Breaker size in box VS data plate on unit.

**Dan Sandweg** · 09-06-2010, 09:35 AM

Hope all are having a good holiday......

I have been reporting on the difference between the max breaker size listed on the data plate of the condenser if it does not match what is in the panel box if it is clearly marked A/C. I also take into considereration if it is a long run from the box. ( I will allow a larger breaker)

If the breaker panel is "close" to the condenser, and the 2 do not match, I write it up. Then I was challenged by a buyer as to the size of the fuse on the exterior that protects the unit. I do not pull out these fuses.

How does the size of the exterior fuse influence the sizing of the breaker at the panel or does it?

Am I wrong not to check the pull out blocks?

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James Duffin · 09-06-2010, 10:35 AM

The breaker in the panel feeding a fused disconnect at the condensing unit can be as large as you want as long as the wire is the correct size for the breaker. The fuses at the unit can not be any larger than the rating on the data plate.

Now if the outside disconnect is not fused then the breaker in the panel can't be any larger than the data plate rating.

You do need to check the fuses in the outside disconnect. And a long run of wire does not allow you to increase the size of the breaker.

**Gunnar Alquist** · 09-06-2010, 10:36 AM

Originally Posted by Dan Sandweg

I have been reporting on the difference between the max breaker size listed on the data plate of the condenser if it does not match what is in the panel box if it is clearly marked A/C. I also take into considereration if it is a long run from the box. ( I will allow a larger breaker) If the breaker panel is "close" to the condenser, and the 2 do not match, I write it up. Then I was challenged by a buyer as to the size of the fuse on the exterior that protects the unit. I do not pull out these fuses. How does the size of the exterior fuse influence the sizing of the breaker at the panel or does it? Am I wrong not to check the pull out blocks?

Dan,

The breaker (I assume you are referring to one at the service equipment or a downstream distribution panel) should match the wire size from the panel to the A/C disconnect. That is the purpose for the breaker. I do not address wire length as I believe that is well beyond SOP. The fuse at the disconnect should match the requirements of the A/C. If you do not check the fuse size, you should refer to a licensed HVA/C contractor.

As a matter of course, I generally recommend a service because I do not know when the A/C has last been serviced.

**H.G. Watson, Sr.** · 09-06-2010, 10:57 AM

Originally Posted by Dan Sandweg

Hope all are having a good holiday......

I have been reporting on the difference between the max breaker size listed on the data plate of the condenser if it does not match what is in the panel box if it is clearly marked A/C. I also take into considereration if it is a long run from the box. ( I will allow a larger breaker)

If the breaker panel is "close" to the condenser, and the 2 do not match, I write it up. Then I was challenged by a buyer as to the size of the fuse on the exterior that protects the unit. I do not pull out these fuses.

How does the size of the exterior fuse influence the sizing of the breaker at the panel or does it?

Am I wrong not to check the pull out blocks?

Yes you are apparently wrong if you are not recognizing, misidentifying, overlooking, etc. an intermediate (between the service panel and the equipment) OverCurrent Protective Device and erroneously reporting.

BTW, not all condensors MAY be protected by circuit breaker. The data plate will indicate max OCPD, and if same must be fused, must be circuit breaker, or may be either fused or circuit breaker. The plate will also indicate min. ampacity for the conductors from OCPD to unit.

Not all pull-out disconnects are actually FUSED, either.

It seems some basic electrical theory is lacking.

Here are some topic thread links, take a look at them first. Then, lets get some more specific information from you and get terms straight, and address your specific questions after you've done some reading.

http://www.inspectionnews.net/home_i...t-breaker.html

http://www.inspectionnews.net/home_i...condenser.html

After you've taken a look at the above, post back here with your follow-ups. Thanks.

P.S. What's up with this "allow" business? Are you a home inpsector? AHJ? FHA/VA appraiser? Doing construction stage inspections? Insurance audits/condition reports? What?!? Where in the world are you located (please update profile information, A.S.A.P., Thanks again, in advance!).

