I am finishing my basement and need more capacity. I thought I could add a 60amp subpanel in the basement as I am out of space in the main 200amp panel - Square D QO model panel (circ. 1985).

Questions:

1) What size wire for the subfeed?

2) If large, how do I exit the main box? Both top and bottom of the box are already used for the service feed and the heat pump? Not sure the 60amp feed will fit through any other knockouts.

3) Do I need two slots vertically or horizontally for the subfeed? Or does it matter?

4) To make room in the main panel I will need to tandem some more circuits. The tandems I have in there now are the lengthwise tandems, 2 breakers switches side by side horizontally, and are a tad longer than single breakers. I see only half-slot tandems (i.e., side by side vertically) at the HD/Lowes. Have my longer tandems been replaced by this new design or do I need to keep looking for the same style?

The basement needs are just lights and outlets, plus a fan for the bathroom and 1/2 HP (max) sewage ejector pump.

Thank you.

 

1) # 6 AWG copper wire. You'll need 3 insulated conductors, plus a bare or green ground. You can use a 6/3 cable assembly or EMT conduit with individual THHN wires.

2) There must be 1 or 2 more large knockouts. Possibly on the sides? My 150 amp Sq. D panel, which is 10 years older than yours, has large KO's on the top and bottom and on each side, so yours probably has a few more. They might be concentric KO's which means they have 2 or 3 different parts that will pry out to accomodate fittings of various sizes.

3)You'll need two slots vertically, or one right on top of another for your double pole breaker which will feed your subpanel.

4)Square D no longer uses the tandems you are referring to. If I understand you correctly, you have the type with two full-sized handles mounted next to each other horizontally, rather than the new style with two skinny handles mounted one on top of the other. My panel originally used the old style and I have installed some of the new style with no problems. Just be aware that there are 2 different types of the new tandems. One has a hook on the bottom that goes into a slot on the mounting rail, and the other just has the standard QO mounting clips that snap onto the rail.

Are you sure a sub panel is really necessary? You might possibly be able to use a few more tandems and get all of your circuits into the service panel. As long as your panel will accept the tandems, it is a perfectly sound solution. Not to mention a bit easier.

 

1. 6/3
2. Find another knockout. There should be a variety of sizes. It is unlikely that they are all taken.
3. Two slots, one above the other.
4. Get the model number of your panel. Get the model number of the breakers you are considering. Call SquareD to find out if they are compatible.

 

Thanks. This is very helpful. I think you may be right about the side knockouts, but of course they mounted the box between two studs. I guess that will work, though, assuming I can get through the stud.

Hotarc, your idea about simply adding to this box has merit. Maybe I'll take another inventory and see if I can fit them all. I had plans to add dedicated circuits for the media room equip and a separate 20 amp to my workshop, but a surge surpressor will probably do fine for the media room and I may still be able to get another 20 amp in there.

Running 12/2, and 14/2 cable certainly would be easier. Though the distance is less than 8 feet to where the box would go.

As for the tandem breakers, I saw the ones with the hooks at the HD. My box uses the clips. Just to clarify, are you saying those hooked ones will not work with my box?

thanks again

 

Transfer existing circuits from the Main panel to the new S-P. This will gives acess to the enclosure of Main panel for the Feeder cable-connection ,and will provide space in the Main panel for inserting a 2-pole C-B.

Good Luck & Enjoy the Experience!!!!!!!

 

Thanks, Pattbaa. One thing that I did not make clear is that the subpanel will be located in the basement which is almost vertically under the main.

My main panel is mounted on a section of wall in the garage to the left of the g-door opening (facing out). There is barely enough room for the main panel before you hit the wall separating garage from mud room. I could mount the subpanel on the adjacent wall in the garage that separates garage from mud room, but prefer to take it downstairs if possible.

So, if I wanted to relocate circuits, and put the subpanel in the basement, how would I extend the wiring to the subpanel for the circuits I am moving? There are 2 circuits currently serving the basement. Those will be pretty much replaced anyway. No problem there, but if I needed to relo 2 others, can I junction in the main box and run the cables down to the sub? Or would that normally be done in a separate junction box ouside and next to the main?

thanks, this is most informative and helpful

 

If the tandems in your panel have the clips on them, then use that type. Some QO panels will have slots in the mounting rails that accept the "hook" type of tandem. If your panel has the slots in the mounting rails, purchase the type with the hooks. If the rails are solid, then use the type with the clips. Some panels are designed with the slotted rails to limit the number and positions of tandem breakers installed.

