Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 03-07-2009, 02:08 PM   #1
Newbie
 
Join Date: Mar 2009
Posts: 13
Rewards Points: 10
Default

Maximum wattage question


hey-I just bought a house and it was built in the 60's.i know the very basics about how many watts you can use with 15, 20 amps and so forth.(about 80% of the max ampage, correct?) My questions for the electric gurus are: 1.how long will the wiring in a house this old be good for with constant use of electricity? 2.If Im using all of a 20 amp breakers capacity on a single 120 volt outlet, will the wiring at this outlet become too hot and hazardous, as a result of all of the power going to one outlet?? 3. what is the difference/benefit to using a 120v power cord from an appliance as opposed to a 240v plug? 4. If i use a solid quality extension cord, could I run a 1500 watt portable A.C. off of it safely? If not, why? Please respond only if you know your stuff-Thanks.
J

Electricnewb is offline   Reply With Quote
Old 03-07-2009, 04:39 PM   #2
Member
 
Join Date: Jan 2009
Location: Boston, MA
Posts: 241
Rewards Points: 150
Send a message via AIM to Bocolo
Default

Maximum wattage question


I am hesitant to post answer because of your quote "Only respond if you know your stuff", understand that I am by no means an electrician and some of the answers may not be complete.

1. Wiring in the house should be good as long as there are no shorts or loss of power. If you are referring to being up to code then you need to check what code your municipality is on. As long as you do not do any major (I don't know if major means adding 1 circuit or 25 circuits) renovations you do not need to worry about bringing the house of to code. Any new wiring you do has to be to code.

2. If you are using a 20 amp breaker with 12 gauge wire you should not have a problem. You should not use a breaker that is rated higher than your wire. For example: use 15 amps for 14 gauge, 20 amps for 12 gauge, 30 amps for 10 gauge. Do not use 20 amps on 14 gauge wire.

3. I really don't understand the question.

4. I don't believe it is recommended. The main reason for spacing requirements for receptacles is to avoid the use of extension cords. Why? That is what code states and it could be a fire hazard.

As to watts to amps, I believe a 15 amp breaker will give you a max of 1800 watts and a 20 amp breaker will give you a max of 2400 watts. The is something about the 80% rule but I am not to clear on it. I believe it means that you should not go over 1440 watts on a 15 amp and 1920 watts on a 20 amp. I am sure someone will let us both know if any of this information is incorrect. Thanks.

__________________
One Pound of Knowledge Requires Ten Pounds of Common Sense In Order To Be Useful
Bocolo is offline   Reply With Quote
Old 03-07-2009, 04:41 PM   #3
Member
 
Join Date: Jul 2008
Location: Pennsylvania, USA
Posts: 272
Rewards Points: 250
Default

Maximum wattage question


Quote:
Originally Posted by Electricnewb View Post
1.how long will the wiring in a house this old be good for with constant use of electricity?
Wiring is not affected by "constant use of electricity" within the design limits of the conductors. However, wiring conductors and insulation are damaged by situations where:

-- excess current was allowed to occur (putting a 30A breaker on a 14AWG circuit),
-- where damaged by heat from loose connections, repeated surges, or use in areas with high ambient temperatures, etc.
-- where susceptable to mechanical damage
-- and many other improper uses of wiring

Quote:
2.If Im using all of a 20 amp breakers capacity on a single 120 volt outlet, will the wiring at this outlet become too hot and hazardous, as a result of all of the power going to one outlet??
Not if the wiring was correctly installed, used, and maintained.

Quote:
3. what is the difference/benefit to using a 120v power cord from an appliance as opposed to a 240v plug?
You'll have to clarify what your are asking. The entire circuit components must match - meaning if your appliance is rated 240VAC, you must use the proper power cord, with a listed 240V plug on the end of it, plugged into a listed 240V receptacle, connected to a properly sized and wired 240V circuit, which is fed from a properly installed double pole breaker which is sourced by each of your two legs of power in the panel.

If your appliance is dual rated, meaning it can be wired for either 120V or 240V, you can wire it to a 120V receptacle if the circuit is large enough.

Quote:
4. If i use a solid quality extension cord, could I run a 1500 watt portable A.C. off of it safely? If not, why?
Your portable air conditioner probably has instructions that tell you NOT to use an adapter plug or an extension cord. This is for basic electrical safety.

