What to consider before buying a new boiler

If your reading this your probably in the process of getting a new boiler installed or your considering it, either way it’s a large financial commitment, so being well educated on a sizeable purchase is always a good idea. On that note we have compiled a check list outlining what you should know and think about before you start obtaining quotes.

What size boiler do you need?

The average combi boiler comes in one of four sizes 24-25kw , 28-30kw, 33-35kw and 40kw, as a rule of thumb a 24-25 is ideal for most flats and any smallish 2-3 bed house with anything roughly up to 10 radiators, a 28-30 would be for a medium to large 3-4 bed house with up to 15 radiators, a 33-35 and a 40 kw would be for a large house with anything up to 20 rads. For hot water the higher demand (how much hot water you use) the higher kw (kilowatt) boiler required, however no combi boiler can cope with 2 showers running at the same time.

Location of boiler.

The easiest and cheapest place for any boiler to be installed is in the same location as the old one, the reason for this is that the pipes are all in the vicinity, if your going from a combi to a combi then every pipe will be there, however if your converting from a system boiler to a combi( a sytem with a hot water cylinder and header tank), there is a good chance that the cold and hot water pipes will have to be “run” to the new boiler. A boiler can basically be installed on any wall as long as its near an outside wall in order for the flue to exit and a drain (explained later), also needed are gas,flow and return(radiator pipes), hot and cold water pipes.

A pipe must leave the boiler and exit in to a drain.

All boilers by law must have a sedbuk efficiency rating of A, this means that they must be “condensing”, all condensing boiler’s produce condensation, this condensation leaves the boiler (in liquid form) via a waste pipe, this waste pipe must exit in to a drain, either an outside drain or it can “tap” in to a sink/bath/washing machine waste inside the property, the pipe must have a downward slope of at least 5 degrees.

What Brand and make of boiler to choose?

This depends on your requirements and budget, Worcester Bosch are generally the best but are also the most expensive, give us a call with your requirements and we will advise you further.

What size is my gas pipe?

If your a bit savvy with this sort of thing, or you have access to your old boiler installation instructions, then check the size of the gas pipe going in to the boiler it should be 22mm in diameter, if its 15mm thick it will need to be increased. if your boiler is over 35kw you may need a gas pipe as large as 28mm. We can advise on this

What thermostatic controls do i need?

With any new central heating system you must have a minimum of a room stat, the cheapest and best option is a wireless room stat. Contrary to popular belief there are no laws stating that you must have thermostatic radiator valves ( i have contacted gas safe and had this confirmed), what they say is that an installer should recommend them, to a customer and quote for them, but you don’t have to have them, but i do advise getting them installed in bedrooms at least. new boiler plus regulations state that you must have either a smart thermostat or load compensating thermostat installed.

Getting the system flushed.

Your warranty will be void if your new boiler becomes damaged because of sludge from your system. To prevent this the system must be flushed, its also advisable to get a central heating filter installed which will help combat sludge build up for as long as its installed.

Water pressure.

Every combi boiler has a minimum cold water flow rate requirement, it is vital that this is tested prior to the new boiler being installed

How long will it take?

An average combi to combi exchange will take 6-10 hours (normally done in one day) a conversion (system boiler to combi) would normally take 2-3 days, so be prepared for at least one night without hot water or heating if getting a conversion

Latest articles

Independent customer reviews

Thank you to our lovely customers for leaving us glowing reviews across three of UK's most trusted platforms! Take a look...

Very thorough & hardworking

"Complete system and boiler renewal, Dave and Adam were very knowledgeable and approachable. They were..."

Read more

All round excellent service

"I've used Gas Angel a number of times and never been disappointed. The engineer came to perform a gas fire removal..."

Read more

First class installation

"New central heating boiler installed. Excellent service. First class installation. Helpfull and curtious service throughout..."

Read more