Help with electric heater connection!!

[the_bosun_mate]

I am installing a Dimplex EWA40c31 4000w/240v Surface mount electrical heater. In my service box I have a empty double 20amp circut breaker. Can I use the double 20AMP service breaker or do I have to upgrade to a double 30AMP breaker. The basic electricity book (its old) that I have, says that you can use 20AMPS up to 4800W??? also plan on using #10 wire any problems??

[jadnashua]

If I remember right, a continuous load shouldn't exceed 80% of the breaker, so you'd need a 30A circuit (you're close, but over that). See what the pros say as they've got access to the code book, or know it for sure.

[Igor]

If I remember right, a continuous load shouldn't exceed 80% of the breaker...

Quite correct, and fixed electric heaters are considered to be a continuous load.


See what the pros say as they've got access to the code book, or know it for sure.

The NEC is available online for free (although you have to register) viewing at the NFPA.org website. Article 424 covers Fixed Electric Space-Heating Equipment. 220.19(A)(1) & 220.20(A) deal with continuous loads. Try this link and see if it works: Online NEC (http://www.nfpa.org/freecodes/free_access_document.asp?id=7008)

[leejosepho]

With your #10 (30-amp) wire being plenty heavy enough and with your load being 80% of only 20.83 amps, I would at least try the 20-amp breaker before buying a 30 ... and I would check the breaker after an hour or so to see whether it is running hot ... and if it is, I would go ahead and get a 30 to avoid having to deal with a breaker possibly tripping whenever the voltage might be a bit low.

[Redwood]

With your #10 (30-amp) wire being plenty heavy enough and with your load being 80% of only 20.83 amps, I would at least try the 20-amp breaker before buying a 30 ... and I would check the breaker after an hour or so to see whether it is running hot ... and if it is, I would go ahead and get a 30 to avoid having to deal with a breaker possibly tripping whenever the voltage might be a bit low.

Redwood just shakes his head and wonders why some people post what they do...:confused:

[hj]

What, and why, is the question being asked? You are apparently installing a new #10 circuit, so why would you then try to low ball and reuse the 20 amp breaker instead of installing the correct 30 amp one. We would have a real problem if you had #12 wire and wanted to upgrade to a 30 amp breaker, but that does not seem to be the case here.

[Redwood]

It's funny but I don't really like to try things that may not work.:cool:
For some reason the NEC says that the c/b must be a certain percentage under its full load rating...
Could it be that is what makes it function reliably?:eek:
The fact that it may not trip with slightly over its rated 20 amps is not worth considering!
Do it right! Do it once! Don't be a hack!

[jadnashua]

Please don't suggest people do things that don't meet code! If you choose to do it yourself, I hope you don't live near me! In this case, for probably less than $10, it's easy to do it right and never have any problems. Burning up a breaker could damage the bus bar and create other problems. Keep in mind also that if the voltage drops to 220VAC instead of 240, you're at 90%, and during a brownout, it could even get higher. They write the code for a reason...

[leejosepho]

Redwood just shakes his head and wonders why some people post what they do...:confused:

Has the thought of asking crossed your mind?

In my own actual experience, and however limited that might be, resistance heaters do not always draw their stated wattage. So, it is at least possible the load in question is actually *not* more than 80% of 20 amps ... and that would mean everything might just be fine without having to spend the money for a 30-amp breaker that at least possibly *could* help guarantee a bit of overheating somewhere if the heater or thermostat might somehow malfunction. Lighter-gauge wire would definitely be a bad idea, but as far as I know, and please correct me here if I am wrong: A borderline breaker would at worst be a nuisance when it trips.

[jimbo]

. Keep in mind also that if the voltage drops to 220VAC instead of 240, you're at 90%, and during a brownout, it could even get higher. ...

If the voltage drops, the fixed resistance of a heating element does not change, so the circuit current goes down....not up.

[jadnashua]

My typing gets ahead of my brain sometimes...

More used to electronic circuits that pull more current to do their thing when the voltage drops...

Regardless, do it to code!

[leejosepho]

If the voltage drops, the fixed resistance of a heating element does not change, so the circuit current goes down....not up.

Oops, I too was wrong about that ... and my guess about the heater possibly not running at its stated wattage was also bad. I have a 4000-watt heater I plan to install in my workshop, and I just went out and measured its resistance ... and that leaves me with these numbers in my own situation:

240 volts
13.2 ohms
4363.64 watts
18.18 amps (80% of 22.725)

So yes, a 30-amp breaker is the way to go!

