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

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

Closed Thread
 
Thread Tools Search this Thread Display Modes
Old 03-02-2010, 06:31 PM   #16
Electrical Contractor
 
jbfan's Avatar
 
Join Date: Jun 2004
Location: Newnan GA
Posts: 5,743
Share |
Default

Strange 240v outlet


Quote:
Originally Posted by BearcatBengal View Post
If the circuit is rated for 50A why wouldn't I be able to use a 30A space heater (assuming I use an adapter)?
Anything over a 20 amp receptacle must match the receptacle and rating of the device, so a 30 amp device can only be matched to a 30 receptacle on a 30 amp breaker.
You will not find any portable 120v heater rated higher than 1500 watts.

__________________
Yes I am a Pirate, 200 years too late. "Jimmy Buffett"
jbfan is online now  
Old 03-02-2010, 06:33 PM   #17
A "Handy Husband"
 
rjniles's Avatar
 
Join Date: Feb 2007
Location: South Carolina Low Country
Posts: 3,979
Default

Strange 240v outlet


Quote:
Originally Posted by BearcatBengal View Post
An alternative would be to use several of the most powerful 120v space heater I can buy. It looks like most 120v space heaters top out at 1500W because at 1500W they are near the threshold to trip a 15A breaker (threshold ~= 15A rms * 120V rms = 1800W rms). However, my apartment does have some 20A circuits so I should be able to use a slightly higher wattage heater (20A * 120V = 2400W threshold) perhaps a 2000W space heater.

I'm well aware that you don't want to overload a circuit for risk of starting a fire. I will be sure to put each heater on its own circuit and proceed with caution. That said, is it possible to buy a 120v space heater that draws more than 1500W anywhere?

Otherwise I'm going to have to make do with the 240v which could be significantly more expensive due to the wire gauges (as I anticipated).
Based on the wording in this post you have some knowledge of electrical capacity. I have made my thoughts known in my previous posts based on the electrical code and safe practices. If you wish to proceed beyond that you do so at your own risk.
__________________
Location:
Coastal South Carolina
rjniles is online now  
Old 03-02-2010, 06:49 PM   #18
Newbie
 
Join Date: Mar 2010
Posts: 9
Default

Strange 240v outlet


Now I am at a bit of a roadblock here. If its true that 30A is the largest space heater one can find for 240v, then my 50A circuit will not be ideal for the space heater (could burn up the space heater in theory). Perhaps adding a series resistance to the circuit would limit the current draw enough to allow me to safely use a 30A heater on a 50A circuit. Any other ideas? A single 1500W heater is not going to be nearly enough. I need to heat a space up to ~120F.
BearcatBengal is offline  
Old 03-02-2010, 07:07 PM   #19
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Default

Strange 240v outlet


Quote:
Originally Posted by BearcatBengal View Post
Now I am at a bit of a roadblock here. If its true that 30A is the largest space heater one can find for 240v, then my 50A circuit will not be ideal for the space heater (could burn up the space heater in theory). Perhaps adding a series resistance to the circuit would limit the current draw enough to allow me to safely use a 30A heater on a 50A circuit. Any other ideas? A single 1500W heater is not going to be nearly enough. I need to heat a space up to ~120F.

No "in theory" about it...if you feed 50a to a 30a heater you WILL fry it
Series resistance ? for an extra 2400w of power ?
There isn't anything you can do that will be safe & meet code using a 50a circuit & a 30a heater
You burn down that Apt you will be found at fault & liable for all damages

You MIGHT be able to connect a 30a & 20a heater to use the 50a
I'm not sure how or if that will work or meet code/be safe
Scuba_Dave is offline  
Old 03-02-2010, 07:20 PM   #20
Member
 
Join Date: Dec 2009
Location: Hagerstown, MD
Posts: 364
Default

Strange 240v outlet


Not trying to hijack this thread, but after reading it, I just want to know something...

What's the difference between, running a 30amp heater off a 50amp circuit, and running a lamp off a 20amp circuit?
Tonglebeak is offline  
Old 03-02-2010, 10:20 PM   #21
Member
 
Join Date: Jan 2008
Location: Alabama
Posts: 608
Default

Strange 240v outlet


Quote:
Originally Posted by Tonglebeak View Post
Not trying to hijack this thread, but after reading it, I just want to know something...

What's the difference between, running a 30amp heater off a 50amp circuit, and running a lamp off a 20amp circuit?
POWER!!!

