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A review of the Worcester CDi Classic Greenstar see what really matters.

Our boiler review of the Worcester Cdi Greenstar Classic Combi

Think of installing a Worcester Greenstar CDi combi boiler in your home or next heating project? Then read on.

The Greenstar CDi Classic is a high end boiler range which is best used for installation in flats or houses with one or two bathrooms as the Classic enjoys some of the best domestic hot water flow rates. There are four different models to choose from so which one is right for you? This is a question that we get on our trade counter all the time from our customers. Let’s see if we can help you.


A premium product the Cdi Classic offer high hot water flow rates which are amongst the best on offer. The Classic is suitable for 1 or 2 bathrooms in larger properties with high pressure showers or even large baths so the boiler is great for people that enjoy a good old fashioned long soak.

Flow Rate and Heating Outputs

Greenstar 29CDI has an output of 30kw to both hot water and the central heating system and will give a hot water flow rate of 12.3 litres per minute at 35 degrees centigrade.

NOTE  I prefer a slower flow rate at a higher temperature, boiler manufacturers use 35 degrees which is a bit on the low side so reduce the flow rate a bit if you want hotter water at the delivery point.

34Cdi Classic will give you 30KW to the heating circuit and hot water flow rates of 14.3 litres per minute at the standard measure of 35 degrees centigrade.

38Cdi Classic Once again the heating system is 30KW which is enough for a substantial system but the hot water is a whopping 40 KW giving a flow rate of 16.4 litres a minute at 35 degrees.

Finally the 42Cdi Classic gives 30KW to the heating system (bit of a theme here) but a truly massive 42 KW to the hot water with a stonking flow of 17.2 litres which will keep up with most high delivery hot water systems in domestic properties.

Size does matter

The Classic Greenstar is not the smallest boiler around but the dimensions are not excessive for the power within. This is not a cupboard fit boiler though. Measuring 760mm high and 440mm wide and a depth of 360mm this is a wall mounted model.


That depends on how the boiler is installed and by who. By using a few of Worcester fitments like a filter and a Comfort controller the Cdi Classic can enjoy up to 10 years warranty but must be installed in accordance with Worcester’s instructions. If so you will enjoy their no quibble warranty.

Which Cdi Classic do I need, a simple guide.

29Cdi a medium sized property with 10-14 radiators and one high pressure bathroom outlet being used and not several at once.

34Cdi Classic for a medium sized property with 10-14 radiators, a high pressure shower and a bath or two showers simultaneously.

38Cdi Classic Medium to larger property with 10-14 radiators with two showers and a bath and shower running at the same time.

42Cdi Classic will be suitable for a large property maybe 5 bedroomed and can run two showers and a bath at the same time.

Whilst these figure are a good benchmark MDS stongly suggest that your heating engineer does a heating calculation and measures your incoming water mains pressure and flow rates. Remember when it comes to a combination boiler you can only get out what you can put in. Poor mains flow will remain poor floor flow so make sure your cold water supply is sufficient. Call MDS on 020 8778 2887 or just drop into our trade counter,

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Worcester boilers