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I have a hot tub. It is wired with 6/3 teck cable to a pull out disconnect switch. The pullout is wired with 8/3 teck cable to the main GE panel with a 50amp standard breaker.

It was roughed in with the 8/3. The spa calls for 6awg.

My plan is to replace the pullout style disconnect with a spakit CHOME250SPA which has a GFCI 50 amp breaker ( THQL2150 ) - mostly because the panel breaker isn't GFCI and the pull out disconnect wire fill is too large.

Some references online seem to indicate that you can pull 50amp via 8/3 teck cable as the cable can handle higher temperatures but the 50amp breaker in the main panel is rated 60C/75C for copper/aluminum. Does this mean 60C for copper or 75C for aluminum? A reference online seemed to suggest that these conditions aren't related and the breaker is saying it is good for 60C/75C/Copper and aluminum. This doesn't make a lot of sense to me as saying it is good for 60C is superfluous if you say 75C. I can't replace the 8/3 wire without doing extensive surgery on the house across 3 levels or having a nasty teck cable running up my siding.

The UL standard for circuit breakers states:

(1) Breakers rated 125 A or less must be marked for use with 60°C, 60/75°C, or 75°C only wire.

Given that it seems like the breaker is fine for 75C copper. I haven't done the research to know exactly how a breaker works, thinking about it, it is probably heat based so the rating probably just indicates that the breaker is lab tested under all those conditions.

My initial electrican put the 8/3 in place with the pullout disconnect way before I had selected a spa. A new electrician put the 6/3 teck cable to the pullout disconnect but didn't think I needed GFCI since it is a tub on a deck and not near the ground. He didn't mention the fill issue I only found it when I noticed the plate for the disconnect that covers the wire connections wasn't installed. A third electrician says I should have GFCI and recommended the spakit. He said that the teck cable is good for 50amps but that the breaker is probably not rated for 75C.

Searches seem to indicate 8/3 will handle 50amps but reach 75C which the teck cable is good so if the breaker is ok with 75C on copper I should be good?

Thoughts?

Reference talking about teck cable in wall being 8/3 instead of 6/3 NM. https://forums.mikeholt.com/threads/hot-tub-wire-size.2567630/

Reference talking about all 4 breaker possibilies are fine. https://forums.mikeholt.com/threads/8-on-50-amp-breaker.2580600/

UL Reference on circuit breaker labeling: https://www.se.com/ca/en/faqs/FA278582/

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That slash rating explained

The 60°C/75°C "slash" rating on a breaker is simple: it means that the breaker termination requires 60°C limited wires (NM and UF, as well as old R/RW and TW wires whether in conduits or in a cable assembly) to be used at their 60°C ampacity rating, but can permit 75°C rated wires (most SE cables, as well as modern wire types such as THHN/THWN, XHHW, THW, and RHH/RHW-2 whether part of a cable or as individual wires in conduit) to run at their 75°C ampacity rating.

Since Teck90 cable universally uses 90°C rated wire insulation, you're good to use the 8/3 cable for your 50A circuit.

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I think what's throwing everyone off, is the term "teck cable". Is this type MTW, Machine Tool Wire? If it is, then it would be good for 75 degrees C if installed in a dry area (run through a building), or 60 degree C if buried in the ground. Meaning if it was run under ground or in a wet location it only allowed to carry 40 Amps. Otherwise you would be allowed to connect it to a 50 Amp breaker. NEC Table 310.4 (1).

Also it needs to be connected to a GFCI or an SPGFCI per NEC 680 Par IV, and within 5'.

It probably would not hurt to consult you AHJ (municipal inspector) to see if they have any specific instructions.

How far is this hot tub from the panel? You need to find the nameplate rating and check for voltage drop before determining the size conductor that needs to be run.

Also, yes if the manufacturer finds that the feeder was a #8 and they have recommended a #6, They will probably void the warranty in the event of a malfunction.

Maybe not good news but I hope this helps.

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  • Does this help? northerncables.com/products/teck90
    – Fresh Codemonger
    Commented Sep 9 at 22:18
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    In Canada, teck cable is defined by CSA standard C22.2 No. 131[2] and carries the type designation of TECK90, the 90 referring to the maximum conductor temperature in degrees Celsius that the cable may be used at in a maximum 30 C ambient environment without de-rating its ampacity. en.wikipedia.org/wiki/Teck_cable
    – Fresh Codemonger
    Commented Sep 9 at 22:20
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    TECK is basically a MC cable construction, and some but not all TECK cable is MC/TECK dual-rated (Belden's TECK cables are dual-rated, for instance, but not all are)
    – ThreePhaseEel
    Commented Sep 9 at 22:25
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    @FreshCodemonger - Your length is going to get you about a 3% voltage drop from the panel to the tub which is right on the edge of acceptable for motors. Also if you are using the entire 43 Amps as a start up adding 25% will get you to 53.75 Amps. That means you are stressing your 50 Amp breaker at startup. Are you running this in Canada or the US? Is there a maximum circuit breaker size on the name plate? I still recommend you check with your AHJ.
    – Retired Master Electrician
    Commented Sep 10 at 12:40
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    Teck is a Canadian invention (by the hard rock mining industry). NEC sees it as an enhanced MC cable with additional ratings by UL. This is authorized by NEC at 330.10(A)(6) and (12)... and 330.12(2).
    – Harper - Reinstate Monica
    Commented Sep 12 at 5:39

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