control panel building

[Jimmie_Ohio]

25% free space goes away quickly... I'd say in 25% free space in a panel lasts from 1-24 months most of the time.

I built control panels from the time I was 13 (1970) until I went into consulting (1992). Then I reverted to just designing, testing, and programming them.

Everyone is always hung up on "spare panel space". Automotive companies paved the way with specifications that spelled out 10%, 20%, or whatever. Murphy's Law now enters in. If you have 20% spare, your need 25%. If you have 25%, you need 30%.

Now I work for a company that deals in power plant equipment. The panels for this equipment are usually mounted on "Unistrut" in buildings that you can fly an airplane in. MCCs control the motors. If I need spare anything, it's I/O. For this I simply furnish extra chassis space or cards with wired spares. Never had a problem yet.

Plus, against what everyone with a bad back has said, I put terminals horizontal along the bottom. This is for good reason. In plants that may have a lot of condensation, water cannot run uphill in the conduits, so they are bottom entry. If the conduits originate overhead and don't dip below the botom of the panel (like a trap in a drain), the panel will fill with water.

The people who mount the panels in my business are the same guys who land the wires, so they mount the panel at a decent level, so they can work on it. I also help by specifying 4"-6" of empty panel space below the terminal strips. Other ways are to put the mounting information on a drawing or locate the pushbuttons at a level that will dictate where the panel is located (eye level).

BOTTOM LINE:
We are all in different industries. These industries have different needs. You, as the designer, must know what your specific needs are. If somebody mounts your panel under a table or so high that you need to be Frankenstein to operate the disconnect, that is just plain stupid (not to mention potential code and safety issues.)

 

[MarkTTU]

BOTTOM LINE:
We are all in different industries. These industries have different needs. You, as the designer, must know what your specific needs are. If somebody mounts your panel under a table or so high that you need to be Frankenstein to operate the disconnect, that is just plain stupid (not to mention potential code and safety issues.)

Very good point; no one else could possibly know your application better than you (or at least I hope not).

 

[TConnolly]

If you have water in your conduits then that problem should be addressed, not designed around.

 

[Jimmie_Ohio]

If you have water in your conduits then that problem should be addressed, not designed around.

If a control panel is installed where condensation happens (like outside), bottom conduit entry is the norm. It solves the problem.

Not all control systems are located inside, in controlled environments. And with that in mind, a good electrical contractor knows the difference between an inside and outside panel. This means using breathers, drains, etc. where needed.

Plus, you can't air-condition the outside world.

 

[Sliver]

On my bottom entry panels I found the best practice was to have a horizontal terminal strip that accomodated every wire of every cable including all spares. No loose wires snaking around the bottom. Then a vertical terminal strip to wire to every I/O point.
Then interwires from I/O terminal to Field terminal with all wire ids and tb locations included on a database or excel.
Makes it super clean and retrofits are a snap.

Brian.

 

[TimothyMoulder]

Tnis thread gets my nomination for "Most Useful Thread of 2005". Thanks to everyone, lots of good stuff here.


TM

 

[rsdoran]

Plus, against what everyone with a bad back has said, I put terminals horizontal along the bottom. This is for good reason. In plants that may have a lot of condensation, water cannot run uphill in the conduits, so they are bottom entry. If the conduits originate overhead and don't dip below the botom of the panel (like a trap in a drain), the panel will fill with water

As Alaric mentioned if water/moisture/condensation is an issue then that should be addressed. Maintenance electricians are constantly having to vacuum/dry panels because of engineering design flaws along these lines. The conduits filling with water is just as detrimental as the panel filling with water.

I do not have a bad back and I do not think it is part of the issue. When terminal strips are located at the bottom of the panel that means you have to, IN MOST CASES, work below eye level AND in closer proximity, physically, to the electrical equipment. Vertical mounted strips offer a better view without having to bend over or work around any devices. As a reference here are 2 examples that have been provided by Norm and Eric:
http://www.plctalk.net/qanda/showpost.php?p=55623&postcount=15

http://www.plctalk.net/qanda/showpost.php?p=55566&postcount=5
Norm's cabinet, I think, is floor mounted (no legs) so it will be easier to access the terminals without being close to the devices.

