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Old 09-06-2017, 06:20 PM   #1
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Default Breaker Sizing Heater

Found a grey area on picking the breaker sizing I never really thought about until I encountered it. Sorry it's a lot of reading. My situation is regarding heating, but while I'm on the topic, I'm also wondering what the rules would be if it were for a general device that doesn't have it's own section in the code book or a device that doesn't specify a breaker size in the product manual.

I know in the motors section in the book, it says you have to size up or down your breakers based on their section rules. But the heating section I don't see anything like that for sizing down.

Short story before the long story...Can you put a 240v 500W heater using only a couple of amps draw on a 20A breaker or does it have to be downsized to 15A to trip faster since that is more appropriately sized? I can't find any rule saying I have to go to the lesser breaker size. 62-110 (2) and 62-118 (5) and section 8 says as long as the circuit can handle the load, it should be okay, but thought I'd ask for a second opinion. It's an existing circuit on my own place so just trying to save the effort and cash of running a new line and new breaker in existing drywall if I don't have to.

Product manuals don't list a breaker size, or what the current rating of the housing and components are all rated for the heaters I can read up on. One manufacturer of a heater said on the phone that a 20A breaker would be fine. Another company said they don't know.

Normally when sizing a breaker with an outlet, and doing what the code book tells you, you size the breaker to protect the cable and the outlet and make sure the cable and outlet match the rating of the breaker. The load requirement of a device that you plug in could change or may be unknown at the time of install so you may not be able to factor that in. If you know the load, you install all your components to be able to handle the load. Pretty straight forward.

So I'm wondering what decision do you make for a device that is hardwired without an outlet? I'm thinking as long as the breaker is sized to handle the cable, then you should be able to hook whatever you want hardwired up to the other end, as long as it isn't too big of a load that is going to cause nuisance tripping. Just never really given much thought much about having a load that is too small, we usually only worry about loads that are too big.

So I'll probably go ahead and install a 500, 750, or 1000w wall heater with fan or possibly a convector without a fan using the existing 240v, 20A breaker, 20A 12AWG cable unless there was any objections. The only other thing on the line is a hoist that gets used for a few minutes out of the entire year in the summer so the hoist and heater would never run at the same time. I can't just remove the 20A breaker and put a 15A in because that wouldn't be fair to the hoist since it may trip.

Last edited by 746 Watts; 09-06-2017 at 06:22 PM.
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Old 09-06-2017, 08:06 PM   #2
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Well....your question makes me wonder if you are "playing" in the electrical field.....an amatuer with an interest....or were you asleep in class ?
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Old 09-06-2017, 08:59 PM   #3
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Neither.
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Old 09-06-2017, 11:02 PM   #4
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Simple answer is the overcurrent is to protect the wire, not the equipment.
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Old 09-11-2017, 03:24 PM   #5
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I've wondered about this before, out of convenience instead of running new runs. Has anyone ever tapped in to an existing 240v circuit, so that you can get 120v off of one leg for a 120v device?

I drew up a hypothetical scenario based on maxed out full loads off of what I have where the feeders are all the same gauge. I can kind of see how it may work, but I'm used to only seeing the diagram the way it would be on an Edison 3 wire not on a 4 wire if that is even possible at all.

I'm not actually putting the 20 A receptacle in, I'm just curious if it would even work.
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Old 09-11-2017, 03:33 PM   #6
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That is the kind of stuff you see DIY'rs doing. Yes it would work but that does not mean it is right or even ok. This is the kind of stuff that burns houses down.

An edison 3 wire? What does that mean?
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Old 09-11-2017, 03:33 PM   #7
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Old 09-11-2017, 03:34 PM   #8
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Quote:
Originally Posted by eddy current View Post
That is the kind of stuff you see DIY'rs doing. Yes it would work but that does not mean it is right or even ok. This is the kind of stuff that burns houses down.

An edison 3 wire? What does that mean?
You beat me to it ... by less than a minute
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Old 09-11-2017, 03:39 PM   #9
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I was looking at the drawing .,, all I will say .,,

techally I know it can work but I would not mess with it.

that sound like DIY turf I been see it before and I use this term very loosely .,, either redneck or iceneck depending on the area.,,

Oh yuh .,, 3 wire Edison it mean both 120 and 240 Volt circuit. very common called MWBC .,,
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Old 09-11-2017, 03:50 PM   #10
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Ok, good. Normally I'd run a new circuit. I just thought maybe I have not been taking advantage of easy circuits like other guys would if they are right there.
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Old 09-11-2017, 03:50 PM   #11
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Quote:
Originally Posted by 746 Watts View Post
I've wondered about this before, out of convenience instead of running new runs. Has anyone ever tapped in to an existing 240v circuit, so that you can get 120v off of one leg for a 120v device?

I drew up a hypothetical scenario based on maxed out full loads off of what I have where the feeders are all the same gauge. I can kind of see how it may work, but I'm used to only seeing the diagram the way it would be on an Edison 3 wire not on a 4 wire if that is even possible at all.

I'm not actually putting the 20 A receptacle in, I'm just curious if it would even work.
Probably numerous code violations ...

The biggest problem is that you would be overloading the Neutral wire!
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Old 09-11-2017, 03:52 PM   #12
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Probably numerous code violations ...

