# Toggling a timer



## subelect (Nov 25, 2007)

Once again, I have a simple question that is wrapped up in a long, boring story. 
My questions are; for a Timer, Delay On, shouldn't it be toggling to the "reset" position (NC contacts closed, NO contacts open) when power is removed? Is there a required period of time with power removed before it can function again?



The long boring story is that our city has a 240 volt, 3 phase pump that is normally controlled by their computer system. When the computer calls for the pump to start, the desired effect is to have a 110 volt solenoid provide pre-lube water to the pump before the pump actually starts up. 
Once the pump's contactor kicks in, the solenoid deenergizes. 

This has been a running battle with this equipment. 
1st trip: the boss tells me to replace the existing timer because it is bad and he jumpered out the contact so the pump functions without the timer. Actually, the solenoid had a faulty 240 volt contactor which I had to order from the supply house.
2nd trip: Replaced the contactor, figure out that the city utility installed the new water solenoid in backwards so no flow to pre-lube. Also, the boss gave me a Delay Off timer to install. After much arguing, he orders a Delay On.
3rd trip: They corrected the solenoid orientation, this time actually got to test the system, the timer just will not toggle. I just can't bring myself to believe that the equipment is miswired (the 110 volt branch circuit that is routed thru the solenoid contactor also feeds the timer coil; the only time it is toggled is when you cycle power to the entire pump house.) In the course of my bumbling around, I smoked the 3 phase monitor. Not making any brownie points with the customer, or my boss. Significant amounts of butt-chewing ensue.
4th trip: I changed the wiring such that when the pump is in "Auto" and the computer calls for it to start, it starts the timer, powering up the solenoid contactor and solenoid for 25 seconds and then starts the pump. But, it only does this correctly the first time after you cycle power to the entire pump house. 
The power signal (not the high leg) that would power up the pump contactor feeds the 110 volt timer coil (terminal 7 with a neutral on terminal 2) and also terminal 8. The NC contact (terminal 5) feeds the solenoid contactor and the time-delayed NO contact (terminal 6) powers up the pump contactor. 
It only works correctly the first time power is restored, after that, when the computer calls for the pump to start, it starts immediately with no time delay.
Have you ever had problems with a timer not toggling?
Thanks,
Rick


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## RePhase277 (Feb 5, 2008)

Are you sure the delay-on-make power signal is actually being cycled when the computer calls for the pump to start? I mean, if the power isn't interrupted to the timer, it won't begin another timing operation.

Is there any way that power may still be reaching the timer, maybe through a backfeed from another phase through a device? Can you isolate the power to the timer from the motor power supply?


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## subelect (Nov 25, 2007)

I did not check to see if the signal calling for the pump contactor to start would completely disappear when the pump switch was turned off. 
As far as getting backfed from another device, there does not appear to be another device. 
It is actually a very simple setup that should not be anywhere near this painful to get straightened out, but it has been a bear.


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## wwilson174 (Apr 25, 2008)

subelect said:


> I did not check to see if the signal calling for the pump contactor to start would completely disappear when the pump switch was turned off.
> As far as getting backfed from another device, there does not appear to be another device.
> It is actually a very simple setup that should not be anywhere near this painful to get straightened out, but it has been a bear.


If the source of the signal that triggers the timer is a solid state device you may be having a problem with minority carriers leaking enough current to keep the timer on. connect a resistor in parallel with the timer and the signal will disappear. Good luck, BillW


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## PLCMentor.com (Apr 15, 2009)

This may be a little off subject, but you mention the pump is controlled by a computer. I would assume you mean a PLC. Why didnt they just put the solenoid and timer in the PLC? Would have been simple flexible and cheaper.


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## subelect (Nov 25, 2007)

I have never asked the question why the timer was incorporated in the PLC program. Probably left as much of the old equipment in place as possible to save money.
If I do need to place a resistor in parallel with the timer's coil terminals, what value resistance do you recommend starting out with?
Thanks,
Rick


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## wwilson174 (Apr 25, 2008)

5-10k 1w for starters if it runs cool and does the job you're done. BillW


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## subelect (Nov 25, 2007)

Yesterday I think that I finally put this problem to rest.

I tried twice to arrange a time to unlock the pump room and install the replacement 3 phase monitor (for the one that I smoked because I am an idiot) and straighten out the timer ckt.

They called and said that the motor was not operating at all.

I got there and found that the 110 volt timer had failed and the NC contacts were constantly energizing the water solenoid contactor.
Once again, the first time you restore power to the ckt, the timer and all connected stuff worked correctly. 
But, as soon as you turn off the pump, the voltage to the timer jumps up to 216 volts to ground. It ruined my timer coil.
I triple-checked; the high-leg was not being used for any portion of the control circuit. But, I could not explain why I was getting that weird voltage fed back into my timer.

I wound up using a 240 volt timer that had an indicating light to tell what the state of the contacts were. The light showed that it was staying toggled after power was removed.
My final solution was to use that 240 volt timer; put the 110 volt water solenoid's 240 volt contactor in parallel with the timer coil (terminals 2&7 on the 8 pin socket) by routing one side of the wires thru the NC contacts on terminals (?) 1&4. 
It worked and just about everything else I tried did not work. If I tried putting the water solenoid contactor across on the same side of the timer ckt as the pump contactor, the timer would stay toggled after the pump signal was removed.
I should have tried the bleed resistor that you guys suggested, but I did not get my act together and order one ahead of time.

Thanks for all your advice.
Rick


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## wildleg (Apr 12, 2009)

subelect said:


> But, as soon as you turn off the pump, the voltage to the timer jumps up to 216 volts to ground. It ruined my timer coil.


might be a good idea to draw the ckt out on paper (no loose neutrals ?)


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