I've been racking my brain trying to find this in the code book, but I have a customer who has a 100 amp service and all but two slots are full. He wants a total of three circuits added. One of them is for a 50 amp hot tub. I just need to know what amperage will this panel max out?
Maximum amperage of circuits in service panel
- Thread starter slapnuts
- Start date
- Status
- Location
- Massachusetts
Re: Maximum amperage of circuits in service panel
Just a guess, 100 Amps.
bphgravity
Senior Member
- Location
- Florida
Re: Maximum amperage of circuits in service panel
If the service is 100-amps, then most likely the service entrance conductors are only rated for 100-amps. The 100-amps was originally calculated for the total demand load that the dwelling would draw.
To add a load as large as 50-amps will most likely require you to upgrade the service to handle the additional load. To be sure, calculate the total connected load of the existing system, apply the demand factors, and add in the new circuit loads. If you come out larger than about 24,000 volt-amps, you will need to increase the service size.
If you come in below 100-amp service load, the circuits can be added to the panel unless you exceed 42 circuits or the total amount of circuits allowed per the manufacturers specifications of the panel. You may also add a sub-panel off the service panel if desired.
If the service is 100-amps, then most likely the service entrance conductors are only rated for 100-amps. The 100-amps was originally calculated for the total demand load that the dwelling would draw.
To add a load as large as 50-amps will most likely require you to upgrade the service to handle the additional load. To be sure, calculate the total connected load of the existing system, apply the demand factors, and add in the new circuit loads. If you come out larger than about 24,000 volt-amps, you will need to increase the service size.
If you come in below 100-amp service load, the circuits can be added to the panel unless you exceed 42 circuits or the total amount of circuits allowed per the manufacturers specifications of the panel. You may also add a sub-panel off the service panel if desired.
Re: Maximum amperage of circuits in service panel
The service will "max out" when it reaches 100 amps long enough. The number of breakers and the sum of the face value of these breakers have no bearing on the situation. You need to do a load calculation with the known loads being used on a daily basis.
In reality, I would suggest a service upgrade. A typical home with a Hot Tub has out grown a 100 amp service.
Roger
The service will "max out" when it reaches 100 amps long enough. The number of breakers and the sum of the face value of these breakers have no bearing on the situation. You need to do a load calculation with the known loads being used on a daily basis.
In reality, I would suggest a service upgrade. A typical home with a Hot Tub has out grown a 100 amp service.
Roger
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Re: Maximum amperage of circuits in service panel
Roger is correct an upgrade should be considered. Adding one or two more circuits, 20 A is no problem. The hot tub would most likely be the major load on the panel if added.
Roger is correct an upgrade should be considered. Adding one or two more circuits, 20 A is no problem. The hot tub would most likely be the major load on the panel if added.
frenchelectrican
Senior Member
- Location
- Nord'est Wisconsin et Paris France
Re: Maximum amperage of circuits in service panel
i work on few homes have hot tubs there with 50 amps feeder to hot tub and i have a habit to change over the service from 100a to 200a to advoild the conflect ( sorry for spelling) and have more room to upgrade as need few of my comster were little suprsed what i say to change over from little 100 to 200 and i say best thing i always do is check the load what they use it everyday including central air or whatever is the largest load on it then sum it up and many time it was pretty close to the limit with 100 amp service and one house i did work on not too long ago i have to up grade from 200 to 400 amp service ( a suprise have big hot tub and swimming pool there ) so that slove my headache there
but really best way to be ahead of game if heard word hot tub best bet to check the service to see have room only 2 house i work on i left on 100 due that comuster have mostly gaz fired devices including hot tub that was my first one to hear a gaz fired unit
merci marc
i work on few homes have hot tubs there with 50 amps feeder to hot tub and i have a habit to change over the service from 100a to 200a to advoild the conflect ( sorry for spelling) and have more room to upgrade as need few of my comster were little suprsed what i say to change over from little 100 to 200 and i say best thing i always do is check the load what they use it everyday including central air or whatever is the largest load on it then sum it up and many time it was pretty close to the limit with 100 amp service and one house i did work on not too long ago i have to up grade from 200 to 400 amp service ( a suprise have big hot tub and swimming pool there ) so that slove my headache there
but really best way to be ahead of game if heard word hot tub best bet to check the service to see have room only 2 house i work on i left on 100 due that comuster have mostly gaz fired devices including hot tub that was my first one to hear a gaz fired unit
merci marc
Re: Maximum amperage of circuits in service panel
Bennie, How about reconsidering your response by going to the National Electrical Contractors site for code of the day... at .....http://neca-neis.org/cqd/index.cfm?fuseaction=showArchiveQuestion&id=859
Bennie, How about reconsidering your response by going to the National Electrical Contractors site for code of the day... at .....http://neca-neis.org/cqd/index.cfm?fuseaction=showArchiveQuestion&id=859
- Location
- Massachusetts
Re: Maximum amperage of circuits in service panel
[ July 03, 2003, 05:44 PM: Message edited by: iwire ]
So does this mean I can put in a 200 amp breaker and draw 200 amps?
