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[abc1667xxxxx537]

Will the AM466 survive being run 9 hours per day with a motor load of 1/6HP and steady state run current of 3.7A?

[Knightrider]

I've had one running a 1/3 HP motor on a fan in the attic (high/low temps) whenever the temperature hits 70 degrees in Ohio.  This will be the third year that it's been working.

[dave w]

I agree with Knight, should be no problem, but are you sure about 1/6 horse drawing 3.7 amp? That is a pretty inefficient motor, 1/6 horse, but pulling over 400 watt(?). Did you measure that current or is that on the motor's spec plate? If it is from motor spec plate, it probably factors in starting current, so run current would be less. Anywho you are in the "good to go" zone, I have run Appliance Modules over their ratings (1500W space heaters and 3/4HP sump pump motors) with no problems. The relay contacts are pretty heavy.

[abc1667xxxxx537]

Thanks.

The ratings come from what I have seen quoted on the internet many times over. I questioned the values myself but trying to get a straight answer to what should be a simple question anymore is like pulling teeth.

It turns out for the horsepower that it was 1/8 HP and the person who gave me 1/6HP (I contacted the manufacturer) admitted to making a mistake. Regardless, the numbers don't exactly jive and I am hoping the 3.7 is the inrush current at startup as an answer is not readily forthcoming.

[Knightrider]

Hey Dave W,

I may need you to correct some math I did a long time ago.  Isn't 15 amp resistive comparable to 1800 watts?

P=IV

Where V=120 and I=15 (amps)

In the winter time, I put a 1500w ceramic heater in the cab of my pickup truck with a module on it.  As a result, I never have to scrape my windshield.

I just checked the spec sticker on an appliance module and it comes back to 15 amps resistive and 1/3 HP motor.

Just pulling stuff out of the cobwebs in my head, I think (probably wrong here) that 1HP=760watts, so the OP's motor drawing that kind of amperage must be starting the motor on a heavy load.

[dave w]

Hey Dave W,

I may need you to correct some math I did a long time ago.  Isn't 15 amp resistive comparable to 1800 watts?

P=IV

Where V=120 and I=15 (amps)

In the winter time, I put a 1500w ceramic heater in the cab of my pickup truck with a module on it.  As a result, I never have to scrape my windshield.

I just checked the spec sticker on an appliance module and it comes back to 15 amps resistive and 1/3 HP motor.

Just pulling stuff out of the cobwebs in my head, I think (probably wrong here) that 1HP=760watts, so the OP's motor drawing that kind of amperage must be starting the motor on a heavy load.

Knight, you remember it the same way I do. I think the "3.7" amp quoted by the manufacturer must be start-up currrent, not run current. My guess would be a 1/8 HP motor (fan? small pump? etc) would have a run power of something around or less than 100Watts.
BTW the heater in the truck is a great idea. My problem would be driving off with the heater running, so if I borrow your idea I best make sure the module and heater plug be outside the vehicle door. Sort of the "automatic disconnect" feature. 

[abc1667xxxxx537]

Just measured the current. It is 3-3.2A steady state with inrush (don't have anything to make peak measurements, so had to go by eyeball) up to 4-4.5A. The manufacturer said anything on their sticker is steady state (the sticker says 4A) but I agree the 4A is probably more along the lines of their startup current. Either way, they stand by the 1/8HP assertion and didn't want to get into debates on efficiency as to them it is relative.

However, with 746W being 1 HP (slight correction to what was said previously) and this thing drawing 3.2A that would put it more in the slightly over 1/2HP bracket in terms of the electical load/burden it represents.

So, my next questions are:

1) For those who have claimed running a 3/4HP motor, was that all day, day after day?

2) Did the AM466 appliance module have to break contact while the 3/4 HP motor was running (arcing being the result)?

[dave w]

1) For those who have claimed running a 3/4HP motor, was that all day, day after day?

2) Did the AM466 appliance module have to break contact while the 3/4 HP motor was running (arcing being the result)?

Good questions which made me reconsider.
The Appliance module driving the 1500W heater is always cycled with the load energized, but the heater had only a small fan, so not much inductive kick occurred. Still I am sure there is at least some small arcing taking place.

The sump pump module usually started under pump load, but the pump typically turned off before the module. I had no problems but this jury rig was used for less than a year.

The contacts in the module are pretty heavy. I have run 12 inch equipment rack fans, cycled several times a day, every day, for years with no problems. They probably are rated at 1/6 or 1/8 HP but inrush is likely to be  low since it is a fan. If your motor does not have a starter cap, or starter winding I would not worry about it.

Also if the contacts arc and carbon up, my experience has been the module starts the "clickty-clickty-click" problem. This ques me to clean the contacts (I have a thread on this in the forum, if you search "clickty-clickty-click" you should find it).

[JeffVolp]

Something you fellows are missing is that the motor is an inductive load.  The power formula is actually:

        Voltage x Current x cosine of phase lag between

For DC loads, there is no phase lag, and the formula simplifies to just Voltage x Current

If there is significant phase lag due to the reactive load, the current can be much higher than expected from the wattage consumed.

