Proper sized breaker/wire for this HVAC

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Sparky617

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Is my take on this correct? The minimum size circuit is 17 amps, max breaker is 30 amps. So if I run 12 gauge wire with a 2 pole 20 amp breaker I'm good to go? Wire and breaker have to match. It is for a Trane/Mitsubishi mini-split HVAC. This is the plate on the outside unit.
HVAC.jpg
 

Sparky617

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Is the branch already run? Why wouldn't you use a 10/3 with a 30 2-pole?
For the same reason I don't run premium gas in a car that doesn't need it. The added cost doesn't bring a benefit if a 20 amp circuit is all that is required.
 

afjes_2016

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I think the comparison is a bit off. If you run premium gas in a car that does not need it it won't hurt the car. If you compare this to using a 30amp circuit instead of a 20amp circuit we are not talking that you are just wasting money on the materials that are not needed you are talking about using a circuit rated to protect an appliance etc that may end up damaging it or causing other serious problems. Reason is that the breaker won't trip in time before damage is done. This is a bit different than using premium gas.

The ratings etc are on the name plate for a reason.
 

Sparky617

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I think the comparison is a bit off. If you run premium gas in a car that does not need it it won't hurt the car. If you compare this to using a 30amp circuit instead of a 20amp circuit we are not talking that you are just wasting money on the materials that are not needed you are talking about using a circuit rated to protect an appliance etc that may end up damaging it or causing other serious problems. Reason is that the breaker won't trip in time before damage is done. This is a bit different than using premium gas.

The ratings etc are on the name plate for a reason.
The breaker is there to protect the wire, not the unit. If the unit tries to draw more than 20 amps continuously the breaker will trip to prevent the wire from overheating. The extra expense, like running premium in a car that doesn't need it, isn't needed if the minimum protection required is 17 amps. 20 amps exceeds the minimum.

Decent video on the subject.
 

Hamberg

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... you are talking about using a circuit rated to protect an appliance etc that may end up damaging it or causing other serious problems. Reason is that the breaker won't trip in time before damage is done.
Can you guys help out the electrically-engineered ignorant here? I read that plate as needing a minimum breaker of 20 amp (17 amps) and a max of 30 amps - is that correct?

If so, isn't the manufacture saying the device can withstand (wrong terminology i'm sure) up to 30 amps?

In my mind, as this is an HVAC unit, there could be an initial (startup) load over that 17 amps (probably above the 20 amps) and if so, would it trip that 20 amp breaker??

On the gas analogy, I could (easily) fill it with premium for a tank or two if they were out of regular, but it'd be a PITA to (re)run a 10/3 branch if the 20 amp keeps tripping.
 

bud16415

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I was going to comment the other day when you posted but didn’t and wanted to see how the rest felt.

Here is my logic I think both would work and both will be safe and I think the cost ether way spread out over the life of the home will not be that noticeable. What I would be thinking is maybe down the line this unit will meet its expiration date and the replacement might like the larger conductor and breaker for whatever reason. So I would do it now.
 

billshack

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People also ask




How many amps can 10 gauge wire handle at 220 volts?


30 Amps

The wire and cable gauge is 10gauge. 30 Amps is the max.
 

afjes_2016

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I have to stop responding to threads early in the morning before I finish my first cup of coffee. :coffee: It seems I don't express myself well enough and get caught on it.

Yes, I know the breaker protects the wire etc.
 

Sparky617

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I was going to comment the other day when you posted but didn’t and wanted to see how the rest felt.

Here is my logic I think both would work and both will be safe and I think the cost ether way spread out over the life of the home will not be that noticeable. What I would be thinking is maybe down the line this unit will meet its expiration date and the replacement might like the larger conductor and breaker for whatever reason. So I would do it now.
I get future proofing, I just spent a couple of hundred dollars putting in a 50 amp GFCI protected circuit into my garage for an electric vehicle I don't even own, yet. The breaker alone was nearly $150. We could go all kinds of directions in future proofing our homes. There are some who think that we'll be phasing out natural gas heat in favor of electric heat pumps, gas ranges with induction cooking, gas water heaters with heat pump water heaters. This may happen, and if it does, we'll all probably need 400 amp services. I'm not going to go through that expense for something that may happen long after I'm no longer the owner of this house or even alive. Back in the late 1990s or early 2000s running ethernet cable all over the house was done in the name of future proofing. Technology has moved on and now most devices, including the PC I'm typing on are connected via wifi. Would it be faster to be connected via a cable,? Probably, is it needed, no. I'm getting 60 mbs down and 48 mbs up. Which is plenty fast enough to stream anything without buffering. The TVs are all connected via wifi and we have no problem streaming to multiple sets at one time.
 