Your unit must be fed from a grounded receptacle, that's why they tell you to not use an adapter plug (although a there is no guarantee that a 3-prong outlet is properly grounded just because it has 3-prongs).

Also, many people would try to use any old extension cord they have which would be too small for the current draw of the unit.

If the air conditioner is 120V, I would not worry about using a SHORT length of 10AWG extension cord to run it. Don't use a 50 footer and run it from one room into the next where it will become a tripping hazard or where it would likely be damaged.

If it is 240V, no extension cord.
__________________
Willis
williswires is offline   Reply With Quote
Old 03-07-2009, 08:25 PM   #4
Newbie
 
Join Date: Mar 2009
Posts: 13
Rewards Points: 10
Default

Maximum wattage question


cool-that about answers all of my questions-Thanks to you both for taking the time to answer.anybody else-feel free to chime in. by the way-how would one be able to tell whether or not the house was wired correctly, and whether or not there is hazardous wiring in the house?
Electricnewb is offline   Reply With Quote
Old 03-07-2009, 08:30 PM   #5
Newbie
 
Join Date: Mar 2009
Posts: 13
Rewards Points: 10
Default

Maximum wattage question


In regards to my third question(apparently it didnt make sense-my apologies-my knowledge is limited on these topics) Im basically wondering what is the difference between a 120 v and a 240v power cord. Ive heard that you can pull more amps off a breaker with a 240 then with a 120, but that the wattage amounts to the same..Is this accurate?
Electricnewb is offline   Reply With Quote
Old 03-07-2009, 08:40 PM   #6
Member
 
Join Date: Jan 2009
Location: Boston, MA
Posts: 241
Rewards Points: 150
Send a message via AIM to Bocolo
Default

Maximum wattage question


I don't think you mean power cord. If you are talking about a 240 volt circuit then you are talking about multi wire in the circuit. Typically you have a white, black, red, and ground. The black carries 120 volts, the red carries 120 volts which equal 240 volts. You can get more wattage if you use bigger cable and a bigger breaker. For example 10/3 cable (10 gauge, 3 wires, 1 ground) with a 30 amp breaker. In regards to inspecting your electrical wiring best is to hire an electrician. I guess you can check wire size to correct amp breakers and voltage coming in at receptacles, and fixtures, check wires for continuity and so on but you will not be able to see what is hidden behind the walls unless you take them down.
__________________
One Pound of Knowledge Requires Ten Pounds of Common Sense In Order To Be Useful
Bocolo is offline   Reply With Quote
Old 03-07-2009, 09:35 PM   #7
Newbie
 
Join Date: Mar 2009
Posts: 13
Rewards Points: 10
Default

Maximum wattage question


for example, my a.c. unit has an option to use a 240v three pronged plug or a 120v.same with my ballast for an aquarium bulb.supposedly id be using less amperage with the 240 power cord than the 120?
Electricnewb is offline   Reply With Quote
Old 03-07-2009, 10:06 PM   #8
Member
 
Join Date: Jan 2009
Location: Boston, MA
Posts: 241
Rewards Points: 150
Send a message via AIM to Bocolo
Default

Maximum wattage question


I am not too informed on 240 volts. Others in here are very knowledgeable on electricity. Give it time and someone will answer your question. Thanks.
__________________
One Pound of Knowledge Requires Ten Pounds of Common Sense In Order To Be Useful
Bocolo is offline   Reply With Quote
Old 03-07-2009, 10:31 PM   #9
DIYer
 
Join Date: Oct 2008
Location: Virginia
Posts: 910
Rewards Points: 500
Default

Maximum wattage question


Electricnewb it depends on how the device is designed, but if it uses the same amount of watts at 240 volts that it uses at 120 volts, then the amps will be halved at 240 volts.

Regarding "pull more amps off a breaker at 240v than 120v"... no that is not how it works. A 240 volt breaker is twice as wide as a 120 volt breaker and is more similar to two 120 v breakers that trip at the same time. Also, while you can get more wattage at 240v, the ampacity of the wires for a given size does not vary by voltage.
Gigs is offline   Reply With Quote
Old 03-07-2009, 10:46 PM   #10
Newbie
 
Join Date: Mar 2009
Posts: 13
Rewards Points: 10
Default

Maximum wattage question


Gigs, so if I have a 15 amp breaker, and I want to use a 15 amp A.C. unit without maxing out my amps, and the a.c. is designed to use the same amnt of watts with both 240v and 120v, then the a.c. will use half of the amps?In other words id be using 7.5 amps but the same amount of wattage if i was using 120v?
Quote:
Originally Posted by Gigs View Post
Electricnewb it depends on how the device is designed, but if it uses the same amount of watts at 240 volts that it uses at 120 volts, then the amps will be halved at 240 volts.

