Remote Latching Klixon

[itsmoked]

This must exist.

We have a heater in a remote location protected by a typical normally closed klixon bi-metal temperature switch.

Normally the Klixon would be in series with the power contactor and would shut down the heating if an over temperature was detected. But also would then take over temp control, running the system at the Klixon's temperature until it welded shut and all evidence was lost in the resulting cataclysmic fire.

I don't do 'normal'. I want the heating circuit shut down until a human has to push a button to restart it. No, I can't use a manual reset Klixon as it needs to be mounted out of normal reach and view.

What I need a box with a button on it. The heater contactor circuit needs to run to the Box. The Klixon wires need to run to the box. If the Klixon opens the heater circuit opens. The Button must be pushed to restart the heating.

Keep in mind all the usual latching circuits will not work as this system will lose all power regularly causing them to drop out and require manual resetting after every power cycle. This is not a possibility in this application.

So! Got any ideas or even a name to call this Box With Buttons?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[dpc]

Mechanical latching relay?

 

[itsmoked]

Hi dpc;
Do they stay latched through power cycles?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

A latching relay will have a "Close" coil and an "Open" coil.
How about a double throw relay ahead of the latching relay.
In normal operation, the Klixon keeps the DP relay energised and the closed contacts energize the heater. When the Klixon Klix, the NC contacts send an "Unlatch" signal to the latching relay.
Or, put a reset solenoid in front of a reset type Klixon.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[jraef]

Keith,
What is going to stop the average doofus operator from just manually resetting it and duplicating the "auto-destruct" you have now?

For my peace of mind, I would use a LOGO (smart relay) and program a Latching Relay function to the enable circuit for the contactor, unlatching it only when the Klingon opens. Then require a manual reset from an input, but put in a "minimum time before reset" timer to prevent rapid cycling.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[ScottyUK]

The mechanical latching relay would work fine - use the Klixon to set it and the push button to clear it. Why would two coils matter?


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[itsmoked]

Hi Bill; I was coming to that conclusion too.

Hi Jeff; This is a high power coil heater in a air plenum. If the blower fails we need to alert the operators. Having to ever reset the unit would indicate a serious problem that would require a phone call verses the stagnant coil quietly cycling until disaster. I'm seriously considering a LOGO! as it's a smaller physical fixed solution.

I still can't believe someone hasn't made an OTS gizmo for this.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[itsmoked]

Scotty; Not following the scheme. Got some more detail?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Ok... I think I see where you are heading with this now. My bad for reading too quickly!

The latching relay deals with your manual reset and power loss requirements, but you need a latching relay which doesn't require power to latch, correct? How about something like an ANSI code 86 protection relay which is a trip & lockout function. Once it trips you need to push a button on the front otherwise it remains tripped indefinitely. Something like

http://www.areva-td.com/solutions/liblocal/docs/MVAJ/mvaj05-20_en_1754.pdf.

That assumes you have a normally open Klixon, otherwise you'll need to invert it to get a NO function.

Have you got access to a switchgear graveyard? Pretty much any older board will have relays similar to this on the front.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[itsmoked]

you need a latching relay which doesn't require power to latch, correct?

Well, we need a latching relay that stays latched thru a power failure...

Thanks for the link. Interesting but um...

Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

'...um...'

Ouch!


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[itsmoked]

LoL

What I mean is I need to read that thing before I understand it. And I have no switch gear dumps. And it doesn't look cheap. (er, inexpensive)

Keith Cress
kcress -

http://www.flaminsystems.com

 

[fangas]

It's early, and I'm still drinking my AM coffee but here's a thought (If i read tis right).

Gang two circuit breaKers together, one at your load value, one at some much lower value.

Drive your Klixon into a relay. Use the NC contacts of the relay to drive a small load (lamp, etc) powered by the smaller CB. Make this load greater then the CB rating.

When the Klixon "Klix" open, the relay drops out, load turns on, small breaker trips, drags larger breaker with it.

It's off. And stays off until reset. And it should happily ride through any power problems

Hey, it 6:45. It's a thought.

Ed

 

[DRWeig]

ITSmoked,

Lots of mechanically latching relays available that will hold whatever their current position is through a power outage. GE RR-7 is a heavy duty one, should be about USD$25. Idec, Omron,P&B, all have equals. Thumb through a Newark catalog to find 'em.

We use these for alarm / silence controls all the time.

Let us know what works for ya!

Good on ya,

Goober Dave

 

[slavag]

Hi Keith.
What is a current range?
See, you have few options:
LOR - lock out relay with mechnical reset from GE or Elektroswitch, but I think it's expensive, or Areva LOR, what Scotty was present. BTW , like to this Areva LOR, Siemens have a nice LOR, don't remeber type, but I hope, Jraef can help with this issue.
You can google term bistable relay and will found so much options.
Or of course biuld something like to Ed's idea.
Best Regards.
Slava

 

[itsmoked]

Wow nice ideas folks!

fangas; I'd thought of the same thing with fuses. CBs make way better sense though.


DRWeig; I just found several latching relays after chasing your RR-7 which won't directly work being an impulse type. Thanks.


slavag; "Lock Out Relay" Nice. I will check them out. Done. Ugh! Traditional LOCs appear to be for big power. Generators, etcetera. They appear to be pretty large and expensive. In this case I only have to run one 40A 3ph contactor coil...

I think I have a two coil latching relay in my junk bin. I will hook it up on the bench with a second "invert the NC Kixon" signal relay. My only concern with this setup is the race condition that occurs during every power up. This is when the inverting relay is dropped out in the unpowered state. Will it pull in before the latching relay unlatches?

That! is the question.



Keith Cress
kcress -

http://www.flaminsystems.com

 

[ScottyUK]

Keith,

Any reason a normal two button NVR motor starter arrangement won't work? The 'start' function becomes your reset, and the 'stop' button is the Klixon (or an inverted contact driven by it). By definition a no-volt-release won't do anything without manual intervention.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[ScottyUK]

Never mind, it won't stay 'set' after a power outage until someone resets it. My brain is in freewheel this morning...


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[itsmoked]

hehehee Yeah first thing I thought of. So simple so effective... So useless.

I'm going to try those relays when I get to the shop. Didn't have the opportunity today.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[noing]

good day to all
sooooo klixon drive an inverting relay, relay drive a timer,
[to prevent the race at power up] timers normal open contact
switch a cb trip coil,,,,
if klixon open : relay drop then the timer after delay trip
the cb
hope this help's.

p.s this is an amazing forum you guys are grate.