How does an S-Plan heating system work

James Elston
Written by James Elston
Updated on 4th December 2023
Posted on 3rd December 2023
Topic: Boiler Advice
How does an S-Plan heating system work

S-plan heating system – How do they work, diagrams and are they any good?

s-plan system boiler worcester bosch

Within most domestic houses within the UK, there will most likely be one of two heating systems in place. This is referred to as the S-plan and the Y-plan which both are worthwhile in understanding, as they control your heating system.

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In this guide, you’ll learn more about S-plan heating systems, how they work and how you can set up this type of heating system in your home with a new boiler, however, there are a number of benefits and drawbacks to using this heating system, which will be also explained in this article.

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What is an S-Plan heating system?

energy efficient boiler

An S-plan heating system forms one of two basic systems within the average domestic UK home. There are two separate motorised valves that can be found on this type of heating system, of which the first controls the heating, whilst the other controls the hot water.

S-plan heating for zone control

With the S-plan heating system, you have the opportunity of controlling the two valves individually. It is also possible to create more ‘zones‘ in your home that help to control certain areas of the home separately from others too.

Lower energy usage and saving money on bills is the key here. Data published by Ofgem found that in September 2021, the average UK energy bill was £95 per month. This type of heating system can be helpful in having control over your heating and hot water in general.

There are lots of different heating options but this one is by far probably the most popular of them all. It tends to replace many of the older systems in place and could be a good option if you are looking at a new boiler installation.

How does an S-Plan heating system work?

water temperature

Wondering how it all works? The S-plan heating system is in the shape of an S when it’s drawn schematically. It works by using heated water from a boiler, which is then redirected to the hot water coils, or alternatively, the radiators that help heat your home.

The two separate motorised valves help to control the temperature of both the hot water and central heating. The S-plan system also has a cylinder thermostat, a room thermostat and a programmer that helps to manage your home’s heating effectively.

Do S-Plan systems need a hot water cylinder?

Yes. S-Plan systems required a hot water cylinder as they control the hot water to and from the cylinder in each zone. This also means you will need a system boiler or a conventional boiler.

There is no need to use this system with a combi boiler as you control the heating and hot water directly at the boiler with your taps and thermostat. If you want to control zones, then you can just use smart thermostatic radiator valves and a smart thermostat. If you are worried about energy efficiency, see our most efficient combi boiler guide here.

Are S-Plan systems good for new build properties?

It’s often the preferred choice of systems for most modern properties, so you can expect to find them in a lot of new builds across the country.

large house

When the hot water port valve or central heating is required, a 230V runs through the Motor Live wire. This then helps turn the valve, which allows the heating pump to then push the water through. If the valve is pushed all the way open, it pushes a microswitch. This activates another 230V to ignite the boiler.

Once the hot water or central heating has been provided, the power to the Motor Live is cut off and then the valve springs shut.

This can either be caused by the timer going off or being turned off. You will also find it as a result of the thermostat reaching its desired temperature and then switching off.

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How to set up an S-Plan heating system

When it comes to setting up an S-plan system, it’s worth hiring local experts for the job. It’s often much more advantageous to have someone do it for you, rather than doing it yourself.

However, there are some helpful how-to videos online that are worth taking a look at when setting up your own S-plan heating system with new boilers.

cogs for parts

Setting up an S-Plan system

In order to set up your system, you’ll need all the various heating components required to fit it correctly. It’s worth assessing your current plan system in place, and working out how this system would benefit your property better.

If you’re wanting to wire this system in place yourself, make sure to understand what you’re doing and to learn the skill properly. Otherwise, it’s best to call in Gas Safe engineers who have experience installing gas and heating systems.

What are the benefits of S-Plan heating systems?

There are many benefits to this plan system in particular and when you’re exploring all the plan systems available, it’s good to weigh up the pros and cons. Here are some of those benefits for your consideration.

system boiler diagram
  • Close temperature control: There’s nothing more efficient than monitoring your hot water and heating system closely.
  • Multiple zone control: Whether you’re looking to have more than one hot water cylinder or multiple radiators, this system is worthwhile. It provides a wider scope for you to manage different areas of your home.
  • Timed operations for your heating components: Having a time operation in place for all your heating requirements means you can limit and save money as a result.
  • Money is saved on fuel: Talking of money, when it comes to keeping your home in good, financial shape then this one can be useful. Who doesn’t want to save some money on their energy bills?
  • Heating water flow remains consistent: With an S-plan system, you’ll find that there’s no reduction in the heating water flow itself.

