/ Home & Energy

Tricky thermostats – is your central heating out of control?

Some tiny plumbers fixing a radiator thermostat

Keeping our homes warm during those chilly winter months is essential to most of us, but are you spending more money on heating than you need to? Are you in control of your thermostat?

In our recent heating survey we found that around two thirds of people with central heating have a timer to turn the heating on or off. But only half have thermostatic valves on at least some of their radiators. And less than half have individual room thermostats.

To get the best out of your heating system and save money, each house should ideally have a full set of controls:

  • A timer or programmer to set when your boiler should turn on and off.
  • A room thermostat to set the temperature you want your heating to achieve.
  • And thermostatic radiator valves to control radiators in each rooms.

The Energy Saving Trust estimates that you could save £70 per year on average if you were to install a room thermostat (in a typical three-bedroom semi-detached home heated by gas).

A flexible approach to heating

As David W put it in a previous Conversation about heating:

‘What one really needs is a device that compares the ambient temperature with a pre-set ideal and switches on the heating if (and only if) it’s needed, summer or winter. Because if it’s cold, it’s cold, whether it’s August or December.’

A letter we received from Mike Astill suggested the use of portable wireless thermostats. He moves the thermostat from living room to bedroom etc as he moves around the house. He also turns down the radiator valves in the rooms he’s not occupying.

Confusion over complex controls

But even if you have a heating timer, do you know how to use it? Some are quite complex and not at all intuitive. One in five people who have a timer and don’t use it, say it’s because the timer is too complex to use or they don’t know how to use it.

When first installed, your heating engineer should explain how to use the timer and the thermostat, but do they? In detail? And what about if you move into a house that already has a timer, but the previous owner has not left any instructions for the boiler or controls? How do you find out how to use them?

Our research also found that almost one in 10 people who don’t use a timer for their heating say it’s because they believe it’s more efficient to leave the central heating on all the time.

Do you have a full set of heating controls in your home? And do you know how to use the timer? Do you have any tips on how to make the best use of heating controls to save money while still being comfortable in your home?

Comments

My wife & I have lived in the same house (3000 sq ft) some 42 years(along with family over this time, but now on our own). I shall be 77 this year & feel the cold badly (Warfarin). When our heating system was overhauled 25 years ago, we fitted TRVs to every radiator & I set the controls (most are different to each other) by a very simple process of putting in each room in turn a maximum/minimum thermometer in what I thought was the appropriate place (e.g. not close to a rad/putting it on the bed pillow/etc) & calibrating it that way. Soon found the best settings & cross check them every 5 years or so. Works for us.

Heat pumps have been mentioned a couple of times. As I understand them they are best used in ground or water, and have an efficiency of no more than 3:1 – for every kW they use they can produce up to 3kW (heat). If that is the case, then 1 kWh of electricity (say 12p) can produce 3 kWh of heat – 4p a unit. If you would otherwise use gas for heating, you would pay around 3.5p. So they are only around break-even, without considering the capital and installation costs. Do you have better information than this?

Malcolm Duke says:
24 February 2013

I wouldn’t bother with ground or water source heat pumps: it’s a big capital outlay, massively disruptive unless you’re already doing a lot of earthworks, and if it’s not set up properly you can have enormous problems with it. Air source heat pumps are a different matter, and might be a no brainer if you don’t have mains gas.
Although I have solar thermal, and it works well for 7 – 8 months of the year, I probably wouldn’t instal it if I was making the decision today. I’d go for a hot water system with integral air source water heater, such as Ecocent or Air Macht, if you have solar PV (or Economy 7).

Patrick says:
26 February 2013

Some informed and evidence based advice is need urgently! Conflicting and unscientific views prevail over:
1. Timer or not. Leaving the heating on all the time, night and day, may be more economical when the amount of hysteresis in the system is large – i.e. a leaky house. I have yet to meet a CH engineer who knows what hysteresis is, but cannot work out the physics myself.
2. Do TRVs work at all? If so, why do I have to adjust all my rads when the outside temperature changes markedly: and this in my last house, and my current house where all the TRVs are new and presumably working. I understand that individual (programmable) room themostats, communicating with rad valves by infra red, exist – but need to be wired in to the mains!
3. Set-up. The room thermostat tuens the pump on and off, not the system as someone has siad below. I have been advised to tuen the TRV in the room where the thermostat is (the hall, unfortunately) to maximum, the thermostat then to desired temperature, and then other room TRVs to desired level (bearing in mind (2)). This presumably minimises the use of the pump, and cycling of the boiler – but does it depend on whether a modulator is fitted?

