ViperCertified Home Inspector
join:2012-03-22
Toronto | reply to nunya
Re: A/C breaker issue said by nunya:I am a licensed master electrician. You are dead wrong, and so is your chart.
I sure as hell hope you aren't passing this misinformation along to your customers. You are doing a disservice by doing so.
The "rule of thumb" used to be 10A per ton. You could almost always count on a 1-1/2T unit being 15A, 2T=20A, 2-1/2T=25A, and so forth. So, your little chart (and "reputable" source) was wrong even back then.
These days, with high SEER units, all of that is out the window. There is no rule of thumb. I've seen plenty of high SEER 2-1/2 ton units where the MAX breaker size is 15A.
In the end, the manufacturer makes the determination on the minimum and maximum fuse and circuit size, not some inaccurate chart. It's stamped on the nameplate.
Saying every A/C condenser requires at least a 30A circuit is dead wrong. In many cases, a 30A breaker would expose the equipment to damage and void the warranty.
A 15A breaker for a 2.5 ton unit is definitely an undersized breaker situation. Jesus, you put your regular lightening, receptacles (approx. 12) on a 15 amp breaker not an entire air conditioning unit.
If i were you, i would stop going electrical work and maybe get into landscaping.
I have two options here. I either go back and forth with someone who is probably an apprentice (calling himself a master electrician) or is possibly certified by Google (God bless the internet) OR I go with my years and years of experience. I think I go with option 2.
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Certified Home Inspector
Certified Level 1 Thermographer |
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 davidgGood Bye My FriendPremium,MVM
join:2002-06-15
none | said by Viper:A 15A breaker for a 2.5 ton unit is definitely an undersized breaker situation. Jesus, you put your regular lightening, receptacles (approx. 12) on a 15 amp breaker not an entire air conditioning unit.
If i were you, i would stop going electrical work and maybe get into landscaping.
I have two options here. I either go back and forth with someone who is probably an apprentice (calling himself a master electrician) or is possibly certified by Google (God bless the internet) OR I go with my years and years of experience. I think I go with option 2.
and this post is exactly why a home inspector is not supposed to cite code violations. that chart you linked earlier looks like one that comes off a portable generator sizing chart, which does give very general sizing info.
Nunya and Whizkid3, you guys just need to throw out those large bulky NEC code books since you only ever need a simple chart! 
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Lack of Preparation on YOUR Part does NOT Constitute an Emergency on Mine! |
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 nunyaWho is John Galt?Premium,MVM
join:2000-12-23
O Fallon, MO
kudos:8
 ·Charter
 ·surpasshosting
 ·voip.ms
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Just a single example of thousands available. Now, stop spreading your disinformation.
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...because I care. |
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 alkizmo
join:2007-06-25
Pierrefonds, QC
kudos:1
1 edit | reply to Viper
said by Viper:said by nunya:These days, with high SEER units, all of that is out the window. There is no rule of thumb. I've seen plenty of high SEER 2-1/2 ton units where the MAX breaker size is 15A.
A 15A breaker for a 2.5 ton unit is definitely an undersized breaker situation. Jesus, you put your regular lightening, receptacles (approx. 12) on a 15 amp breaker not an entire air conditioning unit. I'm going to use my 14 SEER 2.5 ton A/C as an example.
(Ton X 12000BTU) / (SEER) / 240V = Amps
2.5 ton X 12000 BTU / 14 / 240 = 8.92A
Add to that 8.92A more amps for the fan and other electrics inside and you get about 15A RLA, which is close to what's stamped on my A/C's plate.
Of course, it requires a 20A circuit because of the 80% load limit of a circuit for sustainable draw.
Now take a 2.5 ton 21 SEER unit and you're at 5.9A instead of 8.92A for 14 SEER. That's 3A less, which I can see how high SEER units can work on 15A circuits. |
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ViperCertified Home Inspector
join:2012-03-22
Toronto | reply to davidg
that chart you linked earlier looks like one that comes off a portable generator sizing chart, which does give very general sizing info.
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Certified Home Inspector
Certified Level 1 Thermographer |
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| How about you post who your "very reliable source" is then? |
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ViperCertified Home Inspector
join:2012-03-22
Toronto | reply to nunya
said by nunya:Just a single example of thousands available. Now, stop spreading your disinformation.
First of all you cant tell people what to do. Who made you in charge here? Second of all, you call yourself a master electrician and you have no work to do except for sitting on line all day long and trying to prove others wrong.
Me - however have places to go and people to meet today. You sit here, behind a computer and I have a couple of inspections to do for the day. Its $500 an inspection and debating with an online 'anonymous' is not worth my time.
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Certified Home Inspector
Certified Level 1 Thermographer |
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| reply to Viper
You probably shouldn't be giving advice or trying to discredit experts in their fields. Nonetheless, many here seem to think, as you do, that Google makes them experts in all things.
The manufacturers of A/C equipment have already calculated the minimum circuit ampacity and the maximum over current protective device for the equipment. I can guarantee you they didn't use your little chart. |
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garys_2kPremium
join:2004-05-07
Farmington, MI Reviews:
·callwithus
·Callcentric
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Well, I feel for your customers and only hope that your non-electrical advice is more fact-based than what you've shown here. That table you showed looks like the one hanging from the ceiling at Home Depot to show what's "needed" for different types of circuits -- a general guideline at best and quite often incorrect. |
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 mix
join:2002-03-19
Utica, MI | reply to Viper
Viper, are you one of those Toronto area home inspectors I see Mike Holmes lose his hair over on HGTV? |
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 Nick_LPremium
join:2003-01-22
Pittsburgh, PA | reply to Viper
said by Viper:A 15A breaker for a 2.5 ton unit is definitely an undersized breaker situation. Jesus, you put your regular lightening, receptacles (approx. 12) on a 15 amp breaker not an entire air conditioning unit.
