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Which is cheaper-Turn up Boiler or crank up thermostat?


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Old 01-12-2009, 12:00
The Wizard
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Which one of the two is better if you want more heating and which is more economical?

What I'm really asking is, which uses more gas. Do I turn my boiler up so the water comes through alot hotter alot quicker or turn the thermortat up so it warms up slower?

I'm inclined to believe that it's more economical to turn the boiler up and get the rooms up to temperature as quickly as possible than leave the boiler running while it warms up slowly, however I could I'm not sure be wrong. Which is the cheaper option.
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Old 01-12-2009, 12:22
Keefy-boy
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either way you are heating the same volume of air to the same target temperature. my guess would be that either way it will require the same amount of energy to do that.
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Old 01-12-2009, 16:13
Shrike
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Try putting on a jumper.
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Old 01-12-2009, 16:14
!!11oneone
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I found that turning the boiler up made the radiators too hot, so although it warmed the rooms up quicker it was effectively wasted because the rooms got uncomfortably hot and remained so for ages.

Plus it can make your tap water dangerously hot, so be careful if you have children or an elderly relative using them.
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Old 01-12-2009, 16:45
IWantPVR
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Turning up the main thermostat means the house will heat up at the same rate but will get hotter than needed, especially if there are radiators with no individual thermostatic radiator valves on them.

Turning up the boiler means the house will get hotter quicker but when the main thermostat kicks in to stop the boiler, each radiator and all of the pipes will be full of much hotter water which will continue to heat the room to slightly above the set temperature.

Turning up both means the house will get hotter than needed and it will get there faster too.

Best to leave it alone or just set the boiler to about 70% and the thermostats to the right temperature for the house/room. Then, if you want a faster heat-up, set the boiler a bit higher.

The first three options above will cost you more in fuel as opposed to leaving it alone but if you really feel the need to change something, turning the boiler up a bit should be cheaper than increasing the other thermostat(s).
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Old 01-12-2009, 17:26
flicker
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This is a subject which interests me too. I have an outdoor Combi boiler, runs on oil here. The dial doesn't have numbers to control the water temp, just a narrow to wide band. Now I found that the tap water was too hot so I turned it down to the lowest setting, but when the guy came to service it last week, he said that the dial only affected the temperature of the radiators, not the tap water???

Is that possible? Because now it is turned up to the hottest, the rads are a lot hotter, but I swear that so is the tap water. Surely the water flow is going to both the taps and the rads?
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Old 01-12-2009, 17:34
The Wizard
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I found that turning the boiler up made the radiators too hot, so although it warmed the rooms up quicker it was effectively wasted because the rooms got uncomfortably hot and remained so for ages.

Plus it can make your tap water dangerously hot, so be careful if you have children or an elderly relative using them.
Our boiler has a seperate feed and temperature guage for water and heating. I never touch the water however I notice in winter it takes longer to run before it gets hot. It's a combi by the way and rad stats are fitted on all radiators too so these are turned down in rooms which we don't use very often like the office and the bedroom which gets hot cos the door is always shut.

The places we feel we need most heat is in the hall cos we lose heat when we come in and out and the kitchen which only has a small 400mm radiator behind the door. For some reason they installed a single panel rad in the hall which is the coldest room in the house so we turn the rad stats down in the warmest rooms.

My dad told me to set the temperature according to the coldest room in the house and turn the rad stats down in the other rooms to suit.
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Old 02-12-2009, 10:33
IWantPVR
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This is a subject which interests me too. I have an outdoor Combi boiler, runs on oil here. The dial doesn't have numbers to control the water temp, just a narrow to wide band. Now I found that the tap water was too hot so I turned it down to the lowest setting, but when the guy came to service it last week, he said that the dial only affected the temperature of the radiators, not the tap water???

Is that possible? Because now it is turned up to the hottest, the rads are a lot hotter, but I swear that so is the tap water. Surely the water flow is going to both the taps and the rads?
An oil combi? Really? Does it feed hot water to the taps direct from the boiler or do you have a separate hot tank which does that? One temperature control suggests one hot feed to the radiators only. That wouldn't be a combi.

