you ain't just whisperin dixie...
you ain't just whisperin dixie...
I bought a QO 240V, 2p, 20A, equipment GFI - 30ma trip, for the heat trace on the waterline out to my well. Considering the price tag, that CB was pretty special.
In fact the $95 price tag for a 2p, 20A GFI needed for a Jacuzzi steam and jet shower unit is the reason I joined this forum. I was hoping that somebody here would know how to beat the grim reaper on this price.
a 2p, 50amp CFI in a spa sub-panel costs about 2/3 of the price of the 2p 20A. Now I think they sell a lot of the 50s for hot tubs and apparently there is less of a market for the 20s because e-bay is full of the 50s, but 20s are rare and get bid up not so far from the $95 price I was quoted by my distributor.
So, I can buy the 50amp GFI subpanel to install at the shower unit and feed it with a standard 20amp two pole from the panel and still have 20 bucks less invested although this would be slightly unconventional I don't think it would be functionally over the line.
But this gets me back to the question that started the post. I don't understand why there is a neutral on a 2p GFI, because my understanding of what it will be looking for is a difference between amperage in the two hot 220 feeds. Maybe as someone suggested earlier the actual function of sensing is still running as a 120v function so the neutral is necessary, but I can't imagine it would require a neutral capable of carrying the same load as the 220 feeds.
This is not maybe such a big issue on 20amp installs but, even there, 12-3 costs almost twice as much as 12-2 and if this is a small load that could safely be handled with a dedicated say 14 gauge neutral return it would be cheaper to run a 12-2 and 14-2 or in the case of the spa an 6-2 and a 14-2.
Another way around this seems to be to get a GFI that fits the panel. Then your neutral pigtail from the breaker can just go straight to the neutral bus. But it is handy to have the GFI loacted closer to the served appliance given that they trip easily and you want to be able to quickly check if you have cured the fault without running to the main panel all the time.
I have no idea what code says about the size of the covered neutral in such a case, and as you may be able to guess by my moniker, I'm more concerned about the legitimate operational requirements than what the rulebook says. That is not to say that I find them often divergent, but often enough, especially in the as-applied by the 'official' on the site. For instance those inspectors who refuse to accept copper service conductors sized based on copper's resistivity rather than aluminum because they are not used to being confronted with copper in these applications (and these days it is even less likely, think gas is expensive, buy some copper. If I had some spare change I'd be opening a copper mine. Too bad the environmentalists killed the copper mine outside yellowstone, but I digress).
Anyway, final disclaimer is that this more or less parallels a post I attempted to make as a new topic this morning but because I am a new member, my ability to create a new topic appears to be embargoed for the time being. So if someone gets done reviewing it and lets it post, you will find it redundant, although not the second one of my posts seeking a supplier of indexpensive small 120v dusk to dawn photocells.
'Harry'