23amps and 14gauge wire, only used in panel?

[mikescooling]

I can't really agree that one should only use THHN/THWN wire. Those wire types are most certainly the most accessible though. All I would recommend that that one chooses the right wire size and type for their application.

I recently wired a small cabinet for use with temperature control. The cheapest wire I could get was XHHW as it was was free to me. The jacket is super tuff though, my only gripe with the wire. It does meet all my requirements though, so that counts.

There are many factors when considering the wire size if you are going to choose to cut it close. If someone asks me if 14ga wire can handle an ampacity that is pushing the wires limits. I will tell them the truth to the best of my ability, and recommend what I consider the safest. If you goto Home Depot and get a 20 ft cut of wire, the price comparison is almost negligible between 14, 12, and 10 ga. wire. The major price difference is when you are buying 500 ft rolls. Then the difference can hurt the old bank account.

Please also note that the OP has a small transformer and two SSRs in the enclosure from what I can tell. There will certainly be some additional heat thrown off from these devices. Although everything looks good to me from what I saw from the pictures, you have to recognize the fact that if you are going to use a wire that is within 2 amps of the over current threshold for a conductor you could easily achieve a resistive wire snowball effect. Though I don't think a failure in the cabinet would burn down the house, it would most certainly smell, and cause more failures within the system.

I ran 10 gauge for the elements, the lights and switches will be low voltage 24volts (for the most part). I'm still thinking about putting in a fan?

 

[Facinerous]

Well I don't know what wattage your devices would be putting out, a fan may not be necessary. It looks like you have the SSRs attached directly to the panel shell. So your panel will be doing its best to suck the heat from them and dissipate. I don't think you need to worry to much about it. If you do encounter heat problems I would recommend cutting in a louver to allow air to flow. Once again I don't think its necessary, but you'll figure it out as you put things to test.

Good luck dude.

 

[mikescooling]

It's hard to see but their are heat sinks under the ssr's.

 

[John53189]

I can tell you that I used 12 gauge to wire everything inside my panel. And yes 12 gauge should be able to handle 22 amps. During my test runs I checked amp draws on all of the wiring, all was good. After 30 minutes I could feel the wires getting really warm. I replaced all of my contactor wiring to 10 gauge and now it stays cool. Just my 2 cents from 3 weeks ago.

 

[crazyirishman34]

One thing that can cause the wire to heat up is poor connections. It is not necessarily undersized wire. I used 12awg stranded THHN in my 25a circuits and it stays cool to the touch even at full load from a 5500w element for a hour. But i used a ratchet crimper and din mounted distribution blocks.

 

[atoughram]

You should ONLY be using THHN jacketed wire.

MTW is also a good choice and easier to work with but harder to find.

Err... Nevermind I see this was covered...

 

[crazyirishman34]

MTW is also a good choice and easier to work with but harder to find.

Err... Nevermind I see this was covered...

Yes I agree that MTW is an good choice also. But it is hard to find in short lengths and the ratings are different then THHN/THWN.

 

[atoughram]

Yes I agree that MTW is an good choice also. But it is hard to find in short lengths and the ratings are different then THHN/THWN.

I believe the ratings are the same except that THHN is for wet locations - Hopefully one's control cabinet isn't wet inside..

I used THHN because MTW wasn't available at the hardware store I shop at - had it been available, I'd've used that instead as it is much easier to dress the panel with MTW.

 

[lschiavo]

Yes I agree that MTW is an good choice also. But it is hard to find in short lengths and the ratings are different then THHN/THWN.

http://www.elecdirect.com/catalog/a312e543-4274-4fc1-b19b-382b58ffdbc9.aspx

A bit expensive compared to THHN but it is nice to work with in a panel.

 

[crazyirishman34]

I believe the ratings are the same except that THHN is for wet locations - Hopefully one's control cabinet isn't wet inside..

I used THHN because MTW wasn't available at the hardware store I shop at - had it been available, I'd've used that instead as it is much easier to dress the panel with MTW.

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. Both are stranded.

I have never used MTW insulated wire so I can't comment on it's properties. I was just looking at the charts.

 

[atoughram]

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.

 

[crazyirishman34]

I was looking at NEC chart 310.15 not the NFPA chart. So I might be wrong.

 

[ingchr1]

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 and/or MTW wire in control circuits. 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.

 

[crazyirishman34]

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.

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.

 

[atoughram]

I was looking at NEC chart 310.15 not the NFPA chart. So I might be wrong.

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)

 

[crazyirishman34]

I guess that it never hurts to upsize the wire.

 

[ingchr1]

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.

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.

 

[lschiavo]

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)

Says 105C in the link I posted. As stated, the rating of the terminations determines the column used in the ampacity chart. EDIT: Except of course for derating.

 

[ingchr1]

Says 105C in the link I posted. As stated, the rating of the terminations determines the column used in the ampacity chart.

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).

 

[ingchr1]

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)

Says 105C in the link I posted.

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).

 

[ingchr1]

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.

 

[augiedoggy]

Wires carrying element power I would use #10.

Some of the xerox machinery I service uses heating elements and relays and the used #14 wire inside the electric area going to the main relays and triac.... over the years some of these wires have become discolored at the ends and hardened from heat... this heat and damage could only be from the 17-18 amp load on those wires.. Although its more of an issue in the connectors in the heating element wires as Ive seen them crumble and melt over the years and had to replace many.
I guess they saved a good amount on $$ over the thousands of machines they manufactured by going with 14 gauge instead of 12 or 10. but like I was reminded before why take the shortcut here on one panel? sure it will work but heavier wire would be the better choice.

 

[Jerz]

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.

 

[augiedoggy]

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.

I think the point of this thread is they are saying those values dont apply for this kind of environment?

 

[Jerz]

If they didn't apply there would be an exception in the NEC... please point it out.

 

[augiedoggy]

If they didn't apply there would be an exception in the NEC... please point it out.

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..

 

[Jerz]

I did read the thread and that is why I confirmed the wire sizes and overcurrent protection required for the wires. There is no exception for control panels in the code and I think this thread is very misleading.

 

[atoughram]

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 was reading it right off the spool - so I guess it depends.

 

[atoughram]

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..

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.

 

[Jerz]

I was reading it right off the spool - so I guess it depends.

You go by the temperature rating of your teminals... that's all fine and dandy that the spool spells out 90degrees and so does thhn/thwn for that manner BUT you go by the temperature rating of the terminals which will be 75 degrees so that is the column you go by. Ultimately you can do whatever you want though.