Look carefully when you're at Home Depot. They do sell both types of tandems, at least the ones in my area do. Unfortunately, the style with the clips is more expensive.

Splicing in the panel is permitted, but the best way is probably using stand-alone junction boxes mounted next to or above the panel.

 

If my understanding is correct, you need to re-locate two 120-volt-circuits so you will have space for inserting a 2-pole C-B, an you need space in the bottom of the Main-panel enclosure for a 3/4" (trade-size) cable-connector, i.e., a 3/4" K-O.

If the new Feeder cable is to be extended down-wards from the bottom of the existing panel-enclosure, what are the arrangements of the existing cables that connect to the bottom of the enclosure? Do any extend down-wards in the direction of the new S-P? Is there space in the bottom of the enclosure for additional cable-connectors?

Yes, you can dis-connect circuit-wires from their existing terminations in the Main panel, and splice them directly in the panel to new wires extended from the new S-P.

I have the impression that you will have to route the new Feeder cable "down"( vertically) and "across" ( horizontally) to the new S-P location, presuming that the garage-floor is slab-on-earth construction.

 

Pattbaa, you are correct, I must go down (about 6 ft) and to the left (about 2 ft) to get to the basement through the edge joist that forms the edge of the first floor (and forms the first step down into the garage). It is 2 1/2 steps down to the garage floor from the mud room, so the basement is about 2 feet higher relative to the basement than to the first floor.

The bottom of the main panel is where the main feeder from the meter enters. The meter is mounted on the outside of the same wall as the main panel. At the top is the big 100 amp cable that goes to the disconnect subpanel for the heat pump.

There is ample room to bring the subpanel feeder through the bottom left side of the main panel if that is kosher. I have not had a chance to check out the knockouts down there to see if there is one big enough. But 3/4" would sound doable. I was worried about having to manage to put a larger cable through somewhere, but 6/3 should not be too bad.

The space I would free up on the panel will be on the left side so that would keep everything on the same side as well and I would not have to cross over the main feeder at the bottom.

Does this sound ok? In other words is there any problem having two feeders (main from power company, plus feeder to subpanel) out of the same side of a box?


Also, while I am at it, there is one question that I have always wondered about regarding the main feeder for safety's sake. I see that the aluminum ground strands are exposed, but the 2 hot wires are insulated and disappear into their lug locations.

When I have added circuits before, I usually pull the main breaker to make the panel dead. However, I know that there is live current beneath the breaker section of the panel where the main feed comes in. And I avoid that area like the plague. Usually I keep one arm behind my back and try to work one-handed as much as possible to minimize chances of touching something inadvertently.

But what is actually hot? Just the hot wires at the lugs before the main breaker where they must have exposed wire to contact the lugs? Hope this makes sense to ask. Just want to know as much as possible to avoid making a stupid mistake.

I always say to my staff that the only dumb questions are the ones you keep to yourself.

Thanks again. This is fun.

 

Possibly you could use 3/4" Flexible Metal Conduit as the Wiring Method between the old/new panels. The FMC would contain 3 #6 Feeder Conductors,a #8 Green Equitpment Grounding Conductor, and 3 #14 Branch-Circuit conductors ( Black,Red, & White) for the 2 circuits re-located to the S-P.

The Neutral Service Conductor is not required to be insulated.

This requires "fineness" and Caution---wrap electrical-tape around each of the 2 Ungrounded Service Conductors directly under the MCB terminations so there is no "exposed" Conductor at this point. If the terminations were done correctly, you shouldn't have an exposed- Conductor situation under the MCB.Next, wrap the tape around both Conductors to minimize any possible contact with the Conductors- you will have the area under the MCM throughly insulated with tape.

The S-P cable can enter the enclosure adjacent to the Service -Entrance Cable

 

When you turn off the main breaker, the incoming service wires and the lugs they're connected to will still be energized. Don't touch them and you should be okay.

No problem with having two feeders on the same side of the panel.

 

Thanks, hotarc, confirms what I thought.

Thanks for the suggestions, Pattbaa. I certainly would not have thought of bringing them all down in conduit. That makes sense. Much neater, too.

I checked the box again last night. appears there are at least 2 larger knockouts on the bottom of the box I can use.

Unfortunately, though, clearing space in the main will be a bit more challenging as I realized that the two pairs of breakers I will tandem are opposite each other on the panel. This means I'll have to move two circuits from one side of the box to the other, and move two circuits to the subpanel. Oh well, still looks doable.

thanks again. You all have been a great help.