Patrick

A central heating engineer may not be familiar with the term ‘hysteresis’ but will be familiar with it, both in relation to operation of thermostats and how a building responds to heating.

It is very easy to prove that it uses more energy to keep heating on overnight, even at a decreased temperature – simply by measuring gas or electricity consumption. (It’s obviously harder to do this with oil or LPG heating.)

As I mentioned earlier, the problem with ordinary TRVs is that the temperature sensor is close to the heat source, so that TRVs will not control room temperature well. They are a crude way of controlling room temperature. TRVs using remote sensors or zoned heating using additional room thermostats and motorised valves will give much better control. TRVs can stick open or closed, so it is worth fully opening and closing them periodically to check that they are actually working.

On my own CH system, the room thermostat turns off both the pump and boiler. I believe that new-fangled boilers, the pump will continue to run for a period to prevent stressing the boiler but my boiler is over 30 years old and has no electronic controls.

Any radiator system should have a route for water to flow even if all TRVs are closed, though it does not have to be a particular radiator. I choose to keep my bathroom radiator (simple valve) on all the time, which helps keep my north-facing bathroom free from condensation. Commonsense suggests that the room thermostat should be sited in the warmest room and no TRV used (or it should be fully open if fitted). I can understand what a modulator does but cannot comment on how it affects the efficiency of a system in practice.

I have a Honeywell wireless thermostat linked to my aged LPG boiler and also thermostatic valves on all rads. Whilst the sender and receiver units talk to each other without a problem, when the heating comes on in a morning it takes the sender unit about half an hour before it communicates with the receiver unit. After that its fine. I’ve emailed Honeywell a number of times for a solution and get no reply. Searching on the web reveals that this is a problem for other people as well. So whilst in theory, a moveable sender unit is a good idea as you can move it to where you require the heat, in practice there is a problem with time delay when the boiler initially fires up and this wastes gas.

Keith Wood says:
28 February 2013

Consider moving your thermostat to the living room and either don’t heat halls and corridors, or only a little, with thermostatic valves. Have a valve fitted on the pipe between your boiler and hot water tank, so that the boiler is only heating the hot water when you need it, rather than all the time that the heating is on. Turn the heating switches off half an hour before your retire, perhaps with the clock setting/ a timer. Turn the thermostat down before you go out. Draw the curtains when your are out, at least in the evenings.

After retiring to make my home more economical I installed a new condensing combie boiler controlled by a fully controllable Honeywell CM927 wireless thermostat that sits on my coffee table next to my chair. For my comfort I replaced both of my lounge diner rads with doubles. The lounge soon reaches a very desirable temperature but of course the rest of the house has only background heat which is fine by me for most of the time, however when I need the house warmer I open both of the lounge doors which allows the heat to escape and activate the thermostat. i do not have a separate timer as the thermostat allows different temperatures at different times, which of course allows for the house or lounge to be warm upon my return. I have a 3 bedroom detached chalet bungalow and I pay £90,00 per month for my gas and electricity and this keeps me at a very comfortable temperature.

Derek Graham says:
2 March 2013

Had Wireless thermostat fitted in British Gas installed condenser boiler.
Kept going wrong. Problem caused by Broadband hub.
Replaced with ordinary Thermostat

Matthew says:
3 March 2013

I work from home two days a week in an attic room office. To have this room heated in the winter I had to turn on the central heating for the whole house, which seemed such a waste, or turn every other radiator off manually.

The solution that I came up with in the end was to zone the house into four zones which can be independently heated. To do this I used Honeywell CM927 wireless thermostats connected to Honeywell V4043H motorized valves. The valves were installed by a plumber and he had to find points on the existing pipework where the pipes supplied the zones that I had identified. He had to cut into the pipes to fit the valves so the whole system had to be drained and it took a whole day.

