Combi boiler advice, please

Hi everyone,
Hope someone can help.
We're looking to have our loft converted, giving us a 3 storey house. The conversion will be two bedrooms, each with one radiator.
We currently have two bathrooms, one with an electric shower and one with a shower fed from the hot water tank.
The existing gas boiler is between 15 - 20 years old and is getting beyond its use, especially for a young family such as ours. This is located in a recessed, closed off cupboard area on the ground floor.
I'd like to have a new combi boiler fitted so that we could have on demand hot water, ideally over a couple of appliances / outlets at a time.
Could this be installed as a straight swap for the existing boiler, or am I right in thinking these have to be located higher up, ie probably in the loft, to work properly.
Thanks in advance for any advice.
Regards,
Dave.
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Dave Jennings

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Hi Dave,
Combination boilers are more commonly fed from the main cold water supply, so it could literally be fitted anywhere in the house that allows a proper flue to be installed, and it will still give you hot water to your appliances. The only draw back about combi' boilers in situations like yours, is that they all give a very poor output on the hot water side. This is because of the time they take to heat the water to a decent useable temperature. This fact, coupled with long pipe runs, makes them very poor at supplying more than one appliance at a time and it usually takes ages to draw heated water to the place you want it.
My advice would be for you to go with a conventional boiler feeding two hot water storage tanks. One tank would feed the upstairs appliances and one supplying the downstairs system. This way you'll always have a decent hot water supply to every appliance in the house when you need it.
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BigWallop wrote:

<snip>
Thanks for the info - I really appreciate it!
Regards, Dave.
--
Dave Jennings

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IMM wrote:
<snip>
Many thanks for your advice - I really appreciate it, and all points are noted!
Regards,
Dave.
--
Dave Jennings

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Dave I think you are me in another lifeform. We have a young family and are doing a conversion to put in an extra bedroom and a 2nd bathroom. We are going to put in a gas combi as gas is new to our area and do away with the tanks (oil, water, hot water). We are also planning a extension to our kitchen and a complete refit. The bill is so high we are hoping to DIY as much as possible. If you find any useful information or encounter problems, let us know, it would be invaluable.
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Try the Worcester High Flow and I think Vokera Linea Max. They incorporate a heat bank and are standard washing machine sized so will fit in with a normal kitchen. Se my response to the OP.

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flow rate and pressure for what you intend.
If you want to run two bathrooms, do make sure that you install a large enough boiler. A shower takes 10 - 15 litres/min to be in any way decent, so you need to have enough water supply capacity and enough heating capacity to cover this.
A very large combi boiler (in the sense of heating capacity) is needed to supply the flow rate required. Bear in mind that a shower is normally run at about 40 degrees. The mains water in winter can be as low as 5-8 degrees. Since combi boilers are specified with a flow rate for 30 or 35 degrees temperature rise, you can easily work out that under these conditions, the boiler will be flat out supplying water that is just about hot enough for a shower. Ergo, you need to have one that will do 20 litres plus per minute if you don't want to have reduced shower flow rate in the winter.
This can be done, but you do need to make adequate provision in the choice of appliance and also that the water and gas supplies are adequate.
People have been disappointed so it is worth taking care with checking and selecting suitable equipment and its supplies.
.andy
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Andy Hall wrote:

Thanks Andy,
I'll make sure to bear all these points in mind.
Regards,
Dave.
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Dave Jennings

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