Usually a non-combination boiler just provides hot water at one temperature setting which mostly goes to feed the rads. Some is diverted to the house hot water tank, usually an immersion cylinder, and passes through a heat exchanger which allows some of the heat from the dirty CH water to transfer into the clean water in the hot tank.

The cylinder will usually have a thermostat and a motorised valve and when the water in the tank reaches the pre-set temperature, the motorised valve is closed and the hot boiler water no longer flows through the heat exchanger.

An immersion cylinder also has an electric element to heat the water when the boiler is off. I'll assume that isn't in use as the boiler is on. Therefore, the clean hot water can never get to a higher temperature than the CH water.

If the hot thermostat is set higher than the CH temperature, or the motorised valve is stuck open, your hot water temperature will be closely tied to your CH temperature.

If everything is working as it should be and the boiler is set higher than the hot thermostat, the hot temperature shouldn't exceed that on the thermostat.
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Old 02-12-2009, 10:54
flicker
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An oil combi? Really? Does it feed hot water to the taps direct from the boiler or do you have a separate hot tank which does that? One temperature control suggests one hot feed to the radiators only. That wouldn't be a combi.

Usually a non-combination boiler just provides hot water at one temperature setting which mostly goes to feed the rads. Some is diverted to the house hot water tank, usually an immersion cylinder, and passes through a heat exchanger which allows some of the heat from the dirty CH water to transfer into the clean water in the hot tank.

The cylinder will usually have a thermostat and a motorised valve and when the water in the tank reaches the pre-set temperature, the motorised valve is closed and the hot boiler water no longer flows through the heat exchanger.

An immersion cylinder also has an electric element to heat the water when the boiler is off. I'll assume that isn't in use as the boiler is on. Therefore, the clean hot water can never get to a higher temperature than the CH water.

If the hot thermostat is set higher than the CH temperature, or the motorised valve is stuck open, your hot water temperature will be closely tied to your CH temperature.

If everything is working as it should be and the boiler is set higher than the hot thermostat, the hot temperature shouldn't exceed that on the thermostat.
Hi thanks for replying. The boiler I have is this one -
http://www.grantuk.com/userfiles/download_27.pdf

I don't have an immersion tank, the water comes straight off the boiler to the kitchen taps, and then up through the ceiling across the loft to all the various rads and bathroom taps. That to me would seem that the temp of the water in the taps would be the same as the rads, so I wonder if the bloke knew what he was talking about. It's a bit technical for me though, so maybe you can tell from the spec. It's not vital, just something I wondered about and of course which option is the cheapest, like you've already explained elsewhere. Each of my rads has it's own thermostat, and I leave the controls on 24/7 but just turn the master thermostat dial in the hall to turn everything on/off/hotter etc.
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Old 02-12-2009, 14:04
IWantPVR
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Hi thanks for replying. The boiler I have is this one -
http://www.grantuk.com/userfiles/download_27.pdf

I don't have an immersion tank, the water comes straight off the boiler to the kitchen taps, and then up through the ceiling across the loft to all the various rads and bathroom taps. That to me would seem that the temp of the water in the taps would be the same as the rads, so I wonder if the bloke knew what he was talking about. It's a bit technical for me though, so maybe you can tell from the spec. It's not vital, just something I wondered about and of course which option is the cheapest, like you've already explained elsewhere. Each of my rads has it's own thermostat, and I leave the controls on 24/7 but just turn the master thermostat dial in the hall to turn everything on/off/hotter etc.
Sure looks like a combi from those details but I'm no expert. Seacam may be along with more details. You wouldn't want to shower in the water which circulates around your radiators, so there has to be two hot feeds from the boiler, one to the rads and one to the taps.

It certainly has an expansion tank which is used to store a small quantity of pre-heated hot water to allow a quicker response when you turn on the taps. It's a bit like keeping your kettle on the boil all day.

It's potentially wasteful if you don't use hot water 24 hours a day as a lot of the heat you put in there is constantly leaking away and the boiler will have to fire again to keep it hot. You may have a timeswitch which causes the expansion chamber to only be heated certain hours of the day and left cold for the rest.

