Our house has all its electric power generated on-site, so an electrically heated spa pool was just not feasible. So Allan designed a wood-burning heater, made of stainless steel that could sit inside a cedar hot tub to heat the water.
The firebox is top loading and burns downwards, the flames passing into the large secondary burn chamber where it completely double burns and finally exits the chimney with NO visible smoke
The heater has been carefully designed to maximise the heat transfer from the heater to the water in the hot tub.
Wood burning heater + Flue
$1380 + GST
Cedar Hot Tub
Price on request
Water circulating pump and filter
Price on request
Protective wooden fence
Price on request
The heater is bolted to the seat inside the hot tub so that the top of the firebox will be just above the level of the water in the hot tub when the tub is filled.
(This picture shows one of the earlier heaters with no water jacket on the flue.)
With a good supply of dry wood, a fire can be started in the firebox. The secondary burn chamber allows hot air from the firebox to come into close contact with the water in the hot tub. The water jacket around the bottom of the flue decreases heat loss and increases heat transfer from the hot air to the water.
A wooden fence can be used to protect people sitting inside the hot tub from the heater.
A small pump is used to circulate water through a filter and to move the tub water around. Our 1800 litre hot tub takes about 6 hours to heat to 37°C from cold. If the heater is used every day, it will reheat in about an hour and needs only about an armful of dry gorse. Perhaps I should say that we have a good supply of mature gorse. It much prefers dry wood and we also burn our ‘burnable’ rubbish which includes citrus skins.This is a brilliant way to have a cosy hot tub on a cold, dark night – using next to no electricity. You are very welcome to come and try it for yourselves.