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Re: Is it possible to run a Federal STL-10 or STH-10 on 120V
Posted: Sat May 23, 2020 12:44 am
by Synther
Many people have ran 240v single phase sirens on half voltage (120v) and have experienced no issues. I've personally ran my STH-10B on 120v and it ran just fine (albeit at half speed). It is not an ideal setup though. Just go all out and install a permanent setup.
Re: Is it possible to run a Federal STL-10 or STH-10 on 120V
Posted: Fri Jul 10, 2020 1:56 am
by OHIO Desperado
OK, several folks have said what will REALLY happen. Which is it will run, NOT burn down your house or anything else like that.
This is the siren I just finished putting back together. I remembered this topic thread, so I went ahead and tried it. Here are the video recorded results.
20200709_180351 by
kb8vul, on Flickr
Re: Is it possible to run a Federal STL-10 or STH-10 on 120V
Posted: Fri Jul 10, 2020 3:27 am
by Ohio_Man
Interesting that it sounds almost like an STL 10. I'm sorry for doubting that it would run.
I figured it would over amp the breaker since the manual for the STH10B says it pulls 56 amps on 240V for the single phase model and most houses have a 10-15 amp breaker per circuit.
So if it isn't pulling more than 15 amps what kind of amperage is it pulling?
The motors definitely original, or at least a federal signal OEM. It's just listed as pulling nearly 4X the amps on twice the Volts.
This confuses me, because when I play with a bench powersupply, turning up the voltage on a computer fan (for example,) they draw half the amps at twice the Volts, and vice versa.
If you have a multimeter could you do a reading for us? It's just defying its own specs and that's odd.
Re: Is it possible to run a Federal STL-10 or STH-10 on 120V
Posted: Fri Jul 10, 2020 10:17 pm
by OHIO Desperado
So now for the explanation of WHY it's not drawing 100 amps and burning down the house.
You have to understand something of Ohm's law for any of this to make sense, but the short version is this.
Power (wattage/horsepower) is current times voltage.
And current is voltage divided by resistance.
So if you lower voltage, the resistance is going to remain the same. so the power and the current are REDUCED, as well the power is reduced. SO, your 10 hp 220 motor is ONLY going to make 5 hp on 110.
The way that a dual voltage motor works is you need to change the wiring in the motor to have it run on the reduced voltage at the same horsepower rating. The reason that a computer fan motor will decrease current draw is that it's got a circuit that it driving the motor. It will try to draw the same power to get the desired RPM output.
Re: Is it possible to run a Federal STL-10 or STH-10 on 120V
Posted: Mon Jul 20, 2020 1:27 am
by Stormsetter4
There is a lot of misinformation running in this thread. For starters, a single phase Federal siren doesn't utilize a typical squirrel cage industrial motor and thus does not have the same current characteristics that everyone is basing their calculations on. Keith has done a good job in the above post with the ohms law calculations and how the motor will have reduced horsepower/current at a lower voltage. A repulsion motor's current is generally a linear function of it's speed and load. The faster they spin, the more current they draw. On 120v these motors really don't draw that much-I have seated brushes on a 2T22 before using a 120v power feed and I don't think the current ever exceeded 15 amps. I wouldn't advise doing it very often as these motors weren't designed to run at 120v but you shouldn't damage anything if you run it a few times like that. Worst case you'll trip a breaker out.
Re: Is it possible to run a Federal STL-10 or STH-10 on 120V
Posted: Mon Jul 20, 2020 9:14 pm
by Timmy-73
Ohio_Man wrote: ↑Fri May 22, 2020 1:53 am
kb8vul wrote: ↑Thu May 21, 2020 10:09 pm
uncommonsense wrote: ↑Thu May 21, 2020 9:52 pm
Absolutely not. Its possible if you want to burn your house down from an electrical fire. The draw would be far too much for 120V to handle.
You SURE about that?
An STH/L-10 is fused at 50 amp at 240 volts.
So the the current draw from the same load and half the voltage would be half the current.
So 25 amps. Mind you a 15 amp breaker which is typical for a run of the mill outlet would pop almost immediately.
But a 20 amp or 30 amp breaker, fed with the correct wire, would probably hold and run the motor up to not quite half speed.
That being said, if you would need to run a new circuit, why not install a CORRECT circuit with a proper 50 amp outlet and a manual disconnect (could use a 50 amp welding outlet)
and just be done with it.
But as far as burning down the house,,,, only if the wiring in the house was improper, the fuse / circuit breaker was improper would you chance a house fire over the attempt.
If everything was right and you were to try it, the 15 amp breaker would just pop and that would be the end of it.
"No Tim I don't think that's right" -Al Borlean, Home Improvement.
Volts X amps=watts.
