Geothermal nameplate

[kwired]

I'm beginning to wonder if anyone what reads what I write.. I sent him an email with a link to the instructions/manuel to help prove that the external pumps were figured into the MCA. But my aguement is that in Mass we have changed 334.80 to this:

So in my install there is no thermal insulation and the amb. temp. is not above 86f . but if were and I did need to derate for temp ,.the temp rating I would get to start from is 90c or 40 amps ....so per that stupid note I do in fact have a "WIRE" rated for 40 amps ... What say any and all ????

Even without your local amendments you still have a conductor that must be sized for 60 deg, but you are allowed to use 90 deg values for derations. I did not comment on your initial mentioning of the local change because I did not see that it made any difference in this installation. The biggest change I see in the amendment is removal of the second paragraph of the NEC content. Most of the rest of how it is worded still has same requirements just worded differently. I question whether or not this is a good idea to remove the second paragraph. I have seen demonstrations of loaded (not overloaded) cables encased in foam insulation and the temperature gets suprisingly high inside that insulation, the more cables you encase close together there the more heat you can develop in there.

They wrote that section for good reason.

 

[M. D.]

Kwired, the reason I mention it (mass 334.80) is that it is my understanding that the NEC would require you to derate nm from the 60c ,and that we in Mass get to derate NM from the 90c or 40 amps provided there is no therm insulation .. and that stupid note (2) from Climatemaster only refers to the wire ,, how do I prove the NM wire has a 40 amp rating you may ask? I offer Mass 334.80 and ask If I did need to derate for amb.temp what ampacity do I start from ? Answer = 40 ....so since that stupid note only mentions the wire and not the circuit ampacity I still say that the "wire" does indeed have a capacity of 40 amps.. Yes ?

 

[kwired]

Kwired, the reason I mention it (mass 334.80) is that it is my understanding that the NEC would require you to derate nm from the 60c ,and that we in Mass get to derate NM from the 90c or 40 amps provided the temp is ok and there is no therm insulation .. and that stupid note (2) from Climatemaster only refers to the wire ,, how do I prove the NM wire has a 40 amp rating you may ask? I offer Mass 334.80 and ask If I did need to derate for amb.temp what ampacity do I start from ? Answer = 40 ....so since that stupid note only mentions the wire and not the circuit ampacity I still say that the "wire" does indeed have a capacity of 40 amps.. Yes ?

From your quote of local amendments:

334.80. Delete the second paragraph and revise the first paragraph to read as follows:
334.80 Ampacity. Type NM, NMC, and NMS cable shall have conductors rated at 90?C
(194?F). Where installed in thermal insulation, the ampacity of conductors shall be that of 60?C
(140?F) conductors

All I see that was accomplished was deleting the second paragraph:

Where more than two NM cables containing two or more current-carrying conductors are installed, without maintaining spacing between the cables, through the same opening in wood framing that is to be sealed with thermal insulation, caulk, or sealing foam, the allowable ampacity of each conductor shall be adjusted in accordance with Table 310.15(B)(3)(a) and the provisions of 310.15(A)(2), Exception, shall not apply

which eliminates the recent NEC change of having to derate when passing multiple NM cables through a framing member that is sealed with foam, caulk, or similar material. The rest of what was re-written looks to me like it just paraphrased what is already said in the NEC and no actual requirements in the NEC were changed. That said lets go through what the NEC actually says a little more.

The ampacity of Types NM, NMC, and NMS cable shall be determined in accordance with 310.15. The allowable ampacity shall not exceed that of a 60?C (140?F) rated conductor. The 90?C (194?F) rating shall be permitted to be used for ampacity adjustment and correction calculations, provided the final derated ampacity does not exceed that of a 60?C (140?F) rated conductor.

334.112 does say that conductor insulation must be 90?C rated, so the first sentence in your amendment is also already covered as is in the NEC already.

334.80 basically says NM cable must be sized according to 60?C rating, but can use 90?C rating for ampacity adjustments. So does your local amendment.

If thermal insulation is involved then you do have some difference - your amendment seems to imply that you use
60?C rating for selection as well as ampacity adjustment - but that does not apply to your case here.

