I am using 120V and 240V notation. The original question includes 110V, 220V and 230V. For all practical purposes, 110V, 115V and 120V are the same and 220V, 230V and 240V are the same, and the bigger number should be exactly double the smaller number. Current standard convention is 120V/240V.
The diagram is a bit confusing. But as I understand it:
- Main panel feed to subpanel should be a 50A 4-wire (hot/hot/neutral/ground) feed. Note that the hot colors listed in the diagram do not matter. You can use black and red or two blacks instead of red and blue. Also note that the 100 foot maximum distance between main panel and subpanel really doesn't matter, except in theory with respect to voltage drop. The 50A breaker can be larger (60A is typical) if the wire is sized appropriately.
- Subpanel has 2 GFCI breakers (20A single 120V breaker, 30A double 240V breaker).
- Distance from subpanel to hot tub should be as listed - minimum 5 feet (you don't want it in literal reaching and splashing distance) and maximum 50 feet (because it needs to be in line of sight; also should not be around the corner or blocked by bushes or a fence)
- The heater (most likely) connects to the 30A breaker and gets 240V. The rest (controls/pump?) connects to the 20A breaker and gets 120V using L2 and Neutral.
- Since L2 is only used for the 30A breaker, it has 20A excess capacity available. So there should be no problem connecting a 20A single 120V breaker to L2 and Neutral. If the subpanel is a typical odd/even left/right stack then you should have the 30A double on one side, the 20A single on the other side and an empty space below the 20A - use that for another 20A breaker.
- All breakers in the subpanel should include GFCI protection.
- The 60A breaker is a waste, as Harper already noted, because you can't use it for the 20A 12 AWG or 30A 10 AWG circuits.
Update Based on Image
Based on the image of a 2-space so-called-panel with a double 60A Square D breaker and lots of plastic, it appears you have one a QOE250GFINM:
Picture from Amazon $279 - don't buy one there! Link from Home Depot $145 - don't buy one there either! But don't get one of these at all! (You already have one. This is a warning to anyone else - don't spend 3x the cost of a 6 space panel to get a 2 space panel. That's just backwards.)
The problem is that this is (a) over-priced and (b) 2 spaces. In theory 4 circuits, but you can't use it that way if you need GFCI, which you absolute do. In addition, all the specs I have been able to find indicate that this box is rated for 50A. So even as a feed to another subpanel, it is limited to 50A, which is OK for this application, but not with the currently installed breaker.
You have two options:
- GFCI feed from the main, new breakers here
GFCI is simply not available in quad breakers. So you can't put a 20A single and a 30A double in this box and GFCI protection. Which means GFCI protection has to be upstream. If your main panel can (legally, technically, not just "shove it in there") use this 60A GFCI breaker, and your feed wire is legal for a 60A breaker, move this breaker to the main panel, replacing whatever is currently there (logically it would have a 60A non-GFCI breaker). Oops, can't do that because this panel is limited to 50A. See if you can swap the 60A for a 50A, or buy a 50A GFCI breaker that matches your main panel. Then install a 20/30/30/20 quad breaker here, which I believe is a QO20303020. Which is (a) ridiculously expensive (yes, online prices (not including Amazon, which is worse) can be much higher than in-person prices at a real supply house, but still crazy, and (b) is apparently really a QO2030 + QO3020 + handle tie - I'm not sure if that would be legitimate for 30A double breaker since that needs to be common trip. But in theory (the experts will chime in if I'm wrong) that should do the trick. And then you would have a 20A single available for your new circuit.
This is what I highly recommend doing. For example, you can get this Square D Homeline 100A 6 space subpanel:
for < $50. Square D QO and other brands available for similar price, this is just the first one that came up on Home Depot's web site. Just make sure it is outdoor rated.
Add breakers. Again, putting in a GFCI breaker at the feed will save you money. If that isn't possible or practical, you have 6 spaces here and you will only need 4 even with GFCI - 2 single 20A, 1 double 30A.