# what size breaker in main for a sub w/ 125 amps



## docfishwrinkle (Jan 9, 2010)

hey folks quick question. im looking to run a sub panel w/ 110 & 220. i have it laid out to where i need 125 amps to be in my comfort zone. ill probably want more just in case of future so lets say 150amps. ok now my question is what size breaker should i put in my main box? 150? if they even make that in a double pole.


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## Pot Belly (Jan 9, 2010)

Yes.  The breaker that feeds the sub-panel is sized to protect the wire that feeds the sub-panel.


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## docfishwrinkle (Jan 9, 2010)

thx pb. i got this. going to store now to pick up my supplies. 3 awg wire for that sub feed line?


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## nouvellechef (Jan 9, 2010)

You wired yourself before?


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## docfishwrinkle (Jan 10, 2010)

yeah ive added about 4 new circuits in my house. really not that hard just common sense & a lil knowhow accompanied by a book/internet & all is good. wire the recepticles then, the sub, & then just pop in breaker to main panel & good to go. always wire grounds first, then neutral, then hot. this is in case you arc out, the ground will hopefully do something to help you in a bad situation.


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## viper (Jan 10, 2010)

be careful you dont overload the main panel ---- putting a 150 amp breaker in a 200 amp main house panel that is already loaded , well lets say ive never seen a 150 amp stab in breaker for a sub panel put in a 200amp house main , have seen 125s ----  its all AWG but a # 3 is not rated for 150 amps unless you use types fep,fepb pfa but we dont use those types in residential --- i would suggest staying with the 125 amp and using # 2 thhn --- be careful , electricity is nothing to fool around with , you just cant keep adding and adding to a panel as you see fit --- everything is sized and rated to formulas and calculations -- if you like, ill help you size it all to be safe .


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## docfishwrinkle (Jan 10, 2010)

good to know viper. yes i would like you to look over my game plan. well i thought i had a 200 service but upon looking @ main breaker its a 100 so im now not sure of anything. so lets start from scratch shall we & go from there. things i need to run:

220 side

5-600w hps 2.7 amps each=13.6

110 side 

2-8" exhaust fans 1.6a each=3.2
2-oscilating fans .4a each=.8
dehumidifier 5a
space heater 12.5a
4-air pumps .04a each=.16

120 side equals 21.66 amps 240 side equals 13.6 combined equals 35.26 so leave room for future make it a 50 amp panel. wow this is why we put things in a thread so we can talk/work things out. it was very early yesterday morning when i decided to draw this project up. so im a lil shy of proposed plan....lol guess ill just have to keep all that extra money in my pocket.


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## viper (Jan 10, 2010)

ok cool , and after a little exploratory work you figured it out , well done 
50 amp sub panel still gives you a little wiggle room . 50 amp panel , 8 guage wire .

keep in mind for when you go to buy your sub panel that your 5 240 volt lights are gonna take up 10 spaces in your sub panel and then the space heater needs to be dedicated so theres 11 spaces and however your gonna plug the rest of your equipment in so theres 12 spaces for sure.


most 100 amp panels are federal pacific and are decieving when it comes to breaker spaces , what type of panel do you have and are thgere any spaces left ?


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## WrEkkED (Jan 24, 2010)

You also have to think of how much your house is already running. If your  main is 100amp and you need a 50 sub, you can't have more than 50 running on the main. Now, if your in the position that you need a sub on a 100 amp panel I'm guessing your going to go over. You also have to remember that wire is only rated to take 80%. Example, 14 AWG is good for 15 amps, but is only allowed 12 amps. 

I think for what you're demanding you need a new service put in. Probably a 200 amp main. =$$$.

For all the things you mention you might be able to find them all in 220 and thus minimize your amperage draw. Good luck!


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## viper (Jan 26, 2010)

the 80 % rule doesnt apply to branch circuits in residential houses ,,, only resturaunts , commercial and industrial buildings --- im not sure about apartments - id have to check --- but i do agree he needs an upgrade , my guess is he has a 30 plus year old house , most likely its an ol federal pacific split bus panel which has lost its UL rateing . 

anyhow ! hey doc hows it going bro ? did you do anything yet ?


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## docfishwrinkle (Jan 26, 2010)

viper said:
			
		

> ok cool , and after a little exploratory work you figured it out , well done
> 50 amp sub panel still gives you a little wiggle room . 50 amp panel , 8 guage wire .
> 
> keep in mind for when you go to buy your sub panel that your 5 240 volt lights are gonna take up 10 spaces in your sub panel and then the space heater needs to be dedicated so theres 11 spaces and however your gonna plug the rest of your equipment in so theres 12 spaces for sure.
> ...


my panel is a westing house & i have 4 spaces left


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## docfishwrinkle (Jan 26, 2010)

viper said:
			
		

> the 80 % rule doesnt apply to branch circuits in residential houses ,,, only resturaunts , commercial and industrial buildings --- im not sure about apartments - id have to check --- but i do agree he needs an upgrade , my guess is he has a 30 plus year old house , most likely its an ol federal pacific split bus panel which has lost its UL rateing .
> 
> anyhow ! hey doc hows it going bro ? did you do anything yet ?


 
yeah house was built in '41. iv replaced most of the wiring about 6 years ago. i really cant go for a 200 amp service unless i absolutely have too. we conserve power pretty good. ive recently installed a attic fan to try & cut out ac as much as possible. i do have a pool also, but am willing to run pump on off cycles to my lights. this plan has been put on hold until late spring early summer.