This outlet will provide 12,000 (yes THOUSAND) watts of power and will not trip the breaker. By comparison, a 20 amp circuit can only supply 2400 watts of power.

Think of it as the difference between being given the keys to a mopped vs. an Indy Car.
HooKooDooKu is offline  
Old 03-02-2010, 10:26 PM   #22
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Default

Strange 240v outlet


Quote:
Originally Posted by HooKooDooKu View Post
POWER!!!

This outlet will provide 12,000 (yes THOUSAND) watts of power and will not trip the breaker. By comparison, a 20 amp circuit can only supply 2400 watts of power.

Think of it as the difference between being given the keys to a mopped vs. an Indy Car.
That in no way answers the question of why a light bulb & lamp that uses .5a can be plugged into a 20a circuit & a 30a heater can't be plugged into a 50a circuit

.5a/20a = using 2.5% of the circuit
30a/50a = 60% of the circuit
Scuba_Dave is offline  
Old 03-02-2010, 10:37 PM   #23
Member
 
Join Date: Jan 2008
Location: Alabama
Posts: 608
Default

Strange 240v outlet


Quote:
Originally Posted by Scuba_Dave View Post
That in no way answers the question of why a light bulb & lamp that uses .5a can be plugged into a 20a circuit & a 30a heater can't be plugged into a 50a circuit

.5a/20a = using 2.5% of the circuit
30a/50a = 60% of the circuit
Assuming what jbfan is saying is NEC code, I'm sure there's specific reasons, and if you know the reasons then please share them.

Otherwise, I'm trying to think of reasons why the NEC says what it says when they don't always provide reasons for what they say.

In this case, I'm drawing a comparison with a 50 amp circuit = Indy Car while a 20 amp = Mopped. In the case of a mopped, it doesn't mater if you run it at 0.5% or 100%, the potential for damage is less compared to turning someone loose with an Indy Car regardless of whether you are driving it at 5 mph or 300 mph... cause even if you're only driving at an Indy Car at 5 mph, it only takes a small press on the pedal to unleash the power to jump to 300 mph.


At least that's on general reason to try to explain in a non-technical terms that I can think of.
HooKooDooKu is offline  
Old 03-02-2010, 10:44 PM   #24
Member
 
Join Date: Jan 2009
Location: South of Boston, MA
Posts: 17,248
Default

Strange 240v outlet


Comparison is invalid since a 20a circuit can burn a house down just as easily as a 50a
Its about what can be plugged into what circuit, and how much power a device is rated to handle
Scuba_Dave is offline  
Old 03-02-2010, 10:54 PM   #25
Member
 
Join Date: Jan 2008
Location: Alabama
Posts: 608
Default

Strange 240v outlet


Quote:
Originally Posted by Scuba_Dave View Post
Comparison is invalid since a 20a circuit can burn a house down just as easily as a 50a
It's not totally invalid, after all you can still kill yourself on a moped, it's just a lot easier to do so in an Indy Car.


But I'm sure there are other reasons and other comparisons that can be made.
HooKooDooKu is offline  
Old 03-02-2010, 10:56 PM   #26
Member
 
Join Date: Dec 2009
Location: Hagerstown, MD
Posts: 364
Default

Strange 240v outlet


Thanks for throwing the numbers out there scuba.

I always thought that amperage through a circuit would only increase as more devices, wired in parallel, are used.

V=I/R right? R=I/V? This is what I can remember from AP physics from 5 years ago (can't believe it's been that long since I graduated).

So, 240=I/whatever the resistance rating is of the heater. So if it's a 30amp heater, then it has a resistance of .125 ohms, correct? That resistance isn't going to change, the only variables are voltage and current. Since the resistance is already defined, and we want it on a 240v circuit, then the current draw will be 30 amps. I don't think I can arbitrarily plug 50amps in the formula, because that would change the resistance, which is impossible unless something physically happens to it.

Or am I wrong here?