[Redwood]

Has the thought of asking crossed your mind?

In my own actual experience, and however limited that might be, resistance heaters do not always draw their stated wattage. So, it is at least possible the load in question is actually *not* more than 80% of 20 amps ... and that would mean everything might just be fine without having to spend the money for a 30-amp breaker that at least possibly *could* help guarantee a bit of overheating somewhere if the heater or thermostat might somehow malfunction. Lighter-gauge wire would definitely be a bad idea, but as far as I know, and please correct me here if I am wrong: A borderline breaker would at worst be a nuisance when it trips.

No Lee it hasn't!

I'm heading down to McDees I'm Having a Big Hack Attack!

[jar546]

With your #10 (30-amp) wire being plenty heavy enough and with your load being 80% of only 20.83 amps, I would at least try the 20-amp breaker before buying a 30 ... and I would check the breaker after an hour or so to see whether it is running hot ... and if it is, I would go ahead and get a 30 to avoid having to deal with a breaker possibly tripping whenever the voltage might be a bit low.


Ignor that post.

In a nutshell without showing calculations, you will need:

10awg copper wire, such as NM 10/2 with ground.
25A double pole breaker.

The rating for that heater is 4000W @ 240vac so 16.6A exceeds 80% of a 20A breaker. You must be upsized to the next larger breaker which is 25A as listed in the NEC.

Do not place it in contact with combustibles or below a wall outlet.

[jwelectric]

I was installing a wall mounted electric heater in my house and the inspector told me that the breaker was too small.

I stopped the inspector in the middle of the driveway and told him that the small breaker would only drive me crazy running back and forth resetting it.

The inspector kept telling me that he was not going to sign off on my work until I changed everything and brought it up to code standards.

I kept telling the inspector not to worry that I didn’t have nothing to do but run and reset the breaker each time it tripped.

While we were sitting in the middle of the driveway arguing back and forth the fire truck couldn’t get in to put out the fire and my house burnt to the ground.

Moral of this story is just don’t call the damn inspector as he will not budge and the fire trucks can’t get to the fire and you will lose your house.

On a side note, I am so poor that I had to do the work myself and due to the lack of money I didn’t have any insurance on my house. Now we are a ward of the state and all of them law abiding fools have to support me and my family so maybe things worked out well after all.

I vote to abolish all these codes and just let us do as we damn please. All in favor say aye!

[leejosepho]

Honest question: Would someone please explain how a weak or undersized breaker could start a fire?

I do know heavily-loaded breakers can get hot, and I also know it usually takes a load quite a bit above their stated rating to actually trip them.

Is that the combination that can cause a breaker to actually burn or to ignite something else?

[jwelectric]

Honest question: Would someone please explain how a weak or undersized breaker could start a fire?

I do know heavily-loaded breakers can get hot, and I also know it usually takes a load quite a bit above their stated rating to actually trip them.

Is that the combination that can cause a breaker to actually burn or to ignite something else?

You answered your own question didn't you?

"I do know heavily-loaded breakers can get hot,"

[leejosepho]

You answered your own question didn't you?

"I do know heavily-loaded breakers can get hot,"

Well, I do not actually know, or I do not yet fully understand, so I ask.

A typical breaker in good condition will actually carry a load greater than its stated capacity without tripping, but can a typical breaker in good condition actually carry such a load to the point of either catching fire or starting one?

I would like to believe breaker manufacturers design and make the typical breaker so that it *will* trip before any overload it might be carrying can actually cause it to self-destruct or burn something else. Otherwise, it would be too convenient for a manufacturer to try to hide behind the NEC by saying a given breaker that either caught or caused a fire should not have been used in the first place. And of course, yes, there must be some kind of "code behind the code" that must be met in relation to stated ratings and actual trip levels.

[jwelectric]

A breaker that is overloaded to the point of causing excessive heat can most certainly start a fire.

There are many reported cases where breakers of all manufacturers have failed to open and have started fires in many numerous ways.

The heat can be transferred to the wooden studs or finished wall in the event of wood paneling and start a fire. The flash point of wood is around 575 degrees Fahrenheit.
Should the breaker start arcing at the bus bar then it could easily start a fire.