Could this answer why the hot water runs hotter when the CH is running?

The other possibility is that the water in your HW pipes is being heated by the CH flow pipe as they pass alongside each other on the long run from the outhouse. I have a combi in an outhouse and get almost instant warm water from my hot tap on a morning when the CH has been running! It then runs cold before getting hot again when the water from the expansion vessel finally gets through!

Anyway, if adjusting the boiler temperature to influence the HW temperature works for you then that's fine. As you have thermostats on everything else it shouldn't significantly cost you any more or less in fuel for the CH. It will just mean the radiators get the rooms up to temperature that bit faster or slower.
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Old 02-12-2009, 17:01
flicker
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^^^
Okay, ta muchly. I think I understand.
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Old 04-11-2013, 00:36
richardc1983
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Some professional advice for you here regarding efficient running of a modern condensing boiler system...

Having the flow temp (how hot the radiators feel) set higher means that the rooms will warm up faster. If your comfortable at e.g 21C setting the room thermostat higher e.g 30C WILL NOT mean the rooms warm up any faster as the temperature still needs to get 21C first. Only the flow temp of the radiators will affect how quick the rooms warm up to the set temperature on the controller or the thermostatic radiator valve (TRV).

Modern condensing boilers are most efficient when the return temperature back to the boiler is no higher than 55C. E.G if your flow temp (from boiler to the radiators) is 80C its very difficult to get that differential. Having your flow set no higher than approx 65C should see the return temp (from your radiators back to the boiler) and your boiler will go into condensing mode which is when your boiler is running most efficient. You also need to make sure your radiators are balanced properly and have the correct flow.

How to balance your radiators: http://www.homebuilding.co.uk/advice...ance-radiators - your looking for 12C difference on older boilers (non condensing) or as close to 20C as you can on modern condensing boilers.

Another efficiency feature on many of the newer higher end boilers have is something called load compensation/weather compensation which works by calculating the difference between outdoor temperature/room temperature against the set temperature. E.G if the room temp is reading at 16C and you have set the room thermostat to 21C when the system first turns on it will automatically set the flow temp to be high so as to warm the house up quickly, as the room temperature approaches the set temp on the room thermostat it automatically reduces the flow temperature to a much a lower temperature to maintain the set temperature. It is more efficient to keep the boiler running at a lower temperature maintaining the set temp than it keep turning on/off all the time and heating the radiators up from cold to hot for the set temp to overshoot meaning the boiler turns off completely. You don't have the temperature fluctuations or walk into a room and it feel stifling because of a high flow temp.

If you don't have the above feature on your system or you have an older boiler, whatever type you have you can do this yourself manually by turning the flow temp to high when you are warming the house up from cold and once the house gets warm and up to temperature turn the flow temp to as low as you can that will maintain the house at a nice background temperature you have set on the thermostat. You may have to play around with this and learn your system and how your house heats up to get it spot on as each house is different. A large old un-insulated house will not hold heat so your always going to have to run the radiators at a higher temperature just to maintain comfort so this will cost more so in this situation timed is better than constant. You will have to try it for yourself and see your results.

I do this in my house and I actually leave the system on constant. The flow temp is about 45C and the room thermostat in the hall is set at 19C (during day and at night)-19.5C (when in the house and evenings) the system runs probably about the same time as if it was on timed except the house is warm constantly and at a nice even temperature. There is always someone at home and I have tried both methods of having it on timed/constant and leaving it on constant actually saves money because we are running the boiler at a lower flow temperature to compensate. This means the house isn't cooling down to low temperatures so the boiler is just ticking over rather than having to come on and blast the house up to temperature which can take a while and the house still feel cold because all the walls, furniture and furnishings absorb that heat and have to come up to temperature also. Remember don't abuse the room thermostat and be sensible with it.