So selecting an NM cable from NEC we need minimum of 25.3 ampacity at 60?C that gives us 10AWG minimum no matter what any other derations that may be allowable at higher temperature ratings may leave us at.

Your note (2) complicates the situation since the allowed 40 amp max OCD is higher than the ampacity of the conductor as that note says. So your only choices to comply with that is to either use a 30 amp OCD or use a 40 amp conductor if you want to use the 40 amp OCD.

 

[M. D.]

Ah,..I see sorry,.. for my confusion... I'm just finding it hard to believe that that stupid note makes moot the NEC and the t instrutions of their own dang chart .No 60c AWG 10 has a capacity of 40 amps yet they instruct that 40 amp HACR is the max for the wire they have instructed the installer to use,.. which by their stupid note (2) seems not to be the case at all .. A cruel and costly joke ..... It is FUBAR for sure. But if the wire does not have the capacity for 40 amps why do we start there for derating ? Also the mass code does allow for 75c of 35 amps if the proper circumstances allow.

 

[kwired]

But if the wire does not have the capacity for 40 amps why do we start there for derating ?

When sizing any conductor you have to use the larger of:

A) The size determined by termination rating (usually 60 or 75?C) or in the case of NM cable as we discussed you must size to 60?C.

B) The size determined by insulation rating (unless older conductors are involved you are almost always looking at using 90?C for this.

The only time you are going to use the 90?C value with NM cable is for ambient temperature deration or more than three current carrying conductors in a cable or bundle of cables or equivelant situation.

In our example in this thread, we need a minimum of 10 AWG because it is the smallest 60?C conductor that can carry the required 25.3 MCA. No matter what value we end up being able to use when derating for insulation rating the conductor in no case can be smaller than 10 AWG.

In our case a 12AWG @ 90?C would be our allowed conductor size when it comes to minimum ampacity based on insulation temperature, but our NM cable is still limited to being at least 10 AWG based on the 60?C requirement for NM cables. If terminals were rated 60?C we would still be limited to 10 AWG minimum if using THHN/THWN.

Does that make sense? This is not just for HVAC, it is for sizing any conductor.

 

[M. D.]

I get that there are other factors that limit the ampacity of that wire but the ampacity from which that # 10 is limited is 40. ... Why on god's green earth would they have that note (2) which undoes their own instructions?? and eliminates what the NEC has permitted for years and years ... I've made one call to them to no avail ,. and I'm waiting for an email which I hope will explain that stupid note (2)

"current carrying capacity of the wire must not be less than the fuse/circuit breaker size used."

So on a test if I ask :What is the current carrying capacity of #10 90c wire ,no other factors involved.
A. 30 amps
B. 40 amps

Answer: A ?

 

[kwired]

I get that there are other factors that limit the ampacity of that wire but the ampacity from which that # 10 is limited is 40. ... Why on god's green earth would they have that note (2) which undoes their own instructions?? and eliminates what the NEC has permitted for years and years ... I've made one call to them to no avail ,. and I'm waiting for an email which I hope will explain that stupid note (2)


So on a test if I ask :What is the current carrying capacity of #10 90c wire ,no other factors involved.
A. 30 amps
B. 40 amps

Answer: A ?

Little tricky question. Based on exactly what you said I say go straight from the 90?C column of the table and it is 40 amps.

Throw in termination temperature and it is either 30 or 35 as you are unlikely to find 90?C terminals, but you can still start derating for ambient temp or number of conductors in raceway or cable from the 90?C value, as long as final adjusted conductor size does not result in a conductor smaller than termination temperature calls for.

Then you also have that note at bottom of table that sends you to 240.4(D) for overcurrent protection, which really doesn't matter for current carrying capacity, but still eventually effects size of conductor selected in some cases, motors and AC/refrigeration are one place where 240.4(D) generally can be ignored - the reason is the motors involved still have overload protection that will prevent the supply conductors from being overloaded even though the fuse or breaker is sized higher than the conductor ampacity.


