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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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Lights dim with swamp cooler.
Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot.
When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. Before anyone launches into "house wiring," etc rest assured it is 11-years old, copper, in metal conduits and all up to code with 200-Amp coming into the house. I used a 14g, 3-wire extension lead in a bunch of other outlets on different circuits and still get the same issue. I then hard wired the extension into the main breaker panel. Same again. I have cleaned and oiled the fan bearings, adjusted the belt and the fan turns quite freely by hand. What can be done to alleviate this momentary voltage drop? Thanks |
#2
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Lights dim with swamp cooler.
On Tue, 11 Jul 2017 14:40:03 -0700 (PDT), "Dave, I can't do that"
wrote: Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot. When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. 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) Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. If you used LED or CFL lighting, you wouldn't see that. Before anyone launches into "house wiring," etc rest assured it is 11-years old, copper, in metal conduits and all up to code with 200-Amp coming into the house. 14ga copper, right? Not the largest. I used a 14g, 3-wire extension lead in a bunch of other outlets on different circuits and still get the same issue. I then hard wired the extension into the main breaker panel. Same again. 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. I have cleaned and oiled the fan bearings, adjusted the belt and the fan turns quite freely by hand. What can be done to alleviate this momentary voltage drop? Unplug swamp cooler, R&R house. snort -- The door of opportunity is marked "PUSH". --anon |
#3
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Lights dim with swamp cooler.
On Tue, 11 Jul 2017 14:40:03 -0700 (PDT), "Dave, I can't do that"
wrote: Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot. When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. Before anyone launches into "house wiring," etc rest assured it is 11-years old, copper, in metal conduits and all up to code with 200-Amp coming into the house. I used a 14g, 3-wire extension lead in a bunch of other outlets on different circuits and still get the same issue. I then hard wired the extension into the main breaker panel. Same again. I have cleaned and oiled the fan bearings, adjusted the belt and the fan turns quite freely by hand. What can be done to alleviate this momentary voltage drop? Thanks 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 |
#4
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Lights dim with swamp cooler.
On 2017-07-11, Dave, I can't do that wrote:
Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot. When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. Still within specs. Why worry about it? Does anything misbehave during those dips? Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. 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. -- Remove oil spill source from e-mail Email: | (KV4PH) Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#5
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Lights dim with swamp cooler.
On Tuesday, July 11, 2017 at 5:40:08 PM UTC-4, Dave, I can't do that wrote:
What can be done to alleviate this momentary voltage drop? Thanks Do you have a way to measure the current drawn by the motor? If you can measure 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 the momentary voltage drop to a level that is acceptable. But will help. Capacitors can be found in junk microwave ovens. Dan |
#6
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Lights dim with swamp cooler.
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 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. |
#7
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Lights dim with swamp cooler.
On Wednesday, July 12, 2017 at 7:41:43 AM UTC-7, wrote:
Do you have a way to measure the current drawn by the motor? If you can measure the current , you can put some oil filled capacitors in parallel with the motor and find a combination that minimises the current. 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. https://www.lowes.com/pd/Dial-Steel-...-Motor/1016109 |
#8
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Lights dim with swamp cooler.
"Dave, I can't do that" wrote in message
... 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 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 |
#9
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Lights dim with swamp cooler.
On Wednesday, July 12, 2017 at 11:09:30 AM UTC-4, Dave, I can't do that wrote:
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. 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 low 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 more 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 |
#10
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Lights dim with swamp cooler.
On Tuesday, July 11, 2017 at 5:40:08 PM UTC-4, Dave, I can't do that wrote:
Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot. When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. Before anyone launches into "house wiring," etc rest assured it is 11-years old, copper, in metal conduits and all up to code with 200-Amp coming into the house. I used a 14g, 3-wire extension lead in a bunch of other outlets on different circuits and still get the same issue. I then hard wired the extension into the main breaker panel. Same again. I have cleaned and oiled the fan bearings, adjusted the belt and the fan turns quite freely by hand. What can be done to alleviate this momentary voltage drop? Thanks 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 or 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 utility company to check it out. Around here, at least, they're usually pretty cooperative. |
#11
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Lights dim with swamp cooler.
On Wed, 12 Jul 2017 11:47:11 -0400, "Jim Wilkins"
wrote: "Dave, I can't do that" wrote in message ... 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 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 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 |
#12
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Lights dim with swamp cooler.
