Zone Control

Hi all,

I have a project now to lay out the control for a 3 zone oven. Each zone will have it's own free standing enclosure with its own power drop and disconnect (That part was set before I inherited the project). There will be one PLC in the main enclosure with remote I/O drops in the other enclosures.

Do you think each enclosure should have its own MCR with associated Start/Stop Pushbuttons or should there just be one MCR in the main enclosure which will only pull in after all three enclosures have been powered on (and a PB at the main enclosure is pressed of course)?

I'm leaning toward the single MCR (with slave relays in the other two enclosures). The operator will still have to be present to start the burner at each zone after the purge cycle so I'm not worried that he may not be there when the MCR is applied. He also has to press a permissive PB at each end of the oven before any of the burners is enabled which forces him to "walk the line" (almost 300ft.) before really starting the oven up.

I have a few samples of other ovens but they all have a single large multi-bay enclosure for all the controls.

Thanks for any thoughts on the matter

nOrM

You have 3 separate power sources, so you would want an MCR in each enclosure. Perhaps those 'slave relays' you spoke about are really contactors that are capable of disconnecting the power source? If so, then those can be used as the local MCR

No need for a start button at each oven, but I'd definately put a stop (i.e latching E-Stop) button on each. Each of these E-Stops would be hardwired to the local MCR (or 'slave relay' if I understood correctly). A second set of PB contacts would inform the PLC that an E-Stop was pressed. If pressing an E-stop at one oven must kill the rest, then they'll have to be hardwired together. IOW, don't rely on RIO to interlock the ovens.

In lieu of the local start button, an output from the RIO can be used to energize the MCR. Since the E-stop is hardwired (and latching), it's still safe.

Here's a crappy ASCII representation...

|                 E-STOP                   |

|               (LATCHING)                 |

|     RIO          ____,                   |

|   "START"        ' |                     |

+-----] [----+----o__|__o----+-----(MCR)---+

             |               |

             |      MCR      |

             +------] [------+

beerchug

-Eric

Hi Eric:

I will definately have an E-Stop at each enclosure. I think your latching MCR contact is drawn around the wrong point. Should it be across the Start?

I was actually thinking of something more on the lines of this (But your RIO Start is appealing):

ndzied1 said:

I think your latching MCR contact is drawn around the wrong point. Should it be across the Start?

Click to expand...

Um, yeah, you're right...

If you have conduit space to run the extra wires, then do it as you planned. I only suggested the RIO start to limit the number of wires you'll need to pull.

I like the addition of the relays that confirm power is indeed ON at each enclosure...

beerchug

-Eric

I do these all of the time.


We always use a seperate MCR and E-stop circuit on each zone control panel.

PRINTS

Hi Norman
How do you get prints like the one you drew for Eric into your post?
I`m an Old Man trying to learn.
Thanks
Tom

jimbo3123:

Are your machines ovens? Also, is there a specific reason that you have starts at all stations? Just wondering.

Thomas,

When you post a message, below the editing window is a place to "Attach a File". I created a .jpg file and hit the browse button to find it and attach it to the message.

nOrM