nuisance trip central vac breaker

[Clare Snyder]

We have a Canavac XLS970 central vac unit ( replacing our original Beam) with an 8.4 inch dual stage Ametec-Lamb motor rated at 13.4amps. It is running on about 50 frrt of AWG14 Romex on a 15 amp breaker. Sporadically, on initial startup, it will pop the breaker (Square D QO15). Upon further investigation, reading Square D's information, I found they make a "high magnetic" 15 amp breaker for "high performance loads" like AC, CwntralVac, and microwave applications with a high "pull-in" current.

Nobody in Ontario has the darn things in stock - Rona did, but since being taken over by Lowes, they no longer even have them available.

I could wait 'till next week and have the electrical supply order me one in - but I wanted to fix it NOW --

Turns out the 240 volt (double polet) 15 amp QO breakers are ALL High Magnetic - and I had a spare one, and a spare slot in my panel - so I've replaced the single pole with the double pole - we will see what happens,

Just thought you guys might be interested in knowing the little tid-bit about the "high magnetic" breaker fix for intermittent nuisance tripping

[Iggy]

replying to Clare Snyder, Iggy wrote: Interesting, I hadn't run into a need for that type of breaker. If not too difficult though, I wouldn't want anything running that close to capacity and would change the circuit to 20-amp on both ends with 12-AWG. I've seen a few wire insulation melts and cracked receptacles with stuff running that close.

[Clare Snyder]

When actually running, the Kill-a-watt reads 7.8 amps with the hose connected, and up to 11 amps running on open circuit(no restriction) Nowhere near the limit for running - and NO WAY I'm fishing a 12awg cable in - it was enough of a problem pulling in the 14, and I was over 30 years younger when I did that!!!

[Iggy]

replying to Clare Snyder, Iggy wrote: Thanks for the very helpful information. Although, not tripping every time may not be related to the breaker and the breaker is handling the normal operation fine, when it's present. I think a call to Cana-Vac may be in order, even if it's just to confirm the need for a high-magnetic breaker.

I presumed it was new and filtered, so it shouldn't be dirty or worn bearings. However, an intermittent trip may be pointing to a short in the branch wiring or the power-head impeller being jammed or defective motor windings. One or more of these could be the cause of your problem, if the Beam was similar in energy usage. New doesn't mean flawless.

[whit3rd]

The usual recommendation is to aim for no more than 2% voltage drop in your connecting wiring.

14 ga copper reaches 2% drop in 30 feet, at 15A. So, your motor might just be voltage-starved and trying to stall, when the breaker pops. The same motor, if it were REALLY 240V would only take half the current (7.7A at 240V is the same motor power as 13.4A at 120V), and thus by convention would be OK for 60 feet of wire, so you might want to enquire with the manufacturer to see if the motor can be re-strapped for the higher voltage.

In other words, in addition to getting the 240V breaker, consider upping the motor voltage as well.

For near-term, check all the screw-down connectioins, if one is loose THAT could be causing the motor to stall, and it only takes a quarter-turn of the screw to fix. Don't get shocked!

[OFWW]

Each trip diminishes the capability of the C/B as well.

[John McGaw]

I had to put a high-trip mag breaker on one circuit which was serving my shop dust collector. Around here it was a matter of going to the nearest big-box store -- both Lowe's and Home Depot had them available -- and this is in a decidedly less populated area than Ontario.

[Clare Snyder]

Bean there, Nothing wrong with the motor (confirmed with Ametec/Lamb

- the manufacturer of the motor)

No electric power head - and any short in the supply wiring would trip the breaker with or without the vac turned on. The Beam was an itty bitty little brother to the CanaVac - with a 5.7 inch Lamb motor, and it never ran oin the breaker, as I changed from fuse panel to breaker panel after replacing the vac. It was on a slow-blow "fusetron" for over 30 years.

We'll know in a couple weeks if the high magnetic breaker has solved the problem

[Clare Snyder]

The Kill-a-watt indicates a maximum draw of 12.3 amps, and a running voltage of 115 volts with the hose connectes,and 114 running "open ciircuit" or "full load". With the vac turned off the line voltage is

117. A 2% drop would be a drop of 2.2 volts, for a reading of 114.8, and it's pretty difficult to "stall" a "universal" motor driving an air turbine

It's a "universal" motor, iggy. They are NOT multy-voltage convertible by their very design.

Not possible. as noted above. A 240 volt and a 270 volt version are avaiable (at about 50% higher price than the vacuum itself - so not going to happen) If the high-mag 15 doesn't solve the issue a high-mag 20 will take it's place.

All been checked, from one end to the other - (only 2 connections - at the panel and at the outlet) The entire house just went through a COMPLETE electrical inspection when the panel was replaced under 2 years ago. - and that's on top of my inspecting the circuit due to this issue.

Square D is aware of this problem and recommends the "high magnetic" breaker as the solution

My point in this post was to bring to the attention of otherwise knowlegable folks on this usenet group that double pole QO breakers were ALL High Magnetic - so using 1/2 of the double pole breaker may solve nuisance trips for "high performance" devices with high initial startup draws - like compessors, AC units, central vacs, etc.

[Clare Snyder]

Correct - but replacing the original breaker with a brand new identical breaker did not help - and thermal tripping degrades a breaker significantly more than magnetic tripping - which does not cause any appreciable heating in the breaker.

Magnetic tripoping is instantanious tripping - thermal tripping is delayed. (due to prolonged overload)

[Clare Snyder]

Home Despot Canada doesn't carry them at all. Nor does Lowes Canada. Rona Canada used to carry them, Rona was recently absorbed by Lowes. Home Despot in the USA apparently DOES carry them but both Buffalo and Detroit are about 3 hours away.

In Quebec Reno Depot carries the high magnetic breakers in their stores. That's well over a 5 hour drive.

[John McGaw]

Sounds like the sort of crap that we had to put up with living in Alaska except that sometimes it was a 3-hour flight rather than a 3-hour drive. Your situation seems so odd -- these are scarcely some sort of rarely-used magical devices and many applications really do need them all the time.

[whit3rd]

[about breaker tripping]

According to the NEC (US electrical safety code) a 20A breaker is not compatible with a 14 ga branch circuit.

[Clare Snyder]

A lot of the problem here is American companies who see Canada as too small a market to bother complying with our bi-lingual labelling requirements. No french labels means no sale in Canada. I think youcan sell in Quebec with french only labelling - which may be why SOME things are avaiable in quebec only - the quebec based outlet doing their own labeling?

[Clare Snyder]

Overcurrent protection for motors is different than protection for other types of electrical loads, and the values you come up with might not seem right based on your experience with other types of applications. Protecting a 14 AWG conductor with a 30A circuit breaker, for example, just looks wrong. But keep in mind that motor branch circuit conductors are protected against overloads by the overload device. That device is sized between 115% and 125% of the motor nameplate current rating [430.32].

The small conductor rule contained in 240.4(D), which limits 15A protection for 14 AWG, doesn?t apply to motor circuit protection. See

240.4(D) and 240.4(G).

[dpb]

...

Nonsense...any of those would not be intermittent.

[krw]

But the OCD's purpose isn't to protect the motor, rather the wiring.

[Clare Snyder]

Just answering questions about code with code.

[krw]

It sounded like justification for a 20A OCD on #14 wire. A larger OCD, local to the motor, I get, but with 30' of Romex between?

[Clare Snyder]

I'm told buy guys more knoledgeable than myself that it iis both legal and common on dedicated motor circuits. The wire is very capable of handling half a second of 40 or even 60 amps - required to start some motors. Short circuit protection is still provided and thermal overload protection of the motor protects the wire from overload.