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Worcester Bosch Greenstar 35CDi Classic System Boiler - Review

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Next up in our series of Greenstar CDi Classic reviews: today, we’ll be getting to know the Worcester Bosch Greenstar 35CDi Classic system boiler. As the most powerful system boiler in Worcester’s Greenstar range, it’s no surprise this model is popular with large, busy families. Our Greenstar 35CDi Classic System review gives you all the essential details, so you can decide if this boiler is right for your home.

Founded in 1962, Worcester Bosch is the best-known boiler manufacturer in the UK. The company has a strong presence in Europe, too, where it faces stiff competition from German manufacturer Vaillant. Here at home, Worcester Bosch has long reigned as the market leader, thanks to its range of highest-quality, energy-efficient boilers for every type of property.

Will the Greenstar 35CDi Classic System be suitable for my home?

The Worcester Bosch Greenstar 35CDi is suited to large homes with 5 to 6 average-sized bedrooms or 4 to 5 large, airy bedrooms. It does a great job of supplying hot water to more than one bathroom. If you’re thinking of buying this boiler, it’s more important to count up your radiators than your rooms. You need to make sure your boiler can supply hot water to all your radiators at once. The Greenstar 35CDi Classic System is made to handle 12 to 18 radiators, which is really a lot for a domestic property.

If you've looked at combi boilers, you will have seen that their flow rate matters a lot. A combi boiler's flow rate determines how much hot water it can provide at one time. With system boilers like the Worcester Bosch Greenstar 35CDi, flowrate isn't a consideration. That's because a system boiler takes hot water from a large storage cylinder, rather than heating it instantly as a combi boiler would do. As such, it can provide a constant supply of hot water to all your taps at the same time, without any loss of pressure. The Greenstar 35CDi also has a powerful central heating output of 34kW, which makes sure your central heating runs efficiently, too.

If you’re weighing up options from different manufacturers, consider the Vaillant 637 Plus 37kW System boiler. It’s likely to offer you the same level of performance. If you have a slightly smaller property, say 3 to 5 bedrooms with 10 to 14 radiators, you might want to go one model down in the Worcester Bosch range: the Greenstar 30CDi Classic System boiler could be a better choice.

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Greenstar 35CDi Classic System Controls

The Worcester Bosch Greenstar 35CDi features the same standard control panel you'll see on just about every combination boiler. It has a simple layout with a small digital display, an on/off button and mechanical dials to adjust hot water and central heating temperature. To get better control over your boiler, you'll need to buy a thermostat.

Without a thermostat, your boiler may not comply with Boiler Plus regulations, introduced in early 2018. The aim of Boiler Plus is to make our boilers more energy-efficient. As part of that, every boiler must have time and temperature controls at the very least.

The Greenstar 35CDi Classic System also comes with an optional diverter valve kit. Well, they call it optional, but it’s pretty much a must-have. A diverter valve directs the flow of hot water to either the central heating or the taps and showers. Installing a diverter valve enables other features of the boiler which you can access from the control panel, including hot water temperature adjustment and frost protection.

Not to mention, if you don’t install a diverter valve, then you can’t use any other controller/thermostat with the boiler. Once you have it installed, you can choose from Worcester Bosch’s wide variety of thermostats. These include the Greenstar Comfort digital thermostat range, as well as smart thermostats, such as the Nest or Hive smart thermostat, which you can adjust via an app on your phone.

Enjoy a free Honeywell smart thermostat

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Greenstar 35CDi Classic System Size

Like most system boilers, the Worcester Bosch Greenstar 35CDi takes up a fair bit of space. The boiler itself measure 760mm x 440mm x 360mm, which is too big for a typical kitchen cupboard. Then there’s the hot water cylinder, which will probably end up in a utility cupboard or loft. This is where all your hot water will live, so understandably it has to be on the bigger side.

If you’d rather invest in a more compact boiler and flow-rate isn’t an issue for you, then you might be better off getting a combination boiler. The nice thing about a combi is that it doesn’t require a great big hot water cylinder.

Greenstar 35CDi Classic System Warranty

Like all other boilers in the Greenstar range, the Worcester 35CDi Classic System comes with a 5-year warranty as standard. We offer a 5-year warranty for free with all of our installations. If you're interested in extended boiler warranties, you can also receive a 10-year warranty for an additional cost.

Energy Efficiency

The Greenstar 35CDi Classic System offers 92% energy efficiency, which means it gets a coveted ErP rating of A. What does that mean? Well, ErP (or Energy-related Products) is a Europe-wide rating system which assesses every boiler’s energy efficiency. The less fuel a boiler wastes, the higher its ErP rating. As you might expect, A is one of the highest ErP ratings you can get. When you replace an older boiler with a brand-new, A rated model, you should expect to see a decrease in your energy bills as an added bonus.

Verdict – Is the Worcester Bosch Greenstar 35CDi Classic System the boiler for you?

Our Greenstar CDi Classic System review gives us two key takeaways: the Worcester 35CDi Classic is highly energy-efficient, and it’s extremely powerful. If you have a very large, older home that’s not very well insulated, this boiler is one of the few on the market that might still be up for the job. If you and your busy family are constantly running taps in the bathroom, kitchen, en-suite and mud room, this system boiler will keep the water coming at a decent pressure.

What’s not to love? Well, there’s that little matter of the hot water cylinder which every system boiler requires. It takes up space, and it only holds a finite amount of hot water – once it’s gone, you have to wait for more to be heated up. But that’s one small disadvantage versus a wide range of other great features.

Added benefits of the Worcester 35CDi Classic include frost protection and Quiet Mark Approval, which means it’s one of the quietest boilers available. Even better, the Greenstar 35CDi Classic System is compatible with Worcester Bosch Greenskies solar panels. How’s that for energy efficient?

If you're interested in the Worcester Bosch Greenstar 35CDi Classic system, we offer this boiler complete with installation, 5-year warranty and a free Honeywell Lyric T6 smart thermostat.

 Worcester Bosch Greenstar 35CDi Classic System
ErP rating (energy efficiency)A (92%)
Size (HxWxD in mm)760x440x360
Heating output (kW)35
Standard warranty (years)5 (extended warranties available)
Other available sizes (kW)30

Get your quote for the Worcester 35CDi Classic today!

All Hometree boiler installations come with a 5-year warranty as standard. Find the right boiler for your home here.

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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 35CDi Classic System 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 35CDi Classic System boiler manual