bud16415

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I get future proofing, I just spent a couple of hundred dollars putting in a 50 amp GFCI protected circuit into my garage for an electric vehicle I don't even own, yet. The breaker alone was nearly $150. We could go all kinds of directions in future proofing our homes. There are some who think that we'll be phasing out natural gas heat in favor of electric heat pumps, gas ranges with induction cooking, gas water heaters with heat pump water heaters. This may happen, and if it does, we'll all probably need 400 amp services. I'm not going to go through that expense for something that may happen long after I'm no longer the owner of this house or even alive. Back in the late 1990s or early 2000s running ethernet cable all over the house was done in the name of future proofing. Technology has moved on and now most devices, including the PC I'm typing on are connected via wifi. Would it be faster to be connected via a cable,? Probably, is it needed, no. I'm getting 60 mbs down and 48 mbs up. Which is plenty fast enough to stream anything without buffering. The TVs are all connected via wifi and we have no problem streaming to multiple sets at one time.
That's why i suggest doing whatever seems correct today. When I was a kid new homes came with 60a services controlled by 4 fuses for 110v (what they called it then) and one set of fuses for 220v for a stove. It was more than enough. Our house now built in 1870 has been upgraded to 200a.

Time moves on tech changes. Other than lighting most of the time current demands go up. When they start factoring in home heating and transportation I hope we have some pretty smart people working on that problem and not just the people pushing for it.

On your project assuming you have to buy the stuff to do the job each way what is the cost difference?
 

afjes_2016

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I'm getting 60 mbs down and 48 mbs up.
I'm very jealous Sparky617 - I only get 25Mbs down and 4 up and it is cable no less. But I live out in the boon-docks so I guess I should be happy with what I have.
 

Sparky617

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That's why i suggest doing whatever seems correct today. When I was a kid new homes came with 60a services controlled by 4 fuses for 110v (what they called it then) and one set of fuses for 220v for a stove. It was more than enough. Our house now built in 1870 has been upgraded to 200a.

Time moves on tech changes. Other than lighting most of the time current demands go up. When they start factoring in home heating and transportation I hope we have some pretty smart people working on that problem and not just the people pushing for it.

On your project assuming you have to buy the stuff to do the job each way what is the cost difference?
I had the 20 amp breakers, though I had to buy the little thing to join the two handles together, cost $2.50. Judging by how far the 50' of 10/2 went for the auxiliary heat I would have needed 100' roll, for the outside unit so $220 versus $125 for 250' of 12/2. If I had a lot of this to do, it would have been cost effective to buy a 250' roll for $300. Once this project is done, I don't see a need for more 10/2. I had the 12/2 on hand. There isn't a neutral on the outside unit so 12/2 or 10/2 was all that was required. Same with the aux heat unit on the inside unit. Could some mythical new unit need 10/3 or 12/3 in the future, possibly, very likely not my problem though. If I were doing it over in the future I'd probably upgrade my outside panel with more slots and a main shutoff. The outside panel is next to the AC units and powers the two originals directly. With the new basement panel and the EV circuit my outside panel is now full. I ran a 100 amp circuit to a new sub panel in the basement and the EV circuit. I had intended on only doing a 50 amp sub panel but the HVAC alone needs 50 amps if it is running the aux heat feature, which will be rare in my part of NC. Right now the house has 2 100 amp sub panels, 3 AC units (one is a heat pump), 2 gas furnaces, gas water heater, gas dryer, gas range and a gas fireplace.

I see a lot of service upgrades in the future in older homes when EVs dominate the market. There will also be a need for upgrades when/if they push to get all the local distribution lines underground. I'm not sure that cost is factored into the multibillion dollar upgrades that PG&E is planning for in California. A lot of homeowners are likely in for a shock when they find out their electrical service needs to be upgraded as part of that project. Oh and the grid is going to need a lot of work for our all electric future. On the units, they are getting more efficient. This system I'm putting in will heat and cool 1000 square feet of basement, with about 1/3 of the walls above grade.
 

