Ask Me Help Desk - Square d sub panel

Quote:

Originally Posted by tkrussell

I need the total square foot of livable space, including a basement that can be finished, no garage, attic, porch. Type of heat. Hot water?

Dimension are:
basement: 19 feet x 26 feet = 494 s.f.
1st Floor: 38 feet x 26 feet = 988 s.f.
2nd Floor: 38 feet x 28 feet = 1064 s.f.
attic: 38 feet x 28 feet = 1064 s.f.
There is no porch/deck.
The heating system is Forced Hot water, Oil Heat, and electric BoilerMate hot water reservoir.
The Air-Conditioner is central Air for the 1st floor + basement,
and 2nd floor. (Interesting that the original house owner has the piping
for a 3rd Air-conditioner for the attic. There are no free circuits in the main panel,
other than the two 20 amp breaker for future attic that the original owner put in place.
so question is, where would have the power come from for the future 3rd AC if
there are no empty slots in the main. Do people think these things ahead?)

Oh, there is a water Jet bath tub (jucuzi ?) in the master bedroom which we never used or never liked it.

The main power eaters in the house are the electric range, central Air, dryer, and possibly
the forced hot water heating system.
Thanks
-Mike

With some assumptions and estimating the actual load of the AC, I arrive at a connected load of 87 amps.

A 2 pole 60 amp breaker will be fine to feed the subpanel.

Quote:

Originally Posted by tkrussell

With some assumptions and estimating the actual load of the AC, I arrive at a connected load of 87 amps.

A 2 pole 60 amp breaker will be fine to feed the subpanel.

Thank you tkrussell,

Question1: Does your 87 amps figure signifies an average household usages for the main panel before the subpanel, or is the 87 amp the total average usage for the household for the main panel and the subpanel combined?

Question2: SquareD (my main panel is Square D Homeline Series) sells dual breakers
That are 50amp, 60amp, etc for the main panel. When I checked online stores,
I noticed that, the 60amp is not their biggest squareD's dual breaker for the main panel.
SquareD has like dual 100amps for the main breaker. Here is the question: you mentioned
That it's not the size of the breaker that's an issue, and it's the load. For my application,
And adding a subpanel that can support future circuits (also to avoid load balancing),
Can I buy the 100amp dual breaker or
The 125amps dual breaker for the main panel to supply the subpanel?
Of course, I would probably need size 2 THNN wire, right ?
Would a breaker with such a heavy current, create an issue for the squared homeline
Main panel. Such as, over heating the bus bar, etc. How much current can
Bus bar take before it melts, or cause problems, or cause even fire hazard?
Does the rating of the panel given by the manufacturer, is mainly for rating
The bus bar? For example, a 125amp subpanel, can have up to 125am
Going through the bus bar ?

Question3: An electrician told me that, since squareD (QO6-12L-100DF for example)
Has only 6 spaces, I should consider MURRAY subpanels that seems to have
16, 24 spaces, etc. Does it make sense to use MURRAY or even GE?
My concerns was that, some manufacture may either merge with others,
Or even go out of business, and thus make it difficult to find parts in a long term.
Also, would squareD QO series be better than MURRAY, GE ?

Question4: An online store says that QO612L100DF, is a single phase. I thought having
The dual 60amp breaker from main going to the subpanel, with 2 HOT, would
Provide 60amp from each phase of the main. So if main is dual phase,
i.e. each bus bar being on a phase of it's own in the main panel, then
The subpanel will automatically be dual phase as well. Am I missing the
Definition of phase?

Thanks again
-Mike

Ps. I love these electrical talks.

My answers are in bold:

Question1: Does your 87 amps figure signifies an average household usages for the main panel before the subpanel, or is the 87 amp the total average usage for the household for the main panel and the subpanel combined?

87 amps represents the calculated connected load, that the service entrance needs to be sized correctly to handle, to include all the mandatory loads that must be figured, total lighting load, appliances, etc. Whether there is a subpanel, or even two, does not matter.

Question2: SquareD (my main panel is Square D Homeline Series) sells dual breakers
That are 50amp, 60amp, etc for the main panel. When I checked online stores,
I noticed that, the 60amp is not their biggest squareD's dual breaker for the main panel.
SquareD has like dual 100amps for the main breaker. Here is the question: you mentioned
That it's not the size of the breaker that's an issue, and it's the load. For my application,
And adding a subpanel that can support future circuits (also to avoid load balancing),
Can I buy the 100amp dual breaker or
The 125amps dual breaker for the main panel to supply the subpanel?

Yes.

Of course, I would probably need size 2 THNN wire, right ?

#4 copper if 100 amp, #2 copper if 125 amp

Would a breaker with such a heavy current, create an issue for the squared homeline
Main panel. Such as, over heating the bus bar, etc. How much current can
Bus bar take before it melts, or cause problems, or cause even fire hazard?
Does the rating of the panel given by the manufacturer, is mainly for rating
The bus bar? For example, a 125amp subpanel, can have up to 125am
Going through the bus bar ?

