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Old 04-05-2012, 01:38 PM   #1
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Input needed on 240 vs. 120v situation


Hey guys,

So my main hobby of interest is home theater and I am getting ready to convert an unused room that is separate from my house (kind of like a pool house except we don't have a pool) into a dedicated theater room. My house has 200amp service, which is split so that 100amp is provided exclusively to the "pool" room. The breaker box for the pool room has a 240v/30amp breaker for the AC unit in said room, along with six 120v/20amp breakers. The room is wired so that each wall has it's own breaker, the ceiling lights have their own breaker, and another breaker powers an external outlet on the outside of the room (for running a pond aerator). Overkill, I know, but my father always made sure things were done overboard or not at all.

Any hoot, I have a subwoofer (Paradigm Sub 25) that is meant to run off of a 240v line for maximum continuous output (the subwoofer is rated at 3000w continuous, 7500w peak output). I want to figure out the easiest/best way to hook this bad boy up so that minimum amount of work is needed (i.e. - rewiring) but also that it has the power it wants to play loud and low.


Option #1 - Split the 240v line that currently powers the AC unit so it will now power the AC unit and subwoofer at the same time. The AC unit in question draws 15amps when at max usage. Is this even possible/allowed?

Option #2 - Isolate one of the 120v/20amp breakers currently in use and wire it for 120v/30amps (the wiring in the wall is thick enough to support 30amps as is....as stated my father made sure to overdo everything) so the subwoofer has it's own dedicated outlet. Granted, this is not 240v but isn't 120v/30amps the same as 240v/15amps?

Option #3 - Run a dedicated 240v/30amp line just for the subwoofer. This option is actually the hardest because the breaker box for this room is full (it only has eight breaker slots, two of which are running the 240v for the AC unit and the other six are for the individual circuits as mentioned). How could I rewire/upgrade my breaker box to accommodate another circuit?


If the subwoofer is rated at 3000w continuous but 7500w peak (for very brief/split-second notes involving very deep and powerful bass) do I need to run enough amperage to equal up to 7500w or just 3000w (i.e. - 240v/30amp vs. 240/15amp)?


Thanks in advance!

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Last edited by BigCoolJesus; 04-05-2012 at 01:43 PM.
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Old 04-05-2012, 01:51 PM   #2
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Input needed on 240 vs. 120v situation


Best bet, run a new circuit.

You could unplug the air conditioner and use its receptacle for the subwoofer if the circuit amperes rating is high enough. Most high amperage equipment and 240 volt equipment needs separate circuits because there is a maximum circuit rating for each piece of equipment. This produces a mathematical conundrum when you need enough amperes altogether if you were to have separate receptacles on the same circuit for two or more pieces of equipment.

It is not desirable to plug in more equipment if hte air conditioner draws more than 80% of the circuit rating, for example 12 amps for a 15 amp circuit.

A circuit with the AC unit hard wired may not be used for anything else when the AC draws more than 50% of the amperes rating.

The 240 volt circuit is suggested because a 30 amp 120 volt circuit must also be custom-strung if one does not already exist. The 30 amp equipment (subwoofer) may not be equipped with a plug that fits a 15 or 20 amp receptacle. Check the subwoofer instructions for the circuit amperes requirements.

The next step up from 20 amps is 30 amps so the latter will be the requirement for the subwoofer drawing up to 7500 watts.

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Last edited by AllanJ; 04-05-2012 at 02:05 PM.
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Old 04-05-2012, 01:55 PM   #3
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Input needed on 240 vs. 120v situation


Quote:
Originally Posted by AllanJ View Post
If the air conditioner plugs in (as opposed to be "permanently" wired in) then it is permissible to install a second 240 volt receptacle on the same line.

But it is not desirable to plug in more equipment if hte air conditioner draws more than 80% of the circuit rating, for example 12 amps for a 15 amp circuit.

A circuit with the AC unit hard wired may not be used for anything else when the AC draws more than 50% of the amperes rating.
The AC plugs into a wall outlet (it is not hard-wired). And as stated, it only draws 15amps at maximum power/cooling setting.

