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Is A 100 AMP Service Enough For Today's World

103K views 61 replies 21 participants last post by  the rock 
#1 ·
Hi All,

My mother-in-law passed away recently and left her home to my wife. For the time being we decided not to sell but rent. My wife thinks the house has only a 100 amp service. Is a 100 amp service enough in today's world of all the high tech gadgetry. The house has oil heat boiler, electric stove and dryer. If we need to increase the service to 200 amps what would the average cost be. The 1600 sq.ft. house is located in Boston and is approximately 65 years old.

Thanks
 
#2 ·
Elec. or gas water heater?

Central Air?

Window units? How many? 110/220?


The only way to know for SURE is to do a load calc. If you google that, I would imagine you'd find some you can use online. Or an electrician can do one for you.

As far as cost..........??(shrug)

$1000-$10,000 should cover it. :)

A lot depends on area. Someone closer to you might be able to shave those numbers down a little.
 
#3 ·
What "high tech gagetry" are you referring to other that the newfangled dryer and range?
Gagetry tends to be low consumption electronics. Things like TV's, computers and phone chargers are power misers in the scope of things.
Just because you have a lot of "things" doesn't mean they'll all draw a ton of power.

If this house was fine before what makes you think it won't be fine now??
 
#5 ·
Soon as you said electric stove & dryer I flag it as not enough. 200 amp service tends to be the most common but a tad over kill. Either way if you're goingto upgrade mind as well.
Around here we are about $2 k for panel, grounds & outside lines. The utility company hands line to the house.
 
#16 ·
I have a 60 amp circuit in my house. Electric stove, dryer and the normal gadgets. Small house 1200 sq ft. Never had a problem. I've been here for 22 years and never once blew the main.
 
#7 ·
How many times have you heard of a main breaker actually tripping?

A friend added a guest cabin with a hot tub and a sauna, both on 50 amp breakers. He has an electric stove and a dryer in the house. He decided to see how it works before upgrading to a 200 amp service. 5 years later, not one trip on the main 100 amp breaker.
 
#8 ·
I think it's an issue of space for more circuits in the box more than anything.

How often are all the circuits going to be loaded to the max at the same point in time anyways?
 
#13 ·
IMO unless you have a dual zone forced air HVAC system and more than 3 bedrooms 100 amps is sufficient.

When it comes to new gadgets, it's true that the average person these days has a different set of gadgets than we had 20 years ago but most of them use much less power.

We went from tube TV's and big stereo systems that gave off enough heat to warm half of the house to pocket sized MP3 players and LED screens that collectively use a fraction of what the floor model cabinet TV used to consume.

In the 80's we used 100 watt light bulbs in every single fixture. Now all 30 CFL's throughout my house use less energy than the 4 incandescent bulbs that were in my kitchen.
 
#14 ·
IMO unless you have a dual zone forced air HVAC system and more than 3 bedrooms 100 amps is sufficient.

When it comes to new gadgets, it's true that the average person these days has a different set of gadgets than we had 20 years ago but most of them use much less power.

We went from tube TV's and big stereo systems that gave off enough heat to warm half of the house to pocket sized MP3 players and LED screens that collectively use a fraction of what the floor model cabinet TV used to consume.

In the 80's we used 100 watt light bulbs in every single fixture. Now all 30 CFL's throughout my house use less energy than the 4 incandescent bulbs that were in my kitchen.
CRT tv's weren't that bad, and few people had multiple 60"TV's in their house back then.
 
#15 ·
Yes... Load calc's are the proper way.... maybe a sparky could indicate (not advise) the fat (extra safety margin) in those calcs.

But overall, unless you suspect renters are going to change anything significantly electrically (like put in a grow house), and you have experienced no problems to date..... many homes that are not abnormally electric dependent, that are 1600 sq feet, do fine on 100A.

And in general over the years, appliances/lights etc, have become much more electrically efficient.
 
#25 ·
The only thing that's changed is the amount of breakers I can put in there. And nothing has really changed. I had a 60 amp fuse panel and there were so many things hooked up to each fuse it wasn't even funny. Now I have exactly the same load on the panel as before. Now each circuit has it's own breaker.

There's suppose to be a ground?? :blink:

It's just attached to a copper water pipe like it was on the old one.

No one's dead yet and it's been 10 years.
 
#27 ·
Yer makin a funny and I don't get it. Play on words I suppose.

I figure the extra 40 amps are roaming around in the panel confused because they don't know where to go.
 
#29 ·
You changed the panel but I hope you changed the SE coming in or it can be a fire hazard. In addition to bonding I believe my apartment is required to install 2 6 ft rods in the ground. Maybe one for each leg I don' know.
Our electrician said a new code in one county he works in is one ground rod per hundred amps...gets a little messy with 400 amp services.
 