Dave, I can't do that wrote:
On Wednesday, July 12, 2017 at 7:41:43 AM UTC-7, wrote: Do you have a way to measure the current drawn by the motor? If you can measure the current , you can put some oil filled capacitors in parallel with the motor and find a combination that minimises the current. 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. 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 |
#13
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Lights dim with swamp cooler.
In article ,
Dave, I can't do that writes Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot. When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. Before anyone launches into "house wiring," etc rest assured it is 11-years old, copper, in metal conduits and all up to code with 200-Amp coming into the house. I used a 14g, 3-wire extension lead in a bunch of other outlets on different circuits and still get the same issue. I then hard wired the extension into the main breaker panel. Same again. I have cleaned and oiled the fan bearings, adjusted the belt and the fan turns quite freely by hand. What can be done to alleviate this momentary voltage drop? Thanks I wonder if a suitable thermistor (ntc), wired in series with the motor would do the job simply and cheaply? E.g. EPCOS B57127P0109M301 -- Chris Holford |
#15
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Lights dim with swamp cooler.
On Wed, 12 Jul 2017 22:30:06 +0100, Chris Holford
wrote: In article , Dave, I can't do that writes Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot. When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. Before anyone launches into "house wiring," etc rest assured it is 11-years old, copper, in metal conduits and all up to code with 200-Amp coming into the house. I used a 14g, 3-wire extension lead in a bunch of other outlets on different circuits and still get the same issue. I then hard wired the extension into the main breaker panel. Same again. I have cleaned and oiled the fan bearings, adjusted the belt and the fan turns quite freely by hand. What can be done to alleviate this momentary voltage drop? Thanks I wonder if a suitable thermistor (ntc), wired in series with the motor would do the job simply and cheaply? E.g. EPCOS B57127P0109M301 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. |
#16
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Lights dim with swamp cooler.
On 2017-07-12, Dave, I can't do that wrote:
On Wednesday, July 12, 2017 at 7:41:43 AM UTC-7, wrote: Do you have a way to measure the current drawn by the motor? If you can measure the current , you can put some oil filled capacitors in parallel with the motor and find a combination that minimises the current. 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. So a digital readout -- common for the LSD (Least Significant Digit) to display some uncertainty. Is this by any chance a Kill-a-Watt? 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. 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. So what do I actually need to do with the caps? I have some oil-filled start caps around the place somewhere. 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. This is the motor. https://www.lowes.com/pd/Dial-Steel-...-Motor/1016109 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. -- Remove oil spill source from e-mail Email: | (KV4PH) Voice (all times): (703) 938-4564 (too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html --- Black Holes are where God is dividing by zero --- |
#17
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Lights dim with swamp cooler.
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#18
Posted to rec.crafts.metalworking
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Lights dim with swamp cooler.
On Tue, 11 Jul 2017 14:40:03 -0700 (PDT), "Dave, I can't do that"
wrote: Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot. When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. The problem is the motor. The type of motor sold at H-D is designed for low inertia loads that start very rapidly. This type of motor draws tremendous starting current - I've seen as high as 80 amps - and at low power factor. The correct solution is to buy a fan duty motor. This type of motor is designed for high inertia loads and is designed to draw only moderate starting current. Your best bet would be to return that motor if you can and buy the correct one from an electric motor shop. If there isn't a shop near you, I recommend the shop where I used to moon-light - Jerry's Electric Motor Shop, Cleveland, TN. 423 472-5959. Tell Jerry that I referred you. If you're stuck with that motor, there are some things that you can do. Foremost is to supply the starting current from a capacitor. The starting current is very low lagging power factor. A motor start capacitor will supply the leading power factor current to offset the motor's lagging current demand so that mostly only real power (low amps) is drawn from the line. The capacitor is simply connected in parallel with the motor's terminals through a current relay. The capacitor can't be left in the circuit. IT must be disconnected once the current draw has dropped sufficiently. This is normally done with a current mode starting relay. This type of relay is normally open with a few heavy turns of wire as the coil. The motor current flows through it AFTER the capacitor. The contacts are connected in series with the motor start capacitor. The inrush current draws in the relay, allowing the capacitor to supply the imaginary power. When the current drops to say, 15 amp, the relay drops out, disconnecting the capacitor. If you're interested in tackling this kind of work, I can spec out the components. John John DeArmond http://www.neon-john.com http://www.tnduction.com Tellico Plains, Occupied TN See website for email address |
#19
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Lights dim with swamp cooler.
