution you will need to do the program.

Where are you located?

As you can see there are some *******---edited by phil--- on this site.It is for a church!!

There are programmable thermostats that have multiple outputs (circuits to turn on each furnace at different times) out there. Do a search and find what you need.

I also disagree that their may need to be major wiring changes, may need to change Thermostats but I am not sure at this point. Many thermostats are just relays...ie the mechnanism triggers by ambient temperature that sends a signal back to a valve or controller to turn on whatever. The same thermostats could be wired using existing wires rerouted to the plc.

As Mike stated there are existing controllers available for this type application.

If you are serious about trying the Zen then give me more info, like thermostat type/model. I will see if I can get the programming software and what may be needed. Not being there this may take some trial and error to get right. I noticed you stated 11 furnaces, I assume 11 thermostats too? Does the Zen have 11 inputs?

I am not doing much this week so I will help if I can. I am going now to see if I can get a copy of the Zen software. I dont this will be that difficult or take that much time. Lets get the details together and see what we can come up with.

IF the Zen wont do it I have an old GE 90-30 and a Maple interace I could setup, this unit may allow more energy management than the ZEN...ie set times for none to start or minimal number, options are endless. As far as cost goes if it comes to that point, I could trade you for the ZEN.

Get back to us/me and lets see what we can get going.

Seems I have tried the Zen software in the past and the trial has expired, isnt the ZEN and the PICO the same thing? I have PicoSoft that works so can use that to start on this.

If it helps....

I have a couple of AB MicroLogix 1000 10 DC in 6 Relay out if that helps. Let me know

Bob O.

That's the thread I immediately thought of. Thanks for finding it, Doug...

Since you're new to programming Randalo, don't be frightened by that thread. Allen's version (post #11) is pretty much ideal for your application... :nodi:

This shouldn't be overly complicated for a new guy. Although, we really don't have enough details to make that call. If the furnaces are scattered all over the complex, then it may become just that, COMPLEX...

If all the T-stats terminate in one location, it should be quite easy to add a PLC as 'the middle-man'. Be forewarned, Randalo that you CAN damage stuff if you make an error in wiring/programming...

beerchug

-Eric

P.S. to Mike W... I'm amazed your 'choice word' made it through. I thought that one was on the ****** list...

Hmmmmm....

I was just playing around with the simulator in PicoSoft. I wrote a quick little program for a 2 furnace setup that should have worked...

| T_STAT_1    INHIBIT                

|---] [---------]/[-------+-----(SET) FURNACE_1

|                         |

|                         +-----(SET) INHIBIT

| T-STAT_1

|---]/[-------------------------(RST) FURNACE_1

|

| T-STAT_2    INHIBIT                

|---] [---------]/[-------+-----(SET) FURNACE_2

|                         |

|                         +-----(SET) INHIBIT

| T-STAT_2

|---]/[-------------------------(RST) FURNACE_2

|

| INHIBIT                       +--------+

|---] [-------------------------| TIM_1  |

|                               | 5 Sec. |

|                               +--------+

|  TIM_1

|---] [-------------------------(RST) INHIBIT

If you turn on T-STAT_1, the INHIBIT turns on and the timer starts timing. While the timer's running, turning on T-STAT_2 won't start FURNACE_2 because INHIBIT is on.

Okay, that seems to work as expected. BUT...

If, while the timer's timing, you turn off T-STAT_1, then turn on BOTH T-STATs, BOTH FURNACEs turn on once the timer expires!...

It seems that the status of INHIBIT is NOT updated immediately. The status only seems to update on the FOLLOWING scan!

Is this just the simulator, or does the Pico operate this way? Did I overlook something?...

Attached is a copy of the program if any one wants to investigate.

beerchug

-Eric

Hi!rondalo,
I'm familiar with Omron Zen and used a lot of those, basically there is only 6 inputs and 4 outputs for the cpu unit, for your requirement you may need at least 11 output(2 expansion unit)to trigger the individual furnace, also verify if there is an auxillary contacts or signal that you may use to tells the furnace is on. You need that signal for proper timing sequence. If there is your lucky, coz zen can only give you 8 timers, you need 9 or 10.

Also ZEN ladder program can be simulated in your computer without connecting the unit. So basically you can virtually check if your program is right.

May be you can send me an email and elaborate your setup and other options that you may want.. I want to help my family are Churh goer too.

Opinions are just that men!

Originally posted by Mike Williams As you can see there are some "expletive deleted" on this site.

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Well, when did having an opinion and being willing to express it deserve name calling?

You have yours, I have mine and that is the way it is always going to be.

Originally posted by rsdoran I also disagree that their may need to be major wiring changes, may need to change Thermostats but I am not sure at this point.

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So changing T-stats is not wiring change? You wait and see. The standard T-stats used in most commercial apps are just like the ones you have at home. Honeywell, round, on the wall with mercury switch in them. No extra contacts to be had and even if they did have them, the extra wiring is something you have to deal with. Imagine the size of a building, no matter its purpose, that has 10 furnaces in it. I have done some energy management work in churches over the years and believe me, it is not for a newbe to tackle.

With more information from the thread originator we may come to other conclusions. We all need to keep in mind that opinions may be at cross purposes, but that as professionals we need to be frank and fair and let the chips fall where they may.

Apparently some think that the Church is looking for something FREE!
Were looking for help and are expecting to pay for it. We have several members experience with electrical wiring etc. However, no one is current in ladder programming. I have a litte knowledge. If I have offended anyone I apologize. I am just looking for suggestion. We have purchased no equipment at this time.


Randalo

Randlo,

Dont take offence to some of the replys here. Most engineers are not graduates of the Dale Carnige course. They mean well but tend to be blunt.

All that aside.. You will need to run up to four wires between the PLC and each T-stat, depending on the existing control circuit.

Do all the T-stats operate on the same power supply? This has to do with inputs and output commons on the PLC. PLC I/O is usually grouped into sets of no less than 4 I/O for each common. More expensive PLCs can offer one output per common. So more detail on the existing setup is necessary.

More on I/O:
As best as I can tell right now, the new system will require all T-stat contacts to share one 24vdc power common. This can be supplied at the PLC panel.

If your controlling compleatly seperate systems that operate from different power supplies, you will need an isolated contact output for each T-stat on the PLC. You can either choose a larger PLC that can provide one common per output, or use a smaller PLC and add relays for each output. (I would go with the bigger PLC).

To start, find a good location to place a cabinet with the PLC near a reliable power supply (115vac). If you can bring a phone line to it this may help later in trouble shooting from a remote location. Provide room for a cabinet size 24"H x 24"W x 6"D. (never too much room)

Start running your 4 wire cable from each T-Stat back to the chosen PLC location. The PLC will use 24vdc for the input voltage. The ouputs will be dry relay contacts that will be wired from the existing wires on the existing T-Stat contacts. Home Depot sells 4 wire 24ga. jacketed cable that may be approperate for this.

I would suggest if your new to this and this will be your only application, you may find that it will be easer to let someone else do the programming altogeather, given the learning curve, and cost of the software necessary.

If you are looking to minimize brownouts due to two or more starts at the same time, I dont belive the 5 min between starts is necessary, just a few seconds will do. You may also wish to prevent simultaneous shutdowns as they can cause spikes.

To be honset with you I'm guessing a lot because the necessary detail is lacking. In fact EVERYBODY is guessing, weather or not they know it. You have not provided enough info for a difinitave answer.

Mike L