Combi Boilers - Users Instructions

Exclusively written by Herts Boilers (2024)

Combi boilers are a good invention. Nowadays small to medium houses are using them a lot.

Working hard.

Boiler diagram

About 10% of boiler preoblems are intermittent. Having said that, we are not refusing to work on intermittent lockouts, but we just want to let you know that it might take more visits and cost more to get your boiler finally fixed.

Programmer

Honeywell T3R

Hive and Nest

 

Programming

70% used by heating

House insulation is't always good.

Still need to programming heating on time to max energy efficiency. When not in home, or in sleep, you are better off to set the temperature down.

System pressure

If you can see a pressure gauge on your boiler, or a separate pressure gauge somewhere likely in your airing cupboard normally near the hot water cylinder, your system is sealed, and it needs to maintain a proper water pressure all times, normally between 1.2 bar to 1.6 bar when system is cold. The red needle is reference and black needle is the real reading.

With expansion vessel being good by a compression air charge, when heating is on and your radiators are getting hot, this system pressure can go up a bit for example over 2 bar but it should still be less than 3 bar.

It is a resident's responsibility to make an occasional system topping up. In heating industry it is commonly accepted that one can make a few times of top ups each year.

You can follow these steps for a system pressure topping up.

The system pressure should be topped up to 1.3 bar to 1.5 bar when system water is cold. When heating is fully on in the winter, the pressure is rising somehow, for example to 1.8 bar or even over 2.0 bar, but not near 3.0 bar. When you use hot water from a combi boiler, the pressure is supposed to maintain the same.

Boiler output temperatures

Both hot water and heating should be about 80-90% of the full scales.

It is not suggested to set a combi boiler’s hot water output temperature at 40C to use,

Radiators

Leave them all on at radiator valves, control your heating by a centrollised room stat.

Room stat

One centrallised one is surfficent for most of households, plus TRV on each radiator to balance each room temperatures.

There on and off concept anymore, just at what time and you set what temperature.

6pm to 10pm, family time 20

12am to 6am, sleep time, set to 15

9am to 4pm, away from home, set to 10

Holiday away

When you are going away for a three week holiday, always leave your combi boiler on. Image if you leave your car not run for a few weeks, can you re-start it once you come back? It is the same!

Some modern boilers have a mechanism to run pump and fan on a regular basis to prevent them being seized.

Put heating temperature to a lower point, and leave hot water on, these will make boiler and pump run briefly everyday.

Herts Boilers also maintain this blog site: https://www.boilerblog.co.uk/