load calculation for 200 amp service feeding two main breaker panels

[cubgirl]

i have 2 120V circuits in that kitchen and the microwave & refrigerator are using them. why put in an extra circuit? just use the ones you already have.

while adding an extra circuit might be easy and cost effective for you, but it's not for me. i'd have to hire someone and be in a real jam (i.e., no enough circuits) to add an extra circuit.

 

[Glock23gp]

That's fine. I was explaining if I were to do it as new construction.

Your range is calculated at 8k not 10k as stated in table 220.55 column C. Up to 12kw is to be rated at 8k (first row)

Your 2k cooktop also on that table falls under column A (first row also) so is rated at 80% of that 2k nameplate or 1600 va

Sent from my SAMSUNG-SM-T337A using Tapatalk

 

[Sahib]

looked it up... OPTIONAL METHOD: ONE-FAMILY DWELLINGS

so it can't be used in this situation.

What if you get two services instead of one now? What is the cost implication in that case?

 

[donaldelectrician]

What if you get two services instead of one now? What is the cost implication in that case?

Well it will make it easier to Split when selling .


Some thing to think about .


Don

 

[kwired]

right but my question was are they left off completely because they're embedded in 220.52A with the kitchen circuits??

they have to be part of the load somewhere... i'm thinking they're hidden in 220.52A

anyway, i took them off the fixed appliance section. made the amp go down a little.

I would add an extra small appliance circuit for them just like how I would wire it if it were new with a dedicated circuit feeding them

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You are required to have at least two SABC's. They are figured in load calculation @ 1500 VA each. If you determine for whatever reason you need more SABC's you need to add 1500VA for each additional SABC.

 

[Smart $]

looked it up... OPTIONAL METHOD: ONE-FAMILY DWELLINGS


so it can't be used in this situation.

I don't know where you got that but actual Code text says "Dwelling Unit". The optional method of 220.82 can apply to any individual dwelling unit, whether a single building or one of a multi-unit building.

220.83 may also apply for both of your units are existing.

 

[cubgirl]

hey again...

i looked up the multi-family optional method. i came across a table 220.32 (attached) which was my 1st clue this method wasn't for me. it didn't have demand factors for 2 units.

so i found this...

"A word about two-family dwellings. The feeder for a two-family dwelling unit is calculated using the standard method in Part III of Art. 220. When that calculated load exceeds the calculation for three identical units using the optional method of 220.84, the lesser of the two calculations is permitted to be used [220.85]."

one of my units is ~ 500 sq ft... the other ~ 1582 sq ft. there are not 3 identical units in this building. so i decided the optional method was not an option in this situation.

also, this building was my office for several years. it has sign lighting outside that i did not include, mostly because i'm not using it, and because i wasn't sure where it went. (maybe under fixed appliances?) because it's a commercial building also zoned residential, i'm using the residential standard method for each unit, not commercial. i'll rent to a business or a resident, depending on the tenant.

my city is still on 2002 NEC. i think i'm using the 2014 standard method and not sure of any changes in the codes. also not sure if this affects anything at all.

bottom line is i wanted to do a sanity check on the electrician's work. i asked for the following:
1) service to be split between the two units
2) grouped disconnects outside (the quick pull rule)
3) 125A to each unit
4) space in unit 2 panel for DP 60A breaker to feed 6-2 wire to new tankless h2o heater

i was told yes yes ok but when they were done, i had my original 200A service feeding two 100A panels in each unit. i became frustrated and started researching electrical systems and found load calcs. before last week i'd never heard about load calculations on electric systems. this week, i'm doing 'em :lol:

i was surprised to find that unit 1 needs 150A and unit 2 needs 125A. had the contractor given me what i asked for, i'd never done my own load calc.

i'll try to figure out your technical comments & utilize anything to make my calculations more accurate. i'm using this data to negotiate a fix on what i've got.

thank you all for sharing your knowledge.
i'm learning a lot fast
cub

 

[cubgirl]

You are required to have at least two SABC's. They are figured in load calculation @ 1500 VA each. If you determine for whatever reason you need more SABC's you need to add 1500VA for each additional SABC.

what is a SABC?

thanks
cub

 

[donaldelectrician]

SABC are the required Small Appliance Branch Circuits in a Residence . You are required to have 2 - 20 A Circuits in the Kitchen , usually Counter Tops and Dining Room SABC Ratted at 1500 W each for for each Residence.Load Calc for each Residence .

