How To Choose The Correct Hot Water Cylinder?
VENTED AND UNVENTED SYSTEMS
Vented systems use a vented hot-water cylinder while unvented systems use an unvented hot-water cylinder.
There are two main differences between an unvented and vented system: the water supply. Ventilated or “open” systems have a cold water tank that is located in the loft. The cold water tank then uses gravity to transport the water through a “ventpipe” to the hot cylinder. It can be made of copper or stainless steel and is usually kept in an airing cupboard. The heated water expands so there must be somewhere to store the hot water. Ventilated systems will see excess water push up the vent pipe into the loft.
Unvented systems get their water supply directly from the mains water. Unvented systems have the following options: the heated water expands and the water is either sent to an external expansion vessel, which is usually installed above the hot cylinder, or into the internal expansion vessel of the hot cylinder. This is often called a “bubble-top” cylinder. The cylinder, like vented cylinders can be made of copper or stainless steel and is usually kept in an airing cupboard.
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You need to consider four factors when choosing the rinnai hot water cylinders that will best suit your customer’s needs and household hot water consumption.
STEP 1 – IDENTIFY THE TYPE OF CYLINDER NEEDED FOR THE SYTEM – VENTED / UNVENTED
A replacement of an old vented valve cylinder is the best and most cost-effective way to get hot water running again quickly and without disruption.
Modern unvented cylinders have excellent heat insulation and are protected by a protective casing for an attractive appearance.
Thermal stores can be integrated into systems that have multiple heat sources, or where the heat source cannot be controlled, such as a solid fuel wood burner.
STEP 2 – SPECIFY THE CYLINDER SELECTING FROM ITS HEAT SOURCE
After deciding whether your household requires a vented cylinder, unvented cylinder, or a thermal storage unit, it’s time to verify the heat source. This will help you decide what type of cylinder you should use.
Electric immersion heater: If heating the cylinder by electricity is the only way to heat it, then you should choose a “direct” model.
Gas boiler or oil boiler?
You can choose between a “solar indirect” cylinder or a “heat pump” one if the property has heat sources that are rentable. Two heat exchanger coils are used to connect to solar indirect cylinders. One is for the connection to the solar heat source, the other to connect to a boiler to heat the water.
Solid fuel, Aga, or any other unregulated heat source: If you have to deal with unregulated heat sources or multiple heat sources, a “thermal stock” is usually the best option.
STEP 3: HOW MUCH HOTWATER DO YOU NEED AND, THEREFORE, WHAT SIZE CYLINDER Do You Need?
You should consider future-proofing the installation when choosing the capacity of the cylinders for your customers’ homes. This includes considering the possibility of their changing hot water requirements, such as if they are planning to have a growing family or add an en-suite bathroom.
Hot water storage is not something that is well-known. It is typically kept at 60 degrees Celsius, but can be heated to a temperature of about 65 degrees. However, hot water is meant to be mixed with cold water to make it usable. 100 litres of hot tub water at 40degC is equivalent to 60 litres at sixty degC. Showers can use 18 litres per minute of hot water at 40°C. This is just 11 litres at 60°C.
As a guide, the following average hot water consumption (40°C) per person per days can be used:
- Consumption is low at 20-30 litres
- Average consumption = 30-50 litres
- Consumption = 50-70 litres
The Old British Standards give recommendations for cylinder sizes per number of bathrooms but don’t take into account the number of users.
STEP 4: OTHER CONSIDERATIONS
Installers must consider the type and capacity of the cylinder, as well as any restrictions that might apply. You should consider the space in your airing cupboard, whether you have to use narrow loft hatches to access the cylinder, and if time is an issue. Here are the main considerations and solutions.
Slimline cylinders – These cylinders have a smaller footprint and a lower height, which can make it possible to fit the cylinder into tight spaces such as loft hatches. You will however compromise the cylinders’ efficiency as taller cylinders lose more heat than shorter, fatter cylinders.
Horizontal Cylinders: A horizontal cylinder is another space-saving option. This allows you to keep cylinder capacity even in areas where height restrictions are applicable. Horizontal cylinders, however, are slightly less efficient and have a higher heat loss.