On Wed, 12 Jul 2017 07:41:11 -0700 (PDT), "
wrote: On Tuesday, July 11, 2017 at 5:40:08 PM UTC-4, Dave, I can't do that wrote: What can be done to alleviate this momentary voltage drop? Thanks Do you have a way to measure the current drawn by the motor? If you can measure 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 the momentary voltage drop to a level that is acceptable. But will help. No. The run power factor, what one would be correcting with a capacitor left in place, would make only a small dent in the start-up draw. The difference is the size cap required. A typical run cap for that size motor would be 5 uF. A start capacitor is an unpolarized electrolytic and would be in the 300 uF range. Capacitors can be found in junk microwave ovens. Again, no. Microwave caps look the same but are of high voltage and low capacity. Typically 5uF at 2500-4000 volts. No need prowling through scrap to get a cap. New ones are quite inexpensive. John John DeArmond http://www.neon-john.com http://www.tnduction.com Tellico Plains, Occupied TN See website for email address |
#20
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Lights dim with swamp cooler.
On Wed, 12 Jul 2017 08:09:24 -0700 (PDT), "Dave, I can't do that"
wrote: 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. https://www.lowes.com/pd/Dial-Steel-...-Motor/1016109 Based on knowing what actual motor you have, I'll modify my previous post just a little. This is a fan-duty motor but it is a very low quality motor, as one of the Lowe's commenters noted. A 1/3 motor should draw 746 watts * 0.33333. = 249 watts real power. That translates to 249 watts / 120 volts = 2 amps. This is the real power the motor is drawing to do the useful work of turning the fan. The rest of the (let's average) 6 amps is "wattless" or imaginary current. The power factor is 2 real amps / 6 total amps = a power factor of 0.35. This is extremely poor. A quality motor when fully loaded will have a power factor of 0.90 or better. As the commenter noted, this is from the motor having little iron and copper inside it. Basically, a cheap chicom substitute. Since this is a fan-duty motor, it probably draws about 6X running current while starting. So 6 running amp * 6 = 36 starting amps. That much current load, applied suddenly, will cause lamp flicker. This flicker will be exacerbated if you have an inadequately sized pole pig (transformer) or more commonly, an undersized drop from the utility. I fought my utility for a long time over this issue. When we built this cabin in 1970, it received a 100 amp box. About 10 years ago we installed a heat pump and a 200 amp box. Severe light flickering happened each time the heat pump started. I traced the cause to the service drop being only 4 gauge aluminum wire, severely undersized for a 200 amp panel. I spent about half my life as a utility engineer so I could take on the engineer at the utility. I provided him hard measured evidence of the voltage drop but he ultimately refused to order a larger drop. So I cut a tree down across the line and pulled it down. The replacement drop is #0 gauge (still too small) and I still get a bit of flicker but not nearly so bad as before. The primary feeding our little mountain community is 25 miles long and is only 7200 volts so some sag is happening on the utility side. So you need to take a look at your service drop and see if you can tell if it's too small. If you have a digital volt meter that has a high/low peak reading function, you can connect it between neutral and an otherwise unused breaker in your panel and record the voltage dip at your service entrance when you start the swamp cooler. If the dip at the panel is much over 3 volts, your drop and perhaps pole pig is undersized. A study years ago determined that the average person could detect the flicker in a tungsten lamp at a 3 volt threshold. Electronic lights (CFLs and LEDs) are even worse because there is no thermal inertia. So my revised advice would be: a) determine whether your utility service is adequate, b) take that motor back and buy a quality name-brand motor such as GE or Emerson and only after that pursue what I described in my previous post regarding fixing the inrush and power factor problem. You asked in your first post if the motor could be soft-started. The answer is yes. Soft starters are available but most use a 3 phase motor (single phase to the soft starter). A quality (non-chicom) soft starter will cost several hundred dollars so I recommend the other things first. John John DeArmond http://www.neon-john.com http://www.tnduction.com Tellico Plains, Occupied TN See website for email address |
#21
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Lights dim with swamp cooler.
