How do I replace an old boiler with minimum change?

One thing you need to be aware of - if the boiler is that old, the gas pipework from the meter will probably need to be upgraded to conform to current standards, and you may also have to move the boiler because of the flue position.

Dave S.
May 2015

The Potterton Myson Heating Marathon 100c is unrated, this means it's obsolete or very old. Probably about 65% efficient...

The Marathon 100c is a Non-Condensing Conventional boiler with a maximum power output of 27.8kw that uses Gas as its fuel source.
Being an Unrated boiler it would be worthwhile replacing it with a higher efficiency 'A' rated boiler.

The Worcester Greenstar Cdi 30 Cdi Conventional is an 'A' rated boiler which has an excellent efficiency of 90.3%.
The Greenstar Cdi 30 Cdi Conventional is a Condensing Conventional boiler with a maximum power output of 30.0kw that uses Gas as its fuel source.
As this boiler is 'A' rated it will provide efficient heating and subsequently reduce fuel bills and carbon dioxide emissions.

https://www.worcester-bosch.co.uk/homeowner/boilers/gas-boilers/greenstar-30cdi-classic-system

Which Best Buy

n the 2014/15 report and for the fourth year running the entire range of Worcester Greenstar gas boilers have been awarded Which? Best Buy, the only boiler manufacturer to have been awarded Best Buy status*.

The Greenstar 30CDi Classic System boiler is our top performing system boiler. It’s suited to bigger properties with a larger heating requirement.


10 year guarantee on primary heat exchanger.

Central heating output: 30kW

*Which? annual boiler report September 2014

Do not be tempted to select a combination boiler (Combi) without understanding the potential drawbacks.


http://www.myboilerservice.com/the-pros-and-cons-of-combi-boilers

Good luck...
April 2015