THERE are many types of hot water cylinders available on the market. It is worth researching the most suitable type for your heating system and water quality to save on expensive replacements and heat loss.
Basic cylinders have one heating coil (single coil) and may or may not have an immersion element. The coil is a rolled up length of copper or stainless steel, which heats the water as the heating system pumps hot water through the tank.
Dual coil or triple coil cylinders have extra heating coils, which can be attached to other heating systems such as back boilers and solar systems. They can also be left unattached and used at a later date.
The longer the coil, the better the heat exchanged. This may be an important factor, depending on the heat source.
Hot water heating from a solar system or from a heat pump (air to water) needs longer coils to give up as much heat as possible. Conventional central heating oil boilers were nearly always plumbed using a shorter coil at the top of the cylinder to pass the hot water through quickly. This was known as domestic hot water priority linked to the heating circuit but now it needs to be two circuits minimum, one for the hot water and one for the heating with thermostatic control to the boiler from the cylinder and thermostatic control from the heating.
One of the thermostats needs to be attached to the cylinder and wired back to a circulating pump that will supply the domestic hot water from the boiler. The other thermostat should be in a hallway or landing and wired back to another circulating pump from the boiler to supply hot water for the heating circuit.
This is a very simple system but it can be controlled, which means saving money and lowering the carbon footprint from the reduction in energy use.
Ideally any house should have a minimum of three to four zones, domestic hot water, bedrooms, kitchen/dining room and sitting room all controlled by their own thermostat.
To future proof your home, it might be wise to invest in extra coils. This gives greater flexibility for any future changes.
It means that adding extra energy saving solutions such as solar panels for hot water, heat pumps or a multi-fuel or pellet stove with a back boiler will be much easier and cost a lot less.
In general, the primary heating source is attached to the shorter coil, higher up the tank, and the secondary source to the longer coil at the base of the tank.
A well-insulated tank will minimise heat loss and save on energy bills. Older copper tanks are not insulated and a lagging jacket can improve this, but the newer cylinders have factory fitted rigid insulation that really reduces the heat loss. This is made of materials such as high grade, flame retardant polyurethane foam and should have a good fire safety certificate and the CE quality mark.
Glass lined stainless steel tanks have a longer life and do not suffer as much from mineral deposits. Over time, the build up of lime scale can reduce significantly the efficiency of the heat exchange. It is worth considering if you live in an area with untreated hard water.
The last thing to consider is the size of the tank. Calculating your water requirements can be tricky, and it's a good idea to check with those installing your heating.
A small tank may heat up quickly but not supply enough water for a bath or showers for all the family. A large well-insulated tank will heat up slower but will hold the heat for longer.
Incorrectly sized cylinders can lead to inefficient water heating, energy wastage and water pressure problems. For safety, all cylinders with more than one heat source need to be properly planned because with too much heat generated by the systems, the plumbing has to be able to release the pressure so make sure there is a good understanding of it. Know the difference between open vent and a pressurised system.

● Sean O'Neill is the managing director of All Natural Heating Company Ltd., based in Lakeside Retail Park, Claremorris, and helps people to save up to 70 per cent on their energy costs and increase the value of their homes for the future, guaranteed.
If you have any questions regarding renewable energy please contact Sean on (094) 9373443 or (087) 2564826.