If the breaker is getting hot and the connections are all good and tight then the conductor itself is getting hot. Here there is more than just the wood to consider for starting a fire. Some common house dusts can have a flash point as low as 150 degrees Fahrenheit and can drop even lower if cooking oils or other oils have settled into the dust.

Should the panel be installed in an area such as closets where things like garments and apparel or even paper and cardboard boxes are stored then the issue is even greater.

In the event of a fault a breaker will let through its listed AIC current which for most residential panels will be 10,000 amps, before damage occurs to the device.
Should the device fail temperatures can raise to as much as 32,000 degrees Fahrenheit in a matter of a fraction of a second. This would be more than enough to start a fire wouldn’t you think?

The question should be will the breaker get that hot before tripping. Most breakers will carry for a period of 20 seconds six times their rating. In other words a 15 amp breaker will let through 90 amps for about 20 seconds. This equates to about 10,800 watts or about 36,700 BTUs. This is enough heat to easily start a fire.
Couple this overloaded circuit breaker and a fault and we have spontaneous combustion of any ignitable material in the area.

One thing to keep in mind is that current in any circuit be it AC or DC rises at an exponential rate. This rate divided into five time constants each will rise at a rate of 63.2% each time. This is also true for current flowing through the human body.

So the simple answer to your question it is very possible for a circuit that is overloaded to start a fire. This is the reason for the codes and the requirement in most areas for the installer to first obtain a license before attempting an installation. It is also the reason for so many who know and understand the theory of current flow to be so hard on the Do-it-yourselfer trying his/her best to do something they know little or nothing about.

Electricity is a lot more in depth than white to white and black to black. Electrical circuits are one of the few things in this world that can be installed completely incorrect and still work. Circuits can be installed in a manner that they are nothing short of a death trap yet they still function.

[jar546]

Just follow post #14 and you can't go wrong.

[beekerc]

unless you have an outdated panel - last year i had to replace a couple of 15A breakers in my circa 1968 Federal Pacific panel to the tune of $27/each - circuit breakers are cheap (<$5 for most single pole 15A and 20A). I now have a Square-D/Home-Line panel and breakers are around $4/each.

from my lay perspective, if you've already got 10/2 wire, which is required for a 30A circuit, why on earth would you not put a 30A breaker there? I just picked one up (i'm running a new 30A line for my servers) for $3.97 at the big box store with orange lettering, the price on the L5-30R receptacle was the killer though. I know that you can put a lower rated breaker than the wire is capable of carrying - ie a 15A breaker on a circuit wired with 12ga - but the point is why would you? If your wattage or ampacity is borderline for the breaker (but within the limits of the wire) why not err on the side of caution and put in the larger capacity breaker? the real problem is when you discover that you're routinely pulling more than 12A (80% of 15A) over 14 gauge wire and the choices become - re-wire with 12 gauge or reduce the load(s).

after making sure the circuit wire gauge is correct, remember - breakers are cheap, rebuilding is expensive.

just my humble, and uncertified, ) $0.02 worth.
BeekerC

[jar546]

unless you have an outdated panel - last year i had to replace a couple of 15A breakers in my circa 1968 Federal Pacific panel to the tune of $27/each - circuit breakers are cheap (<$5 for most single pole 15A and 20A). I now have a Square-D/Home-Line panel and breakers are around $4/each.

from my lay perspective, if you've already got 10/2 wire, which is required for a 30A circuit, why on earth would you not put a 30A breaker there? I just picked one up (i'm running a new 30A line for my servers) for $3.97 at the big box store with orange lettering, the price on the L5-30R receptacle was the killer though. I know that you can put a lower rated breaker than the wire is capable of carrying - ie a 15A breaker on a circuit wired with 12ga - but the point is why would you? If your wattage or ampacity is borderline for the breaker (but within the limits of the wire) why not err on the side of caution and put in the larger capacity breaker? the real problem is when you discover that you're routinely pulling more than 12A (80% of 15A) over 14 gauge wire and the choices become - re-wire with 12 gauge or reduce the load(s).

after making sure the circuit wire gauge is correct, remember - breakers are cheap, rebuilding is expensive.

just my humble, and uncertified, ) $0.02 worth.
BeekerC


You should have replaced your FPE StabLok panel instead of tracking down UNLISTED aftermarket breakers for a panel that is from a company that has been out of business for 20 years.

