# Air Condition and Heat Pump over current protection and wire sizes.

By
Home Inspector with NCW Home Inspections, LLC

Air Condition and Heat Pump over current protection and wire sizes. Chelan County Real Estate Inspections

I see a lot of heat pumps and air conditioning unit.  These are some of the more expensive components of a home.  So when performing home inspections this is an item I look over well along with the associated disconnect.

I will usually remove the disconnect cover and plate to evaluate the fuses and wiring associated with them. But one thing as a home inspector you have to be careful of is proper evaluation of the wire size. (I have been guilty of this on a home inspection).

It is not uncommon to see wire sizes that may be much smaller than normal for a specific breaker or fuse.

For instance you could 10 gauge wire protected by a 50 amp breaker and it would be correct… for that specific AC unit.

The most important thing is to look at the manufacturers label/name plate.  This will give you the information you need to make a quick evaluation in the field.

Here is an example from a recent home inspection-

You can see that this name plate states a minimum circuit ampacity of 20 amps. This tells us what minimum wire gauge we need, which is #12 wire.

The maximum fuse or breaker is 35 amps. So for this piece of equipment we could have 12 gauge wires being protected by 35 amp breaker and it is correct. Really it is that simple.

If you want to be have fun with some math this is how you come up with the calculations yourself.

The air conditioning unit has a 15.3 RLA (rated-load current). For Air-Conditioning and Refrigerating Equipment we can run this at 125 percent of the normal load rating for the conductors per NEC 440.32. This is 19.125 amps and then we add .9 FLA (fan load amps) we come to 20.025 amps, round down to 20 amps. This shows us we can use #12 wire.

For the breaker we use the same information (15.3) but we now multiple by 225 percent per NEC 440.22 and we get 34.425 amps plus the .9 FLA and we get 35.325 amps, round down to 35 amps and that is our maximum breaker or fuse size.

“If you think it's expensive to hire a professional to do the job, wait until you hire an amateur.”

NCW Home Inspections, LLC  is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…

Your Wenatchee and Chelan Professional Real Estate, Home and Structural Pest Inspection Service

www.ncwhomeinspections.com                                               509-670-9572

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Fernando Herboso - Broker for Maxus Realty Group
Maxus Realty Group - Broker 301-246-0001 - Gaithersburg, MD
301-246-0001 Serving Maryland, DC and Northern VA
Good information for all of us... Possibly the most overlooked electrical safety item....undersized wires that are overloaded
Mar 17, 2013 01:24 AM #1
1,954,512
Debb Janes EcoBroker and Bernie Stea JD
ViewHomes of Clark County - Nature As Neighbors - Camas, WA
REALTORSÂ® in Clark County, WA

Hi Donald, I'm going to leave the wire evaluation job up to you. Ha. That's why we hire the pros for our home inspections. I didn't know about this...until today. Happy St. Patrick's Day to you.

Mar 17, 2013 01:25 AM #2
Rainmaker
501,633
Donald Hester
NCW Home Inspections, LLC - Wenatchee, WA
NCW Home Inspections, LLC

Fernando, Thanks . Yeah there are some more specific rules for dedicated equipment that allows smaller wire gauges that used on general circuits.

Debb, You do not want to look at all the minutia ; ) Have a very Happy St Patrick's Day.

Mar 17, 2013 01:34 AM #3
Rainmaker
694,665
Clint Mckie
Desert Sun Home, commercial Inspections - Carlsbad, NM
Desert Sun Home, Comm. Inspection 1-575-706-5586

Hi Donald.

And where was the electrical inspector on this one? The same place they always are when they inspect. Never in the right place doing the right thing. But they still want the inspection fee for the JHA don't they?

Have a great Saint Patrick's day in the great Northwest my friend.

Best, Clint McKie

Mar 17, 2013 01:34 AM #4
Rainer
171,130
Robert Butler
Aspect Inspection - Montreal West Island, QC
Montreal Home Inspector | Aspect Inspection

Thanks for the info Don. I expect most non-inspectors would glaze over with all the tech talk. Few actually do the math, so we should.

Mar 17, 2013 03:33 AM #5
Rainmaker
501,633
Donald Hester
NCW Home Inspections, LLC - Wenatchee, WA
NCW Home Inspections, LLC

Clint, Thanks.

Robert, It really is pretty easy once you know where to look. But math is always fun ; )

Mar 17, 2013 03:37 AM #6
Rainmaker
1,867,863
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

People often ask me why I spend so much time looking at the label, and I tell them I am checking information for further checking later when we look at the panel box.

Great discussion Don.  Suggested, as usual.

Mar 17, 2013 08:06 PM #7
Rainmaker
690,388
James Quarello
JRV Home Inspection Services, LLC - Wallingford, CT
Connecticut Home Inspector

I always check the labels against the wiring and breakers. I have had electricians dispute breaker sizes relative to the data plate. Bottom line, what the plate says is right, period. No need for all that math :)

Mar 17, 2013 09:40 PM #8
Rainmaker
501,633
Donald Hester
NCW Home Inspections, LLC - Wenatchee, WA
NCW Home Inspections, LLC

Jay, That is the same for me, too often I see improper fuses. Especially true if the unit has been replaced.

Jim, Very true. The math is just for those who just have to do some ; )

Mar 17, 2013 11:11 PM #9
Rainmaker
1,867,863
Jay Markanich
Jay Markanich Real Estate Inspections, LLC - Bristow, VA
Home Inspector - servicing all Northern Virginia

Often times, inside the fust box, when they install a new compressor they remove the old fuse and simply wire nut everything together.

Mar 18, 2013 02:50 AM #10
Rainmaker
501,633
Donald Hester
NCW Home Inspections, LLC - Wenatchee, WA
NCW Home Inspections, LLC

Jay, That is why I try to remove those covers to see what going on.

Mar 18, 2013 02:57 AM #11
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Rainmaker
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## Donald Hester

NCW Home Inspections, LLC
Home Inspection Services and Inspection Questions
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