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· Registered
49 Posts
Discussion Starter · #1 ·
We are planning to get a Tesla and want to build out a 14-30 outlet in the driveway for it. The current line that goes near the driveway is a 15-amp and so I will need to run new wire from the breaker. Unfortunately I do not have any open spaces to place a new breaker. Can I plug into an existing 30-amp double breaker? The appliances I currently have on the 200-amp panel are: Electric Stove, HVAC with A/c, Fridge, normal lights and outlets in a 4 room house.

Attaching some pictures of the current panel. The white connectors blocking the view are the Emporia Vue energy monitor. I can remove them temporarily if a clearer picture is needed. Who ever did the earlier jobs seems to have already double plugged the A/C and the Stove on the same breaker box.

Pic #1: Main panel
Pic #2: Sub panel that feeds the A/c. Wires from the top left 50-amp breaker that also feeds the electric stove



· A "Handy Husband"
15,054 Posts
Picture 2 is not a sub panel, it is a unfused disconnect for your AC. The answer to your question is no. You need a panel with more spaces and probably an upgrade to a larger service.

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· Registered
8,183 Posts
It may be legal to split the 30A circuit, depending on what is on it. If either load is hardwired, you can't do it. If both are sockets, then you can have any number of sockets on a 30A circuit. (But as soon as you have a hardwired load that draws >15A, you can't have any sockets at all). Most hardwired loads, particularly EVSE's, must be dedicated circuits.

Some folks emphasize getting panels with lots and lots of spaces. This panel is pretty much the picture postcard of the opposite of that: your house is wildly overpowered and under-spaced, but that happened for an interesting reason.

This panel was never imagined or intended to be a house's only panel. Note the rather large "thru lugs" at the bottom, and note the empty space below them (for wire bending space for fat 250MCM or 3/0 wires leaving those thru lugs). This panel is intended for multi-building sites where power comes in at, say, a shed; there are a few breaker spaces for shed circuits or an RV stand (that's what the 8 are for), and then a full 200A of power goes onward to the main residence via those thru-lugs, to a large 30-40 space subpanel in the residence.

Getting an entire house powered with those "auxiliary" 8 spaces is a feat of engineering!

So I see 3 ways to go from here.

Ignore the Very Full Panel problem altogether; kick that can down the road.

Replace the 50A breaker with a Square D HOMeline HOMT2020250CP breaker, which is a double-stuff with 50 in the middle and 2 independent 20's on the outside.

That will leave a 15 and a 20 still hanging on the duplex breakers below it. Pick a circuit that you can afford to downgrade from 20A to 15A, and swap it with that 20A that's there. So now the lower left 2 spaces has two 15A breakers, *effectively*.

Change that to a HOMT 1515230CP, which provides 30A in the middle and two independent 15As on the outside. Now your inner breakers provide a 30A circuit.

At this point the panel is absolutely maxed. You will not get another circuit in there. Period.

Add a subpanel, following through on the intended panel design.

Here you add a 200A subpanel, and feed it from the "thru lugs" on this panel. As said, I recommend a large panel. Not least, that will permit you to have AFCI/GFCI breakers and the required 8-ish number of dedicated kitchen, bathroom and laundry room circuits.

When houses are recovering from an "out of spaces" problem, I like to see them finish with 45-50 spaces. So by that formula, that would be a 40 space panel. Obviously now, you'll never have trouble with breaker spaces again. That's where you want to be - seriously.

If you want this to be the only panel, get better guts

This looks like a relatively recent panel. So I'd like to see the model number of that panel. My suggestion is to look up that panel in Square D's catalog, which will call out which size of *box* it uses. i.e. the gray metal chassis of the panel. Square D HOMeline only has about 20 sizes of box that they use for all their panels. It'll be like a size 7B or something.

Once we have the box size, now we search the catalog for a panel with that same box size, with a more appropriate number of spaces... and maybe it sacrifices the "thru lugs" if you're really sure you'll never use them.

