Hand Dryer causing voltage drop

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Jeff80

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I have a very small stand alone restroom where the hand dryer is causing the lights to dim and the emergency lights to turn on due to the voltage drop. The drop is caused by the hand dryer and only lasts a second but what is the fix?

Can I add a capacitor to the hand dryer? How would it wire in to the unit could I put it on the feed to the unit even with the heater and moter down stream? How would I find out the correct size cap? Would the cap be in series or paralell?

Is there a better way?
 

drbond24

Senior Member
I'm not a capacitor expert, but I don't think this is a situation where they could help. I believe you're thinking a capacitor would provide additional voltage to the dryer so it would require less from the circuit, but where does the capacitor get its voltage from? The circuit. Now you're right back where you started. However, like I said this isn't my area. Others will have more detail on this.

I would think you have a couple options. You could switch for a dryer that doesn't need so much juice, or install a separate circuit for the dryer if it is that big of a problem.

In the end, is it that big of a deal? The lights in my dining room dim when the microwave is being used. I usually use the microwave and then go to the dining room, so it doesn't matter. People usually only dry their hair once a day for a few minutes. Can't they just put up with the dimming?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
sounds like a lot of voltage drop. Just to satisfy my curiousity can you describe the circuit (wire size, length, etc).
Most of the hand dryers I have seen push the heck out of a 20 amp circuit and pretty much require a dedicated circuit. Sounds like a violation of 210.23 as it is wired.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
I don't understand why the lights only are dimmed for a "second". There is no big inrush current on a hand dryer to account for that. Could this be related to the transformer? I seem to recall something about transformer regulation that could show this symptom under some conditions.
 

ctmike

Senior Member
Every hand dryer i have install has required its own dedicated circuit. perhaps that is your problem what did the mfg instructions say
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Is this one of those hand dryers that has a high wattage heating element and a small blower that blows a stream of warm air, or is it one that has a very powerful blower and small heating element, and works by blowing a very powerful stream of air?

-Jon
 

chevyx92

Senior Member
Location
VA BCH, VA
I believe you're thinking a capacitor would provide additional voltage to the dryer so it would require less from the circuit, but where does the capacitor get its voltage from? The circuit. Now you're right back where you started.

Not true. A capacitor would get voltage from the circuit even when not under load. So being right back where you started is not a true statement. Truth is it would help, but whether it would solve his problems (NEC Violations) or not I don't know. But you can't blanket a capacitor as not going to work, IMHO.
 

Jeff80

Member
The hand dryer is on a circuit by it self, and there are 2 hand dryers (men and women) and both have the same issue. Would it matter if the dryers share a neutral with any other oppisite phase circuit? There is also a coke machine outside and when the compressor is running the dimming is even worse. This is a single phase panel 100amp (a phase 114volt to neutral and b phase 130volt to neutral) and this was a service call not a new install.

I will check all the connections again. If they are all good could ther be a problem in the service drop connections or power company feed?
 

LawnGuyLandSparky

Senior Member
114 to 130 is one B I G spread. Poor neutral connection somewhere between panel and utility transformer. Check voltage between the panel neutral and a known ground that's good. I'll bet all of the 240v loads are running fine?
 

busman

Senior Member
Location
Northern Virginia
Occupation
Master Electrician / Electrical Engineer
There is no big inrush current on a hand dryer to account for that.

There isn't a "big" inrush current on hand-dryers, but there is some. There is the motor inrush from the blower motor. There is also inrush to the heater element that is usually about 50% above FLC of the heater for the few seconds until the element heats up and the resistance increases.

Mark
 

Twoskinsoneman

Senior Member
Location
West Virginia, USA NEC: 2020
Occupation
Facility Senior Electrician
My guess would be you have a loose connection someplace. Check the panel and the outlet in question.

This sounds right on. In a Mike Holt DVD I watched once he said that in this type of situation, I think his example was the cycling of a clothes iron, his bet was a loose connection in the circuit on some receptacle somewhere. I think he said something like 10-1 you've got backstabs in the room. :D
 

e57

Senior Member
Do you think it could be a loose neutral? I did not see any burnt wire or loose line connections
Not something you normaly see per se... Something you test for.... If it is a loose noodle, and it sounds as if it is - it's not something to be left if you cant find it.

If it is a MWBC or effecting a panel, feeder or even from the main - you would test for voltage lowering, on one leg, and raising on another. You would not use customer loads to simulate loads for this type of test - use something of high resistive wattage and disposable. I usually use a bunch (8) of 500w halogen flood lights - load up one leg - then the other(s). Then load up one side higher than the other. Check for voltages to be as even as possible at the main, and see if the same at the sub-panels, etc. Then take voltage readings and use a tempature probe or IR thermometer to isolate the loose one. Where it changes is your problem. The resistive connection will will also be hotter than the rest. Sure melted insulation is a good sign - but not always that obvious.... If it is at the main - it will change voltage if you change the load on one leg or the other. That said, a resistive hot leg can have the same effect - but only on that leg.....

Since this needed a dedicated circuit in the first place, some other factors may be at play other than a loose neutral. Like it being heavily loaded and a few hundred feet long????? Or just generally undersized conductors. (On the branch circuits or feeder....) But your 114 - 130 sounds like High/Low - loose neutral condition.

Good luck...
 
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