#43 ·
I can remember years ago working in an 30 family apt building and having the new owner check the 60 amp panels. The building super put nickels under the fuses because the fuses were blowing all of the time, owner went crazy.

House I just finished working on has 3 br's, 400amp service with a backup generator that runs everything. Automatically starts every week for 1 hour.
 
#49 ·
As said by others a load calc is the best solution. One must also remember that a 100amp service is not the max amp the service can use. One must also remember you do not count how many breakers/fuses there are and add up each breaker/fuse load for the load calc. Otherwise if that were true some folks would need a 1000amp service or bigger. Go through the home and make a list of how many lights at what wattage, list of TV's, appliances, heat sources, water pump? Hot water tank? TV Dish or cable box? Possibility of kids games? Computers? Vacuum?
 
#50 ·
100 amps X 240 volts = 24 kw

24 kw x 8 hours + 10 KW x 16 hours x 30 days = 10560 kwh x 16 cents/kwh =

$1690 a month electric bill if a 100 service was loaded only 8 hours a day.

Anybody pay this kind of bill? If not than 100 amps is more than adequate.
 
#54 ·
The service is based on highest peak load, not continuous draw. So when someone turns on the range and all the oven burners, the MW has the electric dryer and washer going and decides to dry there hair while using an electric heater in the room the main won't blow. Well, until the electric water heater switches on :blink:
 
#55 ·
Load

Actually, a residential service is rated per NEC load calculations including demand factors, not peak load.

The demand factor of 35% or 40%, depending on which method, is based on the probability of loads operating at the same time - coincident.

3 watts a square foot for general lighting, 1500 kva for small appliances and laundry, and so forth.

The question was is a 100 amp service too small? How many people have seen a tripped 100 amp caused by excessive load?
 
#56 ·
Fault.... Welcome aboard :thumbsup:

While you are over here, wonder if I can pose a question that was previously unanswered on the thread that had the AF tripping but only when all three lights were under load.

(I'm a GC, can wire a common residential with help/attention to NEC changes, but I'm clearly NO pro sparky and with only very basic understanding.)

But with regard to arc faults, which I guess is simply/basically current jumping through the air, ..... is the likelyhood of an arc fault situation sensative to (a function of) voltage or current.... or maybe both, or maybe primarily voltage or primarily current. (My reference would be in the neutral where current was limited/defined).

This is basically just curiosity and seeking more understanding.

TIA

Best

Peter
 
#58 ·
But with regard to arc faults, which I guess is simply/basically current jumping through the air, ..... is the likelyhood of an arc fault situation sensative to (a function of) voltage or current.... or maybe both, or maybe primarily voltage or primarily current.
I understand that sentence about as well as you understand arc faults. :blink: :laughing:

The closest answer is going to be "both". Without voltage, you will have no current flow. Without enough voltage to force current across an air gap, there will be no arc.

It takes only a relatively small amount of voltage to force an arc across a gap of 0.001", but it takes thousands of volts to force an arc over a gap of 1".

In either case, such an arc produces radio-frequency energy, which is what arc fault breakers look for. They analyze the intensity and frequency pattern of the signal to determine whether it's most likely a dangerous condition or just "background" noise caused by something like motor brushes.

Uh... what was the question?
 
#57 · (Edited)
Arc fault

The cause of many electrical fires in homes (and Apartments, etc) was determined to be the failure of the standard circuit breaker to detect common occurrences like a bad connection at a receptacle, frayed cords, loose wire nuts, broken appliances, and similar problems. The technology available today is capable of responding to these problems and hopefully, prevent fires.

The whole idea of AFCI was to sense "low level arcing faults" that will not trip a standard circuit breaker but will burn your house down. We have all seen and heard the arcing when a frayed cord shorts out. You can see the arc, a puff of smoke, and hear the "bacon frying" sizzling sound. The nature of this high frequency arcing current is what the AFCI is designed to detect.

Unfortunately the earliest designs would also trip when motor brushes arced, dimmers were poorly designed, switching power supplies of lights and appliances were poorly designed, and so forth. Gave the AFCI a bad rap, and deservedly so.

Newer designs are supposed to be more sophisticated and less prone to false tripping.

In the case of LED fixtures and incandescents being on the same circuit and tripping the AFCI, I doubt the incandescents are the problem. Could be wiring problem like a bad splice, wire broken under the insulation, bad switch or dimmer. I suspect the LED's could be the culprit. Try removing the LED fixtures from the circuit and see what happens.

And Elvis has left the building.....
 
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