[eddy current]

Yep that’s the one. So why not use #8 copper with a 50 amp receptacle on a 50amp breaker?

I don’t think anyone was saying that code does not allow this.
That other thread was using a 40 amp breaker on a 50 amp receptacle which is against code. (Except for a range)
And that the manufacturer spec called for #6

 

[eddy current]

Contact temp rating on a 14-50R?? if its not labeled?? (assuming it's what you mean) use the 60 degree column.
Yep the breaker is rated at 75, just not the device.

14-50R’s do have termination temps on them. 75 degrees

 

[eddy current]

A 50 amp EV receptacle must have a conductor rated at 1.2 its size to comply with 8-104 which is 60 amps.

Although I agree a larger conductor should be used for EV, can you explain why the conductor must be larger than the overcurrent and receptacle? I don’t agree with that.

Rule 8-104 says that any continuous load shall not exceed 80% of the conductor size, not 120%

 

[eddy current]

This is how I have been told to calculate it from the guys at ESA.
The rating of the breaker and receptacle is 50 amps.
Since this is a continuous load at 50 amps (potentially) and no way to limit it to 40 amps, rule 8-104 requires the conductor to be de-rated to 80% or "upsized" by 1.2. The math is 50 amps x 1.2 = 60 amps and #6 is good for 65 amps at 75*. The #8 is only good for 50 amps which is 100% of the breaker and receptacle but not 120% of the potential maximum of the condcutor.

Cheers
John

I disagree.

Can you explain why this is different from any other installation with or without a receptacle?

Say I have a piece of equipment that has a rating of 40 amps ( not a EV). Multiplied by 125% gets me 50 amps. 50 amp breaker, receptacle and 50 amp wire are code compliant correct? (as per 8-104) But you are saying this would require 60 amp wire?

Why is EV different ? (A level 2 EVSE that draws 32 amps can not draw any more than 32 amps BTW, hardwired or receptacle)

And 8-104 says the same for breaker and wire, so why do you think the wire has to be larger and not the breaker?

“A continuous load designated receptacle is 100% of the rating”.

Where are you getting that from? Code reference?

 

[eddy current]

rule 8-104 requires the conductor to be de-rated to 80% or "upsized" by 1.2.

I think this is where the error is. It does not have to be derated or upsized, it just can not have a continuous load of more than 80% of its rating as per 8-104

 

[eddy current]

@eddy current @Costalota It is not my position to defend what the ESA guys say and I have had the same questions / concerns that you are stating.

I also don’t claim to be an expert in code issues, although I think I can dance my way around the codebook pretty good LOL!

Again, this was revisited just recently (two weeks ago) with a bunch of ESA inspectors / Technical Advisors and all are on board with the #6, 50 amp breaker and receptacle. Their justification seemed reasonable and it was inline with what I have tried to explain here and what I have been doing for years. They (the ESA guys) are going back to discuss the “stove receptacle” vice the 14-50R receptacle as the manufacturer markets the items as “dryer and stove” receptacle and not “EV” receptacle in addition to them being “flush mount” vice “surface mount”. They all generally agree that it is pretty low risk, but it does not comply with 2-024 because of the marketing.

All I can say is that I have been doing the #6 awg, 50 amp breaker and receptacle for years and have never had a defect. Yet there continues to be defects for many others that are doing both the #8 awg, 40 amp breaker, 50 amp receptacle and the #8, 50 amp breaker and 50 amp receptacle. There is no doubt that some of this is related to 2-024, but if the equipment is not permanently installed (hard-wired) it is a crap shoot for the inspector.

I think the issue in this explanation is that there are several variables and interconnecting codes; which makes it unnecessarily complicated as well as the ineffectiveness of rule 2-100.

So then I will try again to explain; you can agree or disagree, does not matter to me as I will keep doing #6, 50 amp breaker and receptacle for EV receptacles.

In general (most common) we are looking at a 32 amp EV being connected (plugged in) to a 50 amp receptacle.

I think we all agree that a #8 awg can be loaded up to 40 amps (80% of 50 amps).

I think we all agree that 32 amps is less than 80% of the conductor size (#8 awg).

I think we all agree that a #8 on a 40 amp breaker connected to a 50 amp receptacle is the most logical solution and should work, but rule 26-700 does not allow this.

My opinion is that we should be allowed to use a 40 amp breaker, #8 awg and 50 amp receptacle if we met the requirements of 2-100 (marking). The reality is that rule 2-100 is ineffective.

