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Brandon Whitmore

Couple quick questions......

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My brain seems to be fuzzy right now, so I figure that since I can't remember the code reference, I'd ask here.

Both questions are in regards to the same house, built last year.

1)An air conditioner was added a few months ago. The AC unit calls for a max. of 25 amps fuse of circuit breaker. The fuse block fuses are 25 amps, while the HACR breaker in the panel is 30. Since the fuses are the right size in the switch disconnect, does the main breaker still need to be a max. 25 amps as well?

2)Furnace in attic: The air handler wire (NM-B) is run from the truss top chord area and hangs about 40" to where it enters the air handler with no means of support/ attachment. The wire is not secured near where it enters the furnace (wrong), and does not closely follow building materials (wrong). Shouldn't the wire be run in a sleeve of something such as FMC in order to comply? I guess a 2x suspended down from the top chord so that the wire could be adequately supported.....

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My brain seems to be fuzzy right now, so I figure that since I can't remember the code reference, I'd ask here.

Both questions are in regards to the same house, built last year.

1)An air conditioner was added a few months ago. The AC unit calls for a max. of 25 amps fuse of circuit breaker. The fuse block fuses are 25 amps, while the HACR breaker in the panel is 30. Since the fuses are the right size in the switch disconnect, does the main breaker still need to be a max. 25 amps as well?

Not necessarily. The breaker in the panel should be sized to protect the branch circuit wiring. The branch wiring itself should be sized according to the appliance data plate.

2)Furnace in attic: The air handler wire (NM-B) is run from the truss top chord area and hangs about 40" to where it enters the air handler with no means of support/ attachment. The wire is not secured near where it enters the furnace (wrong), and does not closely follow building materials (wrong). Shouldn't the wire be run in a sleeve of something such as FMC in order to comply? I guess a 2x suspended down from the top chord so that the wire could be adequately supported.....

The cable should follow the framing.

Marc

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I gotta disagree with Marc regarding appropriate breaker sizes and "branch circuit" wiring. This is 240 V wiring straight to the air conditioner, not a branch circuit. And we all know that AC data plates typically say something such as "minimum circuit ampacity 22.7 Amps" with a "maximum HACR breaker size of 40 Amps." For this example I will assume that the wiring is 10 gauge. In that case, if there's a 40 amp breaker I call it good, even though the breaker would appear to be too large for the wiring. But with an air conditioner, we're dealing with a momentary load issue, not constant, therefore the seeming discrepancy.

In this case, the fuse nearest the unit is correct. No problem with a bigger breaker on the panel.

Assuming that all of the wiring -- to and from the disconnect -- is rated to handle at least the minimum load specified on the data tag for the unit, I wouldn't see anything to write up.

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Not necessarily. The breaker in the panel should be sized to protect the branch circuit wiring. The branch wiring itself should be sized according to the appliance data plate.

Hi Marc,

Thanks for answering, but I'm still confused on this one......

The AC manufacturer calls for a max. OCPD of 25amps, and for a min. wire ampacity of X.

In this case, the cable supplying power to the disconnect/circuit is 10 gauge, which is adequate.

The fuses in the switch disconnect are 25 amps, but since those fuses can be easily replaced, I'm not sure they are allowed as the primary OCPD.

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Not necessarily. The breaker in the panel should be sized to protect the branch circuit wiring. The branch wiring itself should be sized according to the appliance data plate.

Hi Marc,

Thanks for answering, but I'm still confused on this one......

The AC manufacturer calls for a max. OCPD of 25amps, and for a min. wire ampacity of X.

In this case, the cable supplying power to the disconnect/circuit is 10 gauge, which is adequate.

The fuses in the switch disconnect are 25 amps, but since those fuses can be easily replaced, I'm not sure they are allowed as the primary OCPD.

I'm not Marc, but I still say you don't have a problem. The fuse AT THE DISCONNECT is correct. A slightly larger breaker in the service panel isn't an issue. So what if the fuses can be changed? So could a breaker in the same location. What's the problem?

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I agree that the pullout fuses at 25amps are correct for protecting the AC unit. As for the feed from the panel to the fuse pullout, if the cable is at least AWG 10, a 30amp breaker in the panel is acceptable.

As far as fuses being able to be replaced, so could any other part of the system be replaced. If a correct configuration is there on the day of the inspection, there is not a problem to report.

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Kevin,

For some reason, I didn't see your first post until now. I must not have refreshed my browser before typing a response.

Your response is what I was thinking, buttt... I rarely see fused disconnects at AC units.

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I gotta disagree with Marc regarding appropriate breaker sizes and "branch circuit" wiring. This is 240 V wiring straight to the air conditioner, not a branch circuit. And we all know that AC data plates typically say something such as "minimum circuit ampacity 22.7 Amps" with a "maximum HACR breaker size of 40 Amps." For this example I will assume that the wiring is 10 gauge. In that case, if there's a 40 amp breaker I call it good, even though the breaker would appear to be too large for the wiring. But with an air conditioner, we're dealing with a momentary load issue, not constant, therefore the seeming discrepancy.

In this case, the fuse nearest the unit is correct. No problem with a bigger breaker on the panel.

