Zelio relay damage

[Ice-Tea]

Hey,

Have 2 ZELIO PLC modules, mainly to switch the lights inhouse. Unfortunately, the relays have a tendency to "stick", the last one with a grand total of 29W of CFL on a 5A relay. Aside from venting my displeasure, I'd like to know if anyone here has refurbished relays for Zelios and would like to share their experience?

Ice-Tea

 

[rpoet]

No specific experience with the ZELIO PLC, but if it's built like most others, the relays are probably replaceable, possibly using a soldering iron. Some relay modules allow you to replace damaged relays through the use of a socket arrangement.

CFL lamps, even they "only" draw low wattage, have very high inrush values. That's why your relay contacts are welding. I strongly suggest using an interposing relay that has the proper rating to switch a load with high inrush.

-rpoet

 

[Ice-Tea]

Well, I was afraid you might say something like that. I specifically installed the Zelio because price per relay was pretty uch the same as for discrete "dumb" modules. Didn't count on having to double them all

Well, I'll pop it open then. Maybe I can replace the relays with higher rated ones. Some version even have specific inrush current versions... If I find the time I'll post some pics/findings.

 

[rpoet]

Maybe I can replace the relays with higher rated ones. Some version even have specific inrush current versions... If I find the time I'll post some pics/findings.

I doubt you'll be able to replace the relays with higher-rated versions; the PC board space on those modules (or any PLC module) is pretty tight.

Chalk this up to a learning experience; the best solution is to use a DC transistor output card, and use it to control hockey-puck style solid state relays. Nothing mechanical to wear out, and the solid state relays are easier to swap if you ever have an overload that damages them. If you oversize them slightly, and protect them with appropriate fuses, you should never have a problem.

Solid-state relays are easy to find on the surplus market, and can be pretty cheap.

http://www.surplussales.com/Relays/RESSPlug-1.html



-rpoet

 

[Ice-Tea]

I doubt you'll be able to replace the relays with higher-rated versions; the PC board space on those modules (or any PLC module) is pretty tight.
-rpoet

True, off course, but in the same series/FF of relays there are part numbers that have better inrush current ratings (but identical steady state ratings). Has to do with plating of the contacts.

I can dream, can't I?

And steady state? Guess I'm a bit averse to the losses in those?

 

[rpoet]

And steady state? Guess I'm a bit averse to the losses in those?

At 29w, your losses will be negligible.


-rpoet

 

[Ice-Tea]

True, but I also have a few lines that do 400W or so.

 

[rpoet]

True, but I also have a few lines that do 400W or so.

Still nothing to worry about with solid state relays. The cabinet backplane will supply plenty of heat sinking, should you need any.

-rpoet

 

[iant]

guy's it is NOT the inrush current tht is the problem.
it is physically breaking the load (Back EMF or Spike) that is eating the contacts.
Contactors use arc quenching - Almost All PLC relays - Including Zelio - are rated at 3 Amps RESISTIVE. CFS aa with most AC lighting is INDUCTIVE.
Interposing rrelays is your only choice.
Also confirm the material of the contacts - Gold Plated are for DC loads Only

 

[iant]

remember the Contacts of the Points in the old car HT distribution system.
the pitting would cause the points to stick and the car would run like a snail