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Figured I'd answer my own question in case someone else finds it useful....
: I recently got a replacement control PCB for my softub T-300+ (5+ years
: old). Last fall, I replaced the original 2 speed pump/motor assembly
: with a single speed pump/motor, and since then the control PCB
: I'm writing because I'm unsure as to how to wire up the replacement PCB.
: The original (2-speed) PCB had 3 board mounted relays and one
: external relay, and the new PCB only has two board mounted relays. My
: main question is whether the external relay is still necessary, or
: whether only the board mounted relays are required to provide power
: to the the pump/motor assembly. Any advice on the correct way to hook
: things up would be much appreciated.
Yes, you do still need the external relay. There are 4 pins on it: two that get connected when the relay is energized (one connects to the incoming hot wire from the power cord, and the other connects to the hot wire that goes to the pump motor), and two to power the electromagnet (which requires 120V AC). One of the pins of the top of the middle PCB mounted relay (there are spaces to mount 3 relays to the PCB but only two are populated on the newer, single speed PCB) provides the "hot" signal which causes the external relay to close.
As an unexpected bonus, the new controller PCB has updated firmware which has features that weren't present in the older version: energy saver mode (hot tub is only heated to target temperature once per day at a predetermined time), overnight mode (tub goes into "standby" mode for 12 hours a day and won't engage the pump during that time), and the option to set the target temperature above 104 (up to 106). Don't know that I would have shelled out $250 just for these features, but they are quite handy (energy saver mode suits my usage pattern perfectly). These features are documented in a recent owner's manual I found online. Another difference - the temperature display now shows the actual temperature of the water in the tub instead of the target temperature (which is only displayed when you push one of the up/down buttons).
Only issue with my softub now is that the power pack seems louder than it used to be. I've noticed that when I apply pressure to certain points on the pump pack, the vibration noise is greatly reduced. Does anyone have any tips on making the pump pack quieter? I've disassembled and reassembled it many times over the years (the only original part in the pump pack is the topside control panel!) and the pump doesn't fit quite as snugly as it used to. I'm thinking the excess vibration is (at least partially) responsible for the increase in noise. I checked the price of a new styrofoam shell and it was way expensive ($700?) so that's not an option (I'd be more likely to fabricate my own using a 3D printer!). I was thinking about putting some straps around the pack to apply tension to hold the styrofoam in place. Any advice on sound dampening measures would be greatly appreciated.
: Thanks in advance...
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