480V vs 120V CONTACTOR COIL

[vanskat]

Just trying to list the pros and cons of using a starter with a 480VAC coil vs a 120VAC coil.

Any suggestions?

 

[busbar]

Except for a very small system, 480V-control reliability and troubleshooting could quickly become nightmares. Spare-parts availability with respect to 480V components could bring outage-restoration costs to new extremes.

 

[Barry1961]

I think the main concern would be running 480VAC to the pushbutton/contact block.

 

[PUMPDESIGNER]

120 volt coils are standard, well stocked, easy to get.
All other voltages are typically special order, but not hard to get.

We tried for a few years to go with 24 volt coils. Easy enough to get but always a hassle, no one anywhere seemed to ever have any, wait a week or two and they will get it.

We have noticed this for most voltages unless someone is stocking for a specific customer.

PUMPDESIGNER

 

[vanskat]

Thanks.

I guess voltage levels would be the main concern.. I got a bit curious after seeing a 30hp motor control cct wired up with a 480V coil. I eventually changed the circuitry and replaced with a 120VAC coil wondering if any harm had been done.

Additionally, with a 480V control circuit pilot lights and other indicating/status devices become a bit tricky to implement.

 

[grobert]

The main reason to use 480v control votage is cost / space. If you have no external control devices (ie: remote stop/start, level switches, etc)then why add a CPT? This can be a cost issue when dealing with nema 7 enclosure or if you have limited physical space for the controller.

 

[busbar]

No offense intended, but I agree with grobert—as long as long-term reliability is of no concern.

 

[peebee]

120-volt is a lot more forgiving to work on live than 480-volt. Especially when the available fault current is throttled way down by a little control transformer. A dropped screwdriver or touched wire will give a little flash on the 120-volt transformer circuit, but could be life threatening with a 480-volt circuit with 100,000 amps of utility power behind it.

At the very least, if you put in a 480-volt control circuit, I'd put some BIG warning stickers on there to alert your electricians. Keep in mind the new flash-hazard sign requirements from the NEC, they might be applicable here.

I'm not trained as an electrician, I'm an engineer, but I will still occasionally open a starter for minor circuit tracing & troubleshooting (only at non-union sites of course). You would not find me poking around in a 480-volt control circuit, though. I may be dumb but I'm not stupid.

 

[vanskat]

Peebee,

I am trained as an engineer myself but often times end up troubleshooting control ccts. I have only five years field experience and only recently eyeballed a 480V control circuit on a small system.

I have gotten a tingle from 120V a few times and with some of these newer and smaller control transformers on the market, there should always be space for one.

It really is not a major issue apart from the safety aspect of which trained personnel should be aware

thanks

 

[jbartos]

Suggestion: The 480V controls is used very rarely; only when it is justified. There are some starters and control panels for 480 Volts that do not use control transformers. They tap and use 480V directly for controls.
220V or 380V control wiring is used in Europe. Visit

http://www.memonline.com/ams_2.html

for more info.