Dude, for your own sake, stop digging while you can still see the top of the hole!
You're not only wrong, you are demonstrably wrong and the above quote proves it. What does lighting load (resistive) have to do with motor (capacitive) load?
Additionally, while no one is perfect nunya and whizkid are two of the most expert and respected posters here and give thoughtful, accurate and VERIFYABLY correct information time after time. Shhhh, you might learn something. |
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 DannyZGentoo FanboyPremium
join:2003-01-29
Erie, PA | said by Nick_L:Additionally, while no one is perfect nunya and whizkid are two of the most expert and respected posters here and give thoughtful, accurate and VERIFYABLY correct information time after time. Shhhh, you might learn something.
But it's been sooooo entertaining watching Viper  make a complete ass out of himself 
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 dosdoxiesPremium
join:2004-12-15
Wallingford, PA | reply to mix
said by mix:Viper, are you one of those Toronto area home inspectors I see Mike Holmes lose his hair over on HGTV?
I was just thinking the same thing. |
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TheMGPremium
join:2007-09-04
Canada
kudos:1 | reply to Viper
said by Viper:A 15A breaker for a 2.5 ton unit is definitely an undersized breaker situation. Jesus, you put your regular lightening, receptacles (approx. 12) on a 15 amp breaker not an entire air conditioning unit.
15A @ 120V is not the same as 15A @ 240V!!!
Let's see...
15A*120V= 1800VA (max 1440VA continuous)
15A*240V= 3600VA (max 2880VA continuous)
Not the same. |
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 whizkid3Premium,MVM
join:2002-02-21
Queens, NY
kudos:9 | reply to Viper
said by Viper:A 15A breaker for a 2.5 ton unit is definitely an undersized breaker situation. Just saying this without mentioning the voltage at all, does not really demonstrate knowledgeability. Neither does picking a fight with nunya, who is one of the most knowledgeable electricians I know. He said your little chart is crap. I agree. At best, its good for the first attempt at educating a layperson who knows nothing about how the electrical system works in a home. That's about it.
Don't knock his credentials. I normally wouldn't either, but you deserve it for placing yourself above that of a Master Electrician. You inspect homes. BFD. Just about any schnook can walk around a house checking a few boxes and then provide a disclaimer that's longer than the report and a $400 bill for basically nothing. My advice would be to not become so impressed with your own credentials. On the grand scale of technical construction careers, home inspector is about one level above being a Burger King fry clerk.
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said by alkizmo:I'm going to use my 14 SEER 2.5 ton A/C as an example.
(Ton X 12000BTU) / (SEER) / 240V = Amps
2.5 ton X 12000 BTU / 14 / 240 = 8.92A Unfortunately, Alkizmo, as much as we like you around here; you don't know what you're doing either. You can't use the average seasonal energy usage to determine the amp rating of an air-conditioner. You can get the average power or amps required, averaged over a whole cooling season. SEER is very useful for determining how much energy you will use over a cooling season. Not very useful for sizing a circuit or breaker which must work under maximum load; although doubling what you get from your calculation could work out to be a good rule of thumb estimate. Stick with the manufacturer's ratings. Nunya showed the best way to get them - check the manufacturer's specs or nameplate. |
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alkizmo
join:2007-06-25
Pierrefonds, QC
kudos:1 | said by whizkid3:Unfortunately, Alkizmo, as much as we like you around here;
YAY! 
said by whizkid3:although doubling what you get from your calculation could work out to be a good rule of thumb estimate. Stick with the manufacturer's ratings. I'm only trying to show Viper that 15A on 2.5 tons SEEMS possible to meeeeeeee 
Im actually surprised, I went to re-check my A/C plate when I got home from work and the running amp rating is 14.7
20A was actually the MAX circuit protection requirement!!! I thought it was the minimum! Another thing that is wrong in this house! (It's currently on 25A fuses). |
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whizkid3Premium,MVM
join:2002-02-21
Queens, NY
kudos:9 | said by alkizmo:20A was actually the MAX circuit protection requirement!!! I thought it was the minimum! Another thing that is wrong in this house! (It's currently on 25A fuses).
Better double-check that. Sounds to me like the MCA (minimum circuit amps) would be about 18 to 20A; and the MOCP (maximum overcurrent protection) would be 25 or 30A. 14.7A FLA (or RLA) may be just for the compressor. Figure 1 amp for the fan (if it has a separate motor); and 0.25 A for the controls, and you get approximately:
14.7A x 125% + 1A +0.25A = 20A = MCA (minimum circuit amps) |
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garys_2kPremium
join:2004-05-07
Farmington, MI | Re: A/C breaker issue All that and still no cite on where that "really good source" table came from. I think I saw one on the back of a Wheaties box, once, that looked like that. |
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whizkid3Premium,MVM
join:2002-02-21
Queens, NY
kudos:9 | reply to Anon
said by Viper:I will be back to see the entertainment here tomorrow. 1. I have a day job in this field, which pays me more than anyone could make doing home inspections. (Which is why I don't do that instead.)
2. I have two businesses. One of which does inspections & assessments on some of the largest commercial buildings in the world. It pays substantially better than home inspection work.
3. I would post my credentials if I really felt like showing why you are one step up from being a fry clerk. But I don't feel the need to keep entertaining those with low intelligence and no class. |
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