It is not uncommon to have Several SABC 's in a Modern Kitchen , Dining Room , Pantry .These 1500 W Circuits will be subject to the Demand Factors of the Service of Dwelling .



Don

 

[cubgirl]

What if you get two services instead of one now? What is the cost implication in that case?

you mean two service entrance cables instead of one? if i could upgrade service, why spend time & money installing two services? the service is split between the tenants at the meter. i don't see a benefit to two separate services but again, my scope is narrow...

 

[cubgirl]

That's fine. I was explaining if I were to do it as new construction.

Your range is calculated at 8k not 10k as stated in table 220.55 column C. Up to 12kw is to be rated at 8k (first row)

Your 2k cooktop also on that table falls under column A (first row also) so is rated at 80% of that 2k nameplate or 1600 va

Sent from my SAMSUNG-SM-T337A using Tapatalk

yes the range stuff is confusing. i should've taken it to the max in my table, 11.99 (NEC limit & limiton spreadsheet). here's what is on the owner's manual (pic attached). why does the NEC not allow folks to put in the actual & limits it? maybe because it's not continuous use??

anyway, i think i should change it to 11.99 kW.

thanks
cub

 

[cubgirl]

SABC are the required Small Appliance Branch Circuits in a Residence . You are required to have 2 - 20 A Circuits in the Kitchen , usually Counter Tops and Dining Room SABC Ratted at 1500 W each for for each Residence.Load Calc for each Residence .

It is not uncommon to have Several SABC 's in a Modern Kitchen , Dining Room , Pantry .These 1500 W Circuits will be subject to the Demand Factors of the Service of Dwelling .



Don

OK, yes they're listed on my sheet under 220.52A. i only counted kitchen circuits in unit 1, not dining room ones. i should fix that. unit 2 is efficiency-type & only has kitchen circuits, no dining room.

thank you for explaining...
cub

 

[Smart $]

yes the range stuff is confusing. i should've taken it to the max in my table, 11.99 (NEC limit & limiton spreadsheet). here's what is on the owner's manual (pic attached). why does the NEC not allow folks to put in the actual & limits it? maybe because it's not continuous use??

anyway, i think i should change it to 11.99 kW.

thanks
cub

Cooking appliances typically do not stay on 100%. The heating elements are cycled to control the temperature. The kW rating value is given as if all heating elements and controls that can possibly be on concurrently are on.

I don't know the exact manner the algorithm and values were determined, but it is what it is and seems to work as it is (we don't have houses burning down because of it)... so it stays as it is and we abide by it.

 

[donaldelectrician]

yes the range stuff is confusing. i should've taken it to the max in my table, 11.99 (NEC limit & limiton spreadsheet). here's what is on the owner's manual (pic attached). why does the NEC not allow folks to put in the actual & limits it? maybe because it's not continuous use??

anyway, i think i should change it to 11.99 kW.

thanks
cub

Cubgirl = The part that gets me with the ranges is I always like to raise the Wire by 25 % thinking i am doing a better job .

It is the Heating part of it that makes me feel the 25% is justified . A continuos Heat Load but it is not a heat Load or continuos Load .

It Ain't . I will run a , # 6 awg. over a , # 8 awg. any day if convent … But I am not saving the day as much as I will like to think .

It is a Non Continuos Load , and they really knock down the amp values for a single range …. and combos .


My Qurek
Don

 

[cubgirl]

Cubgirl = The part that gets me with the ranges is I always like to raise the Wire by 25 % thinking i am doing a better job .