As far as that stupid note (2) in the equipment instructions, life is not always easy. One way around it if you already have cable installed is to make your required disconnecting means a breaker or fused disconnect and only replace the portion between the unit and disconnect with larger conductors. That makes the circuit up to the disconnect a feeder and not the branch circuit supplying the unit. Seems kind of stupid but is compliant.

 

[M. D.]

perhaps stupid note (2) is just a fancy way of asking for a 90c rated wire ..

 

[kwired]

perhaps stupid note (2) is just a fancy way of asking for a 90c rated wire ..

No, you will always have to size it to 75c because of terminal ratings, and if using NM cable will always have to size to 60c because of what 334.80 says.


Leaving that note(2) out if things, I still get the feeling you do not quite grasp the fact that you basically have to determine two different conductor sizes and final selection must be the larger of the two. One is based on 90C insulation, the other based on either 60C or 75C termination rating and in the case of NM cable you treat 334.80 as if 60C were terminal rating.

 

[M. D.]

I get it ... but they could still want a wire with a 90c rating for it's insulation. we have already established that even at 60c the 10awg has the circuit ampacity covered

 

[M. D.]

No, you will always have to size it to 75c because of terminal ratings, and if using NM cable will always have to size to 60c because of what 334.80 says.

In Mass I would , in my circumstance, get to use it at 75 c if the terminals were rated 75 and there were no thermal insulation and no amb temp to worry about.
334.80. Delete the second paragraph and revise the first paragraph to read as follows:
334.80 Ampacity. Type NM, NMC, and NMS cable shall have conductors rated at 90?C
(194?F). Where installed in thermal insulation, the ampacity of conductors shall be that of 60?C
(140?F) conductors. The ampacity of Types NM, NMC, and NMS cable installed in cable tray
shall be determined in accordance with 392.11.

 

[kwired]

In Mass I would , in my circumstance, get to use it at 75 c if the terminals were rated 75 and there were no thermal insulation and no amb temp to worry about.
334.80. Delete the second paragraph and revise the first paragraph to read as follows:
334.80 Ampacity. Type NM, NMC, and NMS cable shall have conductors rated at 90?C
(194?F). Where installed in thermal insulation, the ampacity of conductors shall be that of 60?C
(140?F) conductors. The ampacity of Types NM, NMC, and NMS cable installed in cable tray
shall be determined in accordance with 392.11.

I guess that depends on your interpretation of your local amendment. I see it as saying the conductors shall have 90C insulation (NEC also says this, in a different location) but it does not say anything about using that 90C rating for ampacity selection. Which puts you in same situation you are in when using raceway and THHN/THWN. You have a conductor with 90C insulation but only thing you can use that 90C ampacity for is a starting point for deration, you must still have a conductor with at least 60C or 75C ampacity for the terminations.

I still question what the purpose of your amendment is other than it eliminated the second paragraph otherwise it still appears to have same requirements of NEC on the rest just worded differently. Did not check previoius editions of NEC, maybe they simply reverted it to what it said before the omitted paragraph was removed.

 

[M. D.]

I guess that depends on your interpretation of your local amendment. I see it as saying the conductors shall have 90C insulation (NEC also says this, in a different location) but it does not say anything about using that 90C rating for ampacity selection. Which puts you in same situation you are in when using raceway and THHN/THWN. You have a conductor with 90C insulation but only thing you can use that 90C ampacity for is a starting point for deration, you must still have a conductor with at least 60C or 75C ampacity for the terminations.

I still question what the purpose of your amendment is other than it eliminated the second paragraph otherwise it still appears to have same requirements of NEC on the rest just worded differently. Did not check previoius editions of NEC, maybe they simply reverted it to what it said before the omitted paragraph was removed.

Right but doesn't the NEC limit nm-b to 60c ? In Mass I am quite certain that it has long stood that it is the termination so on a range with 75c termination and a breaker with the same ,.it is permissible in mass to land that #8 nm-b on a 50 amp breaker

I don't have the good book in front of me ,.but the big difference is that NEC 334.80 says something much like the below and Mass requires there to be thermal insulation for that particular restriction ..

....The ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating....

