JRaef

Late entry, but this is essentially correct. In order for you to be able to use the PLC and OLR in that manner, the PLC would need to be UL listed as an OL relay itself, including the necessary fail safe protocols, with the actual field OL Relay acting only as a sensor. No PLC that I know of is so listed, it makes no sense to do it that way. As others have said, hopefully you wired the OLR to the coil and wired the OL Aux to the PLC separately for status indication.

Having had to sort out many similar machine control systems before, I can offer a likely scenario as to how it happened. There was an original design concept that started when PLCs were big and expensive, so for a little task like this they designed it using relay logic and timers etc. Then by the time the budget got approval or the business model warranted executing the project, PLC prices had fallen to where the relay logic began to not make economic sense. But those small cheap PLCs didn't come with an inexpensive way to enter recipes or changes, so they kept the big dial timers as a form of cheap operator interface. So the PLCs just became a less expensive option for executing annunciation or fault sequencing, the run sequencing, i.e. the timers, was left in the old design mode. Most likely the designer had no time to learn and implement an HMI screen for entering timer values or settings. In addition, timer / counter processing feedback is a very old school way of doing things, so I would hazard a guess that the person who designed it was not willing to take the time to learn how to take advantage of all the PLC had to offer.

A point of order here. I notice you are in Canada. I am not, but I have done a lot of work there and I know for a fact that your control panel will need to have CSA approval on it or else it cannot be hooked up, at least no legally. ULc (UL for Canada) is an alternative, but more difficult to attain for you on your own. At the very least you should contact CSA and get a copy of their standards, they are very particular about construction, spacings, devices used etc. etc. They will come out and lable a panel for you on a one-off basis, but that is an expensive option and if you make a mistake, they will charge you again for re-inspection, and again and again until they are satisfied. You might want to consider having your panel built by a CSA approved panel shop, that way they can put their label on it and there will be no problems with installation.

You might be overestimating the cost and complexity of a plasma cutter. A small 120V portable one that will cut up to 3/16 thickness (about 6ga steel) is under $1000. I like the Powermax190c weldersdirect.com link

Ditto on the plasma cutter, especially for SS. For repeat devices, I make a template out of 10ga aluminum and then clamp the template down to where I need the hole. Then just burn a hole in the middle, work the plasma head to the edge of the template, follow it around and move on to the next one. One-off holes are not too much more trouble, I just line up a T-square for each side.

Here's some more advice when comparing competitive bids. You want more than 2 bids because if 2 are within 20% of each other and #3 is 40% lower, chances are really good that #3 either doesn't know what he's doing or made the biggest mistake. Many times when a panel builder makes a big mistake like that they will just refuse to complete the job once they figure it out, which may not be until they are 1/2 way through it. You can technically sue them over it, but they know that your legal costs will likely be more than just paying their higher rate half way through the project. So here's an axiom for Law#34: The lowest price may just be representing the biggest mistake! Specific to your bid though, here are some rough guidelines to be able to figure out if you are being gouged for assembly labor. This is based on 1 panel. When you have multiple IDENTICAL panels some of the layout and setup times can be reduced, but not by much more than 20%. Basic setup / mobilization for each panel; 1 hour. Layout door for pilot devices; 1 hour for up to 10 devices, 10 minutes more for each additional over 10 Layout of back panel; 1 hour for up to 5 devices, 20 minutes for each additional. Includes wire duct layout. Punch holes, mount and wire a typical pilot device, i.e. pilot light, push button, selector switch; 20 minutes each. Mount and wire motor starters (or soft starters); up to 50A, 1/2 hour each; 60-200A, 1 hour each; over 200A, 1-1/2 hours each. Circuit breakers; 10 minutes per pole per breaker (i.e. 2 pole CB = 20 minutes, 3P = 30min.) Mount and wire relays and timers; 20 minutes each. Count relays with more than 4 poles as 2 relays. Mount and wire VFDs or other devices that require specialized control and/or signal wiring (shielded); starter times plus 1/2 hour each. Transformers or electronic devices that just need power supply and a few control wires; 1/2 hour each, 1 hour if over 20lbs. Fans / filters in door or side walls, 1 hour each. Air conditioner / heat exchanger; 2 hours

Note that this is in the 2005 NEC, which has only been adopted in a handful of states at this point.

A little larger, but these are 1 hole mounting. http://www.lascarelectronics.com/products....21EF4023BC91B9F They also have other options as well. http://www.lascarelectronics.com/products....21EF4023BC91B9F Jeff

Another good alternative to the "big 3" (Hoff, Ham and Rit) is Saginaw. I have just recently used their enclosures on a project and found the quality to be as good as Hoffman, definately better than Hammond and still geared towards North American standards (compared to Rittal).