# Head scratcher on a MW resi circuit



## redseal (Sep 22, 2010)

Had a service call today multi wire, one of the kit SA circuits, Dine on one phase and Laundry on the other , micro on this also fed after the kit and dine. All Phases show 120v, untill a load is applied, then the micro goes to 112v. They have burned through 2 micros's already. I have checked all connections and all are good (pannel, hr, recps) No loose noodles, phased correctly, no corrosion on any neutral, Problems on B phase also. Traced all circuits and I am stumped..... I would say faulty micro, but the problem is also with a freezer on the laundry circuit wich is part of the MW??????


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## Cletis (Aug 20, 2010)

*??*



redseal said:


> Had a service call today multi wire, one of the kit SA circuits, Dine on one phase and Laundry on the other , micro on this also fed after the kit and dine. All Phases show 120v, untill a load is applied, then the micro goes to 112v. They have burned through 2 micros's already. I have checked all connections and all are good (pannel, hr, recps) No loose noodles, phased correctly, no corrosion on any neutral, Problems on B phase also. Traced all circuits and I am stumped..... I would say faulty micro, but the problem is also with a freezer on the laundry circuit wich is part of the MW??????


I'm still confused. Can you rephrase or do I need to go down and start drinking for things to make sense tonight ?


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## leland (Dec 28, 2007)

Cletis said:


> I'm still confused. Can you rephrase or do I need to go down and start drinking for things to make sense tonight ?



Exactly!


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## erics37 (May 7, 2009)

How far away is the microwave receptacle from the panel, and what ampacity circuit runs it? 15 or 20 amp?


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## Cletis (Aug 20, 2010)

*Micro*

I bet the micro is on 14 gauge and they have about 117 volts before load kicks it down to 112V. Still shouldn't blow micro's unless you have fancy swedish/european ones ? The alcohol is starting to kick in now....


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## leland (Dec 28, 2007)

redseal said:


> Had a service call today multi wire, one of the kit SA circuits, Dine on one phase and Laundry on the other , micro on this also fed after the kit and dine. All Phases show 120v, untill a load is applied, then the micro goes to 112v. They have burned through 2 micros's already. I have checked all connections and all are good (pannel, hr, recps) No loose noodles, phased correctly, no corrosion on any neutral, Problems on B phase also. Traced all circuits and I am stumped..... I would say faulty micro, but the problem is also with a freezer on the laundry circuit wich is part of the MW??????



#1- Electricians don't call them 'Noodles'. That is right up there with 'JUICE'. (if there was a puke symbol it would be inserted)

#2 - Your Multi wire branch circuit,seems to cover .. The Kitchen,laundry,Dining room&Freezer.

This is a 'Multi-USE' circuit. Looks like too many splices. One is bad.
Trace the circuit and repair ALL splices.

Betcha the problem gets fixed.


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## Cletis (Aug 20, 2010)

*Redseal*

I can't blame you for your typing. Your from a really cold area. What was high today ???


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## kbatku (Oct 18, 2011)

Like always - bad neutral connection somewhere.


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## jarhead0531 (Jun 1, 2010)

If your saying it is a multiwire branch circuit then checking for the bad neutral should be pretty easy to do with some help. At the panel measure the voltage on both phases of the circuit with the microwave on. If the microwave side dips and the other sides goes up the same amount, bingo is you loose neutral someplace.

If the voltage stays the same on the other phase then I would start looking into loose connections on hot side, length of circuit, full load on circuit, etc.... Quick and easy test might be to reduce the power of the microwave(yes you can do that on most of them) and see if the voltage drop is reduced running at a lower power.

After you find the problem, sell them a new dedicated 20A circuit JUST FOR THE MICROWAVE.


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## Dennis Alwon (May 9, 2009)

This is a classic bad neutral either in the circuit or coming from the poco. Get it fixed. Eventually you will get 240 into all your 120V circuit as the problem worsens.


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## local134gt (Dec 24, 2008)

leland said:


> #1- Electricians don't call them 'Noodles'. That is right up there with 'JUICE'. (if there was a puke symbol it would be inserted)


That drives me crazy also, I work with a couple of guys who say that! Hot water heater always irritates me too.


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## MechanicalDVR (Dec 29, 2007)

local134gt said:


> That drives me crazy also, I work with a couple of guys who say that! Hot water heater always irritates me too.


 

So you prefer "cold water heater"?


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## LightsOn81 (Jan 6, 2012)

local134gt said:


> That drives me crazy also, I work with a couple of guys who say that! Hot water heater always irritates me too.


Lighten up man! Some guys say stuff like noodles and juice to keep the day light because we are in a trade that's serious in and of itself. If we all had the personalities of lava rocks then sure but as long as he can get his point across it don't matter.


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## McClary’s Electrical (Feb 21, 2009)

It's wired all wrong. You can't use a SABC for any of the things you mentioned.


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## RGH (Sep 12, 2011)

mcclary's electrical said:


> It's wired all wrong. You can't use a SABC for any of the things you mentioned.