As explained to me, because of rule 26-700, and regardless of rule 2-100, there is nothing stopping someone from plugging in an EV to charge at a higher rate (in excess of 40 amps (80% of #8 awg)) – this is a bit of a “what if” and I am not necessarily a fan of that… but lets keep going. So the approach has been to interpret rule 8-104 at the 50 amp rating and not at the most common value on the market (32 amps).

If the max continuous load is 50 amps, then the conductor required to comply with 8-104 at a rating of 50 amps is #6 (65 amps x .8 = 52 amps). The breaker and receptacle are rated for 50 amps and the rule 8-104 is the conductor only at 80% and does not apply to the breaker or the receptacle.

I use the 120% calc as an easier example of determining what the 80% rule is, which I think is confusing to some people (perhaps I should not have included that in the previous posts) – because it is not the same numbers exactly, but the math always works out.

I take the max current (50 amps) and multiple by that by 1.2 (120%). In this case it is 50 x 1.2 = 60 – so I need a conductor that is good for 60 amps… I see that #6 awg is good for 65 amps (Table 2) and if I needed to “prove it” I would take 65 x .8 = 52 amps, still the same #6 awg. Again that is the way I do it for simplicity, but apparently it has been confusing for some.

So back to the original question, why can’t we use #8 on a 50 amp breaker and receptacle for an EV?

An EV is considered a continuous load and the conductor must be sized for the maximum continuous load at 80% of the conductor’s rating. The maximum current on this circuit is now potentially 50 amps and a #8 is rated at 50 amps at 100%, so the conductor is too small since it can only be maxed out at 40 amps and there is no way to limit the current to 40 amps regardless if we comply with 2-100 because 26-700 requires the 50 amp breaker.

This does not apply to non-continuous receptacles such as general use, exterior, etc where the 80% applies to the max of the circuit; although for #14, #12 and #10 it happens to work out the same (max of conductor); that is why there is rule 14-104 2), as you move up from there it does not work.

I think the real answer is to make a 40 amp receptacle for EVs and you install a 30 amp, 40 amp or 50 amp as required. If that is not an option, then you make a special rule (similar to stoves 26-744) that states you need to install the next larger conductor from Table 2 as required for the breaker size for any EV designated receptacle, notwithstanding other rules (like voltage drop).

Cheers
John

So again here you talk about “non-continuous receptacles” and “continuous receptacles” but have yet to provide an actual code rule to back this up.

Can you please provide a code rule for this ?

8-104 is the conductor only at 80% and does not apply to the breaker or the receptacle.

Um, I think you should go back and read 8-104 because it 100% does apply to the breaker, it always has. In 2018 they added that it also applies to the conductor.

But there are rules that dictate that it is not complaint in some instances such as the EV rules

And what EV rules are you referring to here? Stories of conversations with ESA are great, but again, actual code numbers please

 

[eddy current]

IMHO, we (as installers) don't need a rule about continuous or not for receptacles because that is decided for us by the manufacturer of the device, based on the plug they provide us with.

The continuous load rule is very clear. Everything is a continuous load unless you can meet the requirements of 8-104(3). What a customer plugs in is not relative to the electrical installation requirements.

8-104 Maximum circuit loading
3) The calculated load in a consumer’s service, feeder, or branch circuit shall be considered a
continuous load unless it can be shown that in normal operation it will not persist for
a) a total of more than 1 h in any 2 h period if the load does not exceed 225 A; or
b) a total of more than 3 h in any 6 h period if the load exceeds 225 A.

 

[eddy current]

I have read 8-104 and will provide here again for reference (bold added):

But did you read the whole thing? Like I said it applies to both the breaker and the conductors, not just conductors like you stated. Here I bolded it for you.

8-104 Maximum circuit loading
6) Where a fused switch or circuit breaker is marked for continuous operation at 80% of the ampere rating of its overcurrent devices, the continuous load as determined from the calculated load shall not exceed the continuous operation marking on the fused switch or circuit breaker and
a) except as required by Item b), shall not exceed 80% of the allowable ampacities of conductorsselected in accordance with Section 4;

If this 50 amp receptacle was not designated as a EV receptacle, then 8-104 would not apply... it would magically become a general use receptacle for 50 amps or some other "non-continuous" load for something else. The crux is that it is designated as an EV receptacle and special rules apply to it.

first off 8-104 applies to all, you really need to read the whole rule. And no it would not magically become non-continuous load for something else. Continuous and non-continuous loads are clearly explained in 8-104(3). You should read that one a few times because it’s obvious you don’t understand it.

second, still waiting on these EV codes you keep mentioning that prove your opinion on this. I know section 86 very well as I cover it in my EVITP class so please, enlighten me here. Nothing you have stated is actual code. All you have is a conversation with an inspector, but yet you claim it’s a code requirement, without providing the actual code.

