circuit change

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  #1  
Old 07-16-06, 06:52 PM
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circuit change

Hi, couple of questions that appear simple, but I've only just moved here from the UK, so don't know what the answer is for the US.
I am a qualified electrical engineer in the UK, but not US,lol
We've just bought a new house, and I plan on turning the partially finished walk out basement into an office, but need more outlets(room has one right now)
The ceiling is not finished so access is ok, there is a 220v dryer supply that goes across the ceiling(through the joists). At the box end, it's a twin 30A breaker, the cable I believe is "romex"(orange sheath, solid conductors)
If I take out that twin breaker and drop a single 20A, is there any reason I can't use that Romex cable to feed the outlets? It clearly will be ok current rating wise.
Just not sure if there's a "code" issue.
Second question , and this is more of a curio for me, The US uses radial circuits as opposed to ring, is there code that says ring circuits cannot be used? this would negate a lot of the voltage drop issues I see over here?
 
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Old 07-16-06, 07:07 PM
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Originally Posted by vapochilled
Hi, couple of questions that appear simple, but I've only just moved here from the UK, so don't know what the answer is for the US.
I am a qualified electrical engineer in the UK, but not US,lol
We've just bought a new house, and I plan on turning the partially finished walk out basement into an office, but need more outlets(room has one right now)
The ceiling is not finished so access is ok, there is a 220v dryer supply that goes across the ceiling(through the joists). At the box end, it's a twin 30A breaker, the cable I believe is "romex"(orange sheath, solid conductors)
If I take out that twin breaker and drop a single 20A, is there any reason I can't use that Romex cable to feed the outlets? It clearly will be ok current rating wise.
Just not sure if there's a "code" issue.
Second question , and this is more of a curio for me, The US uses radial circuits as opposed to ring, is there code that says ring circuits cannot be used? this would negate a lot of the voltage drop issues I see over here?
Engineers are not Electricians and visa-versa. There is no reason that you can not down grade the 10/2 that you have, to a 20A ckt. Please make sure that it is fused appropriatly. Some will state that you should continue this ckt with#10. I would make a prominate note in the panel and box from wich extended affixed to the wire in question that there is a smaller gage wire on this ckt. This may be against the (code) law (so isn't speeding). But it would be safe. And the next person would know of the situation.
 
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Old 07-16-06, 07:09 PM
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That orange cable is likely a 10/3. You could certainly use that #10 for two 20 amp circuits.
You could also install a sub panel on the end of the current 30 amp line and have more than two 15 or 20 amp circuits.

I don't know if ring circuits are against code for sure. I think they are but I can't say for 100%.
 
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Old 07-16-06, 09:22 PM
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Can you explain how the ring situation reduces voltage drop?

General purpose circuits are limited to 20 amp circuits in the US. From what little I have read, ring circuits generally are 30 or 32 amp circuits. Would you still be able to effect a benefit utilizing a 20 amp circuit?

There is no problem with using a larger than minimun required conductor. It is common to aid in reducing voltage drop. The notation lectriclee suggested is a good one but not required. If a conductor is upsized to counter voltage drop, it is often reduced back to the minimum size (for overcurrent protection rating) further into the run of the circuit.

As with the others, I too believe the ring circuitry to be against code but I cannot cite a reference to back this up.

Because of its' non use in the US, it would present a safety issue without a warning of the use of it.
 
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Old 07-17-06, 04:06 AM
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thanks for the responses.
The sub-panel is an idea, though may be a little ott for just the office outlets.
The ring circuit reduces volt drop a little simple by having two legs feed the same place, though it's main purpose is to reduce the current load at connection points on outlets.
As for Engineers not being electricians lol, I'll give you that one, though I was a working elec for 11 years as well
 
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