boilder spec

[ssharrow]

Dear all,

We are extending our home and adding a downstairs bathroom which will consist of a shower. We also have an existing shower upstairs.

We currently have a worcester bosch 37 CDi which has been more than sufficient for our needs - our current needs are one shower upstairs, one kitchen sink downstairs. 4 bedroom house.

Once extended, we will have a 5 bedroom house, part water fed underfloor, part radiators. Two showers, kitchen sink, utility sink, understairs cloakroom.

Mains pressure is very good and we have replaced the mains pipe coming into the property (from lead) to blue pipe. 6 bar pressure at stopcock when water company checked in 2008.

I initially thought we would have to instal new system boiler + 210 litre megaflo. However, I have seen that there are some new products now - e.g. Veissmann vitodens 222-f or worcester 550 CDi, which are floor standing combi boilers the size of fridges / washing machines that seem sufficient to supply a 2 bathroom house. Are these a good idea? Seem to be brilliant from a space saving perspective. The Viessmann vitodens is effectively a boiler with a cylinder all in one unit and the worcester seems to be the same.

Anyone had any experience of these?

thanks

 

[D_Hailsham]

I initially thought we would have to instal new system boiler + 210 litre megaflo. ... The Viessmann vitodens is effectively a boiler with a cylinder all in one unit and the worcester seems to be the same.

Yes they are but they don't have 210 litre cylinders. The Viessmann is either 100 or 130 litres; and the WB a measly 51 litres.

Have you done a heatloss calculation for the extended house? If you haven't use Whole House Boiler Size Calculator. You can divide the house into old and new if necessary as your architect/builder should know what the heatloss of the new part will be. You will probably find that your existing WB 37CDi, which produces about 30KW for heating, is more than adequate.

Which just leaves the hot water.

I agree that a basic combi will not be sufficient for your requirements but I doubt if either of your options will do as the HW 'cylinders' are so small. They are there just to provide a good flow for a few minutes, not continuously.

A possible alternative is to retain the WB 37CDi and install a separate large HW cylinder, e.ga Megaflo or similar. The HW side of the boiler could be used just to feed the kitchen sink while the Megaflow would be heated from the CH side, using motorized valves as in the S Plan and Y plan systems

 

[JohnD]

100 litres is enough for a bath, or a profligate shower. While you are running it, the boiler will be heating up more water to replace what you have used, so you will actually get rather more, before all the stored hot water is used up and you drop down to the combi rate.

I do prefer a cylinder or a Megaflo myself, and they have the extra advantage that you can get hot water using an immersion heater when the boiler is out of action.