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Worcester Bosch Greenstar 38CDi Classic Combi Boiler – Review

In today’s review, we’re taking a closer look at the Worcester Bosch Greenstar 38CDi Classic combination boiler. Yes, that name’s a bit of a mouthful! For a more comfortable life, just call it the Worcester Greenstar 38CDi. Our review tells you everything you need to know about this combi boiler, so you can decide if it’s the best choice for you.

Over the past 50 years, Worcester Bosch has grown to become the UK’s market-leading boiler manufacturer. Their closest rival is German company, Vaillant. The Greenstar 38CDi is a high-performing, top-end boiler from Worcester Bosch, designed to heat large properties comfortably.

Will the Greenstar 38CDi Classic be suitable for my home?

If you have a larger home with spacious rooms, the Worcester Bosch 38CDi could be just the boiler you need. It’s built to handle properties with up to 2 bathrooms and 4 to 5 bedrooms. When choosing a boiler, it’s important to consider the number of radiators you have. You’ll need to pick a model with a high enough flow rate to supply hot water for all of them. The Greenstar 38CDi’s flow rate is high enough to comfortably accommodate 12 to 14 radiators, which is more than enough for most of us.

The Worcester Bosch 38CDi also features a central heating output of 30kW and a hot water output of 38kW, which makes it an extremely efficient model. With an excellent flow rate of 16.4 litres per minute (l/m), it’s powerful enough to let you run two showers at the same time. You might struggle to run a shower and a bath simultaneously, but no domestic combi boiler is really up to that task. And remember, no matter how high a boiler’s flow rate, it makes no difference if your water mains pressure isn’t powerful enough to handle it.

The best equivalent boiler from another brand would be the Vaillant ecoTEC Plus 938, which has an equivalent flow rate of 15.9l/m. Compared with the Worcester Bosch 38CDi, the ecoTEC Plus 938 will stick out from the wall a bit more – 140mm more, to be exact. That’s something to bear in mind if space is an issue.

If you have a smaller home with 3 to 4 bedrooms and about 10 radiators, you might be better off choosing the Worcester Bosch Greenstar 34CDi Classic combi boiler. If your home is large, with 5 to 6 bedrooms and 14 radiators, the largest boiler in the Greenstar range the 42CDi Classic, is probably your best choice.

Greenstar 38CDi Classic Boiler Controls

The Worcester Greenstar 38CDi comes with a pretty standard control panel, as combi boilers go. It gives you basic options to reduce or increase heat. You can choose ‘holiday mode’ to turn your central heating off, ‘pre-heat mode’ to get hot water faster or ‘eco mode’ to save energy.

Like all boilers, the Worcester Bosch 38CDi must comply with Boiler Plus regulations issued in April 2018. According to Boiler Plus, every boiler must reach a certain standard of energy efficiency and must have time and temperature controls at a minimum. A combi boiler like the Greenstar 38CDi is also required to have one of four additional features:

Load compensation – this means that water flowing from the boiler changes temperature, depending on how warm the room is.

Weather compensation – again, this changes the temperature of water from the boiler, but this time it depends on how cold or warm it is outside.

Smart control – this increases your boiler’s efficiency, making many processes automatic.

PFGHRD – or, Passive Flue Gas Heat Recovery Device. This is a way to channel flue gas which would otherwise be wasted and then use it to heat water.

To ensure your boiler complies with the Boiler Plus standard, your best bet is to install one of the digital or smart thermostat options offered by Worcester Bosch. The Greenstar Comfort twin channel programmer is a great choice – it lets you set a different time program for heating and hot water on every day of the week if you like. Meanwhile, the Worcester Bosch EasyControl smart heating and hot water thermostat connects with your phone, so you can adjust the heating in each room before you even get out of bed in the morning.

Greenstar 38CDi Classic Size

All that power comes in at a hefty size. The Worcester 38CDi Classic Combi measures 760mm x 440mm x 360mm, which is unfortunately too big for a standard kitchen cupboard.

If you’re looking for a smaller combi boiler that can be hidden away but with similar outputs, choose the Worcester Bosch Greenstar 36CDi Compact combi. The 36CDi Compact has a central heating output of 24kW and a flow rate of 12.9 l/m, so if you have more than 12 radiators in your home, it might struggle.

Worcester Bosch 38CDi Warranty

The Worcester Greenstar 38CDi comes with a 5-year warranty, which is standard for most boilers. However, when Hometree installs your boiler, your warranty will double to 10 whole years, as we are a Worcester Bosch Accredited Installer.

Energy Efficiency

The Greenstar 38CDi Classic has an ErP rating of A, with 92% energy efficiency. When you install it you should expect to see your energy bills go down – that’s assuming, of course, that your new boiler has a better rating than your old one.

ErP stands for ‘Energy-related Products’. It’s an EU-wide rating system which evaluates a boiler’s energy efficiency. The less fuel a boiler wastes, the higher its energy-efficiency percentage, which equals a letter grade. Just like in school, an A rating is what you should be aiming for.

Verdict – Is the Worcester Greenstar 38CDi the boiler for you?

The Greenstar 38CDi Combi offers excellent central heating and hot water output, combined with a strong flow rate, so it’s an excellent choice for a larger home. A boiler like this can handle a lot of radiators in big, airy rooms with cold stone walls, which is no mean feat.

What really makes the Worcester Greenstar 38CDi stand out is that it lets you run two high-pressure showers at once. For a busy household with kids running around, this could be a life-saver. Not to mention, it’s highly energy efficient, and built to last. When you swap your old boiler for the Greenstar 38CDi, you can rest easy that your needs will be covered for a long time to come.

If you’re interested in the Worcester Bosch Greenstar 38CDi Classic Combi, we offer this boiler complete with installation, 5-year warranty and a free Honeywell Lyric T6 smart thermostat.

 Worcester Bosch Greenstar 38CDi Classic Combi
ErP rating (energy efficiency)A (92%)
Size (HxWxD in mm)760x440x360
Heating output (kW)30
How water output (kW)38
Flow rate (litres/min)14
Standard warranty (years)5 (extended warranties available)
Other available sizes (kW)29, 34, 42

The consumer group Which? review each boiler on the market to find the most (and least) reliable boilers according to a survey completed by thousands of boiler owners. In each review, Which? supply a brand score percentage and star ratings for each category. Take a look at the Worcester Bosch Greenstar 38CDi Classic Combi rating below:

Which? Score 
Efficiency rating★★★★★
Brand reliability★★★★★
Brand customer score★★★★★
Ease of repair★★☆☆☆
Ease of service★★★☆☆
Availability of parts and spares★★★★★
Build quality★★★★★
Engineer recommendation★★★★★
Brand score86%

Boiler manual

Worcester Bosch Greenstar 38CDi Classic Combi boiler manual

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