Thinking of a wood-fired hot water system?
Still common in rural areas, and coming back into vogue as power costs rise, is the solar hot water system combined with a boiler connection on a wood-fired heater or cooker. There are a number of options depending on the layout of the house and the plumbing. Ideally there are no pumps required if the building suits the installation. Providing a replacement for an old existing system is straight forward, including it into a new building where it is part of the design is straight forward, but retrofitting an existing building requires a substantial amount of site assessment to determine its suitability. Boosting is usually electric but can be gas.
Water pressure on the hot water is an important consideration. In general a solar hot water system connected with a wood-fired cooker or heater uses a low-pressure tank. If the plumbing in the building has been done to suit low pressure then it is suitable. If the shower uses low pressure on the hot water but high pressure on the cold water, finding the best mix when showering can be annoying. The usual way to solve this is to have a small (13L) balanced feed tank installed specifically to provide the cold water for the shower at the same pressure as the hot water.
Another pressure solution is to convert all the hot water to high pressure by ordering the hot water tank with a heat exchange coil. This means that retrofitting a house, which has been plumbed for high pressure isn’t a problem. However, it does mean a substantial extra cost of the tank, and also the water out of the tap is typically 10 degrees lower than water temperature in the tank, so the tank needs to be kept hotter.
The advantages of a wood-fired hot water system are free cooking, heating and hot water typically for 30 years or more and usually all of that without the need for power
However, it may be difficult to retrofit depending on existing building design and existing plumbing.
Using a wood stove in summer is not wanted so a gas or electric cook top and/or oven is usually installed in the kitchen as well as the wood-fired cooker for those occasions
For very cold winter areas, the concept of a wood-fired stove and solar hot water combination can be scaled up to provide central heating. Hot water is circulated from the tank to hot water radiators mounted in the room or to floor heating in a concrete slab. This is called hydronic heating.
QUALITY ISSUES:
There are a number of quality issues associated with wood-fired hot water.
The slow combustion wood-fired cookers and heaters we supply are not only Australian made but built with high quality for long life. They are available with many options, but most important for the hot water is the rating of the boiler. The cookers and heaters we supply are available with high capacity boilers so there is excellent production of hot water whilst the stove is being used. These boilers start at 5kW capacity, equivalent to a 5-bar radiator when working at maximum.
We only supply stainless steel or copper tanks to provide long life and long warranties. Because these systems can operate at near boiling temperatures, cheaper glass-lined systems are unsuitable.
We also supply frost protected solar panels that DO NOT require glycol-type additives and heat exchangers. This means superior performance as there are not the performance losses associated with heat exchangers (typically 10%), which is most crucial in Winter. It also means less maintenance as there are no heat exchange fluids, which need to be replaced or topped up periodically.
We supply both evacuated tube systems and flat plate systems. Evacuated tube systems require a minimum of 20º pitch and flat plate systems require a minimum of 10º pitch. However, both systems will perform better at >20º pitch. We supply frames to pitch them to suitable angles and directions.
Designing and installing these systems is a specialist field, more than just a plumbing job, and we have been doing it for over 35 years. We have the experience needed to ensure your system works.