 

[kwired]

Right but doesn't the NEC limit nm-b to 60c ? In Mass I am quite certain that it has long stood that it is the termination so on a range with 75c termination and a breaker with the same ,.it is permissible in mass to land that #8 nm-b on a 50 amp breaker

I don't have the good book in front of me ,.but the big difference is that NEC 334.80 says something much like the below and Mass requires there to be thermal insulation for that particular restriction ..

....The ampacity shall be in accordance with the 60?C (140?F) conductor temperature rating....

This is from 2011:

The allowable ampacity shall not exceed that of a 60?C (140?F) rated conductor. The 90?C (194?F) rating shall be permitted to be used for ampacity adjustment and correction calculations, provided the final derated ampacity does not exceed that of a 60?C (140?F) rated conductor.

I have no clue what the intentions are in Mass. Seems odd that NEC has taken some effort to reduce ampacity of NM cables especially with recent changes for foam filled holes containing cables, and Mass. is trying to increase ampacity.

 

[M. D.]

I don't know ,.. if there is no thermal insulation around the wire and the amb. temp allows for good heat dissipation what's the problem? The wire has a 90c insulation that for most,. if not all installations will be held to 75 c ... it's the impedance of heat dissipation that is the villain.. There are 10 of thousands of NM-B installations in mass that have employed that provision and I don't think it's been an issue.. on a side note we seem to have removed that bit about the start point being 90c when there is thermal insulation so I guess we start at 60c ....YIKES:blink: Any other Mass guys out there care to correct me ... I hope

 

[M. D.]

I sent an email to an engineer at Climatemaster I asked for them to either remove or explain Note (2) This is part of his response .The only cited violation was 110.3(b) and the inspector referred to their Note (2) directly. Oh , and I might of said it seemed like a cruel joke ... couldn't help myself. I do agree that stupid note (2) is not a violation of the NEC.

Note 2 in our literature is 100% in agreement with NEC. My response to the removal of note 2. If we did this it would not keep an inspector from red tagging a job. The inspector is going to approve or reject based on NEC and local codes and as was stated you cannot put a 40 amp breaker on 10 gauge wire per NEC. The fact that the inspector did not catch this until he read note 2 is inconsequential, it is against NEC code. We do not put note 2 in our literature because we are trying to be cruel, we do it because it is required by NEC. We provide these notes for the electrician on the job.


​

 

[M. D.]

and for the record what I said was that a #10 AWG with a 60c rating would never have a 40 amp rating,
and not,.. that it could not be protected by a 40 amp breaker.

 

[kwired]

I sent an email to an engineer at Climatemaster I asked for them to either remove or explain Note (2) This is part of his response .The only cited violation was 110.3(b) and the inspector referred to their Note (2) directly. Oh , and I might of said it seemed like a cruel joke ... couldn't help myself. I do agree that stupid note (2) is not a violation of the NEC.

Note 2 in our literature is 100% in agreement with NEC.My response to the removal of note 2. If we did this it would not keep an inspector from red tagging a job. The inspector is going to approve or reject based on NEC and local codes and as was stated you cannot put a 40 amp breaker on 10 gauge wire per NEC. The fact that the inspector did not catch this until he read note 2 is inconsequential, it is against NEC code. We do not put note 2 in our literature because we are trying to be cruel, we do it because it is required by NEC. We provide these notes for the electrician on the job.

Good luck with any conversation with a rep from manufacturer - unless this is for entertainment value of seeing what they respond with

If their product is to carry a listing it does not have to comply directly with NEC, it will need to comply with any listing requirements. The listing requirements may take NEC into consideration though. This note 2 does meet NEC minimum requirements, and in fact goes beyond minimum requirements. Doesn't really make a lot of sense, but if followed you definately do not have a conductor that is too small to safely carry the load.

 

[M. D.]

yeah , and no relief should it fail to start ... I'd have to change the wire .I think a note like this was probably what they were shooting for.
.Note(2): The amapacity of the conductor may never be lower than the ?Minimum Circuit Ampacity? marked on the nameplate of combination equipment as required by NEC 440

 

[texie]

This so called "Note 2" is curious for sure. Can't say I've come across this with a heat pump before. I wonder if because it is supplying other loads through the unit it does not qualify for the normal rquirements in Art. 440.