Guide to buying Joule hot water cylinders

Buying Joule hot water cylinders can be confusing – so let us help!

The most common type of hot water cylinders in Ireland in domestic settings are copper hot water cylinders and stainless steel hot water cylinders.

We have answered the most common queries that we get in this guide and as always our helpful and friendly experts are here to help if needed – just call us for a chat on 0818 888 000 anytime.

Our range of hot water cylinders includes copper and stainless steel models manufactured by Joule who are rightly recognised as one of the leading manufacturers in the UK and Ireland today. These are sometimes called Indirect Cylinders. An indirect cylinder has a coil inside through which the water passes through.

A direct cylinder is a cylinder that is just heated from an immersion heater and does not work with gas, oil or heat pumps etc.

We deliver these hot water cylinders right across Ireland and we have collated the main questions and queries we get to help you get the information you need.

What is better – a copper cylinder or a stainless steel cylinder?

There is no straight answer to this question as everyone has different circumstances and requirements – so you need to consider certain things;

• Are you replacing an existing cylinder?
• Have you any size restrictions?
• Do you have a vented or an unvented hot water system?
• How do you heat your water?
• Do you use well water?

Once you know this information then we can help you navigate the range and get you the right model.

Copper Hot Water Cylinders

Stainless Steel Hot Water Cylinders

What is a single coil hot water cylinder?

A single coil hot water cylinder is the most common found in Irish homes and takes water from one source and heats the water in the cylinder. The main heat sources in Ireland would be a oil or gas fired boiler.

If the boiler is not firing or is turned off then the water can still be heated if there is an immersion heater in place.

What is a dual coil hot water cylinder?

A dual could hot water cylinder is sometimes also known as a twin coil hot water cylinder and this is used when two methods of heating the water are used. The most common instance of this in Ireland would be the use of solar panels to heat the water using the lower coil in the cylinder and the gas or oil boiler heating the water via the upper coil.

What can happen with the use of solar panels in Ireland is that on a gloomy or dull day then the solar panels might only heat a small proportion of the water that is needed. When this happens then the gas or oil boiler will supplement that by heating the water via the upper coil.

Normally the lower coil is the one that has the first chance to heat the water and the upper coil will only be used if the water is not heated to the desired temperature. A wood burning stove can also be used to heat the lower coil. Please note though that if you are using solid fuel as a heat source then the coil needs to be 1” on the stainless steel cylinder.

What is a triple coil hot water cylinder?

A triple coil hot water cylinder is designed for use with multi fuel applications. These have a solar coil along with a gravity coil. The cylinders are suitable for use with a wide range of solar systems now available and are an efficient and environmentally friendly way of providing domestic hot water.

What is it that makes Joule cylinders so good?

Hot water cylinders from Joule are extremely efficient thanks to a unique cold feed diffuser. This improves efficiency by up to 10% as it allows the hold and cold water to remain in layers throughout the cylinder depending on the temperature that the water is at.

This reduces the water mixing and keeps the hot water hotter for longer.

Normal or older traditional copper cylinders wasted energy as they could be over heated. Joule copper cylinders avoid this thanks to the thermostat that is already fitted and in place.

Using this along with a control valve on the boiler circuit keeps the cylinder at the required temperature and so reduces energy consumption from your boiler.

The copper cylinders from Joule also have excellent insulation thickness. This prevents heat loss and contributes to additional efficiency also.

What is the difference between a copper cylinder and a stainless steel cylinder?

The main difference between copper cylinders and stainless steel cylinders is that stainless steel cylinders can withstand higher pressure.

The normal water pressure in Ireland is between 1 and 4 bar and these cylinders are tested up to 9 bar.

So if your hot water system is unvented or high pressure then you must use a stainless steel cylinder.

Copper is an excellent conductor of heat and will heat up the water in the cylinder quicker. It is more efficient at conducting heat than stainless steel but stainless steel is less likely to corrode. That means that stainless steel cylinders will have a longer life span so may be an important consideration to some when deciding what is the best approach.

Copper will also lose heat quicker than stainless steel.

What is the difference between a vented and unvented system?

A vented hot water system is also sometimes called an open hot water system and is supplied by a cold water tank that is normally located in the attic or loft. The water flows down via a vent pipe in to the hot water cylinder.

A vented system can use either a copper or a stainless steel cylinder. As the water is heated up and expands and is pushed back up the vent pipe and in to the storage tank in the attic or loft.

An unvented system gets its water supply from the mains. In this type of system, the heated water goes into a separate expansion vessel as it expands. This expansion vessel is usually placed above the hot water cylinder.

What hot water cylinder do I use for my type of heat source?

If the only way that you can heat the water in the cylinder via an immersion heater (i.e. electric) then you should use a ‘direct cylinder’. A direct cylinder is a cylinder that is just heated from an immersion heater and does not work with gas, oil or heat pumps etc.

If you have a boiler that is powered by either home heating oil or gas then you need an ‘indirect cylinder’. An indirect cylinder has a coil inside through which the water passes through and gets heated by the boiler.

If you use solar power, thermal power or utilise a heat pump then you need a ‘solar indirect’ cylinder.

What size of cylinder do I use?

Unless you are expecting any major changes to the water usage in your house then you should replace like for like in terms of the size of the cylinder that is in place already that you might be replacing.

You also might have restricted space in which you can place your cylinder so you should measure out this available space and check it against the dimensions of the cylinder you have identified.

Adding an extra heat source e.g. solar would normally require a much larger tank as you would need to store more water in the case when there is not sufficient sunlight for a few days. If you were going from a single coil to a twin coil it’s likely that more water could be available and hence a bigger tank makes sense.

What hot water cylinder do I use with well water?

If you use well water then you do need a different type of cylinder that is designed for this purpose. Just call us on 0818 888 000 if you use well water and we can advise the most suitable model.

Other info:

All of the stainless steel cylinders we usually stock are suitable for oil/gas, solid fuel and solar. If one is required for a heat pump they are a different grade – if you require this just contact us and we can order these in for you.

There are different grades of copper cylinders – we stock the standard grade copper cylinders but should you require an enhanced grade then just contact us and we will be happy to help.

What do I do if I need more help?

Just call us on 0818 888 000 and we will be happy to help. We will help gather information from you regarding the points above and will help advise on the most suitable model.