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Spa/bath heater

Discussion in 'Hobby Electronics' started by Greg McFarlane, Jul 14, 2003.

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  1. I am finding that something I first thought would be dead easy may be
    impossible in Australia.

    In Japan, about 10 million houses have a bath where the water can be
    kept hot for hours while everyone in the household takes turns. These
    bath heaters are usually simple gas heaters attached to the bath with
    one inlet and one outlet and where the water is flows through by
    convection only - no pumps, no noise. So you can relax in the bath
    for hours with the water at 43 degrees C (or whatever takes your
    fancy) and without noisy and annoying jets, bubbles and "massagers".

    But can I find anything like it in Australia? Not so far. All that
    the spa companies can come up with are hot pumps with big motors (at
    least 0.5 horse power) and which are limited to 38 degrees.

    So, I came up with the idea of getting a dishwasher or washing machine
    pump (something that can handle hot water and pushes about 2-3 litres
    per minute) and an immersion element heater, hooking them up to a
    controller and attaching them to a normal spa bath.

    But, I realise that there are all sorts of safety issues involved with
    electricity and water, so I don't really want to do this myself. Has
    anyone had any experience with such things? Or know of a plumber or
    electrician that could do it, in Sydney?

  2. I don't know what money you want to spend but how about one of the the
    latest remote control gas heaters hooked into the loop (from spa - heater -
    spa) with a circulating pump of your choice ??
    Any decent plumber should be able to do that and if you don't want to hook
    up the pump then ditto for the electrician.
  3. David

    David Guest

    It might be a bit more complicated than this and I suggest you
    contact Rinnai for advice before shelling out as the flow rate
    versus heat input may need to be adjusted. I would suggest an
    electric heater could only be used if fitted with a duty cycle
    modulating controller with a probe in the outlet line. These can
    be obtained from an industrial electronics supplier (or RS,
    Farnell, etc).

    Don't forget an RCD must be used as well as properly protecting
    the gas and electricals from water - both normally as well as a
    pipe rupture or leak. Oh, also keep in mind the death rate in
    Japan from people who die in overheated baths (its high) and the
    death/injury rate of people who faint as they exit the bath (head
    strike is common). Appropriate positioning and locating
    accessories will help with the latter.

    Good luck, sounds like a good idea. Immersion heaters for baths
    used to be sold but I haven't seen one for a while now.

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