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Your Gas Central Heating System - Frequently Asked Questions

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Should I leave my hot water and heating on all the time or use my timer/programmer?

It's a common misconception that it is cheaper to leave your hot water and heating on all the time. Although the boiler will use more power initially to heat the home and water from cold, the cost of this is greatly exceeded by the cost of keeping the boiler running 24 hours a day.  The principle of an appliance using more power when it starts is quite normal - cars, ovens and kettles are the same - but we don't run these appliances 24 hours a day. Ideally the heating and hot water should not be on for more than 9 hours a day, unless it is extremely cold.

Is it cheaper to have my hot water on all the time?

No, it's almost always cheaper to have your hot water on when you need it, as a full tank of hot water will always lose heat and need topping up by the boiler.  Normally it takes around 30-45 minutes to heat a tank of hot water.  Set your programmer to heat it up for a short time before you are likely to want to shower or bath in the morning and to come on again before you next want heat.  There is often a button on your central heating programmer that lets you get a boost of hot water in between times.

Should I leave my electric immersion heater on all the time?

No, if you have a gas central heating boiler use that to heat your hot water, ideally using your timer/programmer to time your space heating and your hot water heating at the same time. Only use your immersion heater as a top up. You may decide to use your electric immersion heater to heat your hot water in the summer when you no longer need the boiler to heat the radiators. This could work out cheaper if you only use a moderate amount of hot water.

Should I use my portable heater/decorative fire or turn on my central heating system?

Any electric plug-in heater (including oil filled radiators), portable gas heaters or decorative gas fires are an expensive and inefficient way to heat your home.  The heat costs around three times as much per unit as that from a gas central heating system.  A portable gas heater also produces a large amount of condensation which makes the house damp. The only time this is worth considering is if it's a choice between heating one room with a portable heater or all of a large house with central heating.  However, portable heaters or fires should not be considered as an alternative to central heating and should only be used for occasional use, such as at the end of the day, when the central heating has been turned off.

Even when I turn them right up, my radiators don't stay hot all the time - What's wrong?

The temperature of radiators will naturally fluctuate when controlled by TRVs. This is normal.

Why does the boiler keep firing on and off?

The boiler will only fire up when your heating and/or hot water is on.  If you have a room thermostat, the 'firing up' will stop when your home is warm enough.  The boiler will then 'die down' to the pilot light.  When the temperature drops, the room thermostat will tell the boiler to 'fire up' again, re-heating the water to pump round to the radiators.

If I turn the room thermostat to a high setting will it heat up the room quicker?

No, turning it up will not heat the room up quicker; it will heat it to a higher temperature.

I spend most of my time in the living room so have turned off the other radiators - is that right?

No, as condensation may occur in unused rooms.  Also, if you just use one radiator it is not good for the heating system and it could break down.  Therefore, we recommend that you set the TRVs in all the rooms to a 1 or a 2 setting and the one in the living room to a higher setting.

My living room never gets warm enough.  I have the TRV set on maximum all the time.  My room thermostat in the hall is set at 16°C.  I don't like my bedroom to be too hot.  What should I do?

Turn up the room thermostat in the hall to 18°-21°C (66°-70°F).  The living room should get warmer now.  Turn the TRV in your bedroom to a low setting so that the bedroom does not get too hot.

I don't use two of my bedrooms, should I turn the radiators off?

Not really, as condensation may occur in these bedrooms.  Instead, turn the TRVs on these radiators down to a low setting. The radiator will now only come on if the heating is on and these rooms are very cold. Close the doors of these bedrooms to prevent them from draining heat from the rest of the house, too.

My heating is on but the radiator in the living room has gone cool, why?

When the TRV senses that the radiator is warm enough, it closes the pipe and stops hot water flowing into the radiator.  When the room cools, the TRV opens the pipe and hot water flows back into the radiator and heats it up.

Why is a radiator with a TRV on it cold when my heating is on?

The thermostat has shut off the water to the radiator as it has sensed the room is warm enough.