[SewerRatz]

If the voltage drops, the fixed resistance of a heating element does not change, so the circuit current goes down....not up.

Jimbo,

Its been a while since I had to deal with Ohms law. But power is equal to Voltage X Amperage

P = V x A

So if the voltage changes the math would be
A = P / V
In this case
4000 / 240 = 16.66667
4000 / 220 = 18.18182

Now I may be looking at this from the wrong point of view, like I said it has been a long time since I messed with Ohms law. I used to be an electrical tech in the Army many many years ago.

So it would draw more amperage if the voltage goes down if the unit is designed to draw a set wattage.

[SewerRatz]

Jimbo,

I am sorry I dug out one of my old books. If you are correct if the resistance is fixed the and the voltage drops so will the amperage.

A = V / R

Which would also mean if the voltage drops which causes the amperage to drop so will the output wattage.

P = V x A

Again I am sorry for doubting what you said. I had to refresh them brain cells of mine.

[Redwood]

A resistance load will draw lower with lower voltage.

[leejosepho]

If you can tolerate a couple of popups, here is the Ohm's-Law calculator I use:
http://www.angelfire.com/pa/baconbacon/page2.html

Put in any two numbers available and you will end up with volts, amps, ohms and watts.

[leejosepho]

I know you can put a lower rated breaker than the wire is capable of carrying - ie a 15A breaker on a circuit wired with 12ga - but the point is why would you? If your wattage or ampacity is borderline for the breaker (but within the limits of the wire) why not err on the side of caution and put in the larger capacity breaker? the real problem is when you discover that you're routinely pulling more than 12A (80% of 15A) over 14 gauge wire and the choices become - re-wire with 12 gauge or reduce the load(s).

I am still sorting some things out here, but at least now I do understand what you just said about "routinely pulling more than 80%".

My house has wire from at least three eras, and I do not trust some of the oldest wire to carry 20 amps even though it is (or it at least appears to be) #12 wire. So, and with the electrician's agreement when he installed a new panel a couple of years ago, I have only 15-amp breakers for all 120-volt circuits (except for one new one). At least in theory, that limits the voltage available to that old wire, but in reality, even a 15-amp breaker can let enough through to cause trouble ... ?!?

In any case, none of my breakers are even warm to the touch, and I have enough circuits in this small house to spread the overall load around fairly well.

[jwelectric]

I am still sorting some things out here, but at least now I do understand what you just said about "routinely pulling more than 80%".

My house has wire from at least three eras, and I do not trust some of the oldest wire to carry 20 amps even though it is (or it at least appears to be) #12 wire. So, and with the electrician's agreement when he installed a new panel a couple of years ago, I have only 15-amp breakers for all 120-volt circuits (except for one new one). At least in theory, that limits the voltage available to that old wire, but in reality, even a 15-amp breaker can let enough through to cause trouble ... ?!?
In any case, none of my breakers are even warm to the touch, and I have enough circuits in this small house to spread the overall load around fairly well.


I think I know what you are trying to say even though you have said it wrong.

A #12 conductor installed on a 120 volt circuit will have 120 volts present no matter the size overcurrent device installed. A 15 amp breaker does not limit the voltage any more than a 150 amp breaker. What a 15 amp breaker will limit is the amount of current (amps).

If the insulation of the conductors has broken down using a smaller overcurrent device will not help anything at all except limit the load that can be attached.

Voltage is the amount of pressure that is pushing the amperage down the conductor. If the pressure becomes too great the conductor burst open and then we have a problem. If the insulation has broken down then the only solution is to either drop the voltage to a safe level or replace the conductor.

Think of it like a water line. Should I decide to install CPVC plumbing in my home which has a water pressure of 60 lbs I can expect to have problems in about five years as the CPVC will get old and brittle and leaks will spring forward.
But if I reduce the pressure to about 10 lbs this junk might last for 20 years.

The problem with electricity is that we can not regulate the amount of pressure (volts) as the equipment that we use mandates the amount of pressure (volts). When the insulation starts to break down we can not reduce the amount of pressure (voltage) applied therefore the only safe fix is to replace the wiring. Changing the overcurrent device changes nothing except the size of the overcurrent device.

[leejosepho]

I think I know what you are trying to say even though you have said it wrong.

Yes, I did, and yes, you do.