Here is an article about the above points I have just mentioned...

http://energy-surprises.blogspot.co....ng-boiler.html

Hope that helps
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Old 04-11-2013, 00:36
richardc1983
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Also just realised this post is from 2009! Oh well!
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Old 04-11-2013, 01:00
mred2000
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Also just realised this post is from 2009! Oh well!
Well, you must've searched for it just to post your advice...
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Old 04-11-2013, 01:02
richardc1983
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Well, you must've searched for it just to post your advice...
No I was sent the post by someone in my family asking for my opinion on it. It was only after I replied that I saw the date.
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Old 05-11-2013, 08:45
The Wizard
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Hi Richard. Thanks for resurrecting my thread as it's that time of year again. There's some real sound advice there. Whilst my home holds heat, the hall where the thermostat is situated doesn't and rarely gets hot enough to click off the boiler, so running the flow temp at a low setting meant that the wall stat would never shut off because all the heat was disappearing up the stairs so my heating was not only on constantly but was also taking ages to get up to temperature. Ideally we could do with another radiator in the hall but it's not possible. Because of this I decided to turn my boiler up so that the radiator in the coldest part of the house is now red hot and the house warms up a lot faster. Then if say the lounge gets too hot I can always turn it down on the radstat. I've found that this is the quickest way to get the house up to temperature. Although this still hasn't really answered my original question which is to do with costs.

Is is more expensive to heat the house up quicker by having the flow temp turned up high or have the flow temp low and let it gradually come up to temperature slowly?

I decided that one long burst of red hot heat followed by occasional bursts would possibly be more economical than having it running constantly on a lower flow. It's also more convenient if you want instant hot rads and if you want to get the house up to temp quicker but I have no idea if this is costing me more money to run it like this but it's certainly more comfortable and more convenient.

The flow temp on my boiler is set to 75. I tried setting it to 65 but at that setting the temperature in my hall wasn't managing to go higher than 19 and my roomstat is set to 21 so it was running constantly. If I turned the roomstat down to 19 it clicked on and off ok but the rest of the house wasn't warm enough. So the only option was to turn up the flow temp on my boiler so that it got warm enough to heat the hallway to a comfortable 21 and now the thermostat in the hall clicks on and off and is no longer running all the time.
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Old 05-11-2013, 09:03
IWantPVR
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Great info Richard. What's the simplest tool for checking that you have a 20 degree drop accross a radiator? I assume that's checked with the room at target temperature and the trv fully open?
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Old 05-11-2013, 10:37
The Wizard
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The main reason that our hallway is so cold and the radiator is having to work twice as hard is because our kitchen is just off our hallway and we have a flat roofed extension just off that which we use as a utility/wash room. There is only one small radiator in the kitchen which is a meager 90mm x 900mm and our utility room which is situated off the kitchen isn't heated at all so that one piddley little rad is doing nothing. Because of this we have to keep the kitchen door open so the heat from the hallway helps to compensate for the inadequately heated kitchen. If we keep the kitchen door closed we don't have to turn the boiler up as much as the heat in the hallway is retained but then the kitchen is freezing and the utility room starts suffering from dampness and condensation.

Ideally we could do with another radiator in the kitchen/utility room but that would mean major work and possibly ripping out the kitchen units to do it. We considered fitting an electric oil filled radiator but running one of those can be ridiculously expensive.

I've got a guy from our housing association coming to see me next week about dampness and condensation in our utility room where they've built the flat roofed extention. I have a feeling they've neglected to install any damp course or cavity wall insulation which wont be helping the situation.
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Old 05-11-2013, 10:48
richardc1983
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Cheapest way is turn boiler up to max to get the rooms upto temp then manually turn the flow temp down to as low as will hold the rooms warm at and run it or longer less cycling off ok the room stat. As stated in my post most modern boilers do this automatically. If your room thermostat cycles off you can turn the flow temp down a bit lower. If this is too much like hard work then your going to have to find a compromise between efficiency and warm up times. It's not much like hard work though as you learn how your system responds etc so you get used to it. Your aim is to not let the room stat cycle off but hold as close to the set point as it can while the rooms remain warm. Less cycling means less work for the boiler to bring the room back upto temp.

