# Attention elecritians! Home electrical system question... **URL:** \ **Category:** Factual Questions\ **Created:** [March 25, 2003, 5:34pm UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073 "2003-03-25T17:34:46Z")\ **Posts on this page:** 10\ **Page:** 2
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [March 26, 2003, 12:43am UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073/21 "2003-03-26T00:43:22Z")
Amazingly, some house don’t have a main disconnect. If such is the case, you can look at the meter to see how many amps it’s good for. Somewhere on the bottom half of the face will be a number such as 30A or 100A, listing its maximum capacity. Assuming the point of asking potential clients about their electrical service is to identify folks trying to live a high-tech life on a 30-amp service with four fuses, you could ask more basic questions like: Fuses or circuit breakers? How many circuit breakers? What are the numbers (eg: amps) on the double-wide breakers? Probably more useful from an underwriting standpoint is to find out if their wiring is copper or aluminum, and what brand their panel is. Some of the older ones (such as Federal Pacific) have lost their UL listings for being poorly made and won’t trip out ever if overloaded, and poorly-done aluminum wiring connected to a new 200-amp panel can be more dangerous than an old fusebox. I’m assuming and hoping that an agent actually visits new clients to get accurate underwriting info. ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [March 26, 2003, 5:09am UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073/22 "2003-03-26T05:09:39Z")
> [@](#): > > \*Originally posted by Crafter\_Man \* > \*\ ***Whuckfistle** : We’re all in agreement about “adding up breakers.” **NutMagnet** originally said that it’s O.K. if the cumulative rating of all the breakers exceeds the service rating, and I was simply agreeing with him. Please re-read the previous posts. \*\* Right, I wasn`t attempting to correct you. I was trying to back you up with via the NEC. I did read the previous posts and no-one mentioned the NEC or the 80% rule. Sorry if it came off otherwise. ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [March 26, 2003, 1:23pm UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073/23 "2003-03-26T13:23:59Z")
> [@](#): > > \*Originally posted by whuckfistle \* > **I did read the previous posts and no-one mentioned the NEC or the 80% rule.** Appreciate this information. I didn’t know about the 42 circuit limit or 80% rule. ---
**Author:** ![House](https://avatars.discourse-cdn.com/v4/letter/h/90db22/32.png) [@House](https://boards.straightdope.com/u/House)\ **Post date:** [March 26, 2003, 2:15pm UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073/24 "2003-03-26T14:15:43Z")
> [@](#): > > \*Originally posted by ZenBeam \* > \*\*The point of my answer is that you can’t expect people to give you accurate answers to this question. Most people just don’t have that good of an understanding of electricity. 220 is almost certainly the voltage, but 120 might be also. 60 might be the value you want, or it might be the frequency the person is remembering. 60, 75, and 100 might be the wattage of the last light bulb the person remembers changing. > > Presumably, your customers aren’t intentionally lying to you, but how can you legitimately have any expectation that any answer you receive is correct? If I may ask, what is the consequence of them telling you the wrong number? Does it affect their premium? Suppose the person who said they had a 220 amp service really has a 100 amp or 150 amp service, and their house burns down due to an electrical fire. Is their coverage void? There must be some consequence, or else why even ask the question. > > I’ll get off my soapbox now… \*\* Our underwriting guidelines (as well as many other companies) state that if a home’s electrical system has less than 100 amp service, we will not write the policy. We do ask if it uses breakers or fuses to help us determine amperage. Suprisingly, ZB, many people do know their service rating. In many cases where older homes are insured, there may be an inspection to verify this. ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [March 26, 2003, 5:02pm UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073/25 "2003-03-26T17:02:00Z")
