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chris_stfc 12-20-2007 02:38 AM

Plug Sockets - Basic Question
Hi All,

One quick Question. I have a four way plug with another four way plug plugged into that which all the plug sockets are being used for with Computers and Monitors plugged into them? Is that safe?

Many Thanks


AllanJ 12-20-2007 07:19 AM

An entire 20 amp. circuit should not have more than 2200 watts of load (80% is 1760).

An entire 15 amp. circuit should not have more than 1650 watts of load (80% is 1320).

If equipment is going to be turned on for long periods of time, use the 80% figures.

Extension cords must not be run under carpets or run across floors where the cords will get stepped on or tripped over.

Excess length of extension cords must be draped or run freely as opposed to remaining coiled up.

Almost all extension cords and external fittings (4 way receptacle taps, etc.) have lower wattage ratings.

GREGNC 12-20-2007 06:26 PM

[quote=AllanJ;82027]An entire 20 amp. circuit should not have more than 2200 watts of load (80% is 1760).

An entire 15 amp. circuit should not have more than 1650 watts of load (80% is 1320).

allenj i have always used 2400watts 80%=1920 for 20a
1800watts 80%=1440 for 15a
are you required to use 110 for nominal voltage in calculations in your area?
i have been using 120 for branch circuit loads and 115 or nameplate for motor loads.

Spike99 12-24-2007 09:49 AM


Originally Posted by chris_stfc (Post 82010)
Hi All, One quick Question. I have a four way plug with another four way plug plugged into that which all the plug sockets are being used for with Computers and Monitors plugged into them? Is that safe? Many Thanks Chris

A few moments ago I was surfing for other info and came across your above post. Since I was in the same boat (sort of speaking) a few weeks ago, I had to register and help out.

My main floor TV Cluster area consists of a TV, DVD/CD Player, a lamp, Game Box station and a radio. All connected to a shared 15A circuit. Although we never flipped its "shared with other things on main floor as well" circuit, this TV Cluster electronics area kept growing and growing. For a picture, surf:

For piece of mind (and to reduce future breaker trips), I installed a dedicated 12/2 on 20A breaker. From the wall outlet to the main panel. Installed it and connected my TV Cluster area onto its own Surge Protector bar as well. For completed picture, surf:
Note: I just need to add a spoon full of drywall mud, sand to 180 grit and paint. Done and over with.

If you feel that your existing circuit (probably a shared 14/2 wire on a 15A breaker) is over its 50% load, you might want to install your own 20A on 12/2 wire as well. Most people use "over 80%" as their circuit upgrade value but when it comes to extra sensitive computers or electronics, using over 50% load is better. re: Dedicate wire creates much "cleaner" current flow - to your TV Cluster or Computer Cluster area.

Hope this helps as well...


J. V. 12-25-2007 11:37 AM

There are no limits on receptacles in residential dwellings, only locations. You could install 100 recepts on a 15 amp single pole breaker and not be in violalation. But that would just plain stupid. I have to assume you guys are calculating for commercial.

Spike99 12-25-2007 02:05 PM

For my region, the building code states less then 11 outlets are allowed. I like using the MAX 10 outlet limit rule. Their assumption is that an outlet "on average" has a 1.5 Amp device connected to it. And only 80% of those connected devices will be ON the exact same time. To me, I don't like using this minimum building code. To me, one should always manually calculate the needed AMPs at each outlet (like a large 1800W microwave in a basement bar), then decide if a dedicated outlet would be better. Yes, above "local building code" approach. Especially if you know your TV Cluster or Computer Cluster or basement Bar Mircowave will always remain in that exact location - within that room.


For me, I'm not very good with math. Even today, I measure twice before cutting a board. LOL!!!!

When it comes to sensitive electronics (like TV Clusters, Computer Clusters) and other sensitive items, I like to use the 50%-80% rule. For this, I take the number of "normal operating" Watts (or Amps if listed) of the devices on that wire. If watts, I divide by 110. Thus, creating its equivlant of Amps figure. Always keep 20% buffer "Peak Amps" needs. When a device is turned on, its power needs peak.. Thus, 10%-20% short term need for more power (on that wire / breaker).

For a 14/2 - 15A "general used" circuit, I calculate its needed "normal operating" Amps. If over 80% Amps load (re: over 12 Amps), then its wire size and breaker size should be upgraded. Upraded to 12/2 on 20A breaker. If under 80%, then leave the existing 14/2 - 15A "as is".

For my TVs, computers and other sensitive cluster areas, the "cleaner the flow" the better. If "normal operating" AMPs load is above 50%, then upgrade the wire and breaker size. For example, go with 12/2 on 20A breaker. If "normal operating" AMPs load is below 50%, then "leave as is". Leave on the 14/2 on 15A wire.

Is this 50%-80% "over kill"??? Many would say YES. And from a math perspective, I would say YES it is as well. However.... If one is looking for "clean flow" of electrical current for their sensitive electronics (like TVs, Computers, etc.), using the 50%-80% rule works great. Been doing it for years.


Stubbie 12-25-2007 04:03 PM


There are no residential regions to my knowledge that use the 1.5 amp or 180 watt calculation when designing their general purpose branch circuits. This is taken from the commercial building code as J.V. has stated. It was never intended to determine the total number of receptacles, it was and is still intended to be used when determining the building load so that the number of general purpose branch circuits can be determined. It for some reason is used by people to justify the number of receptacles but frankly it would be rather inaccurate to do that. I have absolutely no idea what that was all about as far as the clean flow theory and 50% and 80% loads when determining when to increase the branch circuit rating. I'm hoping that this was just a individual who had his "own" ideas and wasn't basing them on any known electrical codes or design methods.
Unless you are serving a branch circuit with a dedicated continuous load you can load the circuit to what it is rated without effecting the "flow" of clean electricity. The electrical code only requires that a 15 amp receptacle does not supply more than 12 amps (80%) out of that single receptacle if that receptacle is installed on a branch circuit with more than one single receptacle. A duplex receptacle is two single outlets or receptacles. 16 amps for a 20 amp rated branch circuit using the same criteria.. This is addressed in NEC section 210.23 and simply means that one cord connected piece of equipment or one cord connected appliance cannot load the branch circuit at more than 80% of its rating if that branch circuit has more than one outlet. A good example would be a vaccum sweeper on a 15 amp rated branch circuit.

In your case you do not want two four way plugs providing seven outlets connected into a single outlet. Though there is no immediate danger in doing so the duplex receptacle is not rated to operate in this configuration and cannot provide a good connection with the weight of all the cords and connectors pulling on the wipes of the receptacle. It does not have that kind of holding tension. You run the risk of the connection becoming loose and overheating. So if you have a grounding type receptacles (3 prong) and a grounding wire connected to them in the premise wiring then use a good quality surge protector with internal overload to plug your equipment into and then use the single power cord to connect to the duplex outlet. Be sure that total connected cord and plug load to that receptacle does not exceed 80% of the branch circuit rating. Circuits that are custom designed for computers and supporting equipment are fine but are not the norm in a household environment. Proper load mangement with existing circuits generally will keep your electricity flowing cleanly......:wink:

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