Lights dim with swamp cooler.

What do the house lights do when you plug in a 1500W heater in that outlet? Same thing, but worse? (reading on, never mind with this)

If you used LED or CFL lighting, you wouldn't see that. ;)

14ga copper, right? Not the largest.

That little motor is drawing a whopper of a current during startup, it seems. Inductive current draw is normal with motors.

Check with your electric company. Mine recently replaced the drop to my house because it was old and worn and improperly terminated on the house. If you have a feed with half the copper strands broken from age, it -will- cause the drop you see, even at the breaker box. The electric company usually pays for all wiring up to the meter/box.

Unplug swamp cooler, R&R house.

Since you hard wired the motor in the breaker panel did it get its own breaker? I would be surprised if the voltage sagged that much if wire directly to one leg of the 220 volts coming into the panel. Also since you hard wired the thing is the motor perhaps a dual voltage motor? If so changing it to 240 volts and using both legs of the incoming power will make a big difference in the lights dimmimg. This is because the dimming of incandescent lights is not linear with the drop in voltage. A small voltage drop will result in a larger drop of visible light. Induction motors can draw up to 6 times the running current when starting. So the amperage draw can be quite high. Especially when the motor is a crappy one. Lots of import motors are crummy motors. They sometimes use less wire in the start windings which leads to lower resistance and higher current draw. Soft start controllers are available but can be expensive. Is the motor a capacitor start motor? Maybe the cap is not up to snuff. Still, I'm surprised that if the motor is wired to a 100 amp supply the voltage would sag that much if nothing else is using the same leg of the incoming supply the same time. What other loads are connected to the leg supplying the swamp cooler motor? Eric

Still within specs. Why worry about it? Does anything misbehave during those dips?

With that motor -- maybe a loose belt to let it slip as it goes up to speed?

For real soft start, replace it with a three-phase motor and a VFD. You can program the VFD for a fairly wide range of starting times.

Enjoy, DoN.

Do you have a way to measure the current drawn by the motor? If you can me asure the current , you can put some oil filled capacitors in parallel with the motor and find a combination that minimises the current. -In other words correct the power factor. This may or may not be enough to reduce t he momentary voltage drop to a level that is acceptable. But will help.

Capacitors can be found in junk microwave ovens.

Dan

Thanks Guys,

The power drop sometimes scrambled the tiny-brain of an Arduino temp-sensor I have running from the same outlet. It still does the same to the Temp se nsor if I plug it into another outlet. I have some 10K-electro-caps coming for the Arduino 5vdc line, so that should stop that.

Other than that, the dimming is annoying to some members of the household. ;)

Thanks Dan,

Using a watt-meter thingy, on Low it draws about 5.1-A and on High 6.3-A. I say "about" as it fluctuates up/down by 0.1-A or so.

During the start, it very briefly shows 16-A or 17-A but there could be a little over-swing in that too. It comes and goes in the blink of an eye, sometimes I don't even see it at all.

So what do I actually need to do with the caps? I have some oil-filled start caps around the place somewhere.

This is the motor.

The power drop sometimes scrambled the tiny-brain of an Arduino temp-sensor I have running from the same outlet. It still does the same to the Temp sensor if I plug it into another outlet. I have some

10K-electro-caps coming for the Arduino 5vdc line, so that should stop that.

Other than that, the dimming is annoying to some members of the household. ;)

==================

Do you have large resistive loads like space heaters, toasters or coffee pots that you could use to trace the steady-state drop? The problem might be the cable connections in the panel or the meter box.

I had a problem with a poor connection to neutral, which caused the two 'phases' to unbalance when a motor started. Some lights dimmed, others flashed brighter. The power company cured it by replacing the meter box and weatherhead cable. They knew the old aluminum splices tended to corrode.

-jsw

On Wednesday, July 12, 2017 at 11:09:30 AM UTC-4, Dave, I can't do that wro te:

I say "about" as it fluctuates up/down by 0.1-A or so.

little over-swing in that too. It comes and goes in the blink of an eye, s ometimes I don't even see it at all.

art caps around the place somewhere.

The motor is a 1/3 hp motor. One hp is 746 watts so 1/3 hp is 249 watts . and 249 divided by 120 volts is just over 2 amps. So of the 5 amps on l ow speed 2 amps is the real power drawn and about 4.6 is the imaginary amps .

Putting caps in parallel with the motor will reduce the imaginary current. It is pointless to get rid of all the imaginary current. But try putting a cap across in parallel with the motor and see what the current is. Add m ore caps until the current is down to about 2.5 amps instead of 5. And see if that helps to reduce the light dimming. It will help , but may not be a noticeable change.