Stating something is “code” but not actually providing the code is amateur, come on John, you know this.

 

[eddy current]

LOL, that is what is great about this forum, we can discuss and have differing opinions and still drink beer at the end of the day.

@eddy current Not sure what else to say (write) to you. I have shown the reasoning for this, I have provided examples and cited code. Lets just say that I will continue to install the designated EV receptacle with #6 and 50 amp breakers on these circuits and not get defects while you (or your students) can roll the dice with the ESA inspector and install the #8 and a 40 amp or 50 amp breaker...

Once again, I don't necessarily disagree with the #8 and 40 amp breaker perspective (as per my previous posts), but we will see if the ESA comes out with a new bulletin for the EV receptacles requiring what I have tried to explain.

Cheers
John

Never said it could be on a 40 amp breaker, nor did I say I teach it that way, but love how you threw that in there😂

A 50 amp breaker, 50 amp wire and 50 amp receptacle meets code, just like every other type of receptacle circuit. There is no special code that makes this different for an EV. The only reason you would need #6 copper is manufacturer spec which is common, but again not a code requirement.

And no, you have not provided a code that says we must run a #6 on a 50 amp EV circuit because there is no such code.

 

[eddy current]

I thought I was in controversial talk for little while here 😅

Enough arguing just use 250MCM aluminum and call it a day. It's good for your 50 or 60 or 200 amps 😂

In all seriousness, I agree with #8 is good to go on a receptacle for 50 amps assuming the termination temp is 75° on the breaker and receptacle.

As for a charger, that's up to the instructions. If the instructions say to use #4 copper for a 60 amp breaker, so be it. (FYI, Tesla chargers have no termination temp so they have to be wired with #4 copper or larger for the termination temp of 60° if they're on a 60 amp breaker).

exactly. Manufacturer spec on these is all over the place and quite often exceeds code so we need to check it.

And although I think it’s a great idea to use larger conductors for many reasons, it’s not a code requirement.

 

[eddy current]

Yeah this got interesting. I had to bring this one up because 8-104 is a pretty major rule that affects conductor and breakers in most situations of everyday work. When I see someone interpreting it differently, I start to question everything. I think Navy is right to use #6 on 14-50 receptacles, but for the wrong reason. It's TTR. I was going to post the a similar picture as Eddy on the 14-50R 75 degree rating. What it actually says is "use minimum 75 degree wire". The documentation that comes with my flush mount Hubbell 14-50s says "Select conductors having 75 degree C o higher rated insulation having sufficient ampacity in accordance with the 60 degree C column of NEC Tale 310-16 or CEC Table 2". So 60 degree column gives makes us use #6 cu for a 50 amp receptacle. I've definitely done this wrong a few times. I'd still wire a hardwire 50A EV charger with #8awg cu if the TTR is given at 75.

On a side note, if a device specs that we use conductors with a minimum wire temperature should we ever use that as the TTR? I'm thinking base board heaters spec 90 degree wire. Should I have sized them at 60 degrees (no TTR) or 75 degrees off the breaker since 90 degrees is the TTR of the BB? This should be pretty basic, but I'm always circling back.

A lot of equipment will spec a minimum wire temperature, but don’t confuse that with the termination temperature.
like light fixtures always say “use 90 degree conductors” but we must rate their ampacity according to the termination temp.

I’ve wired an elevator controller that spec’d 300 degree conductors because it got so hot in there, but it’s ampacity had to be rated at 75 degrees due to termination temp.

 

[eddy current]

I think the conversation is focusing too much on the semantics of code interpretation. Let's get back to basics...

The 80% rule applies to overcurrent protection only. Mass-produced breakers are mostly thermal-magnetic trip. They get hot, they trip. When breakers are rated at 80% continuous duty, when subjected to continuous load, they can trip at anywhere from 80% to 100% of the rating. Manufacturing tolerances are not very tight and field environmental conditions can vary. A standard 50A breaker serving a continuous load will trip at anywhere from 40A to 50A. There is simply no way to know for sure. All the manufacturer guarantees is that it will hold forever at 40A or less in most normal applications.

The 80% rule does NOT apply to conductors. Case in point: 8-104 [5] allows 100% circuit loading when using 100% rated breakers. 4-004 starts by saying "The maximum current that a copper conductor of a given size and insulation is permitted to carry..." . The only mention of the 80% loading is in relation to overcurrent protection. By definition, tables 1-4 can be read at face value for conductor ampacity.

