Processor Temperature?

[Michael Lloyd 85]

Is there a status word for CPU temperature of a compact logix PLC? L35E.

[Ken Roach 194]

There isn't. I pursued this with Engineering a few years ago and they said there's no sensor, therefore no parameter or variable. What's your reason for wanting the temperature of the CPU chipset, or the inside of the CPU module, rather than the ambient temperature inside the enclosure ?

[waterboy 7]

For the case where someone places a small box or card on top of the CPU blocking the vents

[BobLfoot 302]

[sTART MUSING - JEST] Let me see - Someone Opened an Electrical Enclosure and left a box or card blocking the CPU vents. Well in America that person had better be an "Electrically Qualified Person" since any PLC Cabinet I have in my facility contains 120 VAC and that is more than 50 volts {reference NFPA 70E} So my Electrical Safety program has failed and I have failed when this occurs. I deserve a melted CPU. [END MUSING - JEST] Yeah woud be nice if PLC CPU had sensor like PC CPU , Hint Hint.

[waterboy 7]

And then there is the real world where we never know who strayed into areas where they ought not, nor why on earth they were there. Usually a suit giving a tour. But you are right of course. 2 cases I have seen have been a box of spare fuses. One was duct tape from where they where cutting a conduit hole nearby. You would think that they would know better, but alas...

[Joe E. 259]

At least they thought to cover the vents while cutting. That's about a half-step ahead of some I've seen...

[waterboy 7]

They didn't cover the one under it though. Had the strangest comm errors from that proc until we shook the filings out of it. Thats when we found the tape on the one above it. This "Lowest Bidder" stuff drives me crazy.

[Joe E. 259]

Nice...

[brazierp 1]

Most of my work is on controls on hot presses. I've suffered over the years having to put right overheated panels. Now I always keep a spare temperature input for cabinet temperature and will alarm at 50c (120F) and shut the machine down at 60c (140F). If anyone complains about this, show them the spec sheet on any PLC, I've never seen one which will warrant over that temp. I've also learnt to put vent fans, where possible, at the bottom, preferably underneath the cab as it stops people accidentally covering them and resists dust build up. The current one I am working on has two cabs side by side so I am sucking in from the bottom of one side letting the air thru the top to the other cab (which contains pneumatics) and then blown out the bottom of that cab. If you have an outlet on top, put a wire frame pyramid over it. Peter Edited 15 May 2012 by brazierp

[BobLfoot 302]

Brings to mind a panel we had which included not 1 but 2 heat exchangers so the air inside the panel never mixed with the air outside yet the heat was dissipated. But every once and a while the 140 F shutdown sensor would trigger a system stop and sure enough the panel was hot. Well wouldn't you know it the heat exchangers were drawing off a common "cool" sump for cool water and whenever a hot abtch of material left to process the "cool" sump spike to 100 F which left the HE little room for error. Solution an isolated sump and evaparator/condensor for the panel.