I want to install a combi boiler for heating and water. Can anyone help with size selection please?
I have just moved into a small 3 bed semi which at the moment does not have a gas supply. I am waiting for the supply to be connected. There is just storage heating at the moment.
Thanks in advance for any help!
Liam McGuinness
the Worcester Bosch web site has a wizard which walks you through boiler selection, and then suggests suitable models, from their own range of course.
Do you take baths a lot? Showers a lot?
If you have occasional baths and mostly showers then a 30kW combi will do fine. With a small house you want a boiler that modulates down low on CH to prevent excessive boiler cycling when on CH - the boilers are way over powered for a small house. You don't want a constant click-click of the cycling all night. The excessive power is to heat water instantly, so modulating to a low kW is important.
The Glow Worm 30CXI (rebadged Vaillant) modulates down to 5kW. It has a one piece stainless steel heat exchanger.
I would go for the Glow Worm 30CXI @ 12.3 litres/min flow rate. Great for showers, fills a bath leisurely but not painfully slow, quicker in summer. However the filling time you get used to. You can fill to 1/3 and get in as the bath is still filling - amazing how many never think of that.
The 38CXI gives 15.5 litres/min DHW flowrate, but only modulates down to
6kW. If you take mainly baths then the 38kW is what you want. Fit a Honeywell CM67 stat programmer no matter what boiler, which also has anti cycle control incorporated.Assuming you have a decent cold water pressure/flow.
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