The original central heating timer is still there and this now turn the whole system on and off. Each zone has a wireless unit that can be used to set the times and temperatures of heating in that zone whenever the whole system is running. It’s all worked perfectly for the last year, my gas bill is down by 15% and my office is warm for the first time.

The parts cost £560, the labour was £300 and I’m saving £120 a year so this should pay back in just over seven years.

Alex says:
3 March 2013

We have central heating, but the radiator in the bedroom is in a wrong place in the room, making it inefficient. Also, central heating is rather noisy. This is why last autumn, we programmed the central heating to switch on only during the daytime hours, and bought a small oil heater for the bedroom. So far, I am very happy with this solution.

Derek, Interesting to hear that a wireless thermostat can go wrong due to a broadband hub.I bet British Gas wishes to keep hush on this issue. Anyone else had this happen? Will keep our simple lounge thermostast for the moment.

I believe that it is possible to change the channel on a BT Home Hub, which might sort out the problem.

With increasing numbers of wireless appliances and restricted radio frequencies available, it is inevitable that interaction can occur. It’ hardly fair to blame BT for this, Dave. If British Gas installed the thermostat perhaps they should have asked about what wireless devices were in use and given a warning about possible interference.

Mike Cowlishaw says:
3 March 2013

This shouldn’t be very common — although wireless thermostats use a wide range of frequencies (typically 433-853MHz), a broadband hub is unlikely to affect it (WiFi frequencies are around 2.8GHz). More likely some failed component in some older device such as a microwave or mechanical thermostat was the culprit. I have had two hot-water tank mechanical thermostats fail at various times in a mode that they completely wiped out radio and (old analogue) TV reception within the house. Similar problems are possible with ‘fridge and freezer thermostats.

That’s great theory, Mike, but it’s not that simple. A transmitter can create interference problems even if the frequency is different and since the inverse square law applies, even a low power transmitter can cause problems if close to a receiver operating at a different frequency.

A ham radio operator will be aware of the problems that they can cause neighbours and probably be able to explain the reason in terms of harmonics and deficiencies in circuit design. In the early 80s I had breakthrough on my FM radio from CB radio users nearby, even those in cars. Many people have found themselves unable to unlock or lock their car with their remote control because of some radio frequency transmitter nearby. Microwave ovens, light dimmers, cordless phones and so on, are all potential sources of interference. Simple suppressors can decrease but not eliminate interference caused by mechanical thermostats and other switches.

I came back to find all four windows of my car partly open last weekend. That’s not happened before, and I wonder if radio frequency interference may have been to blame.

Mike Cowlishaw says:
5 March 2013

Hi wavechange … indeed lower-frequency signals can often cause problems at higher frequencies. However, it would be extraordinary for a (relatively) low-frequency wireless thermostat to be affected by a significantly higher-frequency Wi-Fi router, especially as both will have been tested for emissions and sensitivity.

One could speculate about beat frequencies, but the power required would also make this unlikely. Some other source than the router (such as dimmers, microwave ovens, mechanical thermostats, etc., as you suggest) is far more probable.

JSB Bath says:
4 March 2013

There is no “ideal” solution to heating multiple rooms, but we would (ideally) want our Bedroom ON from 7:00 to 8:00am, and from 22:30 to 23:30, the Kitchen/Dining area on all day (lowish heat) from 8:00 to say 22:00, and our lounge from 17:00 to 23:00. Ideal but would only be achievable with Timer Thermostat valves on all individual rads, which we don’t find worth doing. We could set the Rad TRVs by hand, but soon got fed up with doing that every day. Now we leave the TRVs in the rooms we do use set to about halfway, and the lounge to 3/4, and take the Wireless Room Stat in to the lounge to up the heat in the evenings. Not ideal, but it works for us. We also have the Boiler OFF all night (we’re more than warm enough once in bed) and ON all day from 7:30 till 23:00, but overridden by the wireless Room Stat throughout the day.

John Watson says:
4 March 2013

I have a four bedroom house and recently replaced the old boiler in the cellar with a new condensing boiler in the loft.
While I was planning this I decided to replace the fixed thermostat in the lounge and the programmer with a single unit. In addition since the requirements for upstairs are different from down I also placed them into seperate zones controleed by two independeant wireless units.
This gives a very flexible solution ensuring upsatirs is not heated just because the lounge is cold.
Also, if we are in the dining room or kitchen the thermostat comes with us.
The only caution is that you should not place the thermostat in a room which has a TRV unless this is adjusted to max.
I can recomend the wireless controllers and have even heard of them being attached to an old ladies zimmer frame so that the temperature was always right regardless of the room she was in!