Assuming that all of the wiring -- to and from the disconnect -- is rated to handle at least the minimum load specified on the data tag for the unit, I wouldn't see anything to write up.

I don't see the disagreement. We're both saying the same thing, except that the 240 V circuit to the AC is what I consider a branch circuit.

Marc

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Not necessarily. The breaker in the panel should be sized to protect the branch circuit wiring. The branch wiring itself should be sized according to the appliance data plate.

Hi Marc,

Thanks for answering, but I'm still confused on this one......

The AC manufacturer calls for a max. OCPD of 25amps, and for a min. wire ampacity of X.

In this case, the cable supplying power to the disconnect/circuit is 10 gauge, which is adequate.

The fuses in the switch disconnect are 25 amps, but since those fuses can be easily replaced, I'm not sure they are allowed as the primary OCPD.

I am.

Marc

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Not necessarily. The breaker in the panel should be sized to protect the branch circuit wiring. The branch wiring itself should be sized according to the appliance data plate.

Hi Marc,

Thanks for answering, but I'm still confused on this one......

The AC manufacturer calls for a max. OCPD of 25amps, and for a min. wire ampacity of X.

In this case, the cable supplying power to the disconnect/circuit is 10 gauge, which is adequate.

The fuses in the switch disconnect are 25 amps, but since those fuses can be easily replaced, I'm not sure they are allowed as the primary OCPD.

I'm not Marc, but I still say you don't have a problem. The fuse AT THE DISCONNECT is correct. A slightly larger breaker in the service panel isn't an issue. So what if the fuses can be changed? So could a breaker in the same location. What's the problem?

Only problem is the unsecured NM, though it's small fish.

Marc

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The 30 amp breaker protects the #10 conductor. The 25 amp fuses protect the unit.

The installer had to work with the breaker sizes that are available. I think what he did works and there's no hazard.

If the max fuse amps was 20, he could have installed a 20 amp breaker and skipped the fuse block.

I see we have an agreement across the board, I think.

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You don't see very many 25-amp breakers, whereas 25-amp fuses are readily available. In this case, the 25-amp fuse meets the manufacturer's requirement, and the 30-amp breaker is unquestionably OK for the 10AWG wire.

I will bet that the nameplate of the unit would have allowed a smaller wire, and that it said something like "min. circuit ampacity 19 amps." So this begs the question, what if they had used a 12AWG wire? Would it still be OK with the 30-amp breaker? I say yes. In the NEC, 240.4(D)&G) kick this back to article 440, and the fuse satisfies everything that 440.4(B) requires for protection of the AC unit.

Neither the breaker or the fuse is providing overload protection. They are there only to protect against short circuits and ground faults. The AC compressor has overload protection built in. If you could find a 25-amp breaker to replace the existing breaker, it would accomplish absolutely nothing in terms of the safe and proper operation of this equipment.

Before we grant any kudos to the electrician for oversizing the wire to the AC, realize that he probably didn't know what size unit they were going to put out there, and that he is probably the same bozo who strung a wire through the air to the a-coil in the attic.

Douglas Hansen

www.codecheck.com

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Thanks to everyone for weighing in, and Douglas, thanks for the code references.

I did the original inspection a year ago, and yes, the wire was already run. In this case the AC installer switched out the standard non fused disco for a fused one in order to comply with the AC manufacturers requirements.

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Not necessarily. The breaker in the panel should be sized to protect the branch circuit wiring. The branch wiring itself should be sized according to the appliance data plate.

Hi Marc,

Thanks for answering, but I'm still confused on this one......

The AC manufacturer calls for a max. OCPD of 25amps, and for a min. wire ampacity of X.

In this case, the cable supplying power to the disconnect/circuit is 10 gauge, which is adequate.

The fuses in the switch disconnect are 25 amps, but since those fuses can be easily replaced, I'm not sure they are allowed as the primary OCPD.

I'm not Marc, but I still say you don't have a problem. The fuse AT THE DISCONNECT is correct. A slightly larger breaker in the service panel isn't an issue. So what if the fuses can be changed? So could a breaker in the same location. What's the problem?

Around these parts anyway a 30a 2pole breaker and 10g wire to disconnect is standard for most condensing unit hookups.

Most outdoor disconnects are of the non-fused variety ,mostly for the fact that they cause fewer problems

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Dang, you mean running cable like this is NOT OK.

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Where's that sarcasm emoticon when you need it!

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Dang, you mean running cable like this is NOT OK.

Click to Enlarge
tn_201182516384_B094.jpg

56.16 KB

Click to Enlarge
tn_2011825163844_B102.jpg

43.19 KB

Where's that sarcasm emoticon when you need it!

I've busted the company whose sticker is on the furnace cabinet twice in the past month for egregious errors they made. A city inspector had blessed one of the installations and, to his credit, apologized when he was made aware of the flubs.

The realtor for both transactions, whom you know, told the HVAC company supervisor, "At least you're an equal opportunity business. You screwed the rich white people in the $500,000.00 house just as readily as you screwed the poor black man in the $50.000.00 house."

ahahahahahaha . . . .

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And this one was already 17 years old so you know they've been doing it "equal opportunity" for a long long time.

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