 
Spot on ....find the problem first..probably a loose nuetral...but you have to pull a few new circuits into that mix..SABC for the counter tops only..now split that stuff up..or your gonna burn em up..micro hummin then the fridge kicks on..? ouch..:no:


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## Dennis Alwon (May 9, 2009)

​


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## Going_Commando (Oct 1, 2011)

Dennis Alwon said:


> ​


Why do you hate fun?


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## electricalperson (Jan 11, 2008)

whats the voltage on the other phase? does it raise? as a helper i witnessed a friend pull apart a neutral of a MWBC that fed an apartment. i believe most of the apartment were on those 2 circuits. the lights got very bright and the tvs burned out instantly. you heard a pop in the back of them:laughing: i would check all the splices especially in the neutral. DO NOT undo that neutral if the power is on unless you want to replace appliances:thumbup:


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## Dennis Alwon (May 9, 2009)

Going_Commando said:


> Why do you hate fun?



I thought I was having fun.


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## Seattlepro (Jul 28, 2009)

If the wire is AL you might have a nick in the insulation and if its getting wet and turning into powder.


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## leland (Dec 28, 2007)

MechanicalDVR said:


> So you prefer "cold water heater"?



No, Dude. Why do you need a HOT water heater?

It implies the water is already hot.:no:


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## leland (Dec 28, 2007)

LightsOn81 said:


> Lighten up man! Some guys say stuff like noodles and juice to keep the day light because we are in a trade that's serious in and of itself. If we all had the personalities of lava rocks then sure but as long as he can get his point across it don't matter.



NO. 'Noodles' and 'Juice' are terms the GC/home owner uses to try and fit in to our little world.

real licensed guys don't use those terms. We are more 'Manly' than that.:thumbsup:


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## LightsOn81 (Jan 6, 2012)

No dude you're wrong. I'd buy that if you were the only licensed guy I ever talked to but you're not so................:thumbsup:

I do agree that those types do try hard to fit in though


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## leland (Dec 28, 2007)

LightsOn81 said:


> No dude you're wrong. I'd buy that if you were the only licensed guy I ever talked to but you're not so................:thumbsup:
> 
> I do agree that those types do try hard to fit in though



So, You know 'REAL' licensed electricians that use- 'Noodles' and 'juice' as real terms for our trade?

Not a 'macho' thing- just... never hear the real guys use them.


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## LightsOn81 (Jan 6, 2012)

It's not an all day everyday thing but it happens. Like I said, it don't matter what someone call it ALS long as they get their point across. Now I wouldn't go to the boss/GC/ customer talking like that................ Gotta go got a bunch of panels to terminate today


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## Southeast Power (Jan 18, 2009)

I would say that you have a bad splice on one of the hots. It could be under a wire nut or a back stabbed device.


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## mrmike (Dec 10, 2010)

The 112 volts is pretty close to the alowable voltage drop of 5%. Check other appliances plugged into different outlets with an amp reading at the panel- for instance a vacuum cleaner & see if you have the voltage drop with them also. It may be a problem with the power coming in. 

Microwaves use alot more power than what the rating says, and are supposed to be on their own circuit,. As some had stated maybe undersized wires. 
If the freezer starts at the same time as using that microwave-it will probably will cause a lot greater voltage drop...I don't suspect loose wiring as this has went on-thru a few micros already, and usually a loose connection will get worse & break contact over time................
This is just I.M.O. , but if looking for a bad connection-check the receptacle for backstabbing as the last post stated..............


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## Dennis Alwon (May 9, 2009)

Always check the other phase with loads on. If the voltage on the phase is 112 my bet is that the other phase voltage is around 130 or so. Generally if the voltage in the building is 240 (usually it is higher) then the some of the phases will be 240. Thus if phase "A" drops to 90 volts then phase "B" will be 150 Volts. This is a classic sign for a weak neutral.


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## Old man (Mar 24, 2010)

Dennis Alwon said:


>


 No dark sarcasim in the classroom
Hey sparky, leave those MBCs alone.:thumbup:


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## redseal (Sep 22, 2010)

leland said:


> NO. 'Noodles' and 'Juice' are terms the GC/home owner uses to try and fit in to our little world.
> 
> real licensed guys don't use those terms. We are more 'Manly' than that.:thumbsup:


 
Wrong, I am a fully licensed, bonded and insured Electrical contractor. Its just terminology. Your an idiot leland. All "neutral" connections are good, voltage drop shoundt be an issue as its only about 50'. Not Au, its copper. Its not a Utility problem either voltage has been checked.


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## redseal (Sep 22, 2010)

Dennis Alwon said:


> Always check the other phase with loads on. If the voltage on the phase is 112 my bet is that the other phase voltage is around 130 or so. Generally if the voltage in the building is 240 (usually it is higher) then the some of the phases will be 240. Thus if phase "A" drops to 90 volts then phase "B" will be 150 Volts. This is a classic sign for a weak neutral.


 
Tried that other phase only gained 1.6v


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## Meadow (Jan 14, 2011)

It sounds like 2 circuits are doing a hefty amount of feeding. Put all those loads on dedicated circuits (By code laundry is dedicated) and then check wire guage along with all connections; problem should go away.


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