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While attending to a failed capacitor on my HVAC condenser (outside) unit, I noticed that the local circuit breaker in the nearby dedicated box was rated at 60 amps. That struck me as odd as the breaker for the circuit for this unit which is controlled at the main panel is 50 (or maybe 40?) amps. Meaning if an overload or whatever happens, the breaker on the main pane will pop rather than the one outside. If this is by design/code, what would be the reason? (I'd rather replace the outside breaker when necessary than open the inside panel.) And if not by design, is it an issue?

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The breaker in the main panel is protecting the circuit and equipment.The breaker outside is simply a means to disconnect the condenser as required by code. It's probably what the installer had on hand. No need to replace it.

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While attending to a failed capacitor on my HVAC condenser (outside) unit, I noticed that the local circuit breaker in the nearby dedicated box was rated at 60 amps. That struck me as odd as the breaker for the circuit for this unit which is controlled at the main panel is 50 (or maybe 40?) amps.

A circuit breaker is a device which does two things: #1 It automatically trips if current exceeds certain limits for certain times. And #2 it's a manual switch humans can throw to shut it off.

A disconnect is only the second one.

Code requires a disconnect in many, many places. However, when you try to actually buy one, you often find "a disconnect in an enclosure" is more expensive than "a circuit breaker in an enclosure". WTH? The answer is economies of scale. So you install a breaker, even though the "breaker" functionality is superfluous.

Meaning if an overload or whatever happens, the breaker on the main pane will pop rather than the one outside.

LOL no... the feature you're referring to there is called "Selective Coordination". That's when the technical gang do all the right stuff to assure THIS breaker trips before THAT breaker. Yeah, that is only a feature in industrial-tier circuit breakers.

On all this consumer-tier stuff, forget it. The manufacturing tolerances just aren't that tight. Which one trips is largely controlled by Murphy's Law. (if it's raining, the far one will trip).

If this is by design/code, what would be the reason? (I'd rather replace the outside breaker when necessary than open the inside panel.) And if not by design, is it an issue?

Why would you be replacing circuit breakers? They are breakers not fuses, yes? They should not wear out from a couple of trips. Are you dealing with an obsolete panel where acquisition of quality non-Chinese breakers is not feasible?

Code only requires a disconnect. The supply side (inside?) breaker must be the right size to protect the wires. For instance if it is #8 copper NM cable (40A), the breaker must be <=40A.

If you really really wanted to, you could replace the run of #8 Cu NM (40A) with #2 Al SER (90A). The breaker in the main panel can thus be 90A, and the one at the disconnect becomes 40A. A bolted-fault could trip anywhere, but most "slow overload" trips would occur at the outside unit. The disconnect enclosure would need to be 100A rated, but could contain a 40A breaker.

But I've got a better idea of how to have the smaller breaker be outside.

If you're replacing capacitors, the unit is old. If it's old, it has a poor SEER rating (probably 10 at most when it was new). You're wasting a ton of money, two ways.

First, while air conditioning, the thing is so darned inefficient. The newest ones have SEER ratings as high as 38. (that's 38 BTU/hr per watt used, since a watt is 3.41 BTU/hr, that's 11:1 over-unity... wow!) The law says even the el-cheapo units have to be at least 14 or 15 SEER (varying by region).

Second, while heating, it's doing nothing at all and you're forced to burn gas (or worse: electric). There are large swaths of moderate temperatures where you need heat, but you're in the happy zone of a heat pump, where a good one is running a COP of 4 to 6 or even higher. (4 watts of heat made, per watt of energy used). That's so efficient it's cheaper than gas, and it lets you favor the cheaper resource, and even play the rate system, like this guy.

All that to say, maybe it's time for a new heat pump. Fair chance that will use a 20A, 25A or at most 30A breaker, and you can just change the outside breaker to that and leave the 40A feed.

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  • "If you're replacing capacitors, the unit is old." I disagree...the two techs I know well out here in north texas say one of their more common service calls is replacing caps; one does it as a regular maintenance item for systems he installs every 5 years.
    – AA040371
    Jul 23, 2022 at 22:31
  • "Why would you be replacing circuit breakers?" While I didn't actually mention it, In this particular instance the breaker's plastic casing broke/snapped the 2nd time I worked the lever to disconnect the power while I was doing capacitor stuff. It gets pretty friggin' hot where it sits on the wall in some direct sunlight, and it finally decided to give up the ghost, I guess.
    – AA040371
    Jul 23, 2022 at 22:37
  • @mblatz01 well then replace it immediately, don't fool around with broken safety equipment. If you can identify the panel we can identify the correct model of breaker. There are 4 brands which will seem to interchange, but do not actually do so safely. The wrong one will burn up bus stabs and possibly start a fire. Jul 24, 2022 at 2:21
  • Breaker already replaced several days ago with same make and model. My motto has always been "Just say "no" to fires!" :--)
    – AA040371
    Jul 24, 2022 at 13:56

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