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: Hi John, have you had to repair many bad heating elements in the Quanta
: on your service repairs? Just wondering from your experience how
: common it is for the heating elements to go bad. I can't say I'm fond
: of how this element is installed vertically from the bottom, with the
: wires directly beneath the element. It seems like only a matter of
: time for the seals around the coils to age and allow water to make
: its way down the coil with a straight shot to the wiring beneath.
: Judging from the rust on the screw & conduit box there must have
: been a small leak on the "high temp" coil side which
: eventually allowed water a direct path to the wires on that coil
: below and caused a short over time.
: Still trying to figure out exactly how it failed since initially when we
: had found the heating element was malfunctioning the controls to the
: tub were all turned off, but the heating element had come on out of
: nowhere.. without the filter motor turning on (otherwise we'd have
: noticed). I can only see this happening a few ways from the schematic
: and can pretty much rule out the thermostats / thermo-relay since the
: filter would have kicked on. From the schematic, it looked to me like
: Relay #2 and Relay #3 (for the heating coil) are energized all the
: time unless the high temp limit switch is kicked. So then the heating
: elements are just waiting for Relay #1 to be activated (via Relay #6
: thermo-relay)... Relay #1 completing the 240v A/C circuit for both of
: the heating elements. At this point thinking the heating element
: leaking very slowly allowed it to rust & that element heat up
: more and over time start burning the insulation on the wires &
: eventually burnt enough insulation off that it shorted itself to the
: conduit box. So then the heating element had done side connected to
: the high temp 240v A/C breaker & other side connected to ground.
: Does that sound logical?
: I have another question for you regarding removal of the heating
: element. It seems a real bear to remove the hex nut on the old
: element.. it won't budge! That and you can't get in there very easily
: with large channel lock pliers or get much torque on it. I found I
: could snap off the wire contacts from underneath and that allowed me
: to pull the heating element wires out from the top, and that allowed
: me better access with channel locks but still couldn't get the hex
: nut to budge. Is there a specialized tool or some tricks of the trade
: to getting the hex nut off if it's corroded/rusted onto the threads
: of the heating element? Also, it's looking to me like the metal
: conduit box below will have to come out. And if that's the case,
: sadly also then looking like the entire hot tub service panel might
: have to come out if we need to properly seal everything at the bottom
: again. Would be interested in hearing your thoughts there.. I'm not
: near your service area otherwise might consider having you come take
: a look =)
: Picture below, but some additional pictures here:
I've probably replaced more of these heaters over the years than any other tech in New England. They are very laborious and difficult. The secret to removal and replacement is to make it a two man job, one above and one below. I remove the four conductors, ground and bonding wire first. You need a good light and a mirror for that. No need to pull the brown control box. Once the wiring is out, remove the screws holding the enclosure box to the base of the heater. Take that box out of there. Spray penetrating rust buster on the lock nut where it threads to the heater body and let stand for a short time. Take a long screwdriver or chisel, place it on the top of the lock nut and give it a couple of good whacks with a hammer. Do not hit it too hard and do not slip and whack the fiberglass body. You just want to give the rust buster a chance to somewhat dissolve the corrosion between the nut and heater.
Now for the big secret. Let the guy underneath do the turning with a BIG wrench from the left. He may have to remove the shroud over the motor or even remove the entire pump/motor on that side. The guy at the top uses the largest pair of channel locks that he can fit onto the lock nut, but simply HOLDS the nut. It is nearly impossible to turn the nut from the top given the physical constraints. Because I only hold the nut, I can get my 16 inch channel locks in there.
When you go back in with the new heater, put silicone sealant on the flange of the heater, run the heater up through the hole, have the bottom guy hold the heater in its final position with the conduit facing the direction you want and put the lock nut on from the top. You will be able to hand tighten the nut easily from the top because it is new and clean. Get it as tight as possible by hand, then a slight additional turn with the wrench while the bottom guy keeps the heater from twisting. The nut does not have to be killer tight, simply snug. The silicone sealant will make the water seal. Let that dry for 24 hours before filling and leak testing. I wire up the heater last using lights and mirrors. BE CAREFUL YOU DO NOT BREAK OR DAMAGE THE HEATER COLD PINS.
You are way off base as to the nature of the failure. All heaters fail over time. I got 16 years out of my original Jacuzzi heater and I thought that was remarkable. Your joints between the heater elements and the heater body flange are most in danger of galvanic corrosion over time. A functioning GFCI, had you installed one as recommended, would have caught this long ago by tripping out long before you had this near catastrophe. The heating that occurred with the motor off and the thermostats NOT calling for heat was simply one side of the 240 volts (120 volts in this case) travelling through the element and passing to ground. Essentially, the heater element "saw" 120 volts due to the fault to ground from corrosion. The simple application of ohms law indicates that a halving of voltage to the heater results in getting 1/4 of the normal output of the heater. Assuming both elements were faulted without a functioning GFCI to prevent problems, your 12 kW heater was probably putting out 3 kW when the other hot leg was shut down.
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