Dan

plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt ) two speed motor from HomeDepot.

ond from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed.

in the house for that short period.

rs old, copper, in metal conduits and all up to code with 200-Amp coming in to the house.

ent circuits and still get the same issue. I then hard wired the extension into the main breaker panel. Same again.

turns quite freely by hand.

First, 117V is well within specs. That said, a 1/3 HP motor shouldn't load down your system like that. There is likely either a defective feed cable o r a loose connection from the utility. You could check in the panel to make sure the feed cables are tight. Beyond that, you'll have to get the utilit y company to check it out. Around here, at least, they're usually pretty co operative.

I recently had to replace the entire breaker panel at the beach condo. The original aluminum bus bars were corroded, and burned on some high amp breakers. We had several appliance board failures before we figured it out. It was also exacerbated by voltage swings due to the utility replacing all the feeders down the island.

The original breaker panel had paint and texture sprayed on the interior, and had probably been soaked in salt water during Ike because the original builder not only went cheap on the panels, but some of the patio soffits were sheetrock instead of hardie board, causing disintegration and much wind blown water damage to all units. The new ones are copper.

Pete Keillor

Well, if you still get the dip at other outlets when the cooler is wried into the breaker panel, you may have copper creep on the terminals in the panel or the meter box. That is dangerous stuff to work on, so you might want to have an electrician do it (capability to deliver high fault currents).

I have re-torqued the clamp screws on the breakers where the branch circuit wires connect, so you can try doing that. I have occasionally found some of these to be quite loose.

Jon

In article , Dave, I can't do that writes

I wonder if a suitable thermistor (ntc), wired in series with the motor would do the job simply and cheaply? E.g. EPCOS B57127P0109M301

The primary problem is while the start winding is engaged, so it would have to be added to the internal wiring in parallel with the start winding. Add a second "bump" to house an oil-filled AC-rated capacitor. (And *don't* use motor starting caps -- they are only for short power application -- and they might stretch the starting time enough to be a problem both for the starting cap and the phase correction cap.

The best way to tune that value would be with the run winding disconnected, and something keeping the motor from turning -- and just short tests each time to keep the start winding from overheating.

Yes, it is easier to simply compensate the run winding, but that won't eliminate the voltage sag on starting.

Yep -- or as run caps for motors for squirrel cage blowers in HVAC units.

Or -- you can get one of the universal substitute run caps for the AC compressor -- Turbo 200 from Amrad Engineering. It has six different values of capacitors, connected together at a central common terminal, and jumpers (push-on connectors) to add them in parallel. The values, between them, offer a fairly wide range of possible values. Cap values add in parallel, while resistor values add in series. Anyway, this gives you a single device to use to try a number of values.

Enjoy, DoN.

I think it is a pretty sure bet he has a problem with the electrical service to the home - either in the panel. the meter box, or the wires to the house. He needs a good professional electrician to verify it and either repair it or get the electrical service provider to fix it.

So a digital readout -- common for the LSD (Least Significant Digit) to display some uncertainty.

Is this by any chance a Kill-a-Watt?

Without a physical meter needle, it is unlikely that there will be overshoot, and it is more likely that it will be a bit lower than the actual peak value.

Well ... if the actual high current peak is that brief, it may be that compensating just the run winding will help. No need for a separate compensation cap setup for the start winding.

Just connect them in parallel with the AC into the motor, and adjust for minimum running current by adding values in parallel until you get the lowest value.

Kind of skimpy information. Yes, complete copper windings, but perhaps not enough iron in the core. How much does it weigh? That is a good quick way to compare motors of the same horsepower rating.

And there is no suggestion that it could be re-wired for 240 VAC instead of 120 VAC, which as someone else suggested, would reduce the current drain -- as I did with the 1.5 HP motor on my 12" lathe.

Good Luck, DoN.

I think you are absolutely right Clare. It just doesn't make sense to me that this small motor connected directly to its own breaker in a breaker panel could cause so much voltage sag. There must be a bad connection somewhere. In my shop with a 200 amp service the 15HP motor that's connected across both legs doesn't cause this kind of voltage sag when it starts. Eric

I've only worked on older motors that I could take apart easily, most recently a 1970ish Maytag with a broken connection to the start winding. On it I could have connected a cap directly across the start winding, after the centrifugal start switch. Is that generally possible with newer consumer-grade motors?

-jsw

I have a 125 amp service, and rhere is NOTHING that causes lights to dom - not the drier, the central air, the central vac, - NOTHING since my meter base and panel were replaced. Before the new service went in, "occaisionally" I'd get a bit of dimming when the AC cut in. A few years ago I'd get some lights getting brighter and some dimmer when the central vac was started, so I tightened the neutral.Fixed that!!