Central Heating

[alan30]

I have recently moved into a house whith a combi boiler serving rads all with thermostatic valves apart from the towel rail in the bathroom. Apparently at least one rad should not have a thermostatic valve. There is no room thermostat. When the heating is on timed the rads get hot and shut off as temperture is reached, The pump keeps cirulating water and the boiler cycles to heat up the water as the heat drops via the piping and the towel rail. If I fit a room thermostat this would override the system and shut off everything until the temp dropped. My concern is that currently the pump is working all the time and although the living area temp is OK via the thermostatic valves the system keeps heating water and with the rising cost of electricity (pump) and gas (heat water) this is a waste. I can fit a room thermostat and boiler controller for �120.00. How quickly can I recover this cost? I know there are a lot of variables, 10 radiators, boiler size/efficiency, temperature settings, period of heating etc. but I can't begin to see how I can calculate a saving. My wife is disabled and at home all day and as the weather gets colder the heating will be on for longer. Any ideas or even gut reactions welcome.

[ACB312]

Hello, there are a lot of variables here but basically, you need the pump running all the time to supply hot water to the radiators that are demanding heat by dint of the thermostatic valves being open. If you have an area with a thermostat, it will shut down the boiler/pump when that area reaches the set temperature and so the other rooms will cool down until the area with the thermostat calls for more heat which may not be appropriate for the occupied room(s). The electrical power needed for the pump is negligible compared to the gas cost for the boiler. I would suggest your existing system is good but turn down the radiator thermostats in the little used areas to an acceptable level and close the doors to these areas. Heat will always try to migrate from warmer to cooler areas. So, my basic gut reaction is to advise you to let the radiator thermostats do their job and you manage them for comfort. Cheers, Andy

[buildersmate]

I'm not sure I can agree with the above. This chap has got no means of turning off the heat being fed to the towel rail - the room must end up like an oven when all the room thermostats have shut off.
A room thermostat located perhaps in the hall is the general way these types of heating control systems seek to stop the very boiler cycling you describe. It becomes the 'master controller' which when exceeded (in temperature) turns off the pump and the electrical feed to the boiler - preventing boiler cycling.
You main issue is going to be figuring out where you can connect the thing in relation to the timer/controller, which is often part of the Combi itself.

[alan30]

The �120 covers the boiler unit which is essentially the timer control and a room thermostat linked to the boiler unit by wireless signal. All plug in replacement unit and no hard wiring.

[buildersmate]

Hard to guess how much fuel you are wasting - perhaps of the order of 5%.
Payback in 2 years?

[ACB312]

Buildersmate - I agree with your disagreement of my answer. I was perhaps oversimplyfying. I can only draw upon my own experience of my own system. My timer is the ruler of my system. When it says 'go' , if my tank thermostat is demanding heat the valve opens and tells the boiler to fire up. If my room stat is demanding heat the other valve opens and tells the boiler to fire up. I have my room thermostat situated in my upper floor which heats up and cools down quicker than the rest of the house. This has been comfortable and relatively efficient for many years. The main point I was trying to get across was that you need the pump running all the time (that you ask it to!) to feed the radiators that are demanding at that time and that a poorly situated room thermostat can negate the demands from the radiator stats in other rooms. Cheers, Andy

[rabbitygirl]

Interesting. I have no room stat on the system in my rental house. I agree with about �120 to have one fitted as this is what I have been quoted.

I have recently had the energy certificate issued as required for rentals since 1st October.

It states that in my house of 11 rads, the saving I would make over 1 year by fitting a room stat is precisely �21. Quite how the accessor arrives at that I do not know.

Incidentally, according to him, by installing many thousands of pounds worth of solar panels I would also save a good amount per year.....�46.

[KARL]

Nothing to do with the original question, really, but I am always intrigued by the way heating installers, and as a result the public also, talk of X number of radiators to heat a house. Radiators vary enormously in size and output. If my house had been fitted with the wrong size where some of mine are very large, then either it would take an age to bring the respective rooms up to temperature or they would never get there. Mind you, at the time the installers that quoted based their choices on 20 degrees in the lounge and 15 degrees in most of the rest - and I doubt they correctly assessed the matter of windows or insulation. I suspect that serious attention to both of these would be more cost effictive than eliminating circulation as described. My instinct would have been to leave circulation to run through the room of main use (lounge) with a room thermostat regulating it and have the towel rail on a thermostatic valve. Buildersmate is correct that it seems perverse to pump unlimited heat into the bathroom. Perhaps you can reduce the flow to an acceptable level by throttling it down at the valve that must be on either in or out pipe.

[KARL]

An afterthought: Switching the pump to a lower setting will reduce boiler fire cycling but it may lead to unsatisfactory circulation generally - only trying it will tell. This may be a solution at times except when heat losses are high, such as in particularly cold weather.

[alan30]

Many thanks for all the responses.

[buildersmate]

Karl - to an extent you can manage the issue of having rads that are too big by balancing them so they receive relatively little water compared to others (that are more modestly sized).