Ask 'Dr. Spa' Q & A Message Board

: Hi John,

: Thank you so much for your tips on getting the old heating element out,
: I appreciate the time you took to explain the procedure. It's
: definitely good to know it can be done without removing the entire
: control box.. that looked like it could be a ton of extra work. Also
: thanks for the thoughts on how it shorted.. I sortof had that theory
: of it being 120v shorting if it was both hots were coming over to the
: hot tub to make the 240v circuit, but wasn't exactly sure how the
: 240v was coming over. My father is the household electrical wiring
: expert and he mentioned 240v being made of two 120v hot wires but I
: didn't know if that was done at the main panel and the 240v carried
: over with hot/neutral or if it was actually two hots at the hot tub
: panel. I now see that it's two 120v hot wires that are 180 degrees
: out of phase with eachother and together create a circuit for the
: 240v. Anyway between he and I we shouldn't have any issues aside from
: the tight working space under the tub =)

: I'm into electronics repair so mostly have experience with lower voltage
: stuff running off of 120v sources. I got a huge crash course over the
: last few years repairing 30+ pinball machines, skee-ball machines,
: etc -- it's fun taking something dead and getting it working again!
: I'm pretty good at reading schematics nowadays and troubleshooting
: the problems on the older technology.. harder with the newer
: electronics since they're pretty much built to not be repaired with
: SMT, etc. Anyway, it's without a doubt helped me to repair things
: outside the arcade/pinball realm since a lot of the knowledge is
: transferable to other fields. Relays, bridge rectifiers,
: microswitches, etc all used on the arcade games.. just lower
: voltage/amp ratings. I'm a younger guy but I like learning the old
: technology to understand where the new technology came from.. and it
: helps to know the older technology too since there's still a lot of
: equipment out there that's older.

: Back to the tub -- I plan to replace all the 240v relays in the control
: panel, 3 or 4 of those have switch contacts that look like they've
: seen better days. Would you recommend replacing the thermostats and
: high temp limit safety switch? The thermostats seemed to be working
: fine...and from what I can tell those parts may be hard (if not
: impossible) to find exact replacements for, but just wondering if
: it's something to be concerned about at this point. I also plan to
: get new pump housing for the filter pump and get that leak solved
: once and for all.

: Thanks again for all your help and friendly advice!

The three large relays arranged vertically on the left that feed the heater elements are most at risk for failure over time due to the high current arcing that occurs when they make and break. The 12 VDC coils RARELY fail. I cannot remember the last time I had one with a failed coil. Changing them all is certainly easy enough, but probably not necessary. I wouldn't bother replacing functioning thermostats nor the high limit. Replace them only when they fail. If they start to lose calibration, you can either re-calibrate the screw mechanism or readjust the knobs inside the brown control box. As these thermostats age, they tend to run hotter and you can simply turn them down a bit inside the box. If the bridge rectifiers are really old, you may want to replace them. They do tend to fail with age. Use rectifiers that are rated a minimum of 6 amps. I've found some nice, inexpensive 20 amp rectifiers at Mouser and Digi-key.

John