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Old 03-14-2013, 08:21 PM   #1
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A/C Disconnect question


Hi guys,

I am new to HVAC. I started school about 7 months ago. Just have some questions. My disconnect is 240v 30 amps. I know that the line from the breaker goes into the disconnect. And from the disconnect the a/c gets powered. I checked my panel today and I noticed no double pole 30 amp breaker. This A/C has had no issues at all running for years now but I am confused as to why I am not seeing a double pole 30 amp breaker.

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Old 03-14-2013, 08:39 PM   #2
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A/C Disconnect question


Is the disconnect fused for 30 amp.?

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Old 03-14-2013, 08:54 PM   #3
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Is the disconnect fused for 30 amp.?
it says right on the disconnect 30 amp. What do you mean fused for 30 amp?
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Old 03-14-2013, 09:07 PM   #4
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A/C Disconnect question


I would guess that they didn't use a tandem but rather 2 regular breakers sitting next to one another, or even further away from each other. I would open up the panel very carefully and visually locate the 2 breakers. If it's working it's gotta be getting the 240v somehow. This should be corrected as I believe the tandem breaker is required in that case. Otherwise maybe there is a subpanel somewhere you don't know about?
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Old 03-14-2013, 10:48 PM   #5
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A/C Disconnect question


[QUOTE=russiand;1137449]I would guess that they didn't use a tandem but rather 2 regular breakers sitting next to one another, or even further away from each other. I would open up the panel very carefully and visually locate the 2 breakers. If it's working it's gotta be getting the 240v somehow. This should be corrected as I believe the tandem breaker is required in that case. Otherwise maybe there is a subpanel somewhere you don't know about?[

No other subpanel. So, your saying these took 2 15 amp breakers one hot wire to each to create the 240v?
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Old 03-15-2013, 07:35 AM   #6
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A/C Disconnect question


Mike, your electric home panel has two legs of power. Each brings in 120ish volts. Appliances using 240 have a wire to each leg.
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Old 03-15-2013, 08:57 AM   #7
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Mike, your electric home panel has two legs of power. Each brings in 120ish volts. Appliances using 240 have a wire to each leg.
Correct and your point is?
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Old 03-15-2013, 03:32 PM   #8
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A/C Disconnect question


Some double pole breakers dont look double pole, in meaning they dont have two switches side by side with a connector locking them together.

Our box is like that, big double pole breakers but a single switch near the top of the breaker.

Like was suggested earlier, you may also have a situation where someone used two different breakers in different spots to make 220, bad idea! If this is the case, it would need to be corrected for saftey sake.
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Old 03-15-2013, 04:19 PM   #9
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A/C Disconnect question


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Originally Posted by mikem201 View Post
it says right on the disconnect 30 amp. What do you mean fused for 30 amp?
Yes the disconnect is rated for 30 amps. That just means the connectors & the copper bars are sized to carry 30 amps. The key question is, is it a 30 amp fused disconnect or a 30 amp non-fused disconnect. You'll have to take it apart to tell. If you take it apart & there are fuses or a breaker in your disconnect it's fused. If that's the case it's also possible that the A/C doesn't run through the panel in your house at all. Usually I've seen it in mobile homes. The power runs to a pole in the yard, on that pole is mounted a box which sends power into your electric panel. The A/C can be powered from the box on the pole.
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Old 03-15-2013, 04:24 PM   #10
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Yes the disconnect is rated for 30 amps. That just means the connectors & the copper bars are sized to carry 30 amps. The key question is, is it a 30 amp fused disconnect or a 30 amp non-fused disconnect. You'll have to take it apart to tell. If you take it apart & there are fuses or a breaker in your disconnect it's fused. If that's the case it's also possible that the A/C doesn't run through the panel in your house at all. Usually I've seen it in mobile homes. The power runs to a pole in the yard, on that pole is mounted a box which sends power into your electric panel. The A/C can be powered from the box on the pole.
there are two fuses in the disconnect box and another disconnect box under my meter. Both these boxes are wired to each other. How can and A/C not run through the panel? If you need to open up the A/C and you need to cut the power off that makes no sense. So your saying the mounted box carrier a 10 gauge 30 amp wire but how can that box send power to the panel if its not wired to a breaker inside the panel?
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Old 03-15-2013, 05:33 PM   #11
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there are two fuses in the disconnect box and another disconnect box under my meter. Both these boxes are wired to each other. How can and A/C not run through the panel? If you need to open up the A/C and you need to cut the power off that makes no sense. So your saying the mounted box carrier a 10 gauge 30 amp wire but how can that box send power to the panel if its not wired to a breaker inside the panel?
Usually when I've seen them done that way there is a breaker in the box underneath your meter. A wire runs from that breaker directly to the A/C unit. It doesn't need to run through the panel because it has a fuse in the disconnect, it's no different than hooking it up to a fuse in a panel in your house. If you need to cut power to your A/C you just pull the disconnect. If you need to work on the disconnect you turn off the breaker in the box under your meter.

Admittedly it's a wierd setup, but I've seen it before.
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Old 03-15-2013, 06:18 PM   #12
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A/C Disconnect question


We have a couple trailer/mobile home parks where I am and usually the older trailers have a small 60 amp disconnect and even the power supplly box from the park is small. Perhaps to get around that and not have to upsize the panel ( usually is no physical room near the panel in the trailer either as it is in someone's bedroom ) they just take power from the pole below the meter. Is perfectly safe just different. Always amazes and interests me on this site the different stories about different areas and what they use for gas lines/venting/electrical hookups. Just when you think you have seen or know it all.

Mike if you are going to be a service tech try and remember this for the future as it may save your life. ALWAYS check to make sure the power is off at both incoming sides of a contactor as I have had old dried up 2 pole switches where only 1 pole worked/opened and left one side energized and gave me a good buzz. Never assume a switch works 100% or properly. Even worse when standing in wet grass workin on a AC. You end up toast.
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Last edited by yuri; 03-15-2013 at 06:22 PM.
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Old 03-15-2013, 06:30 PM   #13
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We have a couple trailer/mobile home parks where I am and usually the older trailers have a small 60 amp disconnect and even the power supplly box from the park is small. Perhaps to get around that and not have to upsize the panel ( usually is no physical room near the panel in the trailer either as it is in someone's bedroom ) they just take power from the pole below the meter. Is perfectly safe just different. Always amazes and interests me on this site the different stories about different areas and what they use for gas lines/venting/electrical hookups. Just when you think you have seen or know it all.

Mike if you are going to be a service tech try and remember this for the future as it may save your life. ALWAYS check to make sure the power is off at both incoming sides of a contactor as I have had old dried up 2 pole switches where only 1 pole worked/opened and left one side energized and gave me a good buzz. Never assume a switch works 100% or properly. Even worse when standing in wet grass workin on a AC. You end up toast.
what do you mean both incoming sides of a contactor?
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Old 03-15-2013, 07:02 PM   #14
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A/C Disconnect question


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Originally Posted by mikem201 View Post
So, your saying these took 2 15 amp breakers one hot wire to each to create the 240v?
Sorry. I interpreted that question as you not knowing how to get 240 from two breakers.
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Old 03-15-2013, 07:13 PM   #15
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A/C Disconnect question


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Originally Posted by mikem201 View Post
what do you mean both incoming sides of a contactor?
where the 2 supply/hot wires attach to the contactor.

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