HELP PLEASE! Advice about CH, gas units, thermostats.... etc!!!!

becksfaz

We moved in to a new house in the summer (4 bed semi) and I am utterly confused with my heating.
We are going through gas units like there is no tomorrow, approx 15-20 metric units per day and therefore high bills!
I'm very tight when it comes to energy - I flick lights off etc to save electric and if my hubby complains he's cold I tell him to put a jumper on! so I'm confused where I'm going wrong with the gas in this new house.
I have a hall thermostat set to 18 degrees and have the central heating set to constant as I'm in most of the day due to having a new baby, (my understanding is that the heating will only kick in if the house gets below 18). I've noticed that the boiler kicks in, runs for 5-10 mins, rads get warm (not overly warm) and then boiler goes off. Appox 1 hr later this happens again. Why isn't the boiler running to get the rads hot so that the house gets warmer and then takes longer to cool down, thus kicking in the boiler less? I know a boiler kicks in when temp drops below what I've got thermostat set at, but how does it know when to go off?!?!
I've been experiementing - thermostat set at 18 = boiler come on for 5-10 mins before kicking off, rads luke warm and uses 1/2 metric unit of gas. Put thermostat to 21 today, boiler ran for 1 hr before kicking off, rads red hot (all of them) uses 2 metric units. With 2nd option house feels warm and stays warm for so much longer - but thought having thermostat at a lower temp was meant to reduce gas consumption????
Also have TRV on most of the rads (total novice with these too it's my friend that told me I had them) - but these are confusing me too. Since my friends explained how they work I've tried my best with them but still don't understand them - I have the rad in our bedroom (the one fed to 1st) on at number 1 and the rad in the lounge on at 5, yet the bedroom rad gets warmer?!?!?
I'm seriously cracking up trying to figure out how to heat my bloody house without it costing me the earth. Please please help!!!!!!!!!

Cardew

Well firstly 15-20 units a day,(160 - 220kWh) in a 4 bed semi when you are home all day, with the heating on, is not particularly high(£5 to £7 a day)

The wall thermostat set at 18C will switch off the CH when the hall reaches approx that temperature, depending on the type of thermostat when the temperature drops to, say 17C the boiler fires up again and heats the hall back up to the 18C again. So you noticing this happening every hour, means it is correctly 'topping up' the heating i.e. replacing the heat lost through walls/windows etc.

Having a thermostat at a lower temperature does indeed reduce gas consumption - somewhere in the order of 6% to 10% per 1C. Heating it to 21C(instead of 18C) not surprisingly will keep the house warmer for longer, but you will burn a lot more gas.

The TRV(Thermostatic Radiator Valves) shut off the supply of hot water to the radiator when the temperature set on the TRV is reached. They do not control the temperature of the water in the radiator. So it is perfectly possible that your bedroom radiator with the TRV set to 1 will be hotter than the Radiator in the lounge set to 5. It just means that the hot water from the boiler is still being circulated through the bedroom radiator(because the room isn't up to the temperature that corresponds to a setting of '1', However the lounge is at the temperature that corresponds with '5' and no water is passing through the radiator.

There are different types of TRV but the setting are usually 1 = 16C 2 =18C 3 = 20C 4 = 22C 5 = 24C

The interaction between your wall thermostat in the hall and the TRV is just a matter of experiment. It doesn't matter what is set on the TRVs if the hall thermometer is set to 18C and that the temperature has been reached - as the heating is off.