Say we come up with a 20- or 24-space panel that fits in the same box. We inspect to make sure the mounting holes really are in the same places. Then we unhook all the wires from this panel, unbolt the "guts" (the bus assembly) so nothing is left but the empty shell and the wires... then unbolt the new panel's "guts" also and bolt them into this panel. Then reattach the wires and use the new box's cover and label (which is usually on the cover).

Your old guts, cover and labeling go in the new box, and you sell it on eBay or whatever as what it is - a used 200A 8-space panel with thru lugs, in a new case, with nothing wrong with it and it was swapped to get more spaces.

· Registered
49 Posts
Discussion Starter · #8 · (Edited)
It may be legal to split the 30A circuit...
@seharper - I really appreciate the detailed solution! I will try and find the panel # as you mentioned. The first option is what looks it might work in the short term with minimal expense.

Follow-up question: Is there a way to calculate if I could fit in another 2020250CP instead of the suggested 230CP? Or would I need to look at a load calculator?

Either of the remaining solutions will need new panels and an electrician as I am not sure I can move the mains around. I couldn't see any mains shut off at the meter so guessing would have to call the electric company to shut off power when I go this route. Most likely the cost is going to be $700-1000.

I have never seen anything like that.
This is the Emporia Vue Smart Home Energy Monitor System. Shows how much power is coming in from the main and how much each circuit is consuming. Amazon Link:Emporia Vue Smart Home Energy Monitor

· Deleted Member
840 Posts
Follow-up question: Is there a way to calculate if I could fit in another 2020250CP instead of the suggested 230CP? Or would I need to look at a load calculator?

Either of the remaining solutions will need new panels and an electrician as I am not sure I can move the mains around. I couldn't see any mains shut off at the meter so guessing would have to call the electric company to shut off power when I go this route. Most likely the cost is going to be $700-1000.
I don't see a load calc issue with a 50A load, with what you said in your OP.
I personally wouldn't put a Tesla 50A on a tandem or quad though, they generate quite a bit of heat and have caused issues even on full size breakers.

You also have that tap on the 50A breaker that needs to be fixed. That tap goes into what looks like a conduit without a bushing as well.

Keep it at 30A with what seharper said, or get an electrician in to add a panel, small price compared to the Tesla, no ?

· Registered
8,183 Posts
Brric it would, and that's what this panel was intended for.

For my "swap the guts" idea.

Interesting. Square D actually uses that panel as an example on several pages in their catalog here (HOMeline breakers start on page 40). It gets quite a lot of ink; they seem proud of it.

Page 41 of the catalog explains how to turn that model number gibberish into meaningful facts:
HOM = Homeline obviously
816 = number of spaces and circuits
M = main breaker panel
200 = 200A obviously
blank = no ground bars provided
P = ??? undocumented
FT = Feed Thru lugs
RB = Rainproof enclosure
Yup, that's your panel.

Anyway, catalog page 51, near the bottom, this is listed as a HOM816M200FTRB (no "P" in the name, whatevs). The Enclosure Number is a "Type 6R" which is the magic number.

Note that all their feed-thru lug panels are baby 8/16 space panels.

Interestingly, they refer you to the "QO" part of the catalog for the enclosure sizes - in other words HOM panels use QO enclosures. This is good news; QO breakers are only 3/4" tall so they put 4 breakers where HOM only puts 3. Downside: they're more expensive.

Anyway, now we search for panels (also in QO now) that have a 6R enclosure.

On that same page 51, I see (without feed-thru lugs)

HOM2040M200RB = 20 space 40 circuits at 20A. Better.

On page 22-23 I see some QO panels, the first two are convertible (add main breaker). Page 4 has the decoding table.

p. 22 QO130L200GRB = 200A, 30 spaces.
p. 22 QO13040L200GRB = 200A, 30 spaces/40 circuits*
p. 23 QO130M200RB = 200A, 30 spaces, main breaker included. Excellent!
(these 3 appear to be the same thing, just differently optioned)

Notice how QO puts 30 spaces where HOM puts 20 spaces :) QO is a vastly superior line (HOM is perfectly safe). However in favor of HOM, your existing breakers will drop right in; QO is not compatible so you'd need to budget about $140 on all replacement breakers.

