checking out a house's electrical system

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

RustyShackleford

Minister of Fire
Jan 6, 2009
1,028
NC
Knowing that I'm an electrical/computer engineer who has done a fair amount of wiring on my own house, a friend has asked me to look at the electrical system in the house they just bought to "see if anything looks weird". They had a standard pre-sale inspection done, but the guy just did some pretty superficial stuff like checking that outlets were grounded and cover plates installed, and added some boiler-plate about having a licensed electrician inspect the system. There's no reason to believe anything is wrong. I'm not going to be paid, and I don't intend to assume any liability. All that being said, I'm wondering what people would suggest I do in spending an hour or so having a look. Here's what I've thought of so far:

1. Check for correct polarity and grounds using a simple circuit tester (as the pre-sale inspection did).
2. Open up a box or two and see if the wiring seems to have been done "in a workmanlike fashion".
3. Pull the cover off the load-center and see if things look kosher.
4. Turn on most of the big loads and see how much the voltage drops.
5. Note any aluminum wire.
...

TIA.
 
Last edited:

Rusty18

Member
Nov 3, 2018
71
Belpre oh
Depends on the age of the house. Have seen “remodels” that ran Romex out of a new panel right up the attic where it was spliced on original tube and wire. Speaking of the attic, seems to be a good spot for one feed to branch off 8 different ways and make some (attempt to) wire nut connections that have no chance of fitting in the box. Another one is multiple branches running back on one neutral (hard to identify in an hour inspection)(should have same number of neutral/ground/circuits, not a guarantee there isnt some funny business in a box down stream but it’s a good start). I have 12/4 with 3 hot 120’s and a common neutral (thank you previous owner :confused:). since you are gonna have the cover off the panel take an amp clamp to check loads on circuits when you have everything turned on. And finally the condition of the bus bar in the panel, rotten stabs can lead to a full replacement when the rest of the panel looks good.

good luck!
 

EbS-P

Minister of Fire
Jan 19, 2019
1,163
SE North Carolina
What I wish I had done 10 years ago when the house was empty was correctly identify every outlet/fixture to its corresponding breaker. It would have identified that the kitchen remodel that was done before we bought the house had plugged the 1800w microwave as on an old circuit that had 8 other outlets and ceiling fan and lights. I and then I hope I would have found that the just used the push-in connectectors on the back of a 50 year old outlet because the screw terminals were all full. Had an intermittent m wave for a week then no m wave as it melted the wires in the push-in terminal.

bigger job than an hour but worth it I think. I does depend on how many modifications have been made to the original wiring. Mine is all over the place now. Flipping a breaker is kinda like cow plop bingo. You know you end up with some poop but your not sure where.

Evan
 

zrock

Minister of Fire
Dec 2, 2017
1,117
bc
if i was your friend i would have told the inspector to do a proper inspection and if he was uncomfortable doing the electrical to have a licensed electrician do it... If he skimped their where else did they skimp? The inspector should have opened up the electrical panel, outlets, and climbed up into the attic and areas looking for wiring and issues... That's what you pay a inspector for.

Last home inspection i had the inspector did electrical and pointed out half the home was alum wire and a lot of poor connections.. It came down to the house was going to need a total rewire
 
  • Like
Reactions: fbelec

peakbagger

Minister of Fire
Jul 11, 2008
6,460
Northern NH
Make sure the panel is not a Federal Pacific, they have known issues. Open up the panel and see if someone doubled up hots on individual beakers. The vast majority of breakers are only rated for one wire to be connected.
 

RustyShackleford

Minister of Fire
Jan 6, 2009
1,028
NC
And finally the condition of the bus bar in the panel, rotten stabs can lead to a full replacement when the rest of the panel looks good.
Sorry @Rusty18 , but what do you mean by "rotten stabs" ?
 

xman23

Minister of Fire
Oct 7, 2008
2,331
Lackawaxen PA
I have a few of those "rotten stabs" They are a male blade that the circuit breaker is pushed down on. It's a spring contact. Under load it tends to arc and burn the stab. The result is blinking lights.
 
  • Like
Reactions: fbelec

Rusty18

Member
Nov 3, 2018
71
Belpre oh
Sorry @Rusty18 , but what do you mean by "rotten stabs" ?
The part of the bus bar that sticks out and actually makes contact with the breaker.

The 3 or 4 I’ve seen in residential box’s appeared to be from crap being packed around them and holding moisture and/or providing a very low current path to ground causing that one area to corrode faster than the rest of the box (my opinion). Shows the same symptoms as a rotten conductor, browns outs under load, sometimes there’s voltage sometimes there isn’t. When they get that rotten though it will usually break off and come out stuck inside the breaker.
 