Balancing the radiators is done by all trvs fully open or removed from radiator so they don't affect your measurements. All the lock shield valves fully closed then do a radiator at a time you open approx 1/4 of a turn open and then measure the temp with an ir thermometer from amazon for about 9 you measure at the inlet and outlet pipe of the radiator and you get as close to the temp drop as you can. The lock shield valves are fully open after about 1.5 Turns from closed so it's better to start with those closed than open as they are so close to been fully open anyway. Most of my radiators are 1/4 turn open and 1/2 turn open with the smallest ones 1/8 open or 1/16 open.
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Old 05-11-2013, 11:17
The Wizard
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So you would say that keeping the flow at a rate that keeps the temperature constant just slightly under the roomstat temperature so the thermostat doesn't cycle on and off is better than having it getting hot then clicking off repeatedly? Although I appreciate it's less stress on the boiler, I would have thought that keeping the heating running constantly would be more expensive than allowing it to go on and off but if that's the case I'll turn it down a bit and see how I go on.

Maybe then it's a good idea to turn up the boiler to max to get the rooms up to temperature as quickly as possible then say after half an hour to an hour maybe throttle it back so that it's not cycling on/off.

I have radstats fitted but the one in the downstairs bedroom doesn't seem to work properly. I've fitted a new one but I'm still having the same problems. Basically it's either on or it's off. If I turn the radstat down to 3 it's still just as hot as it is when it's set to 5 but when I go below setting 3 to setting 2 the radiator is barely tepid. It's either red hot or luke warm so because of this I always leave it on 5 but then the room has a tendency to get too hot. If I turn it to 3, it's still too hot. Turn it down to 2 and it's too cold. As this is a new replacement radstat have you any ideas why I'm having this problem? I've had an engineer out and he's balanced all my rads but some still seem to be getting hot quicker than others. If they restrict the flow too much I get an annoying hissing.
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Old 05-11-2013, 12:16
oulandy
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The main reason that our hallway is so cold and the radiator is having to work twice as hard is because our kitchen is just off our hallway and we have a flat roofed extension just off that which we use as a utility/wash room. There is only one small radiator in the kitchen which is a meager 90mm x 900mm and our utility room which is situated off the kitchen isn't heated at all so that one piddley little rad is doing nothing. Because of this we have to keep the kitchen door open so the heat from the hallway helps to compensate for the inadequately heated kitchen. If we keep the kitchen door closed we don't have to turn the boiler up as much as the heat in the hallway is retained but then the kitchen is freezing and the utility room starts suffering from dampness and condensation.

Ideally we could do with another radiator in the kitchen/utility room but that would mean major work and possibly ripping out the kitchen units to do it. We considered fitting an electric oil filled radiator but running one of those can be ridiculously expensive.

I've got a guy from our housing association coming to see me next week about dampness and condensation in our utility room where they've built the flat roofed extention. I have a feeling they've neglected to install any damp course or cavity wall insulation which wont be helping the situation.
If you could replace the radiator in your kitchen with one that gives a greater heat output, no major work would be required. I did this in my bedroom and it made a big difference.
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Old 05-11-2013, 12:40
richardc1983
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So you would say that keeping the flow at a rate that keeps the temperature constant just slightly under the roomstat temperature so the thermostat doesn't cycle on and off is better than having it getting hot then clicking off repeatedly? Although I appreciate it's less stress on the boiler, I would have thought that keeping the heating running constantly would be more expensive than allowing it to go on and off but if that's the case I'll turn it down a bit and see how I go on.

Maybe then it's a good idea to turn up the boiler to max to get the rooms up to temperature as quickly as possible then say after half an hour to an hour maybe throttle it back so that it's not cycling on/off.
.
That's exactly how it should be ran. Max temp to get it warm then gradually turn it down as the house keeps warm. It's gonna take trial and error as each home is different but you will learn "how your home heats up" then have it perfected.

You not keeping it running constantly your only running the pump for longer which they are designed for.

No idea about your trv sounds faulty to me have your tried taking it off. You could regulate the temp of this rad by using the lock shield valve and having it so it doesn't get too hot but when you turn the boiler down the whole house should keep warm anyway and no hot/cold spots.
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