My father's old table saw (240V) used to have a box and wall-style switch that he wired into it, and if I recall correctly, the switch seemed to be really hard to throw, and when it did, it seemed to "snap" really hard and fast.
I think I remember Dad telling me that it was a special switch and that it had strong springs that were meant to slam the contacts together very fast and hard to prevent arcing and consequent corrosion/pitting/degradation of the internal contacts.
Am I remembering this right, and can anyone tell me more about this type of switch (what it's called, etc.)? Thank-you.
Look for a motor rated switch. Make sure the switch has a horsepower rating of at least that of the motor (correct voltage and number of poles as well, of course).
I don't know exactly what he had, but it may be a manual motor starter, which is basically a switch designed for the inductive motor load. You can find them at most suppliers that handle motor controls.
. From the UL White book: "AC general-use snap switches are tested ... for motor loads up to 80% of the amp rating of the switch, but not exceeding 2 hp." These are standard wall switches.
A "manual motor starter" is probably more rugged, would probably last longer, and I agree it fits the OP's description.
. According to the White book the 50 cent ones can be used for motors up to 80%/2HP if they are "AC general-use" (not AC-DC). One of the hidden tidbits in the UL standards. (Snap switches, guide category WJQR.)
The 50 cent ones might not be the best choice for what to use.
Bear in mind U/L is only saying these things won't burn your house down when they fail, not that they will actually work for any length of time. Since this is a 240v saw, he already needs the two pole unit and that eliminates the 50 cent jobs. If he gets the 2 pole, 30 amp device it will have that heavy duty click he is looking for and it will hold up to regular use..They have them at most home stores
On Tue, 04 Mar 2008 16:18:31 -0500 snipped-for-privacy@aol.com wrote: | On Tue, 04 Mar 2008 15:10:39 -0600, bud-- | wrote: | |>According to the White book the 50 cent ones can be used for motors up |>to 80%/2HP if they are "AC general-use" (not AC-DC). One of the hidden |>tidbits in the UL standards. (Snap switches, guide category WJQR.) |>
|>The 50 cent ones might not be the best choice for what to use | | Bear in mind U/L is only saying these things won't burn your house | down when they fail, not that they will actually work for any length | of time.
Exactly. UL testing is in regards to safety, not efficacy.
The man has brought out a very important point here that we ignore at the peril of our customers dissatisfaction.
A little history is in order here. When the Great Chicago Exposition was under construction to be a showcase for mans brand new servant called electricity the closest Chicago fire houses had horses literally dying from exhaustion because so many fires of electrical origin broke out. The insurance companies that had insured the exposition saw the specter of financial ruin staring them in the face. The underwriters who had purchased a share of the risk in return for a share of the premiums threatened to withdraw their support and leave the original insurers with the entire risk. They agreed to continue to underwrite the risk under specific conditions. One sample of every single item to be used in the electrical installations was to be delivered to a laboratory that they hired an engineer to set up in a nearby loft building. If that engineer didn't approve it for the list of acceptable components it could not be used without voiding the fire insurance. That was the birth of the "Underwriters Laboratory" and it's listing service.
To make it onto the electrical materials list a device has to pass testing that has nothing to do with service life or fitness for a given use. The testing is only meant to show that the device will fail safe in that in failing it will not serve as an ignition source for a fire of electrical origin. Even the preamble to the National Electrical Code warns that compliance will produce "an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use."
When customers demand an installation that is "just whats needed to pass inspection I have them sign off on a letter that quotes that section and throws their exact words right back at them. That usually serves as the beginning of a discussion that leads to a more rational approach to the job in question. When I asked one fella to sign it he was amazed that I thought it necessary. When I explained that my intent was only to make sure he new what he had asked for he allowed as how he didn't know what to ask for so we went over the prints for his addition together and he got pricing in advance for what he decided he wanted. Long after the job was over I found out he is a consumer rights attorney with a great record of success representing the interest of the buying public in my state. He is also an adjunct professor at a law school and a friend told me he uses that letter in class.
Perhaps the basic principal being discussed here can best be explained by quoting the old Yankee shop keepers warning that "Quality can be illustrated by the purchase of oats. If you want nice clean fresh oats you must pay a fair price. If you will be content with oats that have already been through the horse you may pay slightly less!"
Sounds like just like a common type of isolator which was common until about the 1950's/60's. Probably about 6" high by 5" wide by 4" deep and often silver in colour, and with the switch actuator lever on the right and designed so as to stop the front cover being opened while in the "on" position.
Most switches will contain a spring to ensure that they change state very rapidly to minimise arcing.
Interesting. Sounds like the 1893 Fair, which was the first major defeat for Edison?s DC empire. .
. For some devices, like TVs, it is not possible (or desirable) for UL to determine if the device is actually useful.
The same is true for industrial control panels. They are investigated for safety.
I believe fuses and circuit breakers are investigated for ?fitness for a given use? and ?service life?.
I expect more complicated devices, like GFCIs and smoke detectors to be fit for their intended use and have a useful service life. (Both with testing as required in the listing.)
A lot of other electrical apparatus is tested for more than failing safely.
One of the 3 UL standards I have is a 15 year old one for Snap Switches
- the subject. For AC only switches the tests include the following - at rated voltage:
10,000 operations at rated current
10,000 operations at rated current and power factor around 0.8
10,000 operations at rated current controlling incandescent loads as you know, this involves a high inrush current and IMHO is similar to starting a motor
100 operations at 4.8x rated current and power factor around 0.5 IMHO this is very similar to switching off a stalled motor with running current 0.8x the switch rating IMHO this is testing for ?service life? and ?fitness for use?, and is a reasonable test for use with on motors.
But I still would use a spec grade switch if using it for a motor load approaching 0.8x rated switch current. .
. I have always taken this to be a comment on the code itself. A house with the minimum circuits required for kitchen, laundry, bath and general would be safe but probably would not make a buyer happy.
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