The new Worcester 25Si Compact combination boiler came out in July 2013, and we were one of the first to get one on the wall.  In fact, we were more successful getting hold of a boiler than the sales brochure!

This new Si Compact model replaces the Worcester 25Si combination boiler, which had been in production for around 7 years, and uses most of the same parts as the CDi Compact boiler, launched earlier in 2013.

Like the CDi compact, it has a huge potential market because it is capable (just) of being installed within a standard kitchen wall cupboard.  Up until now the choices have been limited in this regard for a small format combination boiler solution.  The main difference between the new Si Compact and the CDi Compact is the latter’s more efficient hot water production;  the boiler will condense in HW mode all the time in the CDi.  As this job was on behalf of a Landlord rather than the end user, the CDi was not worth the price premium, so the Si model was perfect.


For this case study, we’re in Horley, Surrey.  The Worcester Bosch Si Compact in this instance replaced an old Potterton Combi, which had reached the end of it’s economic life.

The Potterton boiler, taking a well earned rest on it’s back outside

Carrying out the boiler replacement also gave us the chance to remove the saucepan modified flue outlet (this featured in an earlier post) which had erroneously been awarded a landlord safety certificate for the last 4 years.

the famous saucepan flue terminal, as approved by the UK’s largest gas company

New boiler flue, the saucepan has gone too.

With the new boiler the leaseholder could rely on a 7yr manufacturer warranty, taking him to 2020 before any unplanned expenses could occur.

New Worcester-Bosch 25Si Compact in position

This is the second boiler replacement we have carried out for the Landlord in the last 12 months, the first was in his own property.