Is my subpanel wired incorrectly for a 240v circuit?

Question

I have a subpanel in a detached workshop which is supplied by two 50 amp circuits from my home's main panel.

My goal is to add a 240v receptacle to power an air compressor.

I have an existing 14-50R receptacle already installed but I noticed that it's wired directly from the feeder lugs and bypasses any breaker in the subpanel. Is this okay? Seems sketchy.

I have two breaker slots that I could use instead; currently those slots have 20 amp breakers but I don't use those circuits for anything and could abandon them. Would it make sense to replace those breakers with 30 amp breakers and connect a 14-30R receptacle?

Answer 1

Feed-through like that is legal in general (the wires are protected by the breaker in the main panel) - however those lugs are almost certainly not rated to hold down two wires, but rather only one. You need a second set of proper lugs for the feed-through. But also in this case (as NoSparksPlease pointed out) you’re in a detached outbuilding so feed-through is not legal without a local shutoff.

Other possible issues in that box:

• Black wire possibly smaller than 4 AWG remarked to white/neutral. Neutrals smaller than 4 AWG must be a native neutral color (white or gray). Photo is too small to see the gauge markings on the feed wires.
• Blue wire apparently on the neutral bar, again looking smaller than 4 AWG. Must be 4 AWG to be re-marked as neutral, and must actually be re-marked if it is a neutral.
• White wires on the two left breakers. It's OK to use whites as hot for 240V circuits in /2 cable, but these are 120V circuits in conduit. They need to be proper hot colors.
• Panel is Zinsco with known fatal issues that can burn your house down: busbar contact problems, known breaker problems. Should be replaced promptly. Not a big job since this is a small sub-panel. Get more spaces while you're at it.

Answer 2

You have ONE 50A - 240V circuit feeding the shop.

It's protected by a single 50A (double-space this being North American split phase) breaker. It has two hots (through the breaker) and one neutral.

It's therefore fine for it to connect to a 50A receptacle, directly. Edit: comments correctly point out that as a detached building, you need a local disconnect. Other answers point out that this is apparently a known daangerous panel and should be replaced. So, replace it with a panel with a main breaker, and there's your local shutoff.

If you are loading it anywhere near 50A, you can't use much of anything else or you can expect the breaker to trip. On the other hand, if your compressor only needs 30, 25, 20 or 15A, you should not slap a 50A plug on it and "plug-er-in" as the breaker will not protect your compressor from faults correctly in that case.

50A will support a rather large arc without tripping, as I have seen when my oven's heating element blew.

Answer 3

Sorry to say this, but what a mess! For starters, that looks like a Zinsco panel, which are notorious for the breakers not tripping and other failures.

Second, is that really a feed thru panel, or is it supplied from the main panel with 2 wires per leg? It's not code legal to have parallel feed wires on anything but service entrance feeds in a residential installation. What is the gauge size on the feeds?

Lastly if supposedly a feed thru setup, why is there only one neutral?

Recommendation: If Zinsco, rip that thing out and replace it with Cutler Hammer or Square D QO panel.

Answer 4

"I have an existing 14-50R...wired directly from the feeder lugs and bypasses any breaker in the subpanel. Is this okay?"

No.

NEC 225 which applies to Outside Branch Circuits says:

225.31 Disconnecting Means. Means shall be provided for disconnecting all ungrounded conductors that supply or pass through a building or structure.

The code follows with various detail, but you need switches to disconnect everything, the most versatile method while eliminating that fire hazard Zinsco panel is to install a panel with a main breaker.

Most everything else has issues too: White wires used as hots, #8 (smaller than #4) neutrals phased white instead of solid color, Zinsco panel, no space for a 240v breaker, no apparent wire feeding ground rods, multiple wires landed in single-wire lugs.

Check (or download) the Installation Instructions for the compressor, it may specify breaker and wire size that may not directly align with general Code provisions for a 12A installation, but the Instructions are part of the UL/CSA/ETL Listing and must be followed to comply with NEC 110.3.