Keeping the boiler on all the times saves gas?

[agbagb]

Nigel, If it's just the PCB that goes, have you tried geting a refurbished ones? We had an ideal Isar that kept on going until I got refurbished one, they repaired with higher spec components than the manufacturers and it out lasted all the other bits thats started failing. It was about 20% the cost a new one as well.

If repairs are cheap enough and not too frequent, I would keep on nursing it through until it really needs replacing. It's not worth replacing just for the energy saving especially as a new boiler will need repairs as well after a years.

£800 for a flush I think you need a different plumber.

 

[Flyfisher]

Indeed. And of course, there is nothing altruistic about improving energy efficiency, even ignoring the embedded energy of installing kit. Jevons paradox takes care of any carbon we have saved, to ensure that our energy consumption will go up, as society becomes more efficient. Its only worth it if we save money.

Although from a purely green perspective, I suspect there's no overall benefit to the environment if we only go and spend the money we save on heating on something else anyway.

Another factor is the relative temperature. If you want it 10C hotter inside than out, then you will be constantly burning more fuel than if you wanted it 5C hotter. And at night (when in bed), when the outside temperature is lower, and one usually has the heating off, the boiler would be working particualrly hard if it was on 24/7.
[snip]
If anyone has any decent evidence for either way, it would interesting.

I've often wondered if the relative temperature thing could be the most significant factor when it comes to energy saving?

Yes, decent evidence is always interesting but seems hard to find for this particular issue.

 

[Flyfisher]

I had a brand new house in 2006 with zoned heating. There was a thermostat in the hall and the other unit was directly above on the small landing. The problem was that heat from downstairs rose to the landing and kept triggering the upstairs unit to turn off. I had to set the temperature range somewhat higher so it continued to heat the bedrooms, one of which was 25ft long with an en-suite at the end (regularly cold). Had I stayed there longer I would have moved the unit into this bedroom to control the upstairs temperature. Given how large your house is FF, have a good think as to where you position your thermostats.

That's very interesting. I've actually always been suspicious of thermostats in halls because I can't really see how thay can effectively control the temperature within each room - unless all doors are always open so there is just one large space perhaps? I'm planning to rely on TRVs to set the required temperature for each room - is this likely to be a problem?

As for zoning, my plan is to divide the house into at least two zones; one for the rooms we will normally occupy during the colder months (Kitchen, sitting room, one bedroom) and one, possibly two, for the other areas of the house that will be less frequently used. I envisage saving energy by only keeping the 'living zone' at a comfortable temperature and only keeping the chill off the other areas until they are being used. Having lived with no heating for the past few years I know there is a huge difference between completely unheated rooms and even a minor source of heat. Even a 200W electric towel rail can take the chill off an otherwise unheated bathroom (or perhaps it only feels that way when entering from an unheated bedroom with ice on the inside of the windows :lol: ).

Together with a boiler stove, a heat store and partial underfloor heating, it's all a bit experimental but I'm hoping this will be the first winter to yield some actual results - if I can get the heating contractors to get it all installed in time!

 

[LadyArowana]

I am conducting experiments on your behalf. Results so far. If I have the heating on the timer it gets a bit chilly. If I have the heating "always on" it gets a bit chilly. The heating system idea of 21 degrees is vastly colder than the airconditioner idea of 24 degrees. Further research will require investment in extra layers of personal insulation.

 

[wobs]

Indeed. And of course, there is nothing altruistic about improving energy efficiency, even ignoring the embedded energy of installing kit. Jevons paradox takes care of any carbon we have saved, to ensure that our energy consumption will go up, as society becomes more efficient. Its only worth it if we save money.

Although from a purely green perspective, I suspect there's no overall benefit to the environment if we only go and spend the money we save on heating on something else anyway.

Sorry yes, I was perhaps a little unclear.
If you save money, you do indeed spend it elswhere, thus putting money back into the economy.

What I meant was that its only worth it if you realise the financial benefit, and that's about the only benefit (unless your home was hopelessly cold beforehand). Its not alturistic at all.

One way to tackle this paradox is with carbon credits.

 

[agbagb]

That's very interesting. I've actually always been suspicious of thermostats in halls because I can't really see how thay can effectively control the temperature within each room - unless all doors are always open so there is just one large space perhaps? I'm planning to rely on TRVs to set the required temperature for each room - is this likely to be a problem?

I wouldn't use TVRs as the primary control. This should be done with a thermostat that switches the boiler off. Have the thermostat in the room you want the warmest and no TVR in that room. The radiators in the cooler rooms can have the flow turned down with the lockshield valves. If the rads are the right output in each room and everything being equal you should be able to adjust the flows so the boiler switches off when your warm room is up to temperature and the other rooms are a few degrees cooler.