Any panel will list the maximum size branch circuit breaker allowed, to eliminate the risks you mention.

Question3: An electrician told me that, since squareD (QO6-12L-100DF for example)
Has only 6 spaces, I should consider MURRAY subpanels that seems to have
16, 24 spaces, etc. Does it make sense to use MURRAY or even GE?
My concerns was that, some manufacture may either merge with others,
Or even go out of business, and thus make it difficult to find parts in a long term.
Also, would squareD QO series be better than MURRAY, GE ?

Square D makes many panels, with up to 42 circuits, not just a 6 circuit panel. Square D,GE, and Siemens, have been around a long time, and will continue to be available for a long time. Siemens makes Murray. Use any of these you can find available.

Question4: An online store says that QO612L100DF, is a single phase. I thought having
The dual 60amp breaker from main going to the subpanel, with 2 HOT, would
Provide 60amp from each phase of the main. So if main is dual phase,
i.e. each bus bar being on a phase of it's own in the main panel, then
The subpanel will automatically be dual phase as well. Am I missing the
Definition of phase?

All standard residential services are single phase 120/240 volt, each with 2 hots. Both the 120 and 240 are the same single phase. 120 volts is nothing more than a center tap of a transformer between the two 240 volt legs.

Great answer. Thank you so much tkrussell.
I liked this model of SquareD subpanel model number QO612L100DF,
which is available at the home center near me. But this main log
doesn't give me much of future needs. This model has only 6 spaces
for the tandem breakers. I rather buy a 12 spaces. Note that
this model QO612L100DF (with the DF at the end) gives me the
inside wall installation, i.e. the cover has a lip all around, so that
the unit can be installed inside the wall, and the cover would
be flushed with the drywall.

My question is tkrussell: All these codes within the model number are so confusing,
and the web sites I found didn't bother to show the actual pictures,
or just showed generic picture of the main log or no picture of cover,
or no detail descriptions/specifications, so it's hard to
see if it's flush mount with drywall unit. Would you be able to
find the SquareD QO model number that would match the requirements
for my applications, I would appreciate it greatly.
I definitely want to buy the SquareD QO series.
My application
is single phase main lug with flush mount cover (so that it would be covering
the drywall cutout that the panel is in), 12 tandem breakers, 12 number of spaces,
indoor model, size about 14"x18"x3.8", 100amp or 125amp, shielded copper bus, 120v/240v,
preferably includes the ground bar. Enclosure NEMA 1?

Thank you
-Mike

Find the panel you like at:

Square D - A Brand of Schneider Electric

And we can go from there.

Quote:

Originally Posted by tkrussell

Find the panel you like at:

Square D - A Brand of Schneider Electric

and we can go from there.

How does these two models sounds to you: QO112L125G or QO11224L125G?
Both are main lug but they say they are convertible. I think the later one (QO11224L125G)
Has the main installed by factory. Are they saying there would be
A shutoff breaker in the later one?
SquareD makes so many model numbers, and it's so confusing.
Also, QO112L125G says ZERO tandem breakers, and QO11224L125G says 24 tandem.
The tandem breakers are the ones that has two breakers in one, is that correct?
What is the difference between tandem breaker connection to the bus bar that
Makes it not possible to use on QO112L125G, and makes it possible to use on
QO11224L125G?
Thanks
-Mike

Ab, be patient, I will get back to you, yours needs a bit of research and detail, and I got to go see Ghost Hunters.

I believe the difference will be size of cabinet, convertible means you can add a main breaker kit anytime. These are good for keeping inventory down.

Some situations will be called for to not allow any more circuits than limited by the panel, so only some will allow tandems. Yes sometimes a bit too many to choose from, but there are many design decisions and variables to deal with. Sometimes it's called making the world idiot proof.

I'll be back.

Quote:

Originally Posted by tkrussell

Ab, be patient, I will get back to you, yours needs a bit of research and detail, and I got to go see Ghost Hunters.
I'll be back.

Thank you tkrussell, I hope you didn't spend too much time on this. I finally was able
To find a box that I liked at our home center. I bought squareD: QO120L125GC.
You like the QO models, right?
I always like the commercial quality stuff, the home quality stuff tends to be not
Sturdy enough for even residential use. You mentioned in the forum that
The QO is excellent for residential and light commercial use.
I'll be posting other questions on installing this in my basement, please look
For my questions.
Thanks again,

For those interested to continue the topic on my electrical questions,
And for the sake of staying true to the title, I've placed my question in
An article of it's own. You can find my post with the title of
"Finding the right place to install The Main Lug", on this wonderful forum at url: https://www.askmehelpdesk.com/electr...ug-131336.html
Thank you
-Ab