I understand "volts are like pressure" and "amps are like current flow" and "watts are like volume", and I understand volts/pressure can destroy a weak or ill-suited conductor or pipe.



What a 15 amp breaker will limit is the amount of current (amps).

Understood, and it is the "friction" of those amps passing through (back and forth) that can cause heat, correct?


If the insulation of the conductors has broken down using a smaller overcurrent device will not help anything at all except limit the load that can be attached.

Yes ... but that could in effect also at least help to keep an old wire from overheating and pushing its heat out through its poor or weak insulation, correct?


If the insulation has broken down then the only solution is to either drop the voltage to a safe level or replace the conductor.

Since a conductor can do its job with no insulation at all as long as it does not short-circuit or overheat near a combustible, the issue there would actually be friction-amps rather than the condition of any mere covering, correct?


Think of it like a water line.

Yes, and water lines are like bare wire: no insulation at all.


When the insulation starts to break down we can not reduce the amount of pressure (voltage) applied therefore the only safe fix is to replace the wiring.

Yes, in relation to any short-circuit or ignition issues, but not in relation to a wire's inherent ability to carry current, correct?


Changing the overcurrent device changes nothing except the size of the overcurrent device.

... and "limit the load that can be attached", thereby limiting the heat-producing friction that might otherwise be possible, correct?

My point here is not to argue needlessly, but to be sure the professional electrician who agreed it was a good idea to use only 15-amp breakers on my old wiring was not wrong while thereby essentially confirming my thought of doing that in order to reduce the likelihood of a fire from an overheated wire.

[jar546]

What should have happened Lee is that all of the circuits should have been tested with a megger and if there were any problems then they should have been properly repaired.

If you want to do something worthwhile rather than downsize a breaker which is like saying "when we kill you, do you want to be shot in the head with a .45 or a 9mm?" because they both do the same things just at different levels.

AFCI Combo circuit breakers would have been a much better choice rather than downsizing from a 20 to a 15. 15amps makes just about as much heat and spark as 20.

[jwelectric]

Yes, I did, and yes, you do.

I understand "volts are like pressure" and "amps are like current flow" and "watts are like volume", and I understand volts/pressure can destroy a weak or ill-suited conductor or pipe.




Understood, and it is the "friction" of those amps passing through (back and forth) that can cause heat, correct?



Yes ... but that could in effect also at least help to keep an old wire from overheating and pushing its heat out through its poor or weak insulation, correct?



Since a conductor can do its job with no insulation at all as long as it does not short-circuit or overheat near a combustible, the issue there would actually be friction-amps rather than the condition of any mere covering, correct?



Yes, and water lines are like bare wire: no insulation at all.



Yes, in relation to any short-circuit or ignition issues, but not in relation to a wire's inherent ability to carry current, correct?



... and "limit the load that can be attached", thereby limiting the heat-producing friction that might otherwise be possible, correct?

My point here is not to argue needlessly, but to be sure the professional electrician who agreed it was a good idea to use only 15-amp breakers on my old wiring was not wrong while thereby essentially confirming my thought of doing that in order to reduce the likelihood of a fire from an overheated wire.


No Lee, reducing the size of overcurrent device from a 20 to a 15 on a #12 wire does not make it safer and if an electrician has told you it does then he/she is far from being correct.

Yes the electron flow does cause heat but a #12 copper conductor has the ability to carry up to and including 30 amps.
What limits the amount of current on a conductor other than its size is its insulation.

[leejosepho]

AFCI Combo circuit breakers would have been a much better choice rather than downsizing from a 20 to a 15. 15 amps makes just about as much heat and spark as 20.


No Lee, reducing the size of overcurrent device from a 20 to a 15 on a #12 wire does not make it safer and if an electrician has told you it does then he/she is far from being correct.

What he actually said when I mentioned using all 15s was, "Makes sense to me" ... but now I see the reality of "15 amps makes just about as much heat and spark as 20." And, that is essentially what happened in the middle of the night about a year ago when something exploded in the ceiling and near a fan. I never could find the bad spot in that old circuit, so I just cut it out altogether and ran some new wire.

Overall, I thank you, gents!

[frenchelectrican]

To., OP.,

C'est simple get 25 or 30 amp double pole breaker with #10-W/G romex cable that will meet the code no question asked.

While still on the same subject please do remark the white conductor with either red , black , blue marker to indentify it is a hot conductor instead or netrual conductor.

Merci,Marc