Sparky617

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I'm very jealous Sparky617 - I only get 25Mbs down and 4 up and it is cable no less. But I live out in the boon-docks so I guess I should be happy with what I have.
I'm in a pretty affluent suburb of Raleigh NC. I have the choice of Google Fiber, AT&T Digital (also fiber), and Spectrum Cable (Coax). I've had Spectrum (formally Time Warner Cable) for years and switched to GF earlier this year.
 

bud16415

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When I put my hot tub in I ran into similar (what if situation) on wire sizes and length. I need #6 to the sub panel from the main and needed an odd length where one standard length wasn’t enough and another way to long. I went to home depot and the by the foot price was nuts. Told the guy how many feet I needed and he said I just opened a roll for a guy and sold him some by the foot and he had left exactly what I needed and if I took it all I would get the discounted price minus what was gone per foot. That was just amazing on that run. Then I needed 7 single conductors from the sub panel to the tub thru conduit of #8. I wasn’t so lucky there but for the by the foot price I could buy a whole new reel with twice what I needed. I figured I would use it for something or sell it online. I was wiring my big subwoofers for my home theater and I remembered that stranded #8 and said why not. It worked out great and a year later a guy I know was doing a home theater and we wired his subwoofers with it as well. I took 4-5 strands of it and ran them in parallel and made a long ground strap for my welder. Few more projects I will have it used up. :coffee:
 

Sparky617

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Bud said Time moves on tech changes. Other than lighting most of the time current demands go up.

I'd say technology has gotten more efficient over time and actually current usage is going down. HVAC systems are much more efficient today than 20 years ago, and they were more efficient than the ones 20 years before them. Refrigerators, TVs, PCs, PC monitors, clothes washers all are more efficient today than they were 20 years ago. Devices that create heat from electricity haven't improved much over the years, other than heat pumps. Resistance heating is what it is. We all now have TVs that were unimaginable 30 years ago with amazing pictures and very low energy use compared to their tube predecessors. I won't count dishwashers in the efficiency improvement, while their energy use may have gone down, they take much longer with worse results. I replaced an old tower PC with a laptop, the amount of waste heat generated by the laptop compared to the tower is remarkable. Waste heat is energy used and wasted. Flat panel monitors have a bigger view area with a smaller foot print and use less energy than the CRTs they replaced. My electric bill has actually gone down over the past year or two, part of that may be both kids are now out of the house, but there is a certain amount that remains the same regardless of the number of people here. I'm looking forward to seeing what happens with my electric and gas bill with new HVAC systems in the house. In the south AC is a bigger expense than heating.
 

bud16415

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Bud said Time moves on tech changes. Other than lighting most of the time current demands go up.

I'd say technology has gotten more efficient over time and actually current usage is going down. HVAC systems are much more efficient today than 20 years ago, and they were more efficient than the ones 20 years before them. Refrigerators, TVs, PCs, PC monitors, clothes washers all are more efficient today than they were 20 years ago. Devices that create heat from electricity haven't improved much over the years, other than heat pumps. Resistance heating is what it is. We all now have TVs that were unimaginable 30 years ago with amazing pictures and very low energy use compared to their tube predecessors. I won't count dishwashers in the efficiency improvement, while their energy use may have gone down, they take much longer with worse results. I replaced an old tower PC with a laptop, the amount of waste heat generated by the laptop compared to the tower is remarkable. Waste heat is energy used and wasted. Flat panel monitors have a bigger view area with a smaller foot print and use less energy than the CRTs they replaced. My electric bill has actually gone down over the past year or two, part of that may be both kids are now out of the house, but there is a certain amount that remains the same regardless of the number of people here. I'm looking forward to seeing what happens with my electric and gas bill with new HVAC systems in the house. In the south AC is a bigger expense than heating.
You are correct. I’m all for efficiency in regards to all sources of fuel. If you go back 30-40 years energy was cheap and devices were nowhere as efficient as today. Go back 70-80 years and there wasn’t yet a need for all the necessities of today.



When it comes to heating some progress has been made but the real improvements have been in insulation to keep from heat loss. Same for cooling.



I have some neighbors that keep their windows open during the winter but despite it they have zero energy costs. The Amish burn a lot of wood though. I asked him one day how many MPG did his buggy get and he started by telling me it was 4WD, then he showed me a tin cup and said this many oats get me to town and back. About 18 miles.

I don’t think many of us would make it if we had to go backwards 100 years.
 

Guzzle

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What distance from your main panel to the unit?

I get #10 aluminum or #12 copper, based on Ampacity at 60C.

Your main panel is supposed to deliver 5000A in the event of a short circuit. I guess most residential panels can do this. Ours can.
 

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