The biggest problem is that you would be overloading the Neutral wire!
I was wondering about overloading. I can't quite figure out how the current would behave since a normal 3 wire would be L1 minus L2 equals the current on the neutral. But with 4 wires, not sure how to do the math on it.
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Old 09-11-2017, 03:59 PM   #13
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Quote:
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I've wondered about this before, out of convenience instead of running new runs. Has anyone ever tapped in to an existing 240v circuit, so that you can get 120v off of one leg for a 120v device?
.
That case of senicearo .,, that basically a major code volation due if you have two conductor cable and you see Line 1 and Line 2 and the white conductor was repurposed to run on 240 volts ( single 240 volt circuit is fine but once you use the EGC that is a game changer .,, )

But if you have 3 conductor cable L1, L2 and netural then you are fine with it without any code voliation on that.,,

so the key item is the numbers of conductors in the cable.
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Old 09-11-2017, 04:15 PM   #14
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Probably numerous code violations ...

The biggest problem is that you would be overloading the Neutral wire!
Every wire has factory sealed smoke in it.
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Old 09-11-2017, 04:34 PM   #15
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Some trolls are better than others.
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Old 09-11-2017, 05:38 PM   #16
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Would all 3 breakers have to be handle-tied though?
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Old 09-17-2017, 12:05 AM   #17
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Quote:
Originally Posted by 746 Watts View Post
I've wondered about this before, out of convenience instead of running new runs. Has anyone ever tapped in to an existing 240v circuit, so that you can get 120v off of one leg for a 120v device?

I drew up a hypothetical scenario based on maxed out full loads off of what I have where the feeders are all the same gauge. I can kind of see how it may work, but I'm used to only seeing the diagram the way it would be on an Edison 3 wire not on a 4 wire if that is even possible at all.

I'm not actually putting the 20 A receptacle in, I'm just curious if it would even work.
62-110 Branch circuits
(1) Branch circuit conductors used for the supply of energy to heating device sets shall (a) be used solely for such heating device sets; and
(b) have an ampacity not less than that of the connected load supplied.


62-114 Overcurrent protection and grouping (see Appendix B)
(1) Every heating fixture, heating cable set, heating panel set, or parallel heating set having an input of more than 30 A shall be supplied by a branch circuit that supplies no other equipment.
(2) In buildings for residential occupancy, two or more heating fixtures, heating cable sets, or heating panel sets shall be permitted to be connected to a branch circuit used for space heating, provided that the branch circuit overcurrent devices are rated or set at not more than 30 A.
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Old 09-17-2017, 12:44 AM   #18
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If you connect directly to the feeder then it should be ok to share a circuit, as long as you don't connect somewhere in the middle of the circuit is what I get from that rule. 62-118(5) mentions it's okay to have a feeder sent out to mixed heating loads with other stuff.

CEC handbook:

Rule 62-110 Branch circuits
Heating device sets must be connected to branch circuits used for no other purpose. Interconnecting high loads such as heating devices with lighting or other types of electrical loads can cause nuisance tripping of the overcurrent device protecting the supply circuit. Also, it is desirable to turn off circuits serving heating devices
during the non-heating season.

Last edited by 746 Watts; 09-17-2017 at 01:01 AM.
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Old 09-17-2017, 08:27 AM   #19
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Quote:
Originally Posted by 746 Watts View Post
If you connect directly to the feeder then it should be ok to share a circuit, as long as you don't connect somewhere in the middle of the circuit is what I get from that rule. 62-118(5) mentions it's okay to have a feeder sent out to mixed heating loads with other stuff.

CEC handbook:

Rule 62-110 Branch circuits
Heating device sets must be connected to branch circuits used for no other purpose. Interconnecting high loads such as heating devices with lighting or other types of electrical loads can cause nuisance tripping of the overcurrent device protecting the supply circuit. Also, it is desirable to turn off circuits serving heating devices
during the non-heating season.
62-110 is for the demand factors of feeders and services, not for branch circuits.

Connect directly to the feeder then it should be ok? Please don't attempt electrical work that you don't understand yet or are not qualified for.

Last edited by eddy current; 09-17-2017 at 10:13 AM.
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Old 09-17-2017, 01:40 PM   #20
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Quote:
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62-110 is for the demand factors of feeders and services, not for branch circuits.

Connect directly to the feeder then it should be ok? Please don't attempt electrical work that you don't understand yet or are not qualified for.
Thank you for pointing that out, but I think what you mean 62-118 is for the feeders. Looking closer, I lost sight that the feeder rule is the rule for the whole main house calculation, or for a calculation feeding a sub panel that has mixed heating and device loads, so I was miss reading it. The branch circuit section is the proper rule I should have been looking at.

Sorry, I'm getting my terminology mixed up. I didn't mean the main feeder at a panel. I mean the "home run" at the first connection point closest point in the branch circuit connecting the load back to the panel. That would make it the closest point in the branch to eliminate voltage drop from distance.

To correct things, and be compliant you would change the home run of the branch circuit to become a feeder by connecting it to its own subpanel or load centre. If the branch circuit cable is already sized big enough to be the feeder of the two loads, then that shouldn't be an issue.

Looking at the nature of the rule, and why the rule is written is important as well if you can get a exception granted. The only other load with the heat is a hoist that is only used for a few minutes out of an entire year. The hoist cannot be operated in the cold months due to the place it is located. The heater can be thermostatically controlled by a double-pole t-stat ensuring the off position in the warm months. So in theory, neither load will ever be used at the same time.

I know the following from the handbook is for feeders not branches, but the same can be said about other things in code with permission. But, I'm not trying to suggest we make it a common practice to try to break and bend rules at every opportunity.

Rule 62-118 Demand factors for service conductors and feeders

The requirements are general and do not take into consideration very specific
circumstances that might exist in a given installation. The demand factors in the Code might need to be modified, taking into account climatic conditions, building usage, heat loss, etc.
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