You might consider buying one of these from a store with a favorable return policy, and taking some measurements to confirm it's swappable. The lugs above the main breaker are always hot, and you need to ask the PoCo to de-energize them. Touching those without de-energizing them would be sheer insanity since they can arc-flash as high as 10kA (that's 10,000 amps) which will blow your body across the room (and you to the afterlife).


* The 30-space/40-circuit thing is a throwback to when CTL was the rule; you could only have 42 circuits in a panel. CTL panels have mechanical keying to keep double-stuff breakers out of some spaces. Irrelevant now.

· Registered
49 Posts
Discussion Starter · #14 ·
For my "swap the guts" idea.
Thanks @seharper for the suggestions! Let me know if you have a paypal account :wink2:

I am leaning towards getting the HOM2040M200RB instead of the QO version despite lesser available slots.
  1. The panel cost itself is quite low ($87 vs $244), not to mention the new breakers that would be needed.
  2. I don't see myself needing new slots for the immediate future so even with the HOM it looks like I will have atleast 10-15 open slots for future.
  3. I am not one to list the used equipment on ebay to sell them so if I install the QO panel the HOM ones incl the breaker will just lie around.

Given all this I am thinking the below as next steps:
  1. Get the HOM2040 panel from the local HD. They seem to have it in stock
  2. Call the PoCo to shut down mains. Might invest the savings to buy a non-contact voltage tester :)
  3. Remove the energy monitor equipment
  4. Remove the breakers and their wires (black and red). Keep the ground and white as-is
  5. Remove the bus bar (if that is what it is called??). I can see a few screws that seem to keep it screwed into the panel. Hopefully removing them will be the solution
  6. Take the new bus bar from the HOM2040 panel, screws etc and install in the existing panel
  7. Buy 2 new 50-amp 2 pole breakers like these. One for the tesla new connection and another for the current pigtail of the a/c. That way the electric stove (top left in the first image) will be on its own 50-amp breaker
  8. I am thinking of putting 1 of the new 50-amp on line1 and another on line2.
  9. Reattach breakers, add wires, confirm work against the earlier work.
  10. Keep all breakers in off position. Call PoCo to turn on mains. Turn main breaker on and then individual breakers On one-at-a-time.
  11. Route 6/3 using 3/4" conduit till the driveway for the Tesla charging point (The main reason for this whole thread -phew- :biggrin2:). I am yet to figure out what all things will be needed for this. I was thinking of sinking a pole and mounting the RV power panel so that it is closer to where the car would be parked.

· Registered
8,183 Posts
I would practice removing on the new unit first. Basically you'll be removing EVERYTHING that isn't the empty box - it's a gigantic chunk of black plastic everything is attached to. That WHOLE THING comes out, when it's out, what's left is nothing but a metal box. I would NOT attempt to dismantle components out of the big black assembly!

I see 2 screws on wings on the outer side of the neutral bars. There's 2 right there. There must be some at the bottom also. It's that simple.

When you get to running the EV line, for the parts that are conduit, don't run cable; run individual THHN wires. NM-B (Romex) cable is not allowed outdoors, and UF-B cable is not allowed in conduit. (well it is, but the conduit must be 2" diameter for 6/3...)

And I would run 1" conduit. That will let you upgrade in the future to #3 Cu wire, which will let you run 100A to the Tesla charger. Your service should be able to handle that.

· Registered
49 Posts
Discussion Starter · #16 ·
When you get to running the EV line, for the parts that are conduit, don't run cable; run individual THHN wires.
Will definitely practice on the new panel first! Good point. If I understand the above correctly; I would run 6/3 from the breaker to a junction box close to the conduit. From there would use the THHN and terminate it to the post in the driveway.
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