[ July 03, 2003, 05:44 PM: Message edited by: iwire ]
Re: Maximum amperage of circuits in service panel
Iwire....make any conclusion you wish, I will paste the question and answer from the National Electrical Contractors Association....
Wednesday, December 19, 2001
Question:
Could you please explain how you came up with ?a 100-ampere rated panel will have 20 spaces for overcurrent devices?" NEC 2002 ? 408.15 states, that ?a 2-pole circuit breaker shall be considered two overcurrent devices? and since the rating for each space is generally limited to 10 amperes per pole (space), therefore, a 100-ampere rated panel should have only 10 spaces for overcurrent devices.
Answer:
Assuming a 2-pole, 100-ampere, circuit breaker panel, there are two 100-ampere copper bus that serve the panel. Each A 100-ampere bus carries 10 spaces (10 amperes per pole) times the two buses, equaling 20 spaces for a 100-ampere panel. A 100-ampere, 3-phase panel would have three buses and would have 30 spaces.
Section: 408.15
Source: Charlie Trout
Their site is: http://neca-neis.org/cqd/index.cfm?fuseaction=showArchiveQuestion&id=859
Iwire....make any conclusion you wish, I will paste the question and answer from the National Electrical Contractors Association....
Wednesday, December 19, 2001
Question:
Could you please explain how you came up with ?a 100-ampere rated panel will have 20 spaces for overcurrent devices?" NEC 2002 ? 408.15 states, that ?a 2-pole circuit breaker shall be considered two overcurrent devices? and since the rating for each space is generally limited to 10 amperes per pole (space), therefore, a 100-ampere rated panel should have only 10 spaces for overcurrent devices.
Answer:
Assuming a 2-pole, 100-ampere, circuit breaker panel, there are two 100-ampere copper bus that serve the panel. Each A 100-ampere bus carries 10 spaces (10 amperes per pole) times the two buses, equaling 20 spaces for a 100-ampere panel. A 100-ampere, 3-phase panel would have three buses and would have 30 spaces.
Section: 408.15
Source: Charlie Trout
Their site is: http://neca-neis.org/cqd/index.cfm?fuseaction=showArchiveQuestion&id=859
daveb.inva
Member
- Location
- Virginia
Re: Maximum amperage of circuits in service panel
sbshvac,
what you said and whats on that page are two different things.
Just because each buss is rated for 100a doesnt mean that since there are two 100a busses you have 200a of capacity.
All that page is talking about is how they figure how many spaces will be in a panel.
408.15 is just the article limiting lighting and appliance panelboards to 42 overcurrent devices.
sbshvac,
what you said and whats on that page are two different things.
Just because each buss is rated for 100a doesnt mean that since there are two 100a busses you have 200a of capacity.
All that page is talking about is how they figure how many spaces will be in a panel.
408.15 is just the article limiting lighting and appliance panelboards to 42 overcurrent devices.
- Location
- Massachusetts
Re: Maximum amperage of circuits in service panel
All I saw on your link which I looked at the first time you posted it, was how they figure the spaces in a panel.
Well thanks
All I saw on your link which I looked at the first time you posted it, was how they figure the spaces in a panel.
jtb
Senior Member
- Location
- Pennsylvania
Re: Maximum amperage of circuits in service panel
???? Using that logic, I guess you can't have a 15A breaker in any space...???
???? Using that logic, I guess you can't have a 15A breaker in any space...???
websparky
Senior Member
- Location
- Cleveland, Ohio
Re: Maximum amperage of circuits in service panel
I'm with bphgravity
I'm with bphgravity
- Status