Eric's is smaller and I am sure is mounted at eye level, again easy access without proximity to devices.

Here is an example of what I DO NOT LIKE to see.
http://www.plctalk.net/qanda/showpost.php?p=55587&postcount=9
The Drives and terminal strip are on the bottom of a floor mounted cabinet....you either lay or sit on the ground when there is a need to work in the cabinet....I have an aversion in not having the freedom of movement in case of a problem.
NOTE: The cabinet is nicely done and I mean no offense to the builder, I personally just do not like this kind of layout.

As far as spare space goes that would depend on circumstances, I attempt to have more space available regardless...too many variables in the industry. Just recently an engineer I worked with did the layout on a cabinet using an SLC500 with expansion chassis, he did not look at the cable length for the expansion and designed the panel "real tight" but with the racks far apart ...the sad part is I tried to explain the problem and he would not listen...standard engineer thing. He had to purchase another cabinet and do a new layout.

This is my personal opinion based on having to work on panels for over 30 years in numerous situations and conditions. The better part of that 30 years was DEFINITELY outdoors in rain, snow, tornadoes, hurricanes and anything Mother Nature could use.

I do not know much but know what I like and what I dont like.

 

[Jimmie_Ohio]

In summary:

1) If the panel is going outside, use drains, breathers, and bottom conduit entry.

2) If it is going somewhere hot, mount a fan or air conditioner.

3) If it is going somewhere cold or where internal condensation is an issue, mount a heater.

4) If it is going somewhere that is dirty, make sure it is positively pressured.

5) If it is going in a dark area, mount an internal panel light.

6) If it is going where no 120VAC outlet is (for a programming device), add an internal duplex receptacle.

7) If it is going somewhere mounted low, put the terminals within reach.

8) If it is going somewhere high, get a nice safe ladder.

9) If it is going somewhere near flammables, quit smoking.

10) If it is going somewhere that there is no electricity, make sure it is a pneumatic panel.

Did I forget anything???

 

[TConnolly]

What preferences do you all generally have for PLC location in the cabinet? I usually place the PLC at the very top. I realize that the top of the cabinet is usually warmer, but in most of the panels I do thats not really an issue. I place it at the top (with recommended clearances) for two reasons: First, the wires usually exit below the PLC rack, therefore there is little use for a duct above the PLC, conserving panel real estate by top mounting. The second reason is that at the top it is less likely that debirs will fall into the rack during field installation. There are of course times that I have mounted the PLC at the bottom or in the middle, depending upon the neeed, but my general preference is for top mounting. What say you all?

 

[Togadude]

If one were to start building panels as a side job, how do you go about estimating/charging? Does the customer supply all the components?

 

[rsdoran]

Alaric, my preference is as close to eye level as possible depending on situation. I use the LED's on the PLC for troubleshooting so like it where it can be viewed easily. The LED's can tell all in many cases. If the panel is mounted low then the PLC would be easier to view at the top.

Togadude, that depends, even as a sideline in most cases you will need to have a business license, insurance etc to do business with many companies. The sale of some materials may offer some profit margin IF you have a good supplier with appropriate discounting...this also helps to sometimes obtain jobs.

As I said, it depends, all you can do is get the information pertaining to the job and estimate your hours to do the work based on your experience and what you need to make. There are so many variables involved its pretty much depends on the specific job and components involved.

 

[leitmotif]

TO RS Doran

Ron

You mentioned the idea of transferring all these ideas to your website. I think that is a good idea.

Dan Bentler

 

[TConnolly]

I agree Dan.

 

[rsdoran]

Ok

 

[rta53]

If one were to start building panels as a side job, how do you go about estimating/charging? Does the customer supply all the components?

Depends on several factors. How much information is the customer giving you? In other words, if you are given a detailed schematic with specs for the equipment/devices to use and a control description, then your price would be based on the components you have to purchase and your labor to build and test. On the other hand, if a customer says "I have a machine and I want it to do this" then you have a whole different ball game. Also if you are going to have to program the PLC that adds another dimension to the project. My advice would be to start small if you can and move on to larger projects as you learn.