If you are planning to leave your house empty for a longish period of time, there are some things you can do to reduce the likelihood of any issues with your boiler and heating.
Firstly, if you are going away for a substantial period it is worth getting your boiler checked and serviced a month or so before you leave. This will ensure that any potential issues are picked up and that there is enough time to deal with them before you go. Ideally your boiler should be serviced annually in any case, so just adjust the timing based on when you will be away.
If you’re away during winter
If you will be away during the winter, you may not want to leave your heating on all the time, seeing this as a waste of money. You have a few options open to you.
If you are away for a significant amount of time then you might prefer to leave the house completely unheated, but if you do this you’ll need to take certain steps to prevent freezing damage. In addition to turning the heating off you will need to turn off the water and drain down all tanks and pipes as well. This work, as well as refilling and recommissioning of the system upon your return, should be done by a qualified heating engineer.
If this seems a bit drastic or you are not going away for such a long time then another alternative is to leave the water and central heating on and use the ‘frost setting’ on room thermostats to prevent the temperature falling to freezing. This setting is indicated with a snowflake icon and is designed to keep the temperature over 4 degrees celsius so that the water doesn’t expand as it starts to freeze.
This won’t protect water tanks and pipes in a loft though, due to the loft insulation. For this you will need to either allow warm air to rise into the loft by leaving the hatch open or to install a separate electric heater in the loft area, which should also be on the frost setting.
Your other option is to leave the heating on but at a low temperature. If you set your boiler output thermostat to low and the room thermostats to 12 degrees celsius then the heating will only kick in when temperatures fall below this. This means you will only have the heating on when temperatures are low (so won’t be wasting it when it’s warm). An added benefit of this method is that it will also help prevent condensation which can cause mildew and mould and may damage furniture, fabrics and books over time. If you choose this option you should leave radiator valves fully open and thermostatic radiator valves turned up to maximum.
If you’re away during summer
If you have an old boiler with a continuously burning pilot light then it is probably a good idea to turn it off when you’re away during the summer. Modern boilers can also be switched off if the water cistern isn’t coated with polystyrene. However it’s best to run your central heating and hot water occasionally during the summer to prevent the pump and diverter valve becoming seized up, so if you are going to be away for the whole of the summer then either leave it switched on or arrange for someone to come and run it at least once while you are away. If you are just away for a few weeks or a month then it’s fine to turn it off during that time.