You can then open up the lockshields to just give the max. temperature you will want occasionally in the cooler rooms. The TVR's can then be used then to bring the flow back down for the lower temperature without fully shutting off the flow. The balance will be thrown out as the TVR adjust the flow but not nearly as much as if they are used as primary controls (where you could have eg. 10 radiators running or just 1)

 

[JHD]

If the energy lost from your house as it falls from your desired room temperature, say 22oC, to the outside temperature is equal to the energy it takes to reverse the process, then the energy saving from turning your heating off is dependent on the amount of time it rests at the outside temperature. Therefore, if your house doesn't have time to cool to the outside temperature while your heating was turned off then no benefit can be derived. How long this takes will depend on the outside temperature, wind, and your house's insulation.

However, as boilers don't reach their peak efficiency immediately, you won't receive the energy saving benefit of your house sitting at it's coldest point immediately. How long you have to wait will depend on your boiler; the more inefficient it is, the longer you will have to wait.

So, in conclusion, it's impossible to say what your optimum heating strategy is without knowing (a) your desired room temperature, (b) outside weather condition,s (c) insulating properties of your house, (d) efficiency of your boiler, (e) times of day when you want the house to be at your desired room temperature, and therefore whilst in theory a timed thermostat can save you money, I think in reality they fail because users don't know some of the variables and their user interfaces are poor meaning that they tend to get set up once and then left for years.

What's needed are intelligent thermostats that learn how fast our houses cool, download weather forecasts from the internet, measure the outside temperature, monitor and learn our daily activity e.g. when we go to bed or to work, and measure the efficiency of our boilers.

 

[tobydog]

Coincidentally I have just been sent the link below from the guy who organises are oil buying syndicate - Bungay Buyers. He was so impressed with it that he's now bought it. It's called PassivSystems / PassivLiving Heat. It may have been mentioned on a previous thread but what do you think?

http://www.reducemyheatingcosts.com/

Dear Bungay Buyers
Over the summer I was approached by an innovative new company called PassivSystems that provided a product and service that caught my interest.
PassivLiving Heat is a professionally installed boiler control service that manages your heating.
I was sufficiently impressed with the system that I had it installed in my home.
There is remote control feature now provides me with a really easy way of controlling my boiler.. It has also connected my home to the nearest Met office weather station so I no longer program the boilers on/off periods, but instead I tell it what time I would like my home to reach a certain temperature, and it does the rest. The really neat feature is that because I am now in control wherever I am, I can now switch off the heating when I leave the house and reactivate it in time for a warm welcome on my return.
Customer feedback so far has shown that people with the system see an average reduction in energy use of 23% - with some customers reporting savings of up to 50%.
Because homes off-grid have some of the highest heating bills in the UK, PassivSystems is reaching out to local communities using oil and LPG this winter. And because we’re a buying group with buying power, they’re offering a significant discount on their system– 33% if you purchase before end of October Prices start from £499 with this discount.
Because I think this new technology could help with oil use, I’m going to keep you posted on my experience. Over the next few months I’m going to evaluate PassivLiving Heat based on control, comfort and cost savings. I am joined by three of our buying group members so we can also see what their experience is.
In the meantime, you can go to www.reducemyheatingcosts.com to reach their website where you can buy the product directly.
Barney Lodge

 

[Flyfisher]

Interesting idea, but contacting the nearest met office weather station (presumably over the internet) seems a bit of overkill when a simple external thermometer would surely do the same job?

 

[Flyfisher]

I wouldn't use TVRs as the primary control. This should be done with a thermostat that switches the boiler off. Have the thermostat in the room you want the warmest and no TVR in that room. The radiators in the cooler rooms can have the flow turned down with the lockshield valves. If the rads are the right output in each room and everything being equal you should be able to adjust the flows so the boiler switches off when your warm room is up to temperature and the other rooms are a few degrees cooler.

You can then open up the lockshields to just give the max. temperature you will want occasionally in the cooler rooms. The TVR's can then be used then to bring the flow back down for the lower temperature without fully shutting off the flow. The balance will be thrown out as the TVR adjust the flow but not nearly as much as if they are used as primary controls (where you could have eg. 10 radiators running or just 1)

I've never really understood the need for a 'primary' control, apart from the boiler thermostat that controls the temperature of the water in the system.

Isn't the basic concept to pump hot water around a circuit and allowing each radiator to 'tap off' however much heat it needs to warm that particular room to a temperature set by the TRV? If every radiator is controlled this way then every room can be set to a different temperature. When a room is up to the set temperature, that radiator will stop drawing heat from the circulating water.

If rooms are not up to temperature, they will draw heat from the circulating water and the return to the boiler will be below the output temperature, so it will burn fuel to make up the difference. When all the rooms are up to temperature, none of the radiators will draw any heat from the circulating water so the return temperature at the boiler will be the same as the output temperature and the boiler thermostat will shut down the boiler.

With this sort of scheme I don't see the value of a separate room-based thermostat - or am I missing something?

 

[88v8]

......none of the radiators will draw any heat from the circulating water so the return temperature at the boiