Simple eledtrical testing (C) Daniel Friedman Electrical System Wiring Inspect, Install, Repair FAQs
Questions & Answers about inspecting, installing, repairing building electrical wiring, devices, components

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Questions & answers about building electrical system installation, troubleshooting & repairs & electrical hazards.

FAQs about how to install, inspect, & troubleshoot building electrical systems, appliances, components. Questions & answers on how to detect & report electrical hazards, defects in residential and commercial electrical panels, switches, fixtures, electrical wiring & grounding systems. Troubleshooting questions about electrical repair methods.

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Building Electrical System FAQs

DMM range and function indicator dial settings (C) Daniel Friedman

Questions & Answers Posted originally at ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR - home

On 2017-06-03 by (mod) re: grandfathering electrical work in Minnesota & Accessibility of Electrical Junction Boxes


And a tech note about why some comments don't post immediately: sorry that our comments box software blocked your earlier comment. When it sees a . in the middle of text it thinks it's a dangerous link. "... ... " for example. On review I can of course unblock the remark as I've done below.

About grandfathering:

Generally any new electrical work must be done to current codes; in some jurisdictions working on an old circuit, such as remodeling a bathroom, will also prompt a requirement to add what's currently required - such as GFCI.

That buried box really must be made accessible, grandfathered or not: both so that future owners or electricians won't kill themselves trying to find a connector that's gone bad but that is totally hidden, and of course for safety or to permit future work. Even though it may be a pain, if I come across such a box I find a way to give access to its cover.

You can bring the box front out to a finished wall surface using a metal or approved plastic cover and you can even paint it. If there were paneling I'd still provide an access opening.

This U.S. NEC paragraph is quoted by Minnesota's guide for electrical wiring projects:

NEC 314.29 Junction boxes shall be accessible without removing any part of the building.

This Minnesota electrical inspection checklist might be useful to you,

On 2017-06-03 by bobbylgorden

I have a question about grandfather laws. I have house built in 1958 which originally was a 1 BR house. There was a 2 BR addition added and the original BR became the Living room. I am doing some remodeling and was going to add a 6 outlet box about 4 foot off the floor for my entertainment center. It is just my luck the right at the top of my hole for the 6 way box, is a box. Now, I don't know if it is a junction box or the old service panel. I have not uncovered it.

There is 110v and 220v wiring and they are live connections. My question is, can I uncover the "box" and not have to make an access panel on my LR wall, an access cover would be unsightly, and recover it with sheetrock or will I have to uncover it and bring it up to code. I am pretty sure that here in MN, all junction boxes and service panels must be fully accessible but I don't know about grandfather clauses. Thanks for any insight you can give me.

I am doing a slight modification to my home. It was a 1 BR and had a @BR addition. The old bedroom is now the living room. I wanted to add an additional outlet on the living room wall. I know how to wire outlets and understand home wiring.

While doing my project I found a junction box in the old part of the house.At the moment, I can only see the bottom of this mysterious box in the wall. I suspect it is the old service box as it appears to have 110v and 220v wires running into the box. I am in Minnesota and do not know if I must "uncover this box". I always thought any enclosure must be readily accessible. I am afraid to uncover it as it might be "grandfathered in" and if i uncover it, I will have to create and access in the middle of my living room wall which would be very unsightly.

On 2017-05-15 by (mod) - re: best location for a light switch


Generally it makes sense for a room light switch to be located where it would be readily accessible when entering or leaving a room. The swing of the door means you wouldn't prefer a switch by the hinge side of the door.

If your electrician says what you want is illegal or unsafe, despite my sincere wish to be helpful, I'd be really foolish to pretend I could out-guess an on-site licensed expert. But you could certainly give a call to your local building department, ask to speak to the electrical inspector, and without leveling any accusations, just ask what the local code enforcement people where you live - the final legal authority - will permit.

On 2017-05-15 by Karen Garber

PLEASE HELP with indoor wiring and switch requirement for outdoor lights. We are senior citizens:

I want an outdoor light on the left side of my front door but my electrician will not do it because the switch is on the opposite side of the door inside the house. He said that it is not code to have the switch on the opposite side of the door.

The light was there before but he took it upon himself to move it. I think he is just annoyed that we are asking him to change it because he said NO lights or 1 on each side of the door. If he is bringing a wire across the top of the door to power a 2nd light then why can't I have just one light on the side that I want? I have to add that there is no sheetrock by the front door now and we want to do the right thing before the walls go in. I appreciate any information. Karen Garber 516 647-8356

On 2017-05-06 by (mod) re: how much does it cost to add an electrical circuit or to add a ground wire


The answer to a question about the cost of electrical wiring depends on

- where you live, as prices vary by country, province, state, city
- ease of access to a wiring path: e.g. access via a basement or crawl makes running circuit wires easy while running wires in a home built on slab where there is no access to a wiring path requires wall cuts, snaking wires, more time and labor
- distances
- probably cost to replace existing wires as just adding a third external grounding conductor may not be acceptable by local building codes
- number of circuits requiring the repair

But we can put some bounds on the question: to wire a typical North American new home (meaning it's easy to run the wires as walls are not enclosed) is in the $10,000 range. Electricians typically charge $75 to $125/hour. A single small job like running one circuit that's accessible is probably under $500. U.S. while cutting into walls or ceilings and snaking wires to re-wire an existing circuit to add grounding conductor and thus to replace all of the receptacles, could easily be twice that.

On 2017-05-06 by Running ground wire to main panel

How much would it cost to run ground wiring from bath and kitchen to main panel house is about 1300 sft ranch.

On 2017-05-05 by (mod) re: what to do if some electrical circuits are not working


To avoid a fire or death by electric shock I would leave the bad circuit OFF until you can get an electrician to find the problem and fix it. Typically she will find an open wire connection at a switch, wire splice, or light fixture.

On 2017-05-05 01:06:08.413281 by Eric

I have no lights in one bedroom and one bathroom of my mobile home, the electrical outlets still work though in both rooms. What could be the problem?

On 2017-05-03 by (mod) re: can I use 220 wire to power a singlewide mobile home?

Sherrie I'm scared to answer you because a mistake here can kill you or burn the place down. So I have to give a generalized arm-waving reply before I duck:

Generally 220 Volts at a residential property is made up of two 110 volt service entry wires and neutral and ground wires from the electrical company.

That power source can, properly connected through a main disconnect switch to a main electrical service panel, can then deliver power to both 220V and 110V (or 240V 120V) household circuits through individual circuit breakers and wires in the building.

NONE of what I said has addressed the question of wire size - gauge or thickness, number of circuits in the home, location of panels, etc. Be sure you get help from a licensed electrician.

On 2017-05-03 by Sherrie

Can you use a 220 wire to power a single wide mobile home?

On 2017-04-12 by (mod) re: electrical damage after a lightning strike or thunderstorm


Because a nearby lightning strike can damage electrical equipment and leave it unsafe, risking a fire or shock injury, if it were my home I'd call a licensed electrician to ask for help.

A reasonable step to check individual circuits is to turn the circuit breaker to a fully off position, then back on. Sometimes it's not obvious that a breaker has tripped. But more likely there was lightning damage to the electrical feeders to the home or to its electrical equipment.

BE SURE to leave any odd-acting circuits OFF - such as flickering lights.

BE SURE that you have properly-located, installed, and tested smoke detectors working in your home.

On 2017-04-11 by Melaney

Last night we had a severe thunderstorm. There was a lightening strike very near by. The electricity remained on except in the master bedroom and ensuite. There were no switches to thrown to indicate where the problem might be. What can I do to get the electricity back on in those rooms. I am on a limited budget and would rather not have to call in an electrician if at all possible. The diagram in the junction box is not helpful.

On 2017-03-25 by (mod) re: how do I send a photo showing how to jump the white wire to the ground screw to make a receptacle work


You are welcome to use the page top or bottom CONTACT link to find our email to send along a photo for comment.

Our Comments Box software, for security reasons, doesn't let readers include files nor photos.

Watch out: The danger of connecting neutral to ground anywhere but in the panel is that when the circuit is active current is flowing on the grounding conductor or for BX/armored cable it's flowing in the metal BX jacket. Those are not intended to carry normal operating current. Someone can be shocked, even killed from that condition.

It's not just theory, those shocks have actually happened, even in cases I've seen personally. What you propose is a violation of electrical code and it is unsafe.

On 2017-03-25 by mikerosco2004

I have a picture that i'd like to share but can't cause there isn't an option I will have to explain.any 15 or 20 amp 3 prong receptacle.i sometimes have to jump an insulated piece of white wire to the ground screw off of the neutral side terminal because since the neutral and ground go to the same ground bus bar in most of if not all boxes I've worked in including my own 2 panel boxes.either there isn't a path through to ground by mc shielding or a ground wire I have no choice but to do this procedure.

i've just stumbled upon this trick on my own in the field to fool the quick receptacle testers and in thinking that this will ground the user from shock.i wonder if this is a safe work around here in the NE,lol! might frown upon it but like many cancer causing substances can only give you cancer in the state of California and not anywhere else.electric is electric in any part of the world it's just looks different.

On 2017-03-21 by (mod)

Akhila said:
Thank you for the useful information.

On 2017-03-17 by (mod)

Fair question, Tim as the page above is basically an index to articles at

Using the little search box just above for "ELECTRICAL OUTLET WIRING" finds two articles you will want to review - then do ask if questions remain


these Q&As are also helpful


You have to find the wire in the wall, add a junction box (that can't be buried later) to permit getting enough slack to add wires to connect your receptacle, add a box for the receptacle if everything doesn't fit in the first junction box, then do the wiring and secure the box in the wall.

On 2017-03-17 by tim

how do I connect a simple wall outlet to a wire already passing through wall

On 2017-01-23 by (mod) re: how to trace an electrical circuit

There are circuit tracing tools that emit a tone, hooked up in panel. Let's hope nobody buried the junction box.


On 2017-01-23 by Brett

Anyone have any luck tracing circuits inna mobile home ? Have a service ticket, half the kitchen circuits are out, 12/3 leaving panel and 12/2 feeding kitchen receptacles. Looking for a junction point.

Question: air conditioning system circuit wire sizing

(May 29, 2011) paul macgregor said:

hi , i have a install of a/c its a LG single phase ducted system ,32 amps but the cable run is 55 / 65 meters i think this should be 10mm cable ??? or can 6mm be used

(May 31, 2011) electricaldave said:

Canadian Electrical Code requies that the prober size wire be use for the rated load. By the looks of your unit, I would suggest using a #8 cable. This is rated for 40amps. Wire is rated with 80% load rating and with the lenght of the run, this cable would work best.


Thanks Dave.

Recently-posted questions & answers about the building electrical system, originally appearing at ELECTRICAL INSPECTION, DIAGNOSIS, REPAIR

On 2017-01-23 18:30:28.121649 by (mod) circuit tracing tools

There are circuit tracing tools that emit a tone, hooked up in panel. Let's hope nobody buried the junction box.

On 2017-01-23 17:18:57.749933 by Brett

Anyone have any luck tracing circuits inna mobile home ? Have a service ticket, half the kitchen circuits are out, 12/3 leaving panel and 12/2 feeding kitchen receptacles. Looking for a junction point.

On 2017-01-22 00:08:00.259983 by (mod) adding GFCI protection


GFI protection (ground fault interrupter) adds electrical safety for circuits such as wall receptacles (wall plugs or "outlets") in high risk areas such as in kitchens, bathrooms, and outdoors. There are two ways that protection, also called GFCI, can be provided.

1. a special GFCI circuit breaker (or more than one) installed in the electrical panel will protect everything on that electrical circuit

but you may not have any of those devices in the electrical panel. Instead,

2. a GFCI wall receptacle (wall plug or "outlet") may be installed, for example in a bathroom or kitchen. In that case ground-fault protection (you're touching a live or leaky electrical appliance plugged in to that receptacle and you touch a water pipe, causing a fault that lets electricity flow through to the earth - ie you get shocked) - anyhow, if the receptacle is properly wired and IF it has a GFCI receptacle installed, GFCI protection will be provided for whatever is plugged-in to that receptacle AND it will be provided for any wall receptacles that are wired "downstream" from that receptacle.

In other words if a GFCI is wired into receptacle #1 in a bath and that bathroom circuit then sends power FROM that receptacle on to another receptacle in a bedroom or in another bath, those receptacles are also protected.

You can see GFCI devices to see what they look like here at InspectApedia: see and also see

See your other recent comment and our reply at

On 2017-01-21 23:57:29.666517 by (mod)

Re-posting from an obsolete copy of this web page:

AUTHOR:Terry (no email)

COMMENT:I live inva 14x70 mobile home 1984 should I have a gfi breaker in my panel box if so where?

On 2017-01-19 23:05:42.991589 by CallieMom - blue flames shot out of the breaker box

I live in a single wide mobile home, used. I turned the microwave on to defrost meat, circuit breaker tripped. I went to the breaker box and flipped it back on. I tried using the microwave again and the same thing. I also went back to the breaker box and when I flipped it, blue flames shot out.

Then within 2 minutes my whole home went black. No breakers were tripped. I flipped the main breaker switch off then back on, the only thing that come back on was my master bedroom, bathroom and front porch light. I had a friend come look at it. He tightened everything and checked voltage. After he left my home went black again with a loud pop, I started smelling a burning smell in the wall of my kitchen and down my hall.

I woke my children and sent them outside. I flipped the heater breaker off in my hallway, flipped my main breaker in my home off, also the breaker at the meter base off. Come back the next morning, smell is gone, flipped meter at pole on then inside breaker on. All plug ins work, master bathroom has lights, but nothing else will power on. What do I do?

On 2017-01-15 15:12:44.044760 by (mod) can power bumps cause problems with household appliances?


Usually we agree that the simplest explanation is the most-likely one, and I'm not a bit fan of coincidences. So I understand that a power loss can cause several other things to start acting oddly, particulary things connected to the electrical system.

The thermocouple on a gas burner is not, itself an electrical part, though it does control a gas valve that opens or closes to feed gas to the burner. That gas valve is in turn powered by a low-voltage transformer that is electrical. Still I don't think a thermocouple itself would be affected by a power surge or outage.

Your question does suggest a bigger problem here, one that unfortunately leaves me telling you to spend money to hire a licensed electrician to examine the whole electrical system in your home for SAFETY!

Look: even if I were the dope who plugged too many things into one electrical receptacle or circuit in your home, at the worst that should have tripped a single circuit breaker or blown a single fuse that is supposed to protect that specific circuit from overloading - thus trying to avoid an electrical fire.

So if overloading an individual circuit doesn't trip that circuit's breaker, and if instead the main breaker or fuse blows, turning off all power for a time, that sounds to me as if something is wrong with your electrical panel.

Or we're wrong and it was a coincidence and there was a power surge in the whole neighborhood where you live - ask your neighbors if that occurred. If it didn't then there is indeed a problem to find in your home, and until it's found the home is not really as safe as it should be.

Keep us posted.

On 2017-01-15 14:56:10.016345 by Marilyn Mitchell

My Grandson was working on his car, and using a light extension cord to use an electrical tool of some kind PLUS a drop light.
I had warned him to be careful & not to plug in but 1 thing at a time. But we lost power to our complete house for a few minutes and then it came back on, so I knew he had not listened to me. We live in a single wide Mobile Home. The next day long story shortened, I noticed the pilot light to our furnace was out & would not lite.
I called the repair person, & it was the Thermocupler that had went out, & he replaced it, & furnace is working fine.

My question is, can power bumps like I had, can they cause problems with appliances in our home, even say my Well, as now MY PUMP in our well house is acting up >> the water pressure is very low & I can tell something is very wrong. We just had the pump replace in 2013, and they said we never had to worry about running out of water so I know it is not that. I lost my husband last year 2016, so I could use some advice, Thank You Kindly In Advance, for some advice, Marilyn

On 2016-12-30 18:56:42.691983 by (mod) - only the white light switches work


I'm unclear on what are "white light switches" - perhaps you mean the lights work but other electrical devices such as wall plugs (receptalces) do not?

Check for a blown fuse or tripped circuit breaker. If the problem occurs again, leave off the mis-behaving circuits as there is a fire or shock hazard - and ask for help from a licensed electrician.

Keep me posted.

On 2016-12-30 18:55:18.569765 by (mod)


AUTHOR:bellakota (no email)

COMMENT:I have a 1970 mobile scout, and only the white light switches work. What could be the problem?

On 2016-12-19 00:43:54.908322 by (mod)

Also if that electrical receptacle or receptacle that you are installing are in a garage, you probably are required to install GFCI protection on the circuit or at the receptacles.

On 2016-12-19 00:42:12.521205 by (mod) ground wire details


Since I don't understand your situation exactly, I feel comfortable giving a general answer.

Each of your electrical circuits will have its own grounding conductor. Within a single electrical box we connect all of the ground wires in common typically with a shrimp or clamp connector. If the box is a metal box we also connect those wires to the Box using a clip or grounding screw. In addition you will need to leave one or more of the ground wires of that connected group long enough to connect to the ground screws on switches and electrical receptacles.

However I have other concerns about what you are describing. One is that with 12-2 or 12 3 wire you may find that the boxes that you are using are not large enough. Be sure to check the number of wires in the box and the wire size and box cubic inches against the box sizes in the wiring tables in the National Electrical Code of equivalent depending on where you live.

Also you may be required to obtain a building permits and have code approval inspections. I know that's more trouble, but think of it as a free fire/safety inspection by an expert.

I'm always nervous about two separate power circuits running into a single electrical box, even where permitted, having seen people switch off just one of the circuits and then begin work and find themselves getting shocked.

On 2016-12-19 00:17:40.058546 by karl

i have two recp,s in one box both are wired 12-2 and separate circuits one for lights 15 amp. . 20 amp for garage door opener do i need separate ground wire for each one to box or tie all together

On 2016-12-06 01:02:30.561082 by Anonymous

Pushmatic Circuit Panel: 3 wires; black wire to 20 amp breaker / red wire to 15/15 amp breaker, and white to ground. After several years the 20 amp breaker now trips when 15/15 breaker is on, and vise-versa. Could one or two breakers now be defective?

On 2016-11-26 02:27:19.092547 by (mod)

Is it a gas or electric dryer. Surely if electric it's got a dedicated 240V circuit, right?

Overloaded circuit, wiring error, loose connection?

On 2016-11-26 02:26:36.947962 by (mod)

Really posting

AUTHOR:Gabriel (no email)
COMMENT:I bought a new Samsung washer and dryer. Tube washer works fine, but when I turn on the dryer, the power goes our in the bedroom outlet and the dry turns off, but no breakers trip. The power goes out for only a moment. What could it be?

On 2016-11-22 22:31:26.457887 by Anonymous

derating solar wiring in panel

Question: main breaker is not switching off power to the electrical panel

(Sept 1, 2011) Tim Schwartz said:

I have a zebco panel and when i turn off the 100amp main i still have power, any advice?



Watch out: in any electrical panel, if you still have power when the main disconnect is in the "OFF" position then this is a VERY dangerous condition as you cannot, using normal homeowner controls, turn off electrical power in an emergency, and more, it is likely that the main disconnect is not going to trip on a large overcurrent and so is not protecting the equipment and building from an electrical fire.

The brand "Zebco" is not one I know, and I'd like to see photos of the equipment and all identifying labels and markings so that we can research the brand further. Use the CONTACT link found at page top, left, or bottom to send us photographs. (Zebco is a brand of fishing tackle).

On a few occasions I've encountered electrical wiring connections at which power was brought into an electrical panel from more than one feeder, wired or I should say "back-wired" to the panel bus through a subordinate circuit breaker. For example if someone installed a local or backup electrical generator and connected it to back feed the electrical panel through another breaker (without a proper isolation switch) you could find that the panel is energized even though the main disconnect was off.

Panel backfeeding without an isolation switch to prevent both main disconnect and backefeed source from powering the panel at the same time is improper and unsafe and would need to be connected.

Presuming that you don't have a back-fed panel from a second electrical source then you immediately need a licensed electrician to replace the faulty circuit breaker or if necessary the panel.

Question: When were houses commonly built with split outlets/receptacles?

(Oct 12, 2011) Maria S said:

When were houses commonly built with split outlets/receptacles? I am doing research to find out how many houses in the US may not have them.


Interesting Question, Maria.
My opinion based on research is that split receptacles would not have seen widespread residential use before 1965-1970 - I continue to research the topic.

I've posted my preliminary research and opinion above in this article

Question: how to identify the electric panel ampacity and voltage

(Feb 7, 2012) Bill R said:

in an apt bldg, each meter for each of the 50 apts contains an individual electric meter with a disconnect below it that appears to 'span' over 2 breakers but the 'bar' that spans over the 2 breakers reads 60 - does this mean that this is a 60 amp electric service?


Bill, it sounds as if you're describing a 2-pole 60-A main breaker - that's normally giving 240V service and 60 Amps as marked on the breaker.

Question: using a grid inverter

(Aug 21, 2012) inetdog said:

One notable exception to the limitation of one power source at a time is the use of a grid-tied inverter for solar PV generation. The grid-tied inverter is designed to synchronize to the utility voltage, and will only output power when the utility grid is present.

Question: open neutral wire at receptacle

(Nov 30, 2012) gary said:

i have a open nuetral at home showing at the recepacle i used a plug in tester and it shows that,the basement is finished no drop ceiling and upstairs as well where can i go from this point.


You need to trace the circuit wiring, Gary. There are quite a few devices that can help you do that - check online or at your local building supplier.

Question: apartment fire, aluminum electrical wire: does it need to be replaced?

(Mar 7, 2013) said:

A fire occured in a unit of an apartment building. all interior finished on the walls had to be replaced, the electrical wiring is aluminum. Does the wiring needs to be replaced with copper to meet the building code?


Charles, building codes don't explicitly require replacement of aluminum wiring though there are code sections that allow that interpretation.

Watch out: I'm not an expert on repairing fire-damaged wiring but it seems to me the concern would be that the wiring insulation has probably been compromised - made unsafe - by exposure to the heat of the fire. Therefore it's likely that an inspector would want it replaced regardless of whether it had been originally copper or aluminum conductor wiring.

Question: using an electrical tester to find hot wires

(Apr 3, 2014) gm1761 said:

I'm using the usual electrical tester to confirm if some areas where there once light fixtures are "hot." Most of my readings are correct as the tester works on installed fixtures and outlets. My problem arises when the tester does not show a hot area when the switch and light are both on. Any reasons for this?


GM I can't quite figure this one out. The only thought that occurs to me is a wiring snafu; if we connect a neon tester between two hot legs on the same phase (rather than a hot leg and a ground or neutral) it will now show current flow.

Question: power off in one room

(May 4, 2014) Anonymous said:

One whole room does not work


Anon if power is on for all circuits at the electrical panel then an electrician will trace the circuit to find the open connection. Meanwhile turn off that circuit to be safe.

Question: two wire circuit, no ground at switch boxes

(June 3, 2014) DanW said:

I have a two switch box with two wire no ground that controls the lights and ceiling fan. The light works but the ceiling fan does not. I have just installed a new fan and still have the same issue. I changed the switch for the fan to a new one. I am at a loss as to why the fan will not work. I have checked all connections and they are tight and secure. Help!


Typically the two wires to a switch are simply allowing the switch to interrupt the hot wire to a device. You also need a 3rd wire in the box, the neutral wire, to run the fan.

A DMM or VOM can confirm which are hot and neutral wires.mbe sure to reasd our article on using DMMs VOMs safely

By the way, the switch itself probably includes a grounding screw and should be grounded - so the wiring may be incomplete and not safe if you're missing proper grounding.

Question: trouble tracing wires in 24 pin cable

(June 24, 2014) Michael said:

Have a cable with 24 pin plugs on each end. Have good continuity from each pin from plug A to plug B; however, pin x and M are shorted together on Plug A but on Plug B pin x and M read open. How is that possible?


Perhaps an internal short between two wires in the cable or between 2 pins in the plug. On some cable assemblies individual wires may be deliberately joined as well, depending on the application.

(June 24, 2014) Michael said:

Shouldn't the short be able to be seen from either plug A or plug B?

Michael I surely don't have a clear idea of what you are testing.

In general if two wires are shorted together you will see continuity on both, but if you put a test current on A and A is also shorted to B you will probably see the current or signal on BOTH A and B at the other end of the cable.

Question: electrical problems in mobile home

(June 24, 2014) Danny said:

we have an older mobile home that has had no probs for 14 yrs,a few weeks ago all the lights and plugs went from 110v to 220v burned tvs cd players rite up so my ? is dose anyone know the reasons this happend and whats the repair that has to be done...thank you


Danny I'm not clear just what happened. You are describing what I'd expect to be found to be a voltage surge coming in from the power transformer. You'll want to check with your electrical company who may need to check the step-down transformer.

Keep in mind that other failures such as a lightning strike or a short circuit also cause power surges that damage equipment.

The repair will probably include replacing damaged equipment, diagnosing the cause, and if the cause is found to be fluctuating power you'll want to be sure your home has adequate surge protectors installed


(June 26, 2014) sandeep said:

Dear Team,

We are using a condensing fan in a unit input voltage is 380v but wn we are running it on the site its giving 600rpm as per fan specification at delta connection it will give 900 rpm we check the connection also its was delta. When we check this fan in our factory again we 900 rpm as per our desired.
I am confused why is this happening

Hello again sorry i didnt give enough info,there was a water leak under the kitchen sink rite under the sink is a 110v recptl it did not have a gfi present,thats when the trailer surged to 220v but upon inspection of the plug i didnt see any shorts they do however have the plug backwired


Backwiring is not reliable

Question: single wide mobile home electrical problems

(Aug 2, 2014) Anonymous said:

hello we have an older single wide,we have replaced the gas stove and water heater with electric units and they are working fine but although all the outlets read 117v there dose seem to be enough amps being pushed thru them when a load is put on any plugs the lights go very dim or out. thank you...Danny


Danny, we may be confusing voltage (nominally 120V so your 117V is normal) and amps or current. If lights dim I suspect either bad wiring connections or an overloaded circuit - too many things ripunning on one circuit. Check too that the ampacaty of the circuit breaker or fuse is properly matched to wire size so as to avoid a fire. Check too for problem brand breakers that may not be tripping earn they should in rennes to overload - aLso a fire risk.

Question: can I convert radiation into current?

(Aug 4, 2014) prasanna said:

Is there is any possibility of converting radiation into current



Solar radiation is used to heat water to drive a turbine or directly to produce electricity using photovoltaics.

Nuclear radiation is used (dangerously) in nuclear reactors to drive turbines to produce electricity.

Magnetic "radiation" or fields are key in the operation of electric motors.

Question: floors are vibrating

(Aug 14, 2014) said:

Hello. Me floors are vibrating like I have grounding issues. I don't know what it is and electricians are expensive. It is a constant vibration and it is strong, medium and light modes. Any ideas? Thanks!



Sounds like we're confusing building vibration with electrical grounding.

Question: defective light pole sensor dusk to dawn light

(Aug 23, 2014) Paul Catsburg said:

My exterior light pole had a defective sensor (automatic dusk to dawn type); I have since replaced the sensor, but the power to the light pole is non existent. I have checked all breakers at thE main panel, and still no power ? This is in an Onrraio Canada house built in 2003; is there something else that SHOULD BE CHECKED ?


Watch out for a dangerous buried broken electrical wire. I'd shut power off to the pole until an electrician has debugged the circuit.

Question: Eagle brand AC DC receptacle tester operating range

(Sept 16, 2014) al said:

I have an Eagle brand AC-DC 90 to 660 V neon receptacle tester. It works fine on 120 v, but I am wondering if I can stick this into a 240v outlet? It has no other markings on it.



Since your tester is marked as 90 to 660V and also as AC/DC, it is designed to handle voltages up to 660V which is more than the 240V you ask about - so yes.

WATCH OUT: making a mistake can still get you killed - such as touching live contacts or wires.

Question: aluminum ground wire has been cut, breakers are tripping

26 Sept 2014 George Nochta Santee CA said:

I have a rental built in the late '50s. The electric panel is an older 50 amp service with an aluminum wire ground that is routed to the water heater closet where it is grounded to the cold water supply line. My tenant says when she is using her clothes dryer and runs her vacuum at the same time. The 115 circuit breaker blows for the outlet the vacuum is plugged into. The dryer is on a dedicated 220 30 amp circuit. When I checked on my own, I found that the aluminum conductor had been cut apparently when someone had replaced the water heater at some point. Could this severed ground line be causing the interaction between the 200 30 amp dedicated circuit and the 115 15 amp breaker that is tripping?



Watch out: A missing electrical ground connection is DANGEROUS as the electrical system is then lacking a critical safety feature. That shoudl be repaired.

But a missing ground won't explain an overloaded circuit that trips the breaker; more likely the circuit is simply overloaded when both devices are running at once OR one of the devices is shorting to ground somewhere else.

Question: missing ground connection hazards, aluminum wiring, breaker is tripping

(Sept 25, 2014) George Nochta Santee CA said:
I have a rental built in the late '50s. The electric panel is an older 50 amp service with an aluminum wire ground that is routed to the water heater closet where it is grounded to the cold water supply line. My tenant says when she is using her clothes dryer and runs her vacuum at the same time. The 115 circuit breaker blows for the outlet the vacuum is plugged into. The dryer is on a dedicated 220 30 amp circuit. When I checked on my own, I found that the aluminum conductor had been cut apparently when someone had replaced the water heater at some point. Could this severed ground line be causing the interaction between the 200 30 amp dedicated circuit and the 115 15 amp breaker that is tripping?



A missing ground connection is DANGEROUS as the electrical system is then lacking a critical safety feature. That shoudl be repaired.

But a missing ground won't explain an overloaded circuit that trips the breaker; more likely the circuit is simply overloaded when both devices are running at once OR one of the devices is shorting to ground somewhere else.

Comment: U.K. Ring Circuit advantages

(Oct 20, 2014) Anonymous said:
The advantage of the ring circuit system used in the UK was that the circuit loop was fed at both ends so wire size could be halved. generally used in british kitchens. also the 220v circuit allows use of high power appliances like 2.5Kw 4 slice toasters and 3Kw tea kettles etc

Question: sparks when unplugging a hair dryer

(Nov 1, 2014) Anonymous said:
when unpluging and hair dryer had sparks at plug light is two rooms went out fuse isnt tripped but no power at plug


The electrical receptacle that has no power may have been switched off by a GFCI-protected circuit that is electrically "upstream" or ahead of the receptacle where you find no power. Look for a button that's tripped on the receptacle or on other GFCI receptacles such as in other baths nearby.

Watch out: it sounds as if the hair dryer is unsafe (or the local circuit is unsafe).

Question: placement of a light switch downstream from a GFCU

(Jan 2, 2015) curious said:
Can a light switch be placed downstream (load side) from a GFCI outlet to protect the 15a grounded outlet in a porcelain light fixture?


An electrician can certainly place a switch in a "outlet" (they say receptacle) circuit but I'm uncleaer on why that switch protects a light fixture. If you are powering the light from the same GFCI protected receptacle circuit (which is done in some cases) then if the switch and light are downstream from the GFCI and properly wired they should be receiving GFCI protection as well.