**Bob Harper** · 09-06-2010, 11:52 AM

On outdoor fused disconnects, the breaker protects the wiring but the fuse protects the attached appliance such as condenser fan or compressor. You can use larger wiring than needed but the rating plate on the condenser will state the max. fuse/ amperage protection allowed.
HTH,

**Jim Luttrall** · 09-06-2010, 01:36 PM

Originally Posted by Dan Sandweg

Hope all are having a good holiday......

I have been reporting on the difference between the max breaker size listed on the data plate of the condenser if it does not match what is in the panel box if it is clearly marked A/C. I also take into considereration if it is a long run from the box. ( I will allow a larger breaker)

If the breaker panel is "close" to the condenser, and the 2 do not match, I write it up. Then I was challenged by a buyer as to the size of the fuse on the exterior that protects the unit. I do not pull out these fuses.

How does the size of the exterior fuse influence the sizing of the breaker at the panel or does it?

Am I wrong not to check the pull out blocks?

If either the panel or the disconnect have the appropriate sized fuse/breaker then all is well. (given that wire size matches the breaker/fuse.)
In my world though, virtually none of the boxes at the condensing units are fused. Most are a simple disconnect switch.

i.e. if the data plate on the unit calls for a 30 amp and you have a 50 at the distribution panel and a 30 fused disconnect at the unit then your good.
If you have the reversed situation, you are good. Some where in the supply there should be a breaker that matches the data plate.

**Jerry Peck** · 09-06-2010, 02:11 PM

Let's see if I can combine all the above information into one post ... here goes ...

THE MAXIMUM breaker or fuse size allowed is stated on the nameplate of the unit - that is NOT TO BE EXCEEDED regardless of the length of the circuit (which has nothing to do with it anyway).

Now, though, there is another thing you should be checking too - that the circuit size meets THE MINIMUM circuit size required. THAT is really more important than the maximum breaker or fuse size ... or at least equally as important.

Okay, if there is ONE overcurrent protection device - fuse or breaker - then that ONE overcurrent protection device MUST NOT BE RATED HIGHER than that which is allowed on the name plate ... AND ... the minimum circuit size MUST NOT BE RATED LOWER than that which is required on the name plate.

If there are TWO overcurrent protection devices - say a fuse outside and a breaker inside - then the lowest rated one MUST NOT EXCEED that allowed on the nameplate, and if the circuit size is larger than that required by the nameplate, the origination point overcurrent device may be larger to protect the circuit wiring. This may be a bit confusing, so I will give an example.

Let's say you have two overcurrent protection devices, fuses outside and a breaker inside, and let's say the nameplate allows a 30 amp breaker while only requiring a minimum 20 amp circuit ... and you find that a 40 amp circuit was installed between the panel and the outside disconnect ...

In the above case the outside fuses could be 30 amps and the inside breaker could be 40 amps, or, the outside fuses could be 60 amps and the inside breaker could be 30 amps, or, the outside fuses could be 30 amps and the inside breaker could be 30 amps. Follow that? The maximum protection for the condenser unit itself in all three of the preceding is 30 amps. One example protects the 40 amp conductors at 40 amps (which is allowed), the other examples protect the 40 amp conductors at 30 amps (which is also allowed).

Joseph Stevens · 09-06-2010, 06:21 PM

Originally Posted by H.G. Watson, Sr.

P.S. What's up with this "allow" business? Are you a home inpsector? AHJ? FHA/VA appraiser?

I see this term used all the time but it never clicked. What does AHJ stand for?

**Jerry Peck** · 09-06-2010, 06:34 PM

Originally Posted by Joseph Stevens

I see this term used all the time but it never clicked. What does AHJ stand for?

Authority Having Jurisdiction

I.e., the building department, the Building Official, the Board of Rules and Appeals, the Chief Building/Electrical/Plumbing/Mechanical Inspector, etc., all depending on the local setup.