THHN is for high heat
THWN is for wet locations
From looking at the ampacity charts 12awg THHN/THWN is rated at 30a and MTW is rated for 20a.
Hmm... I wonder why it's ampacity is so different. I'll have to look it up in NFPA 79 at work.
THHN is for high heat
THWN is for wet locations
From looking at the ampacity charts 12awg THHN/THWN is rated at 30a and MTW is rated for 20a.
This UL guide should help in answering a lot of questions on cable types and their applications:
UL Wire and Cable Marking and Application Guide
I'm used to seeing type SIS wire in control circuits, but I'm not sure how available it is to general consumers. Not saying that it's what should be used in a brew panel, just stating what I'm used to seeing in industrial/power plant applications.
I was looking at NEC chart 310.15 not the NFPA chart. So I might be wrong.
Just adding some info to the conversation on cable types and their ratings, outside of the NEC and NFPA.That is great info from the UL, but we are talking about the wire you use inside the control box. But thanks for providing that info.
NFPA 70 is the NEC - 310.15 is the right table.
I checked with NFPA 79 and it didn't help.
I think the only difference between mtw and thhn is rating at 75c vs 90c . (I found some MTW at work that was rated at 75c)
This is correct, the terminations are going to determine the overall temperature/ampacity rating. I think NEC article 110 talks about this (my NEC is at work, don't have a copy at home).Says 105C in the link I posted. As stated, the rating of the terminations determines the column used in the ampacity chart.
NFPA 70 is the NEC - 310.15 is the right table.
I checked with NFPA 79 and it didn't help.
I think the only difference between mtw and thhn is rating at 75c vs 90c . (I found some MTW at work that was rated at 75c)
The UL link I posted lists MTW at 90C for dry, but I guess that's probably the minimum per the current standard (if the wire is UL rated).Says 105C in the link I posted.
Just adding some info to the conversation on cable types and their ratings, outside of the NEC and NFPA.
Now if I were wiring controls for an enclosed control panel for my home brew, then I would use the most readily available stranded 12 gauge wire that I could find, rated to the proper voltage. Weather it be THHN, MTW, SIS, etc.
Wires carrying element power I would use #10.
I think the point of this thread is they are saying those values dont apply for this kind of environment?Yeah... just saying but the overcurrent protection for #14 thhn/thwn is 15amps, #12 is 20amps and #10 is 30amps... I don't care what kind of philosophical spin you put on it. If the terminals are rated for 75 degrees (which most all are) then you use the 75 degree column.
If they didn't apply there would be an exception in the NEC... please point it out.
The UL link I posted lists MTW at 90C for dry, but I guess that's probably the minimum per the current standard (if the wire is UL rated).
I'm not the one saying this.
I have no knowledge of this either as I go by the standards you mentioned above... Haven't you read the thread? I believe this is the main point of the discussion here..
I was reading it right off the spool - so I guess it depends.
Yep! This is just a friendly conversation about wire types and some sharing and learning of the NEC. I did look at NFPA 79 last night and it agreed with Jerz - 14awg = 15a, 12awg = 20a, 10awg = 30a, etc, without specifying any difference between THHN, MTW, or others that I dont recall off hand.
But - NFPA 79 is more about wiring practices within machine tool electrical panels. It assumes initial ampacities from NFPA 70 - NEC.
Wires carrying element power I would use #10.
Even if using type SO, I personally would still upsize to #10 to allow some additional margin.It is completely legal and safe to use #12 SO cord for hooking up 25amp elements per NEC table 400.5(A) (Allowable Ampacities of flexible cords) as long as there are only two conductors are current carrying.
Even if using type SO, I personally would still upsize to #10 to allow some additional margin.
For peace of mind for added margin to the cables rating, I'd gladly spend a few extra bucks. Really, what are we talking here maybe 50 cents more per foot at most?BUT
Each to their own - if 12/3 works well, 10/3 wont hurt anything more than your wallet.
For peace of mind for added margin to the cables rating, I'd gladly spend a few extra bucks. Really, what are we talking here maybe 50 cents more per foot at most?
It's not worth arguing for me - it's black and white and in a code book.
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