latch/unlatch for an old Asco 925

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sundowner

sundowner

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West Wisconsin
So I have two separate signals (125VAC) that go into each building on campus - one signal fires a "latch" control relay which closes my Asco 925 lighting contactor - (turning on all my ext. building lights) The next part of the sequence - in the AM, fires the other signal and fires the "unlatch" relay which opens the lighting contactor. (which is mechanically held - fired to open and fired to close)

I want to keep the Asco but would like to replace the two little open style relays labeled - latch/unlatch which fire this.

What can I use that's only one device - I need a relay which will accept two separate inputs to drive two separate output - all independent of one another. Is this possible??

I thought years ago I used a "Finder" brand relay that did something like this but am unable to what I'm looking for right now...???

Any suggestions guys??
 
171222-1400 EST

sundowner:

I have no idea what an ASCO 925 is or was.

An Internet search turned up an ASCO 920, see
https://www.vertivco.com/globalassets/documents/brochures/asco/3206_r3_january_2017_134235_1.pdf

I still really don't know what this is. Likely it is a motor driven switch with internal logic to allow sustained set and reset signals. Probably requires a substantial amount of current for control and thus is not directly suited for long distance control. That is the reason for the small relay controls.

A single relay can be used because the the 920 (possibly 925) can tolerate sustained input control signals.

What is the real problem you want to solve.

See p5 of the above website for control wiring. Very poor literature relative to the control aspect.

.
 
If you wanted to utilize only one maintained signal, I would think that a SPDT relay would do the trick. Normally open for one condition, normally closed for the other. Unless your signal is momentary, then you could use an alternating relay. I have gone to programmable relays. A few I/O is not much more than a decent relay, and you have so much latitude on what you can do. A GE lighting relay may work too.
 
sundowner said:
So I have two separate signals (125VAC) that go into each building on campus - one signal fires a "latch" control relay which closes my Asco 925 lighting contactor - (turning on all my ext. building lights) The next part of the sequence - in the AM, fires the other signal and fires the "unlatch" relay which opens the lighting contactor. (which is mechanically held - fired to open and fired to close)
Click to expand...

Are these two separate signals from the same source on the same circuit? Since you have two existing relays it sounds like they are not.
 
sundowner said:
So I have two separate signals (125VAC) that go into each building on campus - one signal fires a "latch" control relay which closes my Asco 925 lighting contactor - (turning on all my ext. building lights) The next part of the sequence - in the AM, fires the other signal and fires the "unlatch" relay which opens the lighting contactor. (which is mechanically held - fired to open and fired to close)

I want to keep the Asco but would like to replace the two little open style relays labeled - latch/unlatch which fire this.

What can I use that's only one device - I need a relay which will accept two separate inputs to drive two separate output - all independent of one another. Is this possible??

I thought years ago I used a "Finder" brand relay that did something like this but am unable to what I'm looking for right now...???

Any suggestions guys??
Click to expand...

a common latching relay http://www.mouser.com/ds/2/357/105A_755-7090.pdf
using a form c contact
potter brumfield
magnecraft
etc

is the 125 latch/unlatch signal maintained or momentary?
 
Thanks guys...

gar - my 925 is a 1950's version of a modern Asco920 3 pole lighting contactor.

I'd like to clean up this install - it is the exact same in several buildings on campus - they all look like hell and now that I have to maintain these I'd like to make things much neater and a lot more straight forward.

The current set-up is simple - I'm using a remote 120VAC pulse from a central building to pull up my local control relay to fire my lighting contactor - with local control power. Then I fire another pulse to pull up another control relay to open my lighting contactor - it sounds like it should be straight forward and it is - except for the "latch", "unlatch" relays in the circuit.

My "building automation techs" seem to have horned in on this kind of stuff and if I can control exterior lights with a separate piece of electronics - they would be out of the equation.

I also remember doing something like this several years ago - just cant seem to remember the relay I used... I like the IEC stuff because it's nice and small - also like the Square D stuff - very reliable.

Thanks guys!!
 
sundowner said:
Thanks guys...

gar - my 925 is a 1950's version of a modern Asco920 3 pole lighting contactor.

I'd like to clean up this install - it is the exact same in several buildings on campus - they all look like hell and now that I have to maintain these I'd like to make things much neater and a lot more straight forward.

The current set-up is simple - I'm using a remote 120VAC pulse from a central building to pull up my local control relay to fire my lighting contactor - with local control power. Then I fire another pulse to pull up another control relay to open my lighting contactor - it sounds like it should be straight forward and it is - except for the "latch", "unlatch" relays in the circuit.

My "building automation techs" seem to have horned in on this kind of stuff and if I can control exterior lights with a separate piece of electronics - they would be out of the equation.

I also remember doing something like this several years ago - just cant seem to remember the relay I used... I like the IEC stuff because it's nice and small - also like the Square D stuff - very reliable.

Thanks guys!!
Click to expand...

Not sure on how much space you have, but a couple small 'ice cube' relays and a lighting contactor would accomplish your goal easily
 
Pretty much any of the IEC control relay mfrs sell a "latching" accessory for their relays that is an unlatching coil. So you use the regular coil as the "latch" input, and this accessory has another coil that you pulse to "unlatch".

Here's the one from Schneider / Telemecanique Tesis D line IEC control relays:
F4002016-01.jpg

it's important to note that on these devices, regardless of brand, the unlatch coils are never rated for continuous duty. So you either control them with momentary switches, or use a NO contact of the relay to feed the Unlatch coil so that once it operates, it cuts off the coil circuit. You then just need to ensure that when it's time to latch it again, the Unlatch signal is no longer there.
 
171228-2351 EST

sundowner:

The 920 can tolerate sustained latch or unlatch signals. It is not necessary to use pulsed control signals. The 920 automatically turns a sustained input input signal into a pulse of a maximum duration it controls. Thus, it does not require a sustained control signal which would waste power. And/or it allows a way to get high mechanical force internally without high sustained external power. And/or it does not require you to supply a controlled pulse signal to prevent burnout of an internal component.

If the old 925 works the same way, then a SPDT contact in a remote switch can control the 925. This may require large wires if the distance is great. If that is the case, then a single small relay with a SPDT contact can be used as a pilot control. ASCO makes small boards for that purpose as shown in the literature.

.
 
gar said:
171228-2351 EST

sundowner:

The 920 can tolerate sustained latch or unlatch signals. It is not necessary to use pulsed control signals. The 920 automatically turns a sustained input input signal into a pulse of a maximum duration it controls. Thus, it does not require a sustained control signal which would waste power. And/or it allows a way to get high mechanical force internally without high sustained external power. And/or it does not require you to supply a controlled pulse signal to prevent burnout of an internal component.

If the old 925 works the same way, then a SPDT contact in a remote switch can control the 925. This may require large wires if the distance is great. If that is the case, then a single small relay with a SPDT contact can be used as a pilot control. ASCO makes small boards for that purpose as shown in the literature.

.
Click to expand...
If building automation exists, utilizing a simple AI to control a three wire- CO, where one is common and the other two are on/off.

Assuming you have a status input from a photocell or other device, such as manual override, your cost saves on exterior lighting, just in energy, could help justify future upgrades as required.

I was fortunate enough to revamp an older P&S multiple panel interior and exterior lighting control system to a GE component only swap. The easiest part was, integrating photocell control, adding a couple points to the automation, i.e. day/night, pulse on/off and tracking energy saves.



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