> [@](#): > > \*Originally posted by House \* > \*\*I work for an insurance company and when I ask potential policy-holders information about their electrical system, I get a variety of answers. > > Both questions are about amps: How many amps does the electrical system use? I’ve heard of 60, 100, and 200. Are there typically more that can exist in a house (ie 75, 120, etc.)? I’ve been getting people telling me it is 220, but isn’t that voltage? > > Also, if a home uses circuit breakers, does that automatically mean the electrical system is at least 100 amps? > > Thanks. \*\* Amp usage is irrelevant. Amp ratings are typically 60, 100,150, 200 amps available to the user (but the main breaker can only be loaded 80%). The restriction being the size of the feeder coming into the house from the transformer and the size of the main breaker that feeds the service. 240 is the typical voltage present between phases. A house with breakers does not mean that the house has at least 100 amps. There are breaker panels that are rated at 60 amps with a 60 amp main breaker. **Crafter\_Man** - the NEC does not specify a limit of the combined cumulative ratings of the circuit breakers in the panel. In your case you could have a 200 amp panel with 1000 amps of cumulative breaker ratings and not be in violation. The only thing the code specifies is a 42 circuit limit and an 80% load on the main breaker. So in effect you can only load the service up to 160 amps continuous (for your 200 amp panel). Some larger homes will have 2-200 amp panels for the service giving them a 320 amp combined total load capability. ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [March 26, 2003, 6:00pm UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073/26 "2003-03-26T18:00:54Z")
How the hell did that happen? Way ignore the above post. ---
**Author:** ![casdave](https://avatars.discourse-cdn.com/v4/letter/c/c6cbf5/32.png) [@casdave](https://boards.straightdope.com/u/casdave)\ **Post date:** [March 26, 2003, 6:11pm UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073/27 "2003-03-26T18:11:20Z")
The post by **Whuckfistle** is exactly why I stated earlier on that the way to determine the supply to a dwelling, or any other consumer, is to look at the supply contract. I does not matter is you have a 1zillion amp breaker, it does matter what power you are contracted for. In the contract the supplier will state the agreed price per unit, often with additions for consumption above the agreed contract limit, but there will also be some statement in the contract that which will specify the maximum supply. The maximum supply is always higher than the contract supply. The contract supply might even have things in it such as short term peak demand penalties. The distribution system in the dwelling, ie your fuse box-isolator etc, must be able to cope with maximum supply available continuosly and be able to disconnect the system under fault conditions. So if you are contracted for a 100amp supply, then you could have a 200amp isolator and fusebox, however your protection device (the incming supply fuse) would still be rated at 100 amps. This is why you cannot take as gospel the current rating that is moulded into the body of your isolator or fusebox as being your supply from your electricity company. ---
**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\ **Post date:** [March 27, 2003, 5:16pm UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073/28 "2003-03-27T17:16:37Z")
> [@](#): > > In the contract the supplier will state the agreed price per unit, often with additions for consumption above the agreed contract limit, but there will also be some statement in the contract that which will specify the maximum supply. **casdave** , I’ve never heard of anything like that for residences in the US. I _think_ some businesses have contracts set up like that, but I don’t really know that. ---
**Author:** ![Ezstrete](https://avatars.discourse-cdn.com/v4/letter/e/7ea924/32.png) [@Ezstrete](https://boards.straightdope.com/u/Ezstrete)\ **Post date:** [March 27, 2003, 6:26pm UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073/29 "2003-03-27T18:26:16Z")
casdave— Residential contract------ What the heck izzat? Please enlighten ---
**Author:** ![casdave](https://avatars.discourse-cdn.com/v4/letter/c/c6cbf5/32.png) [@casdave](https://boards.straightdope.com/u/casdave)\ **Post date:** [March 27, 2003, 7:17pm UTC](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073/30 "2003-03-27T19:17:32Z")
No matter who your supplier is, there will be a set of terms and conditions. This will stipulate methods of payment, deadlines for payment, possibly who to call in the event of service failure, all that kind of stuff. You may not have the contract in your house, but your supplier will only provide services under certain conditions and these have to be specified. If you do not have the contract, then you will be able to contact your service provider and they are obliged to send you the correct paperwork. Many domestic users are unaware that they have a contract, simply because they have not seen one, it does exist and will not be as complex as an industrial contract but you definately have one, it would be very difficult to sue for non-payment without one because the company has to prove that you agreed to pay for the service they provide. [Previous page](https://boards.straightdope.com/t/attention-elecritians-home-electrical-system-question/164073.md?page=1)