Question: fixing a missing outlet and circuits in a double wide mobile home

(Jan 22, 2015) Anonymous said:
We bought a 1978 double wide mobile home a few months back. My daughter's bedroom was missing a light fixture; upon installing it, we put in one of those bulbs which need to stay lit for at least 45 minutes for maximum effectiveness. When we left to pick her up from school, everything was fine- when we returned, there was no power at all to her room. We don't know what happened, and no matter what we have done to fix the situation, there is still no power... HELP



Question: electrical outlets are melting - what should I do?

3 April 2015 FRAN said:

I live in a rental house about 1400 sq. ft. I have some outlets that are melting from the inside out, I also have outlets that are loose and if you plug a lamp in, it wont turn on. I also have breakers that trip when you use a blow dryer, mini face fan or a leave blower outside. Sometimes the lights in the master bathroom flicker and then I have a wall with an outlet that just doesnt work when you plug in a boom box (this one is outside on my covered patio). I also have outdoor flood lights that only last 1 month. Flood light are expensive to be replacing every 30 days.(thats $51.00 in 3 months) What do I need to do?



Watch out: you are describing a serious building fire hazard that could result in loss, injury or worse.

You need an experienced electrician, on-site, to determine what's going on.

The problem could be that the building circuits are both overloaded and are not properly protected with the right fuse or circuit breaker; or possibly the building is wired with aluminum branch circuits, or there could be other wiring errors, over-fusing, or other mistakes, all of which are unsafe.

I'd much like to see some clear photos of what you are seeing on and inside the melting outlets.

Meanwhile, while waiting for your electrician:

1. TURN OFF any circuits that are behaving as you describe and verify (just plug in a lamp) that they are off

2. be sure that you have working and properly located smoke detectors.

Question: the realtor did not like my inspection report on the building's electrical service

(May 2, 2015) Anonymous said:
I inspected a main service, there was two 125 amp breakers for 250 volts; I wrote it for evaluation the realtor didn't like it.



Can you explain a bit what the defect was and how it was described?

If your report was factual and accurate you did the right thing.

The real estate agent has conflicting interests, wanting the sale to go as smoothly as possible and not liking you to report defects that might sound dangerous or expensive.

But if you as a building professional go to a site and then fail to observe and report on a costly or life-safety hazard that you could have observed, simply by directing your eye in that direction, you are responsible for what happens to building owners or occupants in the future. It's not necessary to kill the new owners to sell a home, nor are many home defects so costly that they raise a legitimate question about the financial viability of the deal.

Question: convert btus to tons

(July 20, 2015) Anonymous said:
55000 btu how many ton



BTU to TON conversions are given and detailed at

and at

Question: My dad wants to see articles cited by university professionals and engineers

(July 30, 2015) linette leong said:
need pro bono work father is 100 i am 64. on exterior of building is 2 wood doors covering an indoor circuit breaker panel and a disconnect switch without a cover. the doors have a horizontal airspace above these items and circular holes over electrical meters? above indoor circuit breaker panel and disconnect letting in rain and fog. these have rust. need better garage doors and locks cause someone comes in to do arson. father is more convinced if the information you send me is internet, written periodical with photos and written by engineering professors.

(July 30, 2015) linette leong said:
please email need pro bono work father is 100 i am 64. on exterior of building is 2 wood doors covering an indoor circuit breaker panel and a disconnect switch without a cover. the doors have a horizontal airspace above these items and circular holes over electrical meters? above indoor circuit breaker panel and disconnect letting in rain and fog. these have rust. need better garage doors and locks cause someone comes in to do arson. father is more convinced if the information you send me is internet, written periodicals with photos and written by engineering professors.


Linette, at the REFERENCES section as well as in the text of articles we include citations of supporting scholarly research. Articles at InspectApedia include a wide range of contributors including scholars and professionals from various fields. Search for ABOUT to see some of these frequent contributors. I agree that that information is an important support for the opinions voiced by repair people, service technicians, building inspectors, and other building professionals: it's necessary, but not sufficient.

Please use the CONTACT link found at page bottom to send me sharp photos of the conditions about which you are asking and we will be glad to comment further.

Question: I split a single 240 V circuit into two separate 110 V circuits.

(Aug 2, 2015) Michael said:
I split a single 240 V circuit into two separate 110 V circuits. I replaced the 240 V breaker with 2 110V breakers but did not pull new wire. Replaced the old receptacle with a junction box and ran the branch circuits from there. Now I read a small voltage, about 1-2 volts across the neutral and ground. Is it possible that a small current is induced in the neutral since the two "hot" lines run together in the same cable?



I suspect there is a nicked wire somewhere or a similar short, or that something is plugged into the circuit and is running.

By the way, if your system is sharing a neutral with two hot wires (as is probably the case from your description) you must tie the two 110V breakers together so that either of them can shut down both circuits.


Reader replies:

(Aug 3, 2015) Michael said:
Thanks Dan. Who would have thought that such a tiny nick (it took me forever to find it) would cause this.
As a follow up, I'm wondering about the need for a common internal trip breaker that you recommend. Obviously, some kind of tie will be needed if work is being performed on either of the branch circuits, but I do not understand the caution about exceeding the rating of the shared neutral.
If the existing circuit services a 40 A, 240 V load, wouldn't the shared neutral be sufficient to service two 20 A, 120 V loads?