By the way, the reciprocal of 0.8 is 1.25, NOT 1.2. Multiply continuous amps by 1.25 to get breaker trip rating.

When a breaker lists a termination temperature of 75deg, that is the maximum temperature of the conductor before the heat from the conductor will significantly influence the trip characteristics of the breaker. #8 NMD90 will happily carry 55A all day long but theoretically the copper temperature could rise to around 90deg. If terminated to a standard 75deg breaker, the hot conductor will adversely affect the trip rating. Hence, NMD90 is de-rated to the 75deg column and 50A. As long as the copper is 75deg or less, the heat from the conductor will not affect the breaker trip characteristics. If load is limited to 50A or less, the copper itself should not rise above 75deg.

Increasing conductor sizing beyond the trip rating has zero benefit outside of voltage drop or tables 5 derating (or similar).

As @emtnut mentioned in a previous post, it is a mandatory requirement for cUL / CSA approval that cord-connected devices only load the circuit to 80% of the cord / receptacle rating. Any legitimate appliance with a factory 50A cord end will only be loaded to 40A. If somehow the EV chargers are getting away with 50A load on a 50A plug, the bottleneck is going to be the breaker, NOT the conductor. Breaker may hold or maybe it will trip. It is impossible to know. BUT there is absolutely no reason to increase wire size. #8 can handle 50A all day long and the CEC supports this over and over.

I agree with the previous posters... 50A breaker, 50A conductors (#8), 50A receptacle, 75deg everything... A-OK.

BIG CAVEAT... none of this overrides the manufacturer instructions. If instructions say #6 wire or larger, nothing in the CEC can contravene this (unless the CEC calls for larger). For a different example, if nameplate says "COPPER CONDUCTORS ONLY", it better be copper! Even though CEC says alum. is fine, manufacturer says otherwise.

All bets are off with 60deg termination temperatures. @Costalota makes a good point. I'm going to look a little closer at the receptacle termination temperatures in the future. IMHO, listing 75deg on the device itself and then 60deg terminations in the documentation is a insanely stupid!

What version of the code are you looking at?
In Older versions, yes the 80% and 100% rules only applied to the fused switch or circuit breaker but that changed in the 2018 Canadian code.

In 2018 rule 8-104 (5)+(6) changed and they added that it also now applies to the conductors.

In Post #29 I posted the actual code with important parts bolded. It clearly states that yes, the rule applies to the conductors.

And this is from the 2018 Canadian Code update course to simplify it.

 

[eddy current]

8-104 indicates the maximum continuous loading of the circuit, not the conductors. The CEC defines the maximum continuous load of the circuit is based on the conductor ampacity OR the trip rating (80% or 100%). It is not the other way around. 8-104 does NOT say the maximum ampacity of the CONDUCTOR is 80% of the table 2/4 ampacity. Conductors are good to whatever the tables 1-5 (or others) say it is.

On the larger services, we frequently do 3000A rated main services with 100% continuous rated main breakers. We push the continuous calculated load right up to 3000A. Main incoming conductors are still 3000A rated, not 3750A.

On an existing service, switching the main breaker to 100% rated is a quick way to get 25% more capacity without upgrading conductors.

The updated CEC language is pretty much moot because the conductor ampacity will practically never be less than the breaker trip rating in most normal circuit applications. Breaker trip amps is almost always going to limit the max circuit loading. I suppose it could apply to a low voltage circuit with #18 securex but that is not really what we are talking about.

Yes the continuous loading of the circuit is the lesser of either the breaker rating or the conductor rating, which could be either 80% or 100%
But the wording in the code is moot? That completely contradicts what the actual code says, and what they explained to us in the CSA code update. They gave us many examples in the code update as well where with this "moot" wording, you can upsize the conductor to help with larger circuits above 800 amps

 

[eddy current]

So for a 2000A service with a 100% continuous duty rated 2000A main breaker, you would size the incoming conductors for 2500A?

No. But are you using single conductors, or multi-conductor cable? (See the pic on post #42 for a simplified version)
With 100% rated equipment it is either 100% of the overcurrent or 100% of the conductors, just like it says in the actual code. (ETA or 85% of the conductors for single conductors)

Now with 80% equipment, it is either 80% of the breaker or 80% of the conductor, which ever is lower. (ETA or 70% of the conductors if using single conductors)
Here, try these examples using single conductors and 80% equipment (These are not mine, they are from the code update)