Regarding "pull more amps off a breaker at 240v than 120v"... no that is not how it works. A 240 volt breaker is twice as wide as a 120 volt breaker and is more similar to two 120 v breakers that trip at the same time. Also, while you can get more wattage at 240v, the ampacity of the wires for a given size does not vary by voltage.
Electricnewb is offline   Reply With Quote
Old 03-07-2009, 11:37 PM   #11
DIY'er
 
jamiedolan's Avatar
 
Join Date: Sep 2008
Location: Neenah, Wisconsin, USA
Posts: 2,032
Rewards Points: 1,000
Blog Entries: 2
Default

Maximum wattage question


Quote:
Originally Posted by Electricnewb View Post
Gigs, so if I have a 15 amp breaker, and I want to use a 15 amp A.C. unit without maxing out my amps, and the a.c. is designed to use the same amnt of watts with both 240v and 120v, then the a.c. will use half of the amps?In other words id be using 7.5 amps but the same amount of wattage if i was using 120v?
Generally the amps used would be the same, but with 240v, it will be split between 2 breakers. So you would be drawing 7.5A on 2 separate breaker slots (via one double pole breaker) for a total of 15A.

Jamie
__________________
Jamie Dolan - Neenah, WI
Jamie Dolan Paw Dogs
Need Help Uploading Photos? Click here.
jamiedolan is offline   Reply With Quote
Old 03-07-2009, 11:38 PM   #12
DIYer
 
Join Date: Oct 2008
Location: Virginia
Posts: 910
Rewards Points: 500
Default

Maximum wattage question


Newb, Just so you know, most devices will not function on either voltage, they are either designed for one or the other.

Last edited by Gigs; 03-07-2009 at 11:40 PM.
Gigs is offline   Reply With Quote
Old 03-07-2009, 11:40 PM   #13
DIYer
 
Join Date: Oct 2008
Location: Virginia
Posts: 910
Rewards Points: 500
Default

Maximum wattage question


Quote:
Originally Posted by jamiedolan View Post
Generally the amps used would be the same, but with 240v, it will be split between 2 breakers. So you would be drawing 7.5A on 2 separate breaker slots (via one double pole breaker) for a total of 15A.
I don't like this explanation. You don't count the amps in a single circuit twice.
Gigs is offline   Reply With Quote
Old 03-07-2009, 11:47 PM   #14
DIY'er
 
jamiedolan's Avatar
 
Join Date: Sep 2008
Location: Neenah, Wisconsin, USA
Posts: 2,032
Rewards Points: 1,000
Blog Entries: 2
Default

Maximum wattage question


Quote:
Originally Posted by Gigs View Post
I don't like this explanation. You don't count the amps in a single circuit twice.
I think the OP was thinking the Air cond. would use less power if it was run on a 240v feed.

I was trying to illustrate that the Air cond. would use the same amount of power (amperage) if it is run on 120v or 240v service.

120v Air Cond Draws 15A

Same Air Cond running on 240v circuit, still draws a total of 15A, it is just split between 2 circuits.

Am I being confusing? sorry.

Jamie
__________________
Jamie Dolan - Neenah, WI
Jamie Dolan Paw Dogs
Need Help Uploading Photos? Click here.
jamiedolan is offline   Reply With Quote
Old 03-08-2009, 01:06 AM   #15
DIYer
 
Join Date: Oct 2008
Location: Virginia
Posts: 910
Rewards Points: 500
Default

Maximum wattage question


Quote:
Originally Posted by jamiedolan View Post
Am I being confusing? sorry.

Jamie
Yes, it's not the same amperage at all, it's half the amperage. It is the same wattage, however.

Gigs is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Question about maximum deck size in Delaware. Doctorsti Building & Construction 13 03-03-2009 08:21 PM
Maximum span without intermediate support question yaryar Building & Construction 2 11-11-2008 11:08 PM
Basement Renovation Question KUIPORNG Remodeling 234 08-26-2008 09:19 AM
hrv question indep HVAC 3 07-17-2008 11:39 PM
One furnace question and one thermostat question lh0628 HVAC 4 10-11-2007 11:17 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.