Power outage

[tdjs]

I need to know how to keep motor starters on when there is a loss of power during an electrical storm . These starters are used to run fans to hold a tarp down on a corn pile. We are using a 120 volt control circuit for 8 motor starters. Could an APC ups battery back up be used for this application?

 

[mdshunk]

Sure, the UPS will do the control circuit, but what are you running the fans with? If they're on a generator, and there's a changeover lag (where the fans are briefly not running), I think you may bump into an OSHA issue with automatically starting equipment.

 

[tdjs]

tjds

tjds

mdshunk These fans are 480 volt 3 phase.They are on 24/7 to suck the air out to hold down the tarp. We are talking about 1 million bushels of corn in a temporary storage pile.When the power is off for a second ,the control circuit drops out.The fans have to be started again but when no body is around at 1:00 AM thats where a back up is needed.Do you think it will work?

 

[hardworkingstiff]

I don't know if this will work, but I once saw a control system on dispensing equipment that used a couple of relays in succession to keep the operator from turning off a dispenser and then back on to steal gasoline. The problem was that when the electric reset completed its cycle, it operated a switch that dropped power on one leg and sent it on another (like a 3-way). The momentary lapse of power during the switch changing caused the control relays to drop out prematurely (the 1st one sent power to the second.... something like that, it was 25 years ago). The solution was to install a capacitor in parallel with the coil of the relay. That capacitor held the coil in long enough for the switching to be made.

It sounds like a momentary lightning strike is causing a flicker in the supply that is dropping out your controls. If that is what's happening, the cap trick may work. If you completely loss power, the controller would not remain on.

 

[hockeyoligist2]

Why don't you just install a simple on-off switch?

 

[hardworkingstiff]

Why don't you just install a simple on-off switch?

If they have remote E-stops, that probably wouldn't work. Mdshunk's concerns need to be addressed also.

 

[hockeyoligist2]

If they have remote E-stops, that probably wouldn't work. Mdshunk's concerns need to be addressed also.

If it has remote e-stops they could replace them with the push-pull type.

 

[foqnc]

If you are loosing power, where are you getting 3 phase for the fans themselves?

 

[hardworkingstiff]

If it has remote e-stops they could replace them with the push-pull type.

That could work (so long as the NC contacts of the push-pull e-stops feed the new switch). The danger would be that if someone pulled the E-Stop back out, the motor would start unless someone had gone to the new on/off switch to cut it off. I don't know what code that might violate, but my gut says there is one out there that says that would be a no/no.

Typically you could have multiple locations for stop buttons but only one start button located near the machine.

 

[hockeyoligist2]

That could work (so long as the NC contacts of the push-pull e-stops feed the new switch). The danger would be that if someone pulled the E-Stop back out, the motor would start unless someone had gone to the new on/off switch to cut it off. I don't know what code that might violate, but my gut says there is one out there that says that would be a no/no.

Typically you could have multiple locations for stop buttons but only one start button located near the machine.

Most machines (unless they have a PLC or some other extra controls) are wired in series thru normally closed contacts, back to the holding contact on the starter. Simply remove it from the holding contact and go thru the on-off switch so it kills the power. I think that the push-pull e-stop falls under a remote disconnect. There are some that have a lockout feature. So I don't believe that would violate OSHA. I have never saw them flag any machine for this.

 

[petersonra]

Sure, the UPS will do the control circuit, but what are you running the fans with? If they're on a generator, and there's a changeover lag (where the fans are briefly not running), I think you may bump into an OSHA issue with automatically starting equipment.

This a kind of a myth. OSHA does not prohibit starting equipment automatically. You can't do it if it creates a hazard, but many, many things start and stop automatically.

You do have to have a means to shut off and keep the power off, but that is something required anyway.

And generally if you have something called an estop, that requires operator intervention to restart.

 

[tdjs]

tdjs

tdjs

The starters are controlled by start-stop buttons in one loaction.The UPS would be located ahead of the stop buttons and circuit breaker that feeds the control switches.Which in turn only is actived when power is off.

 

[hockeyoligist2]

The starters are controlled by start-stop buttons in one loaction.The UPS would be located ahead of the stop buttons and circuit breaker that feeds the control switches.Which in turn only is actived when power is off.

Since that is the case it would be cheaper and more reliable to replace the stop button with a push-pull and install an on-off switch in place of the start button. Remove the holding circuit from the starter and wire it thru the push-pull (NC) then to the on-off switch.

 

[hardworkingstiff]

Since that is the case it would be cheaper and more reliable to replace the stop button with a push-pull and install an on-off switch in place of the start button. Remove the holding circuit from the starter and wire it thru the push-pull (NC) then to the on-off switch.

And if you did it this way, you wouldn't need the UPS.

 

[benaround]

For saftey sake, it would be smart to have an audible device during this

condition.

 

[mdshunk]

This a kind of a myth. OSHA does not prohibit starting equipment automatically. You can't do it if it creates a hazard, but many, many things start and stop automatically.

I didn't mean to suggest that it's not permitted. I only wanted to bring the "issue" to light. I know that there is required signage in the proximity of equipement that starts automatically.

 

[tdjs]

tdjs

tdjs

The push-pull and on-off switch would not work because there are 8 start-stop buttons for each fan control by one control power source.Thats where a UPS could keep all the holding coil energized for each of the 8 fans motor starters. This is only going to be used for very short power outage under a minute.Will it still work?

 

[petersonra]

I didn't mean to suggest that it's not permitted. I only wanted to bring the "issue" to light. I know that there is required signage in the proximity of equipement that starts automatically.

what rule is that?

it is common practice, but that does not make it a requirement.

 

[Smart $]

The push-pull and on-off switch would not work because there are 8 start-stop buttons for each fan control by one control power source.Thats where a UPS could keep all the holding coil energized for each of the 8 fans motor starters. This is only going to be used for very short power outage under a minute.Will it still work?

Perhaps one push-pull e-stop and 8 off-run switches...?

The concept of a UPS would work for keeping the coils energized, but how do you intend to negate it backing up power loss for more than a minute, if one minute is the desired cutoff? ...or is that just an arbitrary figure?

In a similarly critical situation, I once used mitsubishi alpha controllers to automatically and sequentially restart dewatering pumps after power outages. They had to be restarted sequentially because a concurrent restart tripped the main. The system also had a cellular phone notification module in case one or more pumps weren't running for any reason when power was available. Any one pump being down for an extended period would have inundated the entire jobsite!

 

[mdshunk]

what rule is that?

it is common practice, but that does not make it a requirement.

OSHA's 'Machine Gaurding Standard for Agriculture', which requires (in part): "...a sign posted near each motor which warns employees that the motor could automatically start unless the electrical disconnect switch is utilized."