The question isn't the adequacy of the neutral to carry the load. Indeed because the two poles are clipped into (most) panel buses such that we are guaranteed that the two poles are on opposite phases the neutral current is usually lower than the hot line current.

While you can buy "trip ties" that tie two breaker handles together they are not a great idea because of the possibility of a mechanical failure in which one breaker trips and the other does not. A factory-built two-pole circuit breaker has an internal trip mechanism that should trip both poles if there is an overcurrent on either of them. The reason we need this is the shared neutral. Take it from me (who got a hell of a shock), that the un-tripped pole will send live current down the common neutral line if something is plugged in or in use on that circuit.

Please see the details at


(Oct 18, 2015) Anonymous said:
Can I turn a single washing machine outlet into one that provides two places to plug in machine and lamp?


If it won't overload the electrical circuit an electrician can certainly convert a 120V single receptacle to a duplex one. But there may be a safety or other reason that that was not done in the first place - I can't guess without seeing the installation.

Question: what wire should i use 12-2 or 14-2

(Oct 29, 2015) harvey totter said:
i have a house built in the 1950 need to change some wire to so plugs what wire should i use 12-2 or 14-2



the thicker #12 wire is always safe on both 20A and 15A circuits, but you may find that older electrical boxes are overcrowded or wiring is just more difficult with the heavier wire. Or the boxes may be over-crowded, that would be improper, violate code, and be unsafe.

Therefore you can certainly use 14/2 (with ground) on your 15-amp circuits.

Question: Factory riveted ground wire broke

(Nov 21, 2015) Connie said:
Factory riveted ground wire broke when cleaning my Nutone bathroom ceiling light. Do I need
to have an electrician fix this. Light is working fine, and the fan seems to be a separate plug in.
LS 100 Nutone unit is no longer available even though the unit is only 12-yrs. old.


I think one should be able to repair the ground wire connection using a ground screw or clamp connector fastened in the same area of the metal fan body.

Question: insurance policy cancelled because I have a Zinsco electrical panel

(Nov 25, 2015) Wilson said:
I was advised by my homeowner insurance company that my policy is being cancelled because I have a Zinsco breaker panel. They referred me to your website to obtain additional information as it is what is being used by them to make the decision. I have attempted to fully understand the problem, but without success. I acknowledge the concerns over the breaker not providing adequate protection for overload protection. What I am missing is the proof of how many homes have burnt down as a result of the a fire or have just had minimal damage. Is there such documentation or is the company reacting as if "the sky is falling"? It appears the problem is mostly in areas of higher humidity or have continuous heavy electrical draw such as an AC or electric water heater. I live in CA and my house was built in 1981. At this point in time I can't find any information that would help me justify the expense of a replacement or the panel or finding a new insurance carrier. If an electrician inspects the panel and verifies it does not have an issue, should I be able to sleep at night knowing I am safe?



A number of insurance companies object, with reasonable basis, to insuring homes with electrical panels whose track record shows a failure to protect the home at rates stunningly worse than the industry in general. That has been demonstated more with FPE panels; though the data on Zinsco is also compelling the volume of field reports is less. It is important to understand that only a tiny fraction, perhaps 1 or 2% of electrical failures are ever reported through formal reporting mechanisms and that fire cause data is also incomplete as the evidence has burned as because ordinary fire officials are not trained in forensic engineering nor does anyone make the detailed, costly forensic analysis that would be required.

Imagine driving around in your car with seatbelts cut to a mere-thread. You won't be protected in a crash anywhere near the level you would be if you had an intact seatbelt. But, then, no crash has occurred, so you argue that your seat belts are fine: after all you've not been hurt.

No electrician can verify by visual inspection that a Zinsco panel is safe and intact, though she might discover the opposite if she or he observes burns and arcing in the panel or its components. Absence of evidence is not evidence of absence of a hazard. Worse, the physical removal and reinsertion of Zinsco breakers in order to make a detailed examination of the bus for arcing burns may actually increase the risk of a later failure since in some panels scoring the bus increases oxidation, corrosion, arcing later.


The cost of replacing an unreliable electrical component is less than 0.01% of the value of a typical home and in my opinion would be a smart investment. I agree that the case against Zinsco does not have as many field reports as some other hazards, but in my opinion the nature of the reports and an understanding of the failure mechanism makes the argument that these devices are unreliable a compelling one.


(Dec 8, 2015) GARRY LUTTMAN said:
I have a 2000 southern double wide an six outlets on the back outside wall have gone dead. there are know gf. outlets on this wall. were should i look for this problem.. thank you so much luttman-garry @ yahoo . com



If power is ON to the circuit supplying the outlets in question then the problem is somewhere between the breaker and the first receptacle that's "dead" - perhaps a loose or disconnected wire.

If there are other receptacles on the same circuit that go "dead" when you switch off the breaker, the live receptacle on the same circuit that is closest to the first "dead" one may be where the disconnection has occurred.

I'd ask for help from a licensed electrician, and to be most safe, I'd turn off the circuit.

Question: can I flip a ceiling electrical box over to be opened from the attic side?

(Mar 24, 2016) Micklo said:
I realize you can't bury a box behind drywall -but I need to move a light fixture to about 3 feet farther away from its current location. The box is in the ceiling open above to the attic. Is it permissible to pull the receptacle box up into the rafter a bit, then flip it over and put a cover plate on it after running another wire from it to the new receptacle location?


Sure - you are keeping the box visible and accessible.


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