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## viper (Jan 27, 2010)

ok cool ,  if you like , we could do a load calculation on your house to see if you have room for the 50 or even a 40 .


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## docfishwrinkle (Jan 28, 2010)

sounds good to me, viper. like the avatar by the way.


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## nouvellechef (Jan 28, 2010)

Why would he need to use so many breaker spots in panel? Couldn't it be just one breaker with line running to lighting controller, 240V. And another with 120 running into a bunch of outlets? I just tore my grow down. Gonna need to tell electricians how I want my new place set up. That was my thought above?will that not work? You guys sound like you know power.


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## viper (Jan 28, 2010)

thanks doc , let me know when your ready .


hiya nouvell , well his objective is to run a sub panel which requires 2 spaces to get the power source clser to the grow area to elimate extension cords , and make it eaiser to connect , then add the necessary devices off the sub for the equipment in which he intends to use


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## docfishwrinkle (Jan 28, 2010)

ok im ready. need to have plan down so when i get the go ahead im ready. appreciate it


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## nouvellechef (Jan 29, 2010)

Ahh, got it. Gonna stay on this, interested. I am planning on having electrician just plug 40amp 2 pole breaker, run 8/2 Romex to new spot. Then I hope I will be able to figure out how to wire in the C.A.P 8 light controller. Does not look that hard. Electricity scares me.


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## viper (Jan 29, 2010)

ok cool ,  need to know what all you got in ya house ,,,,,,,,,,,, such as 

*square foot of dwelling 

*electric or gas heat ( if electric heat - need to know which is larger , heater or air condition and if its a heat pump and the kw or breaker size of the larger )

*how many small appliances , laundry , range , water heater , dishwaher , clothes dryer , seperately controlled electric heat .


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## docfishwrinkle (Jan 29, 2010)

1400 sq ft. w/ the following electric devices. ac (4 months possible use), pool (4 months use), dryer, washer, fridge, dishwasher, range, &  microwave. ac is a 2 pole 30.


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## ta2dguy (Jan 30, 2010)

this is a good thread with both interesting and valuable information. i am very soon going to be expanding and am going to be in need of a little advice in the power area, i hope it is okay to maybe come askin for a little help when required from ya there viper.

.... sorry to burst in on your thread like that doc   :48: .


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## viper (Jan 30, 2010)

ok by me ta2dguy  --- glad to help , just hit me up when its time


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## viper (Jan 30, 2010)

hey doc , what type of heat you running gas or electric ? and what size breaker is the pool equipment on 50? and is the range a 30 or a 50 ?


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## PUFF MONKEY (Jan 30, 2010)

i looked at you grow room power requierments and am still left wondering why you need anything near 125amps...i may just be totally off course but when i think about what i run and my power requierment(45amps) i just don't get it..something tells me you can get by with much less...i had a certified electrician(good friend)..i can run 4x1000w lights, 1 500w floro light 3 6" vortex fans , 4 air pumps, 2 water pumps, all my shop lights on 45amps...not trying to argue, just save you some trouble.


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## viper (Jan 30, 2010)

he worked it out and realized he didnt need 125 amps


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## docfishwrinkle (Jan 31, 2010)

ta2dguy said:
			
		

> this is a good thread with both interesting and valuable information. i am very soon going to be expanding and am going to be in need of a little advice in the power area, i hope it is okay to maybe come askin for a little help when required from ya there viper.
> 
> .... sorry to burst in on your thread like that doc  :48: .


 
not a problem guy. thats what the threads are for.


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## docfishwrinkle (Jan 31, 2010)

viper said:
			
		

> hey doc , what type of heat you running gas or electric ? and what size breaker is the pool equipment on 50? and is the range a 30 or a 50 ?


 
furnace is gas on a 15, pool is on 20, range is a double 40, air is double 30, dryer is double 30.


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## docfishwrinkle (Jan 31, 2010)

PUFF MONKEY said:
			
		

> i looked at you grow room power requierments and am still left wondering why you need anything near 125amps...i may just be totally off course but when i think about what i run and my power requierment(45amps) i just don't get it..something tells me you can get by with much less...i had a certified electrician(good friend)..i can run 4x1000w lights, 1 500w floro light 3 6" vortex fans , 4 air pumps, 2 water pumps, all my shop lights on 45amps...not trying to argue, just save you some trouble.


 
hey puff i was under the influence when adding numbers...haha. yeah im trying to do a sub w/ 50. you running your 1k's on 240? thanks for the heads up, appreciate it.


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## viper (Jan 31, 2010)

ok doc , are you ready for this ?


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## viper (Jan 31, 2010)

currently with everything on and running at the same time you are roughly drawing 85.5 amps 

and with the additions you want to add which is 5700 watts and not a va more you would be drawing 96 amps ,,, so you would be pushing it close but thats with everything on and running at the sdame time ,,,, and thats a 30 amp sub panel and not a 50 which will carry what you want to add .


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