Ian Rickell says:
5 March 2013

When I had my Worcester Bosch condensing boiler installed I had the heating system split into an upstairs zone and a downstairs zone controlled by valves. The valve for each zone is controlled by a wireless programmable and portable thermostat. I retained the hot water tank (heated by the boiler) because it has immersion heaters wired for economy 7 use. These are not normally used because of the expense even when using the overnight tarrif, but they would provide hot water if the boiler failed. The portable thermostats have 6 settable periods and each day of the week can have different settings. In fact I have them set the same for each day. (I am retired, so every day is the same!) They also have a party function, where the temperature can be set for a number of hours, and a holiday function, where the temperature can be set for a number of days. When the hours or days have expired, the set programme resumes. I find the party function particularly useful. It can be used to override the set programme for evenings out or days out, watching the late film etc.

However, it does not pay to be too mean with the use of energy. For example, the boiler is at its most efficient when it is maintaining a steady house temperature. The flame modulates so that the boiler provides heat at the same rate as it is lost from the house. If the heating is turned off completely for a period and the house becomes cold, the boiler will fire up at its maximum rate, which is when it is at its lowest efficiency. It could be that the loss off efficiency will cost you more than the fuel saved by turning the heat off completely. Thus when I use the party mode, I set a temperature which is only a few degrees lower than normal. I save fuel because of the lower set temperature and the boiler fires efficiently (and I avoid dampness – see below). However, if the set period is long, then the fuel saved by turning the boiler off completely may more than compensate for the loss of efficiency when it fires once more. I have yet to work out the optimum!

Be aware that if one zone is colder than the other, it will act as a condenser for the water vapour given off by the warmer zone. Compromise energy saving and avoidance of damp.

Check whether your boiler has the facility to run the circulating pump from time to time to stop it seizing. If it does, then keep the boiler on all year. It won’t fire up in the warm weather, and you may avoid an expensive repair.

Bob Seymour says:
5 March 2013

I have logged indoor and outdoor temperatures (with a computerised weather station) every half-hour for the past 2 years and this has given me the opportunity to test the performance of the house (a 4-bedroom bungalow built in 2000) and its heating controls. There are several conclusions, some surprising:

1. The rate of cooling of the house when the boiler is off, (i.e. the escaping of valuable heat) causes a 3% loss of the inside/outside temperature difference per hour, with about a half-hour lag. This means that switching off the heating overnight yields a substantial saving, because the loss of heat falls as the inside/outside difference gets smaller. Switching off for an hour or two while we’re out is not important, though, because the inside/outside temperature difference doesn’t get much less in that time, so the heat-loss stays high.

2. A wireless programmable thermostat (Salus RT500RF) can keep the temperature constant with a range of 0.5 degrees between high & low. (It also comprises a timer and a frostguard setting).

3. TRV’s are incapable of keeping the temperature in a room constant to better than about 2-5 degrees because of their excessive exposure to the heat of the radiators. However TRV’s are useful in rooms where the radiators are oversized, to reduce the tendency of those rooms to overheat.

4. Turning off the valves in unused, closed rooms is inconvenient, and the heat savings turn out to be unmeasurably trivial. This may be because the house’s external insulation is much better than the inter-room insulation. (If you do switch off the heating in spare rooms, do switch it on 24 hours before guests arrive so that their bed and other furniture and the walls are not freezing cold to the touch!).

5. For the long-term health of the respiratory system, it is recommended that minimum bedroom temperatures during sleep should be no less than 16 degrees. This can of course be achieved by programming the thermostat to this level. But when the heating is triggered by the thermostat reaching 16 at (say) 4am, it will run for perhaps 30 minutes before cutting out again. For a single bedroom, it is just as effective and far cheaper to use a small electric radiator, say 200W, for an hour in the coldest part of the night.

6. Heat from the sun is very important but the TRV’s seem entirely insensitive to it – the radiators stay hot in rooms warmed to excess by the sun in the afternoons! Perhaps this is a slow reaction problem?