Recently I measured a X10 Maxi Controller.  Its label says it consumes 2W.  The Kill-a-Watt confirmed this on the wattage scale.  Switching to the current scale, the Kill-a-Watt indicated 100mA, which would be equivalent to 12 watts.  However, since this is also a reactive load (due to the capacitor in the transformerless power supply), most of the current is out of phase with the voltage, resulting in relatively little real power consumption.

The same would be true of the motor.

Jeff

[abc1667xxxxx537]

Was already on the power factor thing. Given no power factor data on the motor and not being able to tear the motor apart or get near enough to it to get a good look at it I don't know what its construction is (tech support is less than spectacular from the fan/motor manufacturer). Brought this up with the folks who manufacture the fan and this is what prompted their response on efficiency being relative. Didn't really care to go into it with them or bring it up here. So, for a time I assumed worst case, which is a power factor of 1 and thus the 0.5HP thing previously.

After sleeping on it and taking a leap of faith, by the numbers, their power factor is ~0.2428 (inv cos = ~76° angle between current and voltage). Although, I can't determine leading vs. lagging with my low end equipment, it is likely lagging as their motor "appears" at a distance to be purely a winding (a.k.a. an inductor, as I don't see any typical housings for capacitors and the like) as far as I can see. Since a perfectly inductive circuit will have the current lag the voltage by 90°, then when one figures in the impedance of the various components, it knocks off the 90° by some amount which accounts for everything we are seeing here, in my opinion.

So, what they have is a somewhat inefficient 1/8 HP motor which has an inrush that my eyeball can catch on the meter of between 4-4.5A (obviously higher in that first cycle depending on where in the voltage cycle it hits). A capacitor would bring the power factor back closer to 1 but who cares about such small motors, right.

My concern here was three-fold. One was to make sure that I wasn't going to burn my house down by overloading an AM466 appliance module. Two was not to destroy a perfectly good appliance module as there is no sesne in that. The third, and a bit more insidious, is running such loads through the appliance module for hours on end in an environment which is well above 100°F (up in an attic). Kind of a double whammy and I apologize for not mentioning the ambient temperature thing before as I was attacking one thing at a time.

Electrically speaking, I think the appliance module will work for me assuming the "Motor Load" rating of the module takes into account a motor the likes of which I am using (largely, purely inductive, anyone have any insider information on this?). This being said, the ambient temperature issue is another matter entirely and I am working that angle as we speak.

[dave w]

I used Appliance Modules to control roof vent fans in a Ft Lauderdale house with no problems. I have Appliance Modules in our current attic and it's 95 degrees outside, so attic is much hotter. I think you are worrying about it too much.

[Knightrider]

Very good on sleuthing out the motor (no visible caps) and way above and beyond on testing the shift on the sine.

Jeff reminded me on something that I've obviously forgot from my days of education, and I'm thankful that I have good friends here to catch me on such things.  Hate to re-hash the power factor argument, but in this thread, it was very necessary.

I'm giving a +1 to all you guys.

[evadorev]

i read all of your comments and i want to precise a few things:

1- according to electrical code, the rating for a circuit is 1.25 time  the running current for a  motor REGARDLESS OF THE POWER FACTOR, for such a small motor, PF doesn`t matter.

2- A coil ALWAYS LAG, a capacitor lead. it`s the base of PF correction on large circuits.

3- A motor draws 4-5 time it`s running current at startup.

4- if you have a 1/6 hp motor who draws 4 amps, trash it down. it`s certainly short.

5- I have a dimmable wall switch module for over 4 years in my attic with 450 W of load and it never fails. it`s on for 8 hours during the night.

6- i think you can use the am466 for your motor without problem.


Hope it will help

[Knightrider]

Credit where credit is due,
evadoev gets a +1 too!

[JeffVolp]

4- if you have a 1/6 hp motor who draws 4 amps, trash it down. it`s certainly short.

Motor efficiency is a function of load.  One manufacturer lists efficiency of 64% and 67% for 1/4 hp and 3/4 hp motors respectively.  Efficiency drops to 52% and 60% at half load.  As motor horsepower increases, so does efficiency.  Multi horsepower motors can have efficiencies of 90% or more.

A 100% efficient 1/6 hp motor should consume about 125W.  At 60% efficiency, the actual power consumed would be 208W.  The current drawn by a motor depends on its power factor.

As an exercise, I used my Kill-a-Watt to measure parameters for several tools in my shop with induction motors.  Unfortunately, none have a horsepower number on the label.

    Drill Press    120.6 V    1.85 A    .66 PF    149 W    223 V*A
    Band Saw    120.3 V    1.37 A    .80 PF    133 W    165 V*A
    Grinder        120.6 V    2.04 A    .43 PF    107 W    246 V*A

You can see that due to the grinder’s phase lag and low power factor, its wattage consumption is only 43% of what would be expected from the current measurement.  Doubling those numbers gets us close to those for the 1/6 hp motor in question.  It indeed could be pulling 4A while only producing 1/6 horsepower.

Jeff