http://www.smarthome.com/7115h2c.html
water heater shutoff valve

On Jun 22, 12:08 am, William Underhill wrote:
I've tried Googling on various search terms and haven't managed to find
anything, so here goes:

Does anyone know if there is available on the market a controller for
hot water tanks, whereby a float switch in a drain pan can shut off a
solenoid-operated valve on the cold water inlet and the 230v supply to
the heater elements? Or do the same in the event of a power failure?
Here's a bad ASCII art attempt at a schematic of what I have in mind:

115 Vac
L1 N
| |
) [bkr in svc pl] |
| |
| N/C FLOAT SW RESET (N/O PB) |
| __|__ |
`-----o--.-o--------+---o o---+----------+---(M)---+----------'
| | M | | |
^ `----| |----' `---(S)---'
: SOLENOID FOR N/C VALVE
230 Vac 2 ph :
L1 L2 : N
| | : |
)--- ) [2-ph bkr in : |
| | in svc pl] M .------. |
| `-------------------| |-----------| HTR | |
| M | TERM |-----------------'
`------------------------| |-----------| BOX |
`------'

The idea is that if the power goes off or the float switch opens, the M
coil d-energizes and the M contacts open. Because there's a sealing
circuit in the 120 supply to the coil, the system won't re-energize
until someone comes and pushes the reset button, thus keeping the system
safe if it should trip while I was away on holidays or what-have-you.
Alternatively, the float switch could be a flow switch in the drain line
from the drain pan.

So, anyone know if a ready-made controller like this is available on the
market?

Yours aye,
W. Underhill

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