Bob – As I said at the beginning of this discussion, TRVs are just a crude way of adjusting the heat output of a radiator because they respond to heat from the radiator and not the room temperature. The temperature sensor needs to be away from the source of heat, which is why temperature is best controlled with two or more room thermostats operating two or more motorised valves.

The human body can compensate for changes in environmental temperature (thermoregulation), so there should be no need to control room temperature accurately for anyone other than the sick and the elderly.

The downside of having bedrooms warm is that this promotes growth of dust mites, which many asthma sufferers are allergic to. I wonder if those who recommend bedroom temperatures have given any thought to this.

Bob Seymour says:
6 March 2013

Wavechange – thanks for your comments. To answer your points (not in order):

I suppose we do qualify as elderly (late ’60’s) – we certainly are hugely less tolerant of cold than when we were younger. At 20.5 we are comfortable (with sweaters on), but at 20.0 we are cold and are looking to see what’s gone wrong with the heating! By 21.5 we are casting off the sweaters. TRV’s are indeed useless for this fineness of control for the reasons that you say.

We don’t need zone heating, because (a) we are in a bungalow and don’t suffer from the flight of hot air up the stairwell, and (b) we have a separate, enclosed gasfire in the lounge. A single wireless programmer for the rest of the house is fine. But we have had to experiment with its location, eventually settling on the main bedroom as being best.

Re bedroom temperatures overnight, we both often need to get up a couple of times per night these days, and doing so at 16 degrees certainly feels cold enough! Re dust mites, those in the bedding will be warm at night whatever the room temperature, so it’s just important to let the duvets & pillows air and cool in the daytime. Also they get a good chilling when we are away, which is quite often. In any case we, like most people born in the 1940’s, don’t have allergies!

Sorry Bob. I assumed that you were younger and exploring the science of the subject. I’m certainly familiar with the fact that many older people feel the cold.

Your body may be responding to the decrease in radiant heat when the heating switches off, so it could be more than just the small temperature difference you are measuring.

I agree that it is important to air bedding, which helps get rid of moisture.

Bob Seymour says:
7 March 2013

Wavechange – You’re absolutely right about the sensitivity to radiant heat. Our solution to that is, once the heating has achieved stability each morning, to turn down the circulating water temperature to the point where the pump keeps running most of the time. That way the radiators rarely go completely cold but keep a near-constant warm temperature. The boiler temperature is turned up again last thing at night so as to get a quick warm-up in the morning. In my previous house, with a more primitive CH system, I was able to add a relay into the electronics so that the room thermostat only affected the burner, not the pump (which then became only timer-controlled). This gave an extremely smooth and comfortable heating regime. I wish it were possible to achieve this automatically with our present Baxi Bahama 100.

I notice you mention in another thread, the buffer effect of internal walls. I have found it (as a physicist in a family of physicists) very difficult to convey to others the relationships between heat capacity, heat flow and temperature, and it’s very hard to have a meaningful discussion of heating systems without it. There must be scope for more public education in this area.

I may have guessed your age wrong, but it’s no surprise to learn that you are a scientist. 🙂

I’m very out of touch with heating systems but I don’t believe that CH designers are using proportional control valves yet, despite the introduction of modulators in boilers some years ago.

Domestic solar hot water and PV systems are certainly encouraging some people to understand more about how their heating and hot water systems work, though you and I are probably in the minority of those who have experimented with conventional central heating.

Bob Seymour says:
8 March 2013

Wavechange – Our present house (built 2000) has pretty much exactly the same overall heat losses as our previous house (built 1738). But the heat capacity, I estimate, is between 25-30% that of the old house. This means that the temperature here is much more volatile. It does mean that it is very worthwhile turning the heating off overnight, but the rapid cooling at night attracts comments about the supposedly poor insulation here. I have tried explaining via the leaky water cistern analogy, the kettle size analogy, and the equation temperature change=net heat applied/heat capacity without much success. A significant comment is that if the heat capacity of a house is so important, why is it not given in the house efficiency rating? To which I have to agree. It has a big effect on how you should drive your system.

