Subpanel or not?

[zbang]

(Is this DYI? I guess it is. Close/delete as needed.)
I have the opportunity to rewire about a quarter of my house courtesy of water damage from a burst washer hose, and I'm tossing around whether to put a subpanel in the small basement under the laundry or home-run new/updated things to the panel. (I'm firmly tilted towards a panel because of breaker space.)

The service and panel (Murray, 3 open spaces, already has some tandems) is outside one corner of the house, the laundry is at the other, maybe 50' of crawlspace between them. One floor.
Right now, most of the laundry corner is on one or two circuits, including the washer/dryer, outside lights/recep's, some kitchen recep's, and maybe something in one of the bedrooms. Total mess, been meaning to update things for years, hate crawlspaces .
With most of the plaster basement ceiling removed, I can now get to much more K&T wiring and see the bootleg grounds that somebody put it years ago (EGC to a cold water pipe....).

My thought is to put in a small panel (8-12 space) in the basement, run a 70-80amp 2p feed to that, and move everything I can over. No, I haven't done a load calc yet or even a survey of what I can move to a new panel. Probably new circuits for the laundry, outside lights/outlets, new basement outlet, the 'fridge, break off one of the kitchen counter sets to a new circuit, etc; basically, if I can readily get to the wiring, I move it.

Am I missing something? (right now I'm diving back into Chapter 2 for a refresher/update)

 

[LarryFine]

Am I missing something?

Maybe I am. What's the question? How large a feeder your new sub-panel will need?

That would require a load calc, technically speaking, or at least a decent guesstimate.

 

[zbang]

Is my thinking rational? Or, are there specific reasons not to use a sub-panel here?
(As I said, I haven't don't the calcs yet.)

 

[Srv52761]

I have a garden shed, 12’x 16’ that I also use as a small tool shop. It stores a drill press, a radial arm saw, a table saw, a welder, a small electric heater, a dehumidifier, and a few other corded animals. As the summers get warmer, I am thinking of a mini-split for air conditioning. I already regret only running an 8/16 sub panel.

It is not much more to run a 100-125 amp panel with more spaces. Depending on your layout, be thinking charging station for your next vehicle, possible 240 for a dryer... (California is phasing out gas appliances; no new petroleum fueled internal combustion passenger vehicles or small trucks by 2035, probably other stuff. So the push for electric is now. I expect the rest of the country to follow suit as climate because more of an issue). Better to do that now, then later.

 

[LarryFine]

Yes, rational. I am a fan of sub-panels., especially for a concentration of loads.

Less labor, less wire, and load diversification means much lower voltage drop.

It is not much more to run a 100-125 amp panel with more spaces.

I agree; it will give you a source for future loads at the other end of the house:

 

[suemarkp]

In general, I find it easier to run a handful of NM circuits together than to run a larger feeder (4 cables through a hole that you'd normally have to drill for a fatter feeder). But since your panel only has 3 slots, and if you are going to install Arc Faults, I'd go with a new panel somewhere -- either next to your existing one or start planting sub panels. If it is more than 4 circuits you're changing, then maybe I'd do a panel at the far end for sure.

 

[LarryFine]

To add: I sometimes even use sub-panels in new work, so that shows my opinion.

 

[synchro]

Yes, rational. I am a fan of sub-panels., especially for a concentration of loads.
Less labor, less wire, and load diversification means much lower voltage drop.

Also the feeder to the sub-panel is a MWBC and so the voltage drop on the neutral conductor is reduced.
While MWBCs could also be used on branch circuit home runs from the main panel, there will be more issues to contend with when using GFCIs and AFCIs.

 

[zbang]

Thanks, folks.
Good point on the electric stove, but I'll keep my gas stove until they pry it from my dead hands. And it's only a 100amp service; still might make sense to upsize a few things for later (panel certainly, and the pipe if I go that way instead of cable).

On to the actual planning (and load calcs, sigh).

 

[gar]

200928-1951 EDT

zbang:

I have one main panel, and 5 sub-panels. Will probably add another sub-panel sometime. Something toward 50 breakers. In addition each bench has its own sub-panel fed from some other panel. These are for convenience. And I have rather low average, or even peak load.

I use QO breakers, and many as switches.

Every room has two or more outlet circuits, and separate light circuits.

At each sub-panel there is an outlet on a common circuit from a breaker in the main panel. Power can be cut to a sub-panel, and still have power close by.

Over kill, possibly, but convenient.

.

 

[PeterOven]

A 200 A, 30 space panel is not that much more expensive than a 100 A panel. At some later date if there is a desire to upgrade the service to 200 A, consider whether this new subpanel could at that time become the main panel, at which time the feeder that you are putting through your crawlspace would be reversed to make the original panel a sub panel. Plus if you make the feeder 100 A, and the sub panel 200 A, you don't need to do any calculations right now.

 

[Srv52761]

200928-1951 EDT

...... At each sub-panel there is an outlet on a common circuit from a breaker in the main panel. Power can be cut to a sub-panel, and still have power close by.

I wanted to do that in my shed, but alas, only one feeder or circuit per outbuilding.

 

[suemarkp]

Put a 3-way switch in that outlet circuit, call it a remote switched lighting outlet, and use the exception for "different characteristics" to allow that additional circuit.