It quickly becomes apparent just how useful these systems are and why they continue to be well-used for most properties in the modern day. If you are thinking of adding an S-plan system, find out how much a new boiler cost too as it may be even more cost-effective in the long run.

Boilers for S-Plan systems?

If you are looking for a new boiler and want one that is suited to an S-Plan system, then check out these system boilers that would work well with them:

If you need think a new boiler is out of reach, then you could be in luck. With Boiler Central, you can get a brand new system boiler on finance which means you can spread the cost of a new boiler over 2 or more years. You can even buy now and pay later in 12 months’ time! All these new boilers are hydrogen ready boilers too, so you can be sure they won’t be getting banned in the future!

What are the drawbacks of S-Plan heating systems?

Are there any drawbacks to using an S style system? There can be some common faults that are found with this system in particular and that are worth knowing about if you’re considering implementing the S-plan systems. Check out some of the best combi boilers on the market which may be a better and cheaper option.

Sticking microswitch

S Plan Guide

A common issue found within these systems is the electrical microswitch. This is found in the actuator and can often find itself sticking. This causes the boiler and pumps to run constantly, which isn’t going to be good for the boiler or for the cost of it in your home.

As a general fault, it can also lead to further issues, for example, an overheating boiler. This alone could do significant damage to the equipment and could cost you a lot in repairs.

Water quality issues

Depending on the quality of your water, there can often be issues found with this central heating option. Magnetic sludge can often affect the seat of the valve. This results in the valve spindling stiffening up or seizing.

The actuator also may be restricted in its movements, causing operational issues within the boiler. This is often an issue with boilers when it’s not used during certain times of the year, like in the summer for example.

Room thermostats

thermostat for S Plan

You may find that the room thermostat can sometimes cease working. This may be a simple case of the batteries needing a replacement or the thermostat itself being broken. This is fairly common in its occurrence across all systems. If you have a smart thermostat you should get notified on your phone via the app.

For any problems that occur within the components of the system, whether that’s the hot water cylinder or the valves that connect individually, it’s worth getting it seen to. If you don’t have experience with a hot water system or heating in general, then getting an engineer is probably your best option.

Fixing these issues quickly is going to cause less hassle and it means you’re not going without hot water demand or heating in your home. This is one problem you don’t want to encounter.

Got a large area that needs hot water to flow properly? Check out the other tecnical ways such as a low loss header.

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smart thermostat S plan

S-Plan systems – Final thoughts

If you’re after a highly popular option when it comes to heating your home, then this system is a popular choice. The opportunity to add an additional heating zone can be useful for larger homes and those that want more control over the heating inside their property.

It’s also an excellent choice for keeping both your heating and hot water system separate. That way, you don’t need to be using both all the time.


What is the difference between an S and Y – Plan heating system?

Y plan systems are different to S systems in that they use a mid-position valve that directs the primary flow with both the heating circuit and hot water circuit. S-plan operates with two or more different zone valves making it easy for the user to manage both hot water and heating.

Why is called an S-Plan heating system?

The system gets its name due to the way in which it’s drawn schematically. The layout of the system results in an S shape.

money bag

Where can I purchase 2 port valves from?

If you’re looking to purchase 2 port valves, then this can be found with most DIY stores like Screwfix for example.

If you’re not able to purchase them yourself, then an engineer that’s helping you replace your system or adapt to a 2 port valve, will be able to get it on your behalf.

How much does an S-Plan heating system cost?

The average cost of a new boiler and heating system can be anywhere between £2,000 to £5,000. S-plan options are the most common and therefore probably one of the most affordable ones you could go with.

It’s always good to assess how much you can afford when choosing the right system for your home. You could find that the s-plan is more suitable due to its versatility with both big and small properties.

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Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 3rd December 2023
Topic: Boiler Advice

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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