Rusty18

Member
Nov 3, 2018
71
Belpre oh
B624E86C-5F59-4A6C-861A-0FD23658F438.jpeg
See the “stabs” sticking up down the middle?
 

peakbagger

Minister of Fire
Jul 11, 2008
6,460
Northern NH
Rotten stabs are usually brand specific. It can be made worse by installation practices. The panel should be mounted to a piece of plywood attached to the masonry wall behind it, preferably with spacer behind the plywood to allow air flow. Direct mounted panels on a cold masonry wall can drive moisture from the wall into the panel and it can condense on the internal components. Low grade copper or copper plating can eventually deteriorate.
 
  • Like
Reactions: Rusty18

stoveliker

Minister of Fire
Nov 17, 2019
1,469
Eastern Long Island NY
Not an expert, but go in the attic. And stay there for a while. I found multiple pigtail connections that were not taped and not in a box. with insulation stripped so far back that I could touch live wite... And under the fiberglass batts that were in between the joists. Sparks waiting to happen. I put them all in boxes.
 
  • Like
Reactions: fbelec

RustyShackleford

Minister of Fire
Jan 6, 2009
1,028
NC
Thanks !
 

begreen

Mooderator
Staff member
Nov 18, 2005
89,456
South Puget Sound, WA
Make sure the panel is not a Federal Pacific, they have known issues.
We say that about Zinsco (Sylvania) panels locally.

While in the panel, feel each breaker for warmth. Also, check the screw tightness on each breaker and neutral connection. I was surprised at how many loose ones I have found over the years.
 

Rusty18

Member
Nov 3, 2018
71
Belpre oh
We say that about Zinsco (Sylvania) panels locally.

While in the panel, feel each breaker for warmth. Also, check the screw tightness on each breaker and neutral connection. I was surprised at how many loose ones I have found over the years.
Wadsworth too.
 

fbelec

Minister of Fire
Nov 23, 2005
3,044
Massachusetts
also check the main breaker and the breakers below the main for water stains. if it is wet or there are water stains on the side of the breaker that faces up then those breakers and the main are junk. it would force the home owner to either replace all the circuit breakers or do a panel change. per national electrical code. then first order of business is to check out the service outside. if it is a cable to the top of the meter then make sure the top of the cable where it goes into the meter has uncracked or flexible clay or silicone
 

peakbagger

Minister of Fire
Jul 11, 2008
6,460
Northern NH
Panel replacements seem to be a popular issue that comes up on home inspections when people are selling homes. Rarely do older homes have clean code compliant electrical panels. 60 Amp services were popular up into the 1960s and at one point in the 80s states were trying to limit home services to 100 Amps max to reduce electric demand. I know my 200 Amp panel is running short of spaces as I have a lot of 240 volt standard size breakers taking up space. I could use the half size breakers to take up less space on the bus but that does not help with all the wiring run in the panel. Changing out a old panel is not that hard as long as the incoming capacity does not change but in most cases homeowners or code require an upgrade to higher amperage. In that case the incoming service has to be upgraded and that is above the ability of most homeowners.

I know that when I sold my parents1960s home that the panel was marginal and should have been replaced. I had several offers over asking price so I let the first buyer counter after the inspection knowing that if they came back with a long expensive list I would just call up the next person on the list. I did not get a copy of the report but the panel did not come up. Turned out they hit me up for radon removal. I gave them a discount on their original offer (still over the listing price) in exchange for them signing off for any defect known or unknown to get it over with. The market was not as hot as it is now. No doubt a lot of buyers are eating a lot defects by waiving inspections.

More than a few folks installing solar are using it as an excuse to upgrade their electrical panel so that they can deduct a portion of it using the solar credit.
 

fbelec

Minister of Fire
Nov 23, 2005
3,044
Massachusetts
it's getting harder and harder to do what the home owner wants and keep one panel to curve their confusion. the half breaker is now going away because if you add anything it has to be powered be a arc fault breaker. they don't make them in half size so they take up a full size spot. and with the size of houses and the amount of circuits they have two panels are needed. i serve one home in concord ma that is over 10,000 square feet the house has 4 panels and they are all full next is a 5th panel. if a customer wants a service upgrade we go from 100 amps to 200 amps just because they wanted to. the electric company usually wants to know if there is a current increase and most times no. now with car chargers there will be. so the increase in current means bigger pole transformers or less houses being feed by that transformer.