Has anybody else experieced this on winter evenings:If the outside temp.is say 3-5 degrees C outside and the lounge temp. is a steady 20 degrees C one feels comfortable but if the outside temp. is say minus 3 degrees C or below and the lounge temp. is again 20 degrees C one can feel cold. This raises the question:.Is the body sensitive to the rate of heat loss from the room as well as the actual the temperature.(We have a lounge wall thermostat and a thermometer on the coffee table! ).

I find this occasionally. I wonder whether it is cooler air near floor level rolling down windows and walls. Worth putting the thermometer low down to see whether it is temperature and/or air movement.

The temperature in different parts of a room varies because in the absence of fan circulation (and draughts) all that is circulating the air is convection currents. Radiated heat also affects our temperature and perception of temperature, which is why it is possible to feel very warm sitting in a cold room in front of a fire or beside a radiator. Likewise air movement, as suggested by Malcolm, is a factor.

The walls of a room act as thermal buffers, taking time to become warm and to cool, so a wall thermostat is not just affected by room temperature. Domestic thermometers typically have a slow response time, so if you want to study variation in room temperature a platinum resistance thermometer or thermocouple is more useful. These can respond much faster to temperature change.

Humans will quickly detect when the central heating has shut down in the evening, usually before a temperature change registers on a thermometer. Our immediate response to changing temperature is amazing and even a cold house will seem very warm after being outside in freezing conditions, albeit not for long.

George, Loughborough says:
9 March 2013

Based on the request for experiences with wireless thermostats (movable) in the magazine, below my experience with our heating system;

Our system: boiler fed underfloor heating in kitchen (tiled floor) with fixed, programmable Honeywell thermostat.
radiaters in rest of house with TRV’s on a movable honeywell wireless programmable thermostat. Usually located in living room.
recently replaced boiler (condensing). House built 1998, extended, well insulated.

A few observations:
replacing our 15 year old boiler (parts not available) has given us higher than expected savings. Apart from the efficiency, I expect this to be related to our underfloor heating which is seperate and when it runs only uses little of the hot water (mixer valve) to keep steady. That means our old boiler (on/off only) was cycling while the new one modulates very well.
Though we used to drop the kitchen by 3 degrees at night I stopped this in winter as the delay of the system is very long (2 hours for full warmup) due to the thermal mass. Comfort has improved and we love the comfort of the tiles not being cold. We run it at around 19 in the day and 20 evening, given that underfloor heating requires a lower set temperature for comfort.

The rest of the house is set back to 17 automatically overnight and raised to 19 when we get up. This sorts out the bathrooms etc to comfort level (as these have higher capacity radiators with TRV’s they go above the living room setting. We raise the temperature in the living room manually to 21 when we move there in the day or evening (we have a large dining kitchen where we spent a lot of time in the day). The programme sets it back in the evening in case we forget.
The movable thermostat has been great. No problems with delays (as reported in a mail above). within 20 seconds it stops or activates the system.
Also when for a period we did not use the living room but a different room instead, we just moved the thermostat and reduced the TRV’s in the living room.
Control of temperature in the rest of the house by the TRV’s works best when we reduce radiator capacity a bit in the living room. This means the pump runs more constantly giving the TRV’s the heat to play with. It takes a bit longer for the living room to heat up, but it gets there on time. With the kids studying and gaming in their room their room temperature is well controlled by the TRV’s.

In summary: very happy with boiler fed underfloor heating (self installed when extension was built) and with the two thermostat system and with the movable thermostat.

Mike A says:
9 March 2013

We have a boiler timer (which we use), a (portable) wireless thermostat located in the hall, and thermostatic radiator valves everywhere except the hall – and the whole system works fine.
Your expert was absolutely wrong to state that the thermostat should always be located in the living room.
I used to think that and at one time, that’s where our thermostat was located before I moved it.
But, after we had a new better-insulated patio door fitted in the living room, we found that, while that room stays warm, the rest of the house is cold because the thermostat has cut off the heating.
This is a particular problem when (a) the sun is beaming into that room (eg on a winter day) and (b) when the curtains are closed, the lights (at least 200W) are on, and there is a group of people in the room (each emitting ~300W).
We have had the same wireless thermostat for at least 10 years and it is absolutely reliable.
The sensor unit is still operating on the original set of batteries. I started out thinking I would move the sensor unit around the house, but found that unnecessary.
When the boiler was upgraded 3 years ago, I turned down the option to change the timer to a new fangled electronic unit, on the basis that my wife would outlive me, and she would never fathom out how to use it. So the timer is a simple, old-fashioned mechanical unit which is very easy to understand/use. However on the last service visit, the engineer said we would never be allowed to fit such a unit these days. The timer controls radiator heating and water heating separately, and we have a thermostat on the hot water cylinder.

