quincy qt-54

[scotty95]

Not an electrician here, excuse if it has been discussed also. Quincy says a #10 wire with a 40 amp breaker. al I have read for the last week is 10/2 or 8/2 wire and 30 amp breaker. Can someone please let me know what number wire and breaker to use? thhn, nm-b or? Thanks you for your input. It's a 5 hp and 21 amp draw.

 

[dave*99]

A 30A circuit requires a 10ga wire almost always. Looks like you have a dedicated circuit for a compressor that runs at 21A. The motor startup current will be higher. Hence the 40A breaker is specified. As long as the compressor is the only load on that circuit, all is well.

 

[Rinspeed]

I think 10 GA with a 30 AMP breaker should be fine but you have to remember that the start-up amperage with the 10-15% fudge factor might put you slightly over 30A. The only way to be sure is to measure it.

 

[dave*99]

I suspect Quincy already measured it and chose to recommend a 40A breaker.

 

[71goldss]

I’ve been running my Quincy QT-54, with Baldor motor on a 30A breaker and 10ga wire for ten years now. No problems here.

 

[Slednut]

I’ve been running my Quincy QT-54, with Baldor motor on a 30A breaker and 10ga wire for ten years now. No problems here.

Me too.

 

[Pontiac787]

Same for me with a SB VT-735.

 

[Augus7us]

You can run them on a 30amp but its not code. As others pointed out the surge when it starts is what the breaker is for.

I think i ran 6-2 for my qt5.

 

[71goldss]

You can run them on a 30amp but its not code. As others pointed out the surge when it starts is what the breaker is for.

I think i ran 6-2 for my qt5.

My 30amp breaker has never tripped on start up. I’m not an electrician, but should I have other concerns other than not code? If I’m not mistaken, I believe 10 years ago when purchasing my QT-54, the recommended breaker was 30amp. This was one of the reasons I chose this compressor, since I already had a 30amp source in my garage.

 

[mike93lx]

I think 10 GA with a 30 AMP breaker should be fine but you have to remember that the start-up amperage with the 10-15% fudge factor might put you slightly over 30A. The only way to be sure is to measure it.

FYI, startup current is way more than 10-15%. 4-6x running current (so 80-120 amps) is more typical, but it's fast enough to not pop the recommended breaker

 

[dave*99]

You can run them on a 30amp but its not code. As others pointed out the surge when it starts is what the breaker is for.

I think i ran 6-2 for my qt5.

You sure it's not to code? This is a dedicated branch circuit. It's a very specific code section.

Conductors are sized to 125% of the motor run current. 21A X 125% = 26.25A
The correct conductor for that is 10ga.
The overcurrent (short circuit) protection, commonly knows as the breaker is sized to accommodate the startup current.
Quincy says use 40A breaker.
This meets code.

Now if this was a non-dedicated general purpose branch circuit let's say with a receptacle, a 10ga wire would be limited to 30A breaker.

You will find even larger discrepancies with welders. 10ga wire and 50A breakers etc.

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Motor circuit protection involves understanding the National Electrical Code and equipment nameplate information.

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