The 50amp circuit will supply a MAXIMUM of 50 amps, and not constant, correct?
Tonglebeak is offline  
Old 03-02-2010, 10:56 PM   #27
Newbie
 
Join Date: Mar 2010
Posts: 9
Default

Strange 240v outlet


Quote:
Originally Posted by Scuba_Dave View Post
No "in theory" about it...if you feed 50a to a 30a heater you WILL fry it
Series resistance ? for an extra 2400w of power ?
There isn't anything you can do that will be safe & meet code using a 50a circuit & a 30a heater
You burn down that Apt you will be found at fault & liable for all damages

You MIGHT be able to connect a 30a & 20a heater to use the 50a
I'm not sure how or if that will work or meet code/be safe
Just because a circuit is capable of delivering up to 50 amps does not mean it will always be putting out 50 amps to the load. The load must be factored in to the equation. V/R = I , if the load is sufficiently resistive it will limit the current well bellow the rated 50 amps. In fact, V/R = 240V/(Heater Resistance + Wire Resistance) = (Current to Heater). By this equation the current to the heater should be very similar between a 240V-50A circuit and a 240V-30A circuit.
BearcatBengal is offline  
Old 03-02-2010, 10:57 PM   #28
Newbie
 
Join Date: Mar 2010
Posts: 9
Default

Strange 240v outlet


Quote:
Originally Posted by Tonglebeak View Post
Thanks for throwing the numbers out there scuba.

I always thought that amperage through a circuit would only increase as more devices, wired in parallel, are used.

V=I/R right? R=I/V? This is what I can remember from AP physics from 5 years ago (can't believe it's been that long since I graduated).

So, 240=I/whatever the resistance rating is of the heater. So if it's a 30amp heater, then it has a resistance of .125 ohms, correct? That resistance isn't going to change, the only variables are voltage and current. Since the resistance is already defined, and we want it on a 240v circuit, then the current draw will be 30 amps. I don't think I can arbitrarily plug 50amps in the formula, because that would change the resistance, which is impossible unless something physically happens to it.

Or am I wrong here?

The 50amp circuit will supply a MAXIMUM of 50 amps, and not constant, correct?
See my previous post.
BearcatBengal is offline  
Old 03-02-2010, 10:58 PM   #29
Member
 
Join Date: Jan 2008
Location: Alabama
Posts: 608
Default

Strange 240v outlet


Quote:
Originally Posted by BearcatBengal View Post
Now I am at a bit of a roadblock here. If its true that 30A is the largest space heater one can find for 240v, then my 50A circuit will not be ideal for the space heater (could burn up the space heater in theory). Perhaps adding a series resistance to the circuit would limit the current draw enough to allow me to safely use a 30A heater on a 50A circuit. Any other ideas? A single 1500W heater is not going to be nearly enough. I need to heat a space up to ~120F.
A current limiting resister is totally wrong way to go here. You would be creating way too much heat in the resistor AND dropping the voltage across the heater. That's worst than just running the 30amp heater on a 50 amp circuit. After all, if the 30 amp heater is designed for 240v, and THERE ISN'T ANYTHING WRONG WITH THE HEATER, then it's only going to draw 30 amps even if it's connected to a circuit capable of supplying 300 amps.

But still, this whole idea just doesn't sound safe: Trying to artifically heat a space to 120F inside an apartment?
HooKooDooKu is offline  
Old 03-02-2010, 11:08 PM   #30
Newbie
 
Join Date: Mar 2010
Posts: 9
Default

Strange 240v outlet


Quote:
Originally Posted by HooKooDooKu View Post
A current limiting resister is totally wrong way to go here. You would be creating way too much heat in the resistor AND dropping the voltage across the heater. That's worst than just running the 30amp heater on a 50 amp circuit. After all, if the 30 amp heater is designed for 240v, and THERE ISN'T ANYTHING WRONG WITH THE HEATER, then it's only going to draw 30 amps even if it's connected to a circuit capable of supplying 300 amps.

But still, this whole idea just doesn't sound safe: Trying to artifically heat a space to 120F inside an apartment?
I completely agree with you. The series resistor would be unneeded complexity. I also agree with you about the fact that the 30amp heater should only draw up to 30amps on 240v, assuming its properly designed and not defective. However, the above posters seem to be saying that this does not meet standard code. I don't really give a damn about standard code as long as I can account for all possible issues.

BearcatBengal is offline  
Closed Thread

Tags
240v outlet, adapter


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
240v 3 prong outlet ISSUES!! JanosX Electrical 4 12-05-2009 01:00 PM
Pulling 120V outlet from a 240V circuit? npage148 Electrical 12 11-08-2009 11:29 AM
Strange problem w. wall outlet, please help! yiplong Electrical 15 07-22-2008 04:02 AM
240V Kiln Outlet to Air Conditioner Outlet artman Electrical 8 06-29-2008 06:21 PM
Adding an outlet on a 240V circuit? Kjunk Electrical 6 05-31-2008 09:27 AM




Top of Page | View New Posts

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