It is the Heating part of it that makes me feel the 25% is justified . A continuos Heat Load but it is not a heat Load or continuos Load .

It Ain't . I will run a , # 6 awg. over a , # 8 awg. any day if convent … But I am not saving the day as much as I will like to think .

It is a Non Continuos Load , and they really knock down the amp values for a single range …. and combos .


My Qurek
Don

my range is 12.3 kW. NEC says "For ranges individually rated more than 12 kW but not more than 27 kW, the maximum demand in Column C shall be increased 5 percent for each additional kilowatt of rating or major fraction thereof by which the rating of individual ranges exceeds 12 kW." blah blah

so demand of 8 kW is increased 5% to 8.4 kW. 8400/240 = 35A and 8 cu.

wow, i see what you're saying. seems kind of puny for a range that's really 12300/240 = 52A which would require a 6.

i think a 6 is good regardless of the NEC. you're doing good...
thanks,
cub

 

[Sahib]

you mean two service entrance cables instead of one? if i could upgrade service, why spend time & money installing two services? the service is split between the tenants at the meter. i don't see a benefit to two separate services but again, my scope is narrow...

I thought by obtaining two separate services for the two units. you could use the optional method found in 220.30 for the two units separately, thereby, perhaps, no need for changing the panels already provided.

 

[donaldelectrician]

my range is 12.3 kW. NEC says "For ranges individually rated more than 12 kW but not more than 27 kW, the maximum demand in Column C shall be increased 5 percent for each additional kilowatt of rating or major fraction thereof by which the rating of individual ranges exceeds 12 kW." blah blah

so demand of 8 kW is increased 5% to 8.4 kW. 8400/240 = 35A and 8 cu.

wow, i see what you're saying. seems kind of puny for a range that's really 12300/240 = 52A which would require a 6.

i think a 6 is good regardless of the NEC. you're doing good...
thanks,
cub

Cubgirl - Well a # 6 awg. , will not hurt … but that is how it starts …I do not want to give you MY QUERK .Then you will start justifying it saying , I only carry # 6 AWG. , i don't carry # 8 awg. anymore … more space on the truck now ….


It always gets me , but rarely is a range ever loaded it seems . Thanksgiving ?

This always gets me . I know better but ...

Sigh .



Don

 

[kwired]

my range is 12.3 kW. NEC says "For ranges individually rated more than 12 kW but not more than 27 kW, the maximum demand in Column C shall be increased 5 percent for each additional kilowatt of rating or major fraction thereof by which the rating of individual ranges exceeds 12 kW." blah blah

so demand of 8 kW is increased 5% to 8.4 kW. 8400/240 = 35A and 8 cu.

wow, i see what you're saying. seems kind of puny for a range that's really 12300/240 = 52A which would require a 6.

i think a 6 is good regardless of the NEC. you're doing good...
thanks,
cub

But that range draws full rating if you turn everything on HIGH setting. If you leave everything on high setting for very long you probably are burning something, plus the oven will cycle off/on as needed once it reaches set point. The reality of why they let you use a reduced rating is that even if you actually draw more then the table says, it won't be for very long.

I have never had a service call because a 12 -13kW range trips a 40 amp breaker - they just never are loaded that much or for long enough time to trip.

 

[cubgirl]

I thought by obtaining two separate services for the two units. you could use the optional method found in 220.30 for the two units separately, thereby, perhaps, no need for changing the panels already provided.

you have a point there. i think it may be a lot of $$ to get a 2nd service drop? anyone know?

 

[cubgirl]

Cubgirl - Well a # 6 awg. , will not hurt … but that is how it starts …I do not want to give you MY QUERK .Then you will start justifying it saying , I only carry # 6 AWG. , i don't carry # 8 awg. anymore … more space on the truck now ….


It always gets me , but rarely is a range ever loaded it seems . Thanksgiving ?

This always gets me . I know better but ...

Sigh .



Don

Don, yes you're right about that. we all eat out now