The siren draws 50 amps at 240V. A motors wattage cannot be changed. If you run that motor at 120V, It will pull 100 amps.
Im an electronics guy. This makes me happy
Re: Is it possible to run a Federal STL-10 or STH-10 on 120V
Posted: Tue Jul 21, 2020 2:56 am
by OHIO Desperado
Timmy-73 wrote: ↑Mon Jul 20, 2020 9:14 pm
Ohio_Man wrote: ↑Fri May 22, 2020 1:53 am
kb8vul wrote: ↑Thu May 21, 2020 10:09 pm
You SURE about that?
An STH/L-10 is fused at 50 amp at 240 volts.
So the the current draw from the same load and half the voltage would be half the current.
So 25 amps. Mind you a 15 amp breaker which is typical for a run of the mill outlet would pop almost immediately.
But a 20 amp or 30 amp breaker, fed with the correct wire, would probably hold and run the motor up to not quite half speed.
That being said, if you would need to run a new circuit, why not install a CORRECT circuit with a proper 50 amp outlet and a manual disconnect (could use a 50 amp welding outlet)
and just be done with it.
But as far as burning down the house,,,, only if the wiring in the house was improper, the fuse / circuit breaker was improper would you chance a house fire over the attempt.
If everything was right and you were to try it, the 15 amp breaker would just pop and that would be the end of it.
"No Tim I don't think that's right" -Al Borlean, Home Improvement.
Volts X amps=watts.
The siren draws 50 amps at 240V. A motors wattage cannot be changed. If you run that motor at 120V, It will pull 100 amps.
Im an electronics guy. This makes me happy
Uhhh, NO. And I think I covered WHY.
So here it is again.
The
electrical resistance / impedance (look it up) of the siren motor is going to be a fixed amount. Those that are using the idea that a DUAL VOLTAGE motor with series / parallel windings that WILL draw twice the current to product the same HP output are mistaken, A federal 10 HP 240 volt motor does NOT have this sort of arrangement were it can be wired to 110 natively. If that were the case, then YES, it would draw 100 amps. BUT it's not wound in that manner.
So since the windings are a FIXED impedance when you put HALF the voltage to it, it draws HALF the current and produces HALF the horse power of what it will when the correct voltage is applied.
And again, if you are convinced you are right.... then HOW did I start and run a STH10 on a 14 gauge electrical cord fed by a 15 amp breaker? Hell it didn't even spark when I plugged it in.
Re: Is it possible to run a Federal STL-10 or STH-10 on 120V
Posted: Tue Jul 21, 2020 12:32 pm
by Federal Signal fan
Now that it's been proven, we need to get a circuit for that bad boy to get that 240V... a motor starter too... and control panel... with remote control... and indicator lights. (or strobes)
Just one more wire. That's all it is... right?
I'd also like to point out that general use 3 phase dual-voltage plated induction motors have windings wiring diagrams that depend if using low or high voltage values, so yes - motor winding wiring is key!
Cheers!
Re: Is it possible to run a Federal STL-10 or STH-10 on 120V
Posted: Tue Jul 21, 2020 5:37 pm
by Chem_Boffin_6589
kb8vul wrote: ↑Tue Jul 21, 2020 2:56 am
Timmy-73 wrote: ↑Mon Jul 20, 2020 9:14 pm
Ohio_Man wrote: ↑Fri May 22, 2020 1:53 am
"No Tim I don't think that's right" -Al Borlean, Home Improvement.
Volts X amps=watts.
The siren draws 50 amps at 240V. A motors wattage cannot be changed. If you run that motor at 120V, It will pull 100 amps.
Im an electronics guy. This makes me happy
Uhhh, NO. And I think I covered WHY.
So here it is again.
The
electrical resistance / impedance (look it up) of the siren motor is going to be a fixed amount. Those that are using the idea that a DUAL VOLTAGE motor with series / parallel windings that WILL draw twice the current to product the same HP output are mistaken, A federal 10 HP 240 volt motor does NOT have this sort of arrangement were it can be wired to 110 natively. If that were the case, then YES, it would draw 100 amps. BUT it's not wound in that manner.
So since the windings are a FIXED impedance when you put HALF the voltage to it, it draws HALF the current and produces HALF the horse power of what it will when the correct voltage is applied.
And again, if you are convinced you are right.... then HOW did I start and run a STH10 on a 14 gauge electrical cord fed by a 15 amp breaker? Hell it didn't even spark when I plugged it in.
This^^^^^
Since studying electrics at a higher level it's now easy to understand why Ohm's Law is key to why we can get these devices to work on smaller power supplies.
It may, just may trip a breaker if you're super unlucky. MCBs of the magnetic kind can be and are rather sensitive, even if the load on them is safe.