My only question is if the subwoofer is rated to draw 3000w at continuous power but can draw up to 7500w for split-second instances, how much amperage does said subwoofer need to insure it never runs out of head-room during use?
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Old 04-05-2012, 02:21 PM   #4
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Input needed on 240 vs. 120v situation


Quote:
Originally Posted by BigCoolJesus View Post
My only question is if the subwoofer is rated to draw 3000w at continuous power but can draw up to 7500w for split-second instances, how much amperage does said subwoofer need to insure it never runs out of head-room during use?
Those wattage ratings are most likely the output of the amp. Do the instructions recommend an AC circuit rating? If not, I would call the manufacture or see what others are doing in the home theatre forums.
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Old 04-05-2012, 02:53 PM   #5
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Input needed on 240 vs. 120v situation


The subwoofer comes with two different power cords. One is a standard two prong 120v cord and the other is a NEMA 6-15 plug (250V, 15A) cord. Also, were the power cord plugs into the back of the subwoofer only has two prongs (no third/ground prong) even when using the NEMA power cord. The back of the subwoofer reads "120-230V~50Hz/60Hz, 100W Typical"

The Paradigm technical support person I was speaking to said that 240v/15amps is plenty of power for the subwoofer.


Excerpts from the product page:

Power Factor Correction (PFC). PFC shapes the current so it is sinusoidal and continuous in time, allowing maximum power (95%) to be drawn and with far less noise on the line. To compare: A unit without PFC draws only 60 to 70% of the available power since the line current is switched on and off by the input rectifier (a noise-inducing process in itself!) at twice the frequency. Current flows at the peak of the line voltage only, effectively choking the line. PFC prevents over-heating/tripping of the circuit breakers. Add to this the highly efficient Ultra-Class-D™ design ensuring maximum output and the SUB 25’s amplifier becomes an input / output powerhouse that is simply unbeatable.

Universal Input Power: SUB 25’s Universal Input Power feature allows the subwoofer to operate connected to any line voltage between 108 volts and 265 volts. However, in order to achieve maximum continuous performance we highly recommend connecting to a 240-volt line. (See Dealer for additional information.)


Does all of that information help in answering my options?

Thanks!

Last edited by BigCoolJesus; 04-05-2012 at 02:57 PM.
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Old 04-05-2012, 03:39 PM   #6
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Input needed on 240 vs. 120v situation


Wire size has alot to do with al electrical working correctly. If your wire is rated 30A (10AWG) or 20A (12AWG), it doesnt matter if it's 120 or 240...You want to match your wire to your breaker to your receptacle (or switch) to whatever you need electricity to...They have to match in order for the safest installation of electical items..Example if you have an A/C which has on the nameplate 15A 120V, you should have #12 AWG wire and a 15A breaker and the receptacle should be 120V...Make sure wire sizes are correct
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Old 04-05-2012, 03:48 PM   #7
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Input needed on 240 vs. 120v situation


This is a cord and receptacle device and cannot be connected to a 30 amp circuit like the AC.

Since the existing 20 amp breakers feed receptacles and lighting circuit, those circuits are limited by code to 20 amps max.

Run a new circuit is your only workable option, should be a 250 volt 15 amp circuit with a NEMA 6-15 receptacle. IF your breaker box is full you may be able to add tandem, twin or " half size" breakers to gain space. Tell us the brand and model. The label behind the cover will tell you the breakers it accepts. You may also be able to combine some of the receptacles on the 20 amp breakers to gain the 2 slots you need.
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Old 04-05-2012, 03:52 PM   #8
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Input needed on 240 vs. 120v situation


You're overthinking this.

The subwoofer draws approximately 100 watts. Your 20 amp circuits can easily handle that as they currently exist.

What other loads exist in the pool house? You might be able to connect 2 or 3 of the walls circuits together to run off of one 20 amp breaker or use a tandem breaker. This would free up 2 slots for another 15 amp double pole breaker for your subwoofer.

You could also install a small subpanel for the a/c unit and your amp.

FYI, You can't have a 20 amp breaker feeding a single 6-15 receptacle, NEC 210-21(b). You can use #12 wire though.
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Old 04-05-2012, 04:40 PM   #9
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Input needed on 240 vs. 120v situation


Quote:
Originally Posted by AandPDan View Post
You're overthinking this.

