I thought I could get an answer more quickly from this forum than from the county building inspectors, they’re usually unavailable.
I have a spa, 240 V, the label says it requires 60 A. Poking around in the basement I notice that the electrician used 8 ga. wire for the run to the spa. Is this sufficient? What references I can find say the max current for 8 ga. is 40 A. Is this a potential problem? The spa has been in place for 5 years, the house hasn’t burned down yet. Thanks for the help.
Replies
Without a long run (over 50 feet) 8 Ga should cover 50 amp per the NEC.
3 options.
1 put in a breaker for 50 Amp 2 pole for your 240 and call it a day. If the spa doesn't work (trips out) then change the wire.
2 change the wire to 6 GA for 65 amp max.
3 run parallel* another 8 ga set of wires from breaker to the spa. This is trickier as parallel runs tend to be used for MCM sized wire. The Spa and load center would need to accomidate a pair of lugs** per line or a splitter block to connect the wires to the breaker and the spa.
*This is not a job for the first time effort at electrical work.
**The lugs need be paired if crimp on type, if mechanical lugs try to find a lug that will accomidate 2 wires.
Final thought, as this appears to be a previous owner kludge. Spas are now required to have GFI protection. You need to check that out as well. If the GFI is missing then rewire the mess.
Aw, crap.
I guess the 50 A breaker is an option. I can't even blame this on a previous owner, as there isn't one. When the house was being built, I told the electrician that at some point we planned to put a spa off one corner of the house. I just asked that he put in a circuit and run the wire over to that corner and leave me lots of extra, when the day came I would put it through the wall and into underground conduit. We probably never discussed amperage, and he used what he thought would suffice.
The breaker box is in an exterior wall insulated with that spray foam stuff, so all the wires are embedded in there. I wouldn't even try to pull the old wire and put another one through there. If I did replace the wire, would it be legit to go from the box to the basement using conduit mounted on the interior wall surface?
Thanks for the reply.
Final thought. Most Spa's are 50 Amp. It was a good shot at that size. Possibly you can strip off a circuit or two from the spa and make it work? Light circuit may be separable.
Hey wire is cheap. the breaker will cost you though.
In my humble opinion I wouldn't worry about it. Assuming the #8 has 90 degree C insulation the code allows it to carry 55 Amps. There is another listing that allows a 60 Amp breaker to be put on a conductor rated at 55 Amps as there are no standard 55 Amp breaker made. So so far everything is legit and by code the #8 is not, by itself, a problem.
The problem comes with the lugs on the breaker. If they are rated at 75 degree C then, by code the entire assembly must be rated under the lower rating so the #8 is allowed to carry 50 Amps. The idea being that the insulation on a 90 degree wire running at 90 degree C is happy but it would overheat a lower rated lug connected to it. If the breakers lugs are rated at 90 degree C this is not a problem.
OK you examined the breaker and get the bad news that it is rated at 75 degrees C. What now. Look closely at the breaker supplying the spa. A good flashlight will help. Is the lug discolored. Is the plastic around the lug still in good shape and shiny or is it distorted or charred looking. Compare it to similar breakers in the box. If there is damage you have a problem and something will need to be done.
If the lugs were tight, any loose connection can overheat a breaker regardless of the lugs rating, and the breaker is damaged I would look for a breaker with higher lug rating. Some of the larger companies, aware of this ongoing problem of 90 degree insulation being common but lugs being only 75 degree, have come out with breakers with 90 degree terminations. Checking is free and the newer breakers, if available, are not usually more expensive.
My bet is that you will see no heat damage and that while this is a technical violation and should have been installed differently that the inherent safety factors built into the system will correct for this insult. This is common to electric ranges, heat pumps, and larger spas. I see this several times a week and as long as the panels are maintained I have not noticed a significantly higher burn out rate for the breakers as long as the conductor is copper. Had this been #6 aluminum, also rated at 50 amps at 75 degree C, I would be more concerned. Aluminum terminations are far more likely to generate excessive heat as they age.
The one thing I would do, this is a good idea IMHO for any panel but even more important in your case, is to inspect it once each year. Flip all of the breakers off and back on to redistribute the grease around the pivots and check function. Check all connections for firmness with a screwdriver. Visually inspect everything. Look for charring, heat damage, damaged insulation, flash marks. Sniff for an acrid or hot metal smell. Slightly wiggle breakers and listen for sounds of arcing.
Thanks for that very educational explanation. I assume there must be torque specs for those screws in the breaker that clamp the wires, would you know offhand what they might be or where I could find them? It's a Cutler-Hammer, if that makes a difference. I finally picked up a 3/8" tw for just this kind of thing. Again, thanks to all for taking the time.
The torque listings for your panel should be shown on a sheet glued to the inside of the panel. Usually in pretty fine print so a good light will help. Having done this for years I usually, unless it is a critical application (A nuclear plant comes to mind.) just do it by feel.
I tested this once against a torque wrench and was within the range specified. The irony being that I didn't know the value I was shooting for just that with the tool that fit properly it seemed tight enough. Firm but not straining is about right. The conductor if removed should be marked but not crushed. Aluminum is a bit more finicky. Copper a bit less.
Not only that, you get into tightening and breaking torque. I spent 5 years as an Automotive assembly svr and had a belly full of mechanical newbies. The torque guidlines are put there for people w/o sense. Trust yourself on this one. It is the "I'll secure it later" stuff that causes problems.