High Inrush Breaker - QO120HM - question

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delfadelfa

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Cincinnati, OH
I have a customer that wants to plug in a 15 amp treadmill on a 15 amp circuit. She said the manufacturer suggests upgrading to a "high inrush breaker QO120HM. I can't do that can I??
 
delfadelfa said:
I have a customer that wants to plug in a 15 amp treadmill on a 15 amp circuit. She said the manufacturer suggests upgrading to a "high inrush breaker QO120HM. I can't do that can I??
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Why do you question it?

A 'slow trip' QO120HM will still operate at about the same speed as other manufacturer's standard speed breakers. So, I can understand the treadmill manufacturer recommending it.

And a piece of equipment that draws 15A should be installed on a 20A circuit.

But an existing 15A breaker cannot simply be replaced with a 20A one, unless the existing wiring is rated for 20A (i.e. #12) .
 
When you say 15 amp treadmill do you mean that it can be used on a 15 amp circuit or that it draws 15 amps?

If I assume it is actually a 12 amp treadmill then:

If they were to suggest a QO115HM that should work.
I believe they are recommending the "high magnetic" because it will better tolerate the high inrush currents of the treadmill.

The high magnetic will allow a higher amplitude of current for the same amount of time as the standard breaker.

We installed QOHM all the time for nuisance trip issues due to inrush.
 
weressl said:
There are fast- and slow-blow fuses, but breaker characteristcs are pretty much identical at this level, and adjustable at much larger sizes.
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The standard Square D QO 15 and 20A breakers trip faster than most of those from the rest of the industry. This is why Square D makes some for high magnetic inrush circuits (16-26X).
 
ELA said:
When you say 15 amp treadmill do you mean that it can be used on a 15 amp circuit or that it draws 15 amps?

If I assume it is actually a 12 amp treadmill then:

If they were to suggest a QO115HM that should work.
I believe they are recommending the "high magnetic" because it will better tolerate the high inrush currents of the treadmill.

The high magnetic will allow a higher amplitude of current for the same amount of time as the standard breaker.

We installed QOHM all the time for nuisance trip issues due to inrush.
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This lady did not give me much information and only called to get a quote on replacing a 15 amp breaker with a 20 amp HM breaker. I've never used a HM breaker before only fuses. I told her if the treadmill pulled that much she would need a 20 amp circuit. She refused to believe me and said she would call somebody else.

On another job I am have nuisance tripping on a 15 amp arcfault Square D breaker. It's a condo that is wired in conduit, metal boxes, and MC and was wired when just the bedrooms were on the arcfault. Have you ever had a problem with a plug strip with surge protection tripping an arcfault?
 
delfadelfa said:
This lady did not give me much information and only called to get a quote on replacing a 15 amp breaker with a 20 amp HM breaker. I've never used a HM breaker before only fuses. I told her if the treadmill pulled that much she would need a 20 amp circuit. She refused to believe me and said she would call somebody else.

On another job I am have nuisance tripping on a 15 amp arcfault Square D breaker. It's a condo that is wired in conduit, metal boxes, and MC and was wired when just the bedrooms were on the arcfault. Have you ever had a problem with a plug strip with surge protection tripping an arcfault?
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It's not going to be the plug strip it is going to be what is plugged into the plug strip, that is the problem.
 
Why? Where are the voltage surges shunted to? I could see if there is enough surging going on and there any Line-Ground MOV's that enough current could be shunted to ground to trip a GFCI or AFCI.
 
I question whether the tread mill draws 15 amps. That is a lot of power for a belt that does little work. The idea of a treadmill is that the user is supposed to consume the majority of the energy from fat, carbs, etc stored in their body. 15 amps @120 volts is in the 1 hp range, wouldn't you think 1/6 or 1/4 hp would be plenty of power to run a treadmill?

Treadmills are also soft starting type loads so there is likely little or no inrush like there is for typical across the line motor starting.

I have used QO high magnetic circuit breakers - usually for cut off saws, air compressors, where high inrush is a problem and they do work they have a longer magnetic trip time than a standard QO but still have the same thermal trip characteristics. My guess is there is some other problem - maybe as simple as there is too many other loads on the circuit the treadmill is plugged into.
 
Some of the treadmills do come with a 20A plug on them, doesn't mean that is what they draw, but some are made with a 5-20P
 
acrwc10 said:
Some of the treadmills do come with a 20A plug on them, doesn't mean that is what they draw, but some are made with a 5-20P
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I seen one in a hospital physical therapy room that was 240 volt with 6-15 plug.

Can't imagine the motor driving the belt needs that kind of power, maybe there is other loads involved on some units?
 
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