ChrisP says:
10 March 2013

When I had my old bolier replaced by a new combi boiler, I had my plumber fit two programmable thermostatically controlled motor-valves to separate the upstairs and downstairs radiator loops. (The radiators already had thermostatic valves.) We can now have the heating on downstairs during the day or evening without having any hot water circulating upstairs. The bedrooms are warm enough for us when we go to bed because of heat “leakage” due to convection. In the morning we have the bedroom radiators come on before the downstairs radiators, so saving even more money.

MartinW says:
10 March 2013

Comments for use of portable thermostats.
We inherited a new Combi boiler for an extended 3 bed semi, built 1958 with 300mm insulation in roof and cavity wall insulation (Note: if like us you have cavity wall filled with Rockwool we are unsure if this has settled with time to around half the wall height in less than 10 years. Therefore looks like we shall require a top up. Anyone have any similar experiences?).
Also we were unsure if a Combi was the best solution for a family house and we found that use of a shower which operated via the combi took a long time to warm up. Also the boiler hot water heat exchanger regularly got blocked even after powerflushing. Solution was eventually to change to an electric shower and to extend the 22mm pipes to a longer distance from the boiler. It was only around one metre in 2005 and we extended it closer to 7m for both out and return pipes and haven’t had an issue since.
We had an overhaul of the central heating systemwhen we moved in (2005). We put thermostatic on every radiator bar one (in the lounge/diner where we spend most of the time) and installed a portable wireless thermostat / programmer (Drayton RF3). Previously the thermostat was in the hall. In our opinion this works really well as we can have the thermostat in whichever room we are in and adjust it accordingly. So at night when the children go to bed it is taken upstairs to one of the bedrooms (usually the one that faces north) and kept at 18/19C. The programmer brings the central heating on in the morning to heat up the bedrooms (if necessary) to 18C. It is then taken downstairs to be used. The portability is also very useful if anyone is ill as you can keep it in their room and they can call for more heat if required, rather than having to get up and change it. As other people have done we have adjusted the TRVs so that 18C upstairs is around 20/21 downstairs. Took a bit of time but now works well. Tend to keep rooms seldom used on lowerTRV settings which can be adjusted when necessary. Only issue we found is the Drayton RF3 only adjusts temperatures by 1C where 0.5C may have been more useful for energy efficiency. Usually keep it well away from radiators and other heat sources. Next step when resources allow would be to have separate radiator loops like ChrisP.
Like Mike A we find the heating cuts off and can keep the rest of the house colder if the sun is shining into our south facing lounge/diner. However, since most of the time is spent in that room is we do not see it as so much of a problem.

John Thompson says:
12 March 2013

I have had central heating for many years now in our three bed semi and a while back when I was working a friend who lived fairly close asked how much we paid for our gas. We have houses of similar layout and size.

This friend had her heating on a timer that fired the boiler up twice a day. A couple of hours in the morning and three or four in the evening.

We, on the other hand, had a fixed thermostat in the hallway set at 21 degrees C and left the heating on all day.

My philosophy is that to run your heating twice a day means the boiler is working flat out trying to warm the house to the set temperature. Ours only has to come on periodically to maintain a constant temperature.

We used to get our hot water from a separate multi-point gas water heater that gives you an unlimited supply of hot water.

On top of this we close our curtains when it gets dark and tuck them in behind the radiators so the heat stays in the room

We compared gas bills and found that ours was a lot cheaper.

Recently we had a new combi boiler and new radiators with thermostatic valves set at three fitted. The boiler came with a ‘portable’ thermostat/timer/programmer that is now standing on the top of the previous thermostat in the hallway.

We tried running the house with a lower temperature at night but just one degree lower made the house feel really cold.

It is quite difficult to say if the combi boiler is cheaper to run as the prices keep going up and usage levels are difficult to obtain from the complicate bills.