"Neon John" wrote in message
... On Tue, 11 Jul 2017 14:40:03 -0700 (PDT), "Dave, I can't do that" wrote: Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot. When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. The problem is the motor. The type of motor sold at H-D is designed for low inertia loads that start very rapidly. This type of motor draws tremendous starting current - I've seen as high as 80 amps - and at low power factor. The correct solution is to buy a fan duty motor. This type of motor is designed for high inertia loads and is designed to draw only moderate starting current. Your best bet would be to return that motor if you can and buy the correct one from an electric motor shop. If there isn't a shop near you, I recommend the shop where I used to moon-light - Jerry's Electric Motor Shop, Cleveland, TN. 423 472-5959. Tell Jerry that I referred you. If you're stuck with that motor, there are some things that you can do. Foremost is to supply the starting current from a capacitor. The starting current is very low lagging power factor. A motor start capacitor will supply the leading power factor current to offset the motor's lagging current demand so that mostly only real power (low amps) is drawn from the line. The capacitor is simply connected in parallel with the motor's terminals through a current relay. The capacitor can't be left in the circuit. IT must be disconnected once the current draw has dropped sufficiently. This is normally done with a current mode starting relay. This type of relay is normally open with a few heavy turns of wire as the coil. The motor current flows through it AFTER the capacitor. The contacts are connected in series with the motor start capacitor. The inrush current draws in the relay, allowing the capacitor to supply the imaginary power. When the current drops to say, 15 amp, the relay drops out, disconnecting the capacitor. If you're interested in tackling this kind of work, I can spec out the components. John John DeArmond http://www.neon-john.com http://www.tnduction.com Tellico Plains, Occupied TN See website for email address 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 |
#22
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Lights dim with swamp cooler.
On Thu, 13 Jul 2017 08:55:00 -0700, wrote:
On Wed, 12 Jul 2017 20:13:20 -0400, wrote: On Wed, 12 Jul 2017 22:30:06 +0100, Chris Holford wrote: In article , Dave, I can't do that writes Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot. When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. Before anyone launches into "house wiring," etc rest assured it is 11-years old, copper, in metal conduits and all up to code with 200-Amp coming into the house. I used a 14g, 3-wire extension lead in a bunch of other outlets on different circuits and still get the same issue. I then hard wired the extension into the main breaker panel. Same again. I have cleaned and oiled the fan bearings, adjusted the belt and the fan turns quite freely by hand. What can be done to alleviate this momentary voltage drop? Thanks I wonder if a suitable thermistor (ntc), wired in series with the motor would do the job simply and cheaply? E.g. EPCOS B57127P0109M301 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. 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 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!! |
#23
Posted to rec.crafts.metalworking
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Lights dim with swamp cooler.
On Tue, 11 Jul 2017 17:53:47 -0700, wrote:
On Tue, 11 Jul 2017 14:40:03 -0700 (PDT), "Dave, I can't do that" wrote: Hi, we recently installed a window version of a swamp cooler. As such, it plugs into a wall outlet in the lounge-room. It has a new 1/3-hp (252-Watt) two speed motor from HomeDepot. When it turns on either in Low or High, the voltage dips for almost a second from 125vac to 117vac then back up to 125vac. The dimming is maybe 20% longer for the High speed. Is there some way we can soft-start this or what? It makes the lights dim in the house for that short period. Before anyone launches into "house wiring," etc rest assured it is 11-years old, copper, in metal conduits and all up to code with 200-Amp coming into the house. I used a 14g, 3-wire extension lead in a bunch of other outlets on different circuits and still get the same issue. I then hard wired the extension into the main breaker panel. Same again. I have cleaned and oiled the fan bearings, adjusted the belt and the fan turns quite freely by hand. What can be done to alleviate this momentary voltage drop? Thanks 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 I live in Swamp Cooler Country. Far too many of the low end portables come with utterly crappy motors and Ive seen this many times. It may be better to simply replace the motor with a decent US made motor, with proper run/start caps --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
#24
Posted to rec.crafts.metalworking
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Lights dim with swamp cooler.
On Wed, 12 Jul 2017 12:57:50 -0500, Pete Keillor
wrote: 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 Silver sometimes burns out too... https://photos.app.goo.gl/QR9ktCUdYvqeB5NA3 https://photos.app.goo.gl/fnUHe832D1qVWw202 --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus |
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