Protecting a control circuit

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conmgt

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2 Phase Philly
If you are running a control circuit that extends beyond a motor starter, how is it protected? For example, a Start/Stop button located 30' from a starter that's fed with large conductors and the control wiring is say #14.
An inline fuse? A fuse block?
 
conmgt said:
If you are running a control circuit that extends beyond a motor starter, how is it protected? For example, a Start/Stop button located 30' from a starter that's fed with large conductors and the control wiring is say #14.
An inline fuse? A fuse block?
Click to expand...

How is power supplied to the controls (for example the button?) Whether and how you need to protect the wiring depends on what it could, in the worst case, be carrying, not just what size wire it is. Often the control wiring is large for voltage drop reasons or because the available connecting wire (especially portable cord or NM) is that size.
 
conmgt said:
If you are running a control circuit that extends beyond a motor starter, how is it protected? For example, a Start/Stop button located 30' from a starter that's fed with large conductors and the control wiring is say #14.
An inline fuse? A fuse block?
Click to expand...
Typically control circuit fuses (or breaker) in the starter.
 
conmgt said:
If it's not part of the starter and needs to be field supplied, can you point to a particular product?
Click to expand...
I don't understand how it needs to be field supplied. In general, all starters have an integral control circuit. Please explain, or perhaps provide starter make and model number.
 
If he's coming off of the Line Terminals for his control power he wont have an integral control circuit.

He may have a 240 or 480v coil.
 
In my hand is a Moeller DIL OA M 5hp@240V starter. If I want to control this starter say 30' away, I'd want to use a wire smaller that the #6 feeding the starter. The breaker ahead of the starter could be 100A.
 
What if we are talking about a lighting contactor for warehouse lights. If you tap off of the line terminals (jap) and are going to a wall switch or motion sensor, how would those conductors be protected?
 
jap said:
If he's coming off of the Line Terminals for his control power he wont have an integral control circuit.

He may have a 240 or 480v coil.
Click to expand...
Even so, that would be the control circuit... and it is typically fused.
 
conmgt said:
In my hand is a Moeller DIL OA M 5hp@240V starter. If I want to control this starter say 30' away, I'd want to use a wire smaller that the #6 feeding the starter. The breaker ahead of the starter could be 100A.
Click to expand...
Sounding more like you have the contactor for a starter... not a complete motor starter, at least not by the usual definition.

So use a smaller wire. Tap off the main and connect immediately to a dual fuse block. Load side would be your control circuit.
 
Smart $ said:
Even so, that would be the control circuit... and it is typically fused.
Click to expand...

No it's not.

If you have an open starter and are going to utilize the line terminals for your control power where is the
fusing at if you dont field install it?

That'd be a new one on me.
 
conmgt said:
What if we are talking about a lighting contactor for warehouse lights. If you tap off of the line terminals (jap) and are going to a wall switch or motion sensor, how would those conductors be protected?
Click to expand...

That's more or less the question the OP is asking not me.

What would be your answer?
 
Smart $ said:
Sounding more like you have the contactor for a starter... not a complete motor starter, at least not by the usual definition.

So use a smaller wire. Tap off the main and connect immediately to a dual fuse block. Load side would be your control circuit.
Click to expand...

A motor starter is nothing more than a contactor with on overload relay attached to it.
You were saying you didnt understand why the control circuit protection needed to be field supplied.

Probably because the starter doesnt come with fuse protection for the control circuit so you have to field
install a fuse block or other means of protection for the control circuit.
 
conmgt said:
What if we are talking about a lighting contactor for warehouse lights. If you tap off of the line terminals (jap) and are going to a wall switch or motion sensor, how would those conductors be protected?
Click to expand...

If the circuits feeding the line terminals of the contactor were say, #12, and protected at 20 Amps then you wouldnt have to add any more protection to come off of the line terminals for the control and go as far as
you wanted to.

But, Thats not the case the OP has. He's got a Starter where the Short Circuit Protection is sized to handle
inrush and is going to tap the line side for control power.

In that case he would need to provide some type of protection for the smaller control wiring.

At least that's what I think he's talking about.
 
jap said:
No it's not.

If you have an open starter and are going to utilize the line terminals for your control power where is the
fusing at if you dont field install it?

That'd be a new one on me.
Click to expand...
I've never worked with/on a motor starter that was not in an enclosure. I've modified and repaired plenty of motor starters... I've even built a few motor starters from scratch.

To me, field installed is outside the enclosure for the motor starter. The majority have control circuit fusing inside the motor starter enclosure. The ones that did not, used a remote power source for the control circuit, such as PLC controlled starters, with control circuit protection at the power supply... but the majority of the PLC controlled starter setups I've worked on used the starter incorporated control circuit and the PLC just switched the circuit.

A standard off-the-shelf motor starter (MCC bucket or stand-alone enclosure) will have control circuit protection in the enclosure (with the exception of small motor starters that the motor GF/SC protection is adequate for the control circuit protection).
 
jap said:
A motor starter is nothing more than a contactor with on overload relay attached to it.
You were saying you didnt understand why the control circuit protection needed to be field supplied.

Probably because the starter doesnt come with fuse protection for the control circuit so you have to field
install a fuse block or other means of protection for the control circuit.
Click to expand...
Read my reply to your other post...

Aside from that, "you're preaching to the choir" :happyyes:
 
No, Field installed is anything you have to add after the fact that doesnt come with the piece of equipment to begin with.

Like "Field Installing" an emergency ballast in a flourescent fixture. A lot of times fixtures are shipped ahead without the emergency ballast to expedite arrival. the ballasts are "Field Installed" but they are inside the housing of the fixture would be one example.

No single starter,open or enclosed comes with fusing for the control circuit unless it's ordered with this option (which is very rarely done) or its a combo starter that has a control transformer built into it with primary and secondary fusing.

If his starter had been supplied with control fuses regardless of wether it was open or enclosed I doubt he'd be posting this question.

JAP>
 
I think he's talking about a single starter that you would pull out of the box which includes nothing but the starter itself.

Your talking about a motor control bucket or a combo starter or a prefabricated Motor starter enclosure where the control tranformers are inside like the several that I've built and worked on also.
 
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