Motor Starter for 1/3 HP Motor???

[Bubbles Galore]

I am upgrading my Dryer Pro Tempest system to have the top 2 blowers oscillate. I will be using a 1/3 HP 120VAC motor with a mechanical speed reducer on it for the oscillation. The WW Razor is currently sending a 24VAC signal to turn the dryers on. My question is how should I go about getting the signal to the oscillating motor to turn on when the dryers come on? Can I just use a relay or should I go with a motor starter as well? Do any of you leave your oscillators on all the time? The reason I ask is that I saw this at a gas station just this week for the first time.

Thanks in advance!

John

 

[MEP001]

If your dryer motors aren't on a VFD, you could take one leg from a dryer motor output from an existing starter and run power, common and ground to the oscillator motor.

 

[Bubbles Galore]

If your dryer motors aren't on a VFD, you could take one leg from a dryer motor output from an existing starter and run power, common and ground to the oscillator motor.

I was curious if that was a possibility. I could just jumper off of one leg versus having to run a new set of conduit and such. Is there a downside or any potential issues you can think of?

 

[Washmee]

I was curious if that was a possibility. I could just jumper off of one leg versus having to run a new set of conduit and such. Is there a downside or any potential issues you can think of?

The overload on the motor starter could detect the unbalanced load and trip.
Most fractional HP motors have internal thermal cutoffs, so you just need a small contactor to run the motor.

http://www.mcmaster.com/#lighting-contactors/=hd189g

 

[Bubbles Galore]

The overload on the motor starter could detect the unbalanced load and trip.
Most fractional HP motors have internal thermal cutoffs, so you just need a small contactor to run the motor.

http://www.mcmaster.com/#lighting-contactors/=hd189g

Thanks Jon. I always end up going cross-eyed when I look at all the different options. My switching voltage is 24VAC and my coil voltage would be 120VAC right? I think this one will work that was on the page listed: McMaster #6564K851. Thoughts?

 

[Washmee]

Thanks Jon. I always end up going cross-eyed when I look at all the different options. My switching voltage is 24VAC and my coil voltage would be 120VAC right? I think this one will work that was on the page listed: McMaster #6564K851. Thoughts?

You've got it backwards. The switching voltage is 120VAC and the coil voltage is 24VAC. You need this one, McMaster# 70255k611.

 

[MEP001]

I was curious if that was a possibility. I could just jumper off of one leg versus having to run a new set of conduit and such. Is there a downside or any potential issues you can think of?

I would run a separate conduit anyway just to make sure it meets code, but I can't see any downside.

The overload on the motor starter could detect the unbalanced load
and trip.

If it's a typical thermal overload, it won't "detect" any unbalanced load. They just get hot and trip. The only reason they trip with a dropped leg is because the other two get hot.

 

[watertech24]

John, I would put in a contactor and thermal rated for your motor. Make sure the coil on the contactor is 24vac. then you can simply supply your 24vac signal to A1 and A2 and put your 120vac through your contactor on L1 & L2 and out of the thermal on T1 & T2. Hope this helps.

 

[MEP001]

A 1/3 HP motor hardly needs a contactor and thermal overload, especially when the motor has its own thermal protection.

 

[watertech24]

A 1/3 HP motor pulls 7.2 amps on 115vac. Depending on his current wire size jumping off one leg could cause a tripped condtion. not to mention he has 24vac signal. now he could use a relay but cost and usefullness and sound electrical practices say to use a contactor. you can forget the thermal if you wish but a thermal on a motor will not last if it trips to often.

 

[pitzerwm]

When using one leg of a 3PH, be sure to measure that leg to ground because one leg can be more than 120.

 

[Bubbles Galore]

Thanks for all the tips guys. I will play around with things a bit and see how they shake out once I get the parts in.

 

[MEP001]

a thermal on a motor will not last if it trips to often.

If a motor's built-in thermal protection is tripping too often, the solution is not to add a thermal protection with a contactor. It would be to use a larger motor.

 

[dreese]

For what it's worth, the oscillating motor on the old PDQ LaserDri (220 vac fractional HP motor, but the same principle applies) pulled power directly from the DS main fan motor contactor (first motor to start). Just be sure the setting on the overload on the motor contactor you use can be increased 10 amps (7A load + 25% service factor) to avoid nuisance trips. It's usually best to use L1, but check voltage just to be sure.

 

[MEP001]

It's usually best to use L1, but check voltage just to be sure.

Right, sometimes 3-phase power is two 120-volt legs and one at 277. Always test the leg to neutral or ground to confirm.

 

[2Biz]

And some 3 phase is 120v-208v-120v like mine....Its called "Wild Leg 3 Phase". If you check any two phases you get 240v....If you didn't know about this kind of three phase, it will make you scratch your head because it doesn't logically make since. So Dreese and Mep are right, check voltages first...

 

[MEP001]

And some 3 phase is 120v-208v-120v like mine....Its called "Wild Leg 3 Phase". If you check any two phases you get 240v....If you didn't know about this kind of three phase, it will make you scratch your head because it doesn't logically make since. So Dreese and Mep are right, check voltages first...

Our 3-phase voltage is 208, but each individual leg is usable 120V. The electric company didn't like that we required it because it meant putting a third transformer on the pole, but it means that every breaker slot in the panel is usable.

 

[Bubbles Galore]

Thanks for all the tips guys. I was able to get everything hooked up and running using a spare contactor and pulling from 2 legs of the 3 phase to give me the 208 for the oscillating motor. What a difference the oscillation makes for the top 2 dryers!

 

[mjwalsh]

Our 3-phase voltage is 208, but each individual leg is usable 120V. The electric company didn't like that we required it because it meant putting a third transformer on the pole, but it means that every breaker slot in the panel is usable.

Based on our experience ... some electric utilities actually put a construction charge (or threaten to) for any extra expense to them for adding 3 phase. I suppose if the more convenient to them wild leg is also cheaper for them ... it might affect whether they charge at all or how much they charge. The reality appears to be different in different areas. I am not sure about Whale's Fargo.