barrel hot tub
This one person hot tub, made from a decommissioned wine barrel, can be placed in the remotest of places, and heated up in advance via smartphone. The mini-tub serves as a prototype model in a series of micro-amenities that could be distributed all over, serving as little points of beauty, interest and comfort in the city and beyond.
This first prototype of the barrel hot tub was secretly built on a remote construction barge floating on the Sacramento/San Joaquin River delta. Accessible only by boat, and far away from people or utilities of any kind, the single-person tub is the epitome of 'off-the-grid'. The tub uses a propane-powered heater, and can be switched on remotely by smartphone so that it is hot when you arrive.
Notice the wine stain that saturates the interior of the oak barrel. The tub actually smells pleasantly of cabernet sauvignon.
how it works
The whole system is powered by a 12v dc pump, which pulls water from the supply inlet, pushes it through a filter, and through a pressure-activated propane water heater, which returns hot water into the tub through the return inlet. The pump is controlled by a relay, which is activated by a temperature-reading micro-controller that is connected to cellular signal (and therefore can be triggered on remotely).
Caulked-in inlets suck and return water from the tub in order to filter and heat it. Notice the basket around the supply inlet, which filters out any larger debris, and prevents the line from being blocked, and also prevents suction on clothes or skin. The return valve, which typically would be on the bottom, is on the top in this case, so that it does not trigger a high temperature reading until the whole tub is heated (because warm water rises). This works because the warm water stays at the top, while only the cold water at the bottom is heated and returned above. Moreover, the return water should enter the tub with some clearance of the bather.
This diagram breaks down the systems used to run the hot tub, along electronic and mechanical lines.
assembly guide
heater system
Components
A) 3 x 1/2" shower hose (make sure o-ring is inside of screw-on ends) - $9.11 x 3
B) DC 12v pump - $23.69
C) 20 lb. propane tank (get from gas station) - $50
D) LP hose (comes with water heater)
E) Instant water heater - $94.48
F) 12v 3a power supply - $6.99
G) Timer relay module - $15.80
H) 18 AWG primary wire - $9.89
I) 2 x D batteries - $1.76
J) gas tape - $4.25
total: $234.19
Wiring:
1) Attach power:
Attach timer relay module to DC 12v on the right side (positive [red] to "DC+" port, negative [black] to "DC-" port);
2) Run extra positive wire to “COM”:
Use short (3”) length of red wire attached to “DC+” port on the right and “COM” port on the left;
3) Run negative wire from “DC-“ port:
Attach 2 ft. black wire to “DC-“ port;
Connect other end to pump’s negative (black) wire;
4) Run conditional positive wire from “NO“ port:
Attach 2 ft. yellow (this color indicates ‘conditionally on’) wire to “NO” (normally open) port;
Connect the other end to pump’s positive (red) wire.
Programming Timer Module:
1) Set function to “05” (timed off, timed on loop):
To enter programming mode, hold down ‘SET’ button for >1 second;
Display should show “- - 0 1”, with first digit flashing.
Use ‘NUM+’ and ‘NUM-“ to set display to “- - 0 5”.
2) Now set T1 to “0020”:
Press ‘SET’; display should have new set of 4-digit numbers, with one digit flashing. This is the digit you are currently setting with ‘NUM+’ and ‘NUM-‘. To switch digits, press ‘SWI’.
Set number to “0020”.
3) Now set T2 to “0060”:
Press ‘SET’; display should have a new set of 4-digit numbers, with one digit flashing. Use ‘NUM+’ and ‘NUM-‘ to set T2 to “0060”. To switch digits, press ‘SWI’.
4) Now set NX to “0101” (this just tells it to repeat loop infinitely):
Press ‘SET’; display should have a new set of 4-digit numbers, with one digit flashing. Use ‘NUM+’ and ‘NUM-‘ to set NX to “0101”. To switch digits, press ‘SWI’.
5) Now exit programming mode:
To exit programming mode, hold down ‘SET’ button for >1 second
Your module should now cycle from T1 (relay off) for 20 seconds to T2 (relay on) for 60 seconds. This will turn the pump on for 1 minute, then off for 20 seconds. This is important because the flow rate from the pump is not enough to prevent it from overheating your heater (resulting in automatic shut-off). The 20 second break allows the heater to cool off between 1 minute heating cycles. The heater auto-ignites when water pressure enters the unit from the pump, so the pump itself acts as an on/off switch, controlled from the timer relay module.