The subwoofer draws approximately 100 watts. Your 20 amp circuits can easily handle that as they currently exist.
But the amplifier in the sub can output 3000w continuously........
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Old 04-05-2012, 04:46 PM   #10
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Input needed on 240 vs. 120v situation


Quote:
Originally Posted by rjniles View Post
This is a cord and receptacle device and cannot be connected to a 30 amp circuit like the AC.

Since the existing 20 amp breakers feed receptacles and lighting circuit, those circuits are limited by code to 20 amps max.

Run a new circuit is your only workable option, should be a 250 volt 15 amp circuit with a NEMA 6-15 receptacle. IF your breaker box is full you may be able to add tandem, twin or " half size" breakers to gain space. Tell us the brand and model. The label behind the cover will tell you the breakers it accepts. You may also be able to combine some of the receptacles on the 20 amp breakers to gain the 2 slots you need.
If I had a family friend who is a certified electrician come over one day, how hard/how much work would be involved for him to tandem some of the 120v breakers together and install a double pole 240v/15amp breaker for the subwoofer?
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Old 04-05-2012, 04:53 PM   #11
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Input needed on 240 vs. 120v situation


You have not told us the brand and model of the panel to determine if it will accept tandems.
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Old 04-05-2012, 05:15 PM   #12
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Input needed on 240 vs. 120v situation


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Originally Posted by rjniles View Post
You have not told us the brand and model of the panel to determine if it will accept tandems.
Oops, sorry. I am away from the house at the moment and do not have that information written down.

Is a sub-panel basically a mini-breaker box that is installed at the current 240v outlet? I.E. - If I put a sub-panel at the spot of my current 240v outlet for the AC, would this allow me to hook up both the AC and subwoofer to their own 240v circuits originating from that sub-panel? Effectively it acts as a splitter in the basic sense?

Thanks.
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Old 04-05-2012, 05:45 PM   #13
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Input needed on 240 vs. 120v situation


so what does it say on the back panel of the sub?

From the owner's manual:

POWER REQUIREMENTS

The "Watts" (W) rating indicated on the rear panel is the typical power your subwoofer will draw during normal use. However, when played at levels that will cause the neighbors to call the police, and make your eardrums bleed, the actual wattage draw will vary with the bass content of the progam material. ... Although not generally not required for typical music and movie program material, if the bass content of your program is very loud and more continuous in nature (like War of the Worlds battle scenes on a continuous loop), and if you play your system at very high levels so that the homeowners association will serve you with eviction papers, we recommend connecting subwoofer models with higher power ratings (i.e. over 1200 watts RMS) to dedicated AC circuits.

(I might have embellished a little)
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Old 04-05-2012, 06:15 PM   #14
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Input needed on 240 vs. 120v situation


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Originally Posted by M3 Pete View Post
so what does it say on the back panel of the sub?

From the owner's manual:

POWER REQUIREMENTS

The "Watts" (W) rating indicated on the rear panel is the typical power your subwoofer will draw during normal use. However, when played at levels that will cause the neighbors to call the police, and make your eardrums bleed, the actual wattage draw will vary with the bass content of the progam material. ... Although not generally not required for typical music and movie program material, if the bass content of your program is very loud and more continuous in nature (like War of the Worlds battle scenes on a continuous loop), and if you play your system at very high levels so that the homeowners association will serve you with eviction papers, we recommend connecting subwoofer models with higher power ratings (i.e. over 1200 watts RMS) to dedicated AC circuits.

(I might have embellished a little)
lol. Since this is a different website geared at different topics not immediately associated with home theater components, I will refrain from correcting your embellishment other than telling you that you are incorrect in your thinking, humerous or not.

But I digress.......
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Old 04-05-2012, 06:45 PM   #15
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Input needed on 240 vs. 120v situation


Quote:
Originally Posted by BigCoolJesus View Post
lol. Since this is a different website geared at different topics not immediately associated with home theater components, I will refrain from correcting your embellishment other than telling you that you are incorrect in your thinking, humerous or not.

But I digress.......
So what is wrong with his post? I would say he is pretty close to being right.

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