Monday, August 20, 2012
Call Me Crazy: Zinc Balls & High Current Flow
Then I came home. It was over 100 degrees every day for about the first ten days I was back. Got me all tuned up and back in-the-mode again.
Two things caught my eye after a summer of not thinking much about anything but walking up and down hills and not sweating. The first is this pic I snagged at my local pool wholesale supplier:
Notice the little black sign? SALTWATER PROBLEMS? Sacrificial Zinc Anode. They put stuff behind the counter for easy access to their higher volume articles. They have a whole warehouse of merchandise for sale, and about one hundred square feet of display space behind the counter, and right in the center of that display area are sacrificial zinc balls.
I wrote about zinc balls WAY BACK HERE. It was one of the first pieces I wrote, back when everyone was saying, "the Poolguy's crazy, but you might want to put some Zinc Balls in your skimmer baskets, anyway".
If you look at that photo again, let your eyes wander down from that sign to counter top level, and then over to your left, and you'll see another item for sale on a blue card, it's another variety of sacrificial zinc anode. This one is meant to be installed in the plumbing line so that it has direct contact to the pool's bonding grid. In fact, if you go to POOLTOOL.COM, you'll see that Saltwater Problems have turned into big business for this company. Clearly, their top-selling items are Salt Pool related.
That's really the Smoking Gun, you know, attaching to the bonding grid. That's the same as an admission that Stray Currents are amplified and made much more destructive by these Salt Systems. That's why they want you to attach a sacrificial zinc anode to that grid; to put the least noble (softest) metal out there to bear the brunt of damage from the Stray Currents riding on your pool's bonding grid. The truth is your non-salt pool may have Stray Currents on the bonding gird as well, but you don't have highly conductive salt water to amplify the damaging effects.
Too, there's a chance that the units themselves could introduce Stray Currents onto your pool's bonding grid. No one's really done any testing to see.
Anecdotally, there's the recent article in Pool & Spa News that a salt system manufacturer is suing a pool equipment distributor for breech of contract; not paying for salt systems they received and resold for installation in people's back yard. You know, like YOUR back yard. The distributor explained that the reason they didn't pay was that the systems were faulty, in that they MELTED DURING OPERATION.
Hmmm... don't you hate that when your salt system melts down? It's better than having them EXPLODE, but only a little bit better. One of the installing company was quoted in the article as saying, "They are melting... It's a huge safety issue... I'm afraid someone's going to get hurt. It's a public safety hazard".
Turns out the first installing activity quoted in the article has installed "more than 200" of these systems in people's back yards, and now they're worried that the systems WILL MELT. The article doesn't indicate whether this company has notified these customers about the potential hazards in their back yard.
I'm betting not.
Another company had installed about 40 units, and when failures - READ MELTED SALT CELLS - topped 25% of installed systems, they yanked them all out of their customer's back yards and discontinued sales of the units. So, they're the Good Guys in the story.
Use the link above to the P&SN article and you can see a picture of one of the char-broiled salt cells. If you recognize it as something like what you have in your back yard, RUN!
You see, with most Salt Systems, you're running something less than 20 amps, but not much less. I know 20 amps because the cell fuse for a Goldline AquaRite is a 20 amp fuse. Leave a little + or - room, and you've got somewhere around 15 to 18 amps going through that cell on an average day. If I remember my old safety courses from the Navy, it takes 100 milliamps (one tenth of one amp) to kill you, so this is about 150 to 180 times the current requirements to kill someone. So it's easy to see how it would melt the salt cell. The company who makes this stuff admits that the salt cells melt, but blames it on the installers, saying they didn't properly connect the brass pins to the salt cell, allowing them to overheat and cause melting of the plastic salt cell housing.
The reason they heat up is because with a faulty connection, you have more resistance to current flow. The argument for the safety of putting 20 amps into the water is that with very little resistance between the cell plates, you never have any Stray Current leaking out via other, higher resistance paths to ground. But as you increase resistance to the current flow through a faulty connection, and you have a power supply capable of putting out 20 amps max, you basically have a recipe for disaster.
My blog is full of incidents of pool owners feeling a "tingling" when they grab a ladder or a side rail at their pool. That's Stray Currents, amigos.
I still marvel that we're having a discussion about the advisability of putting a known corrosive (salt) into pool water and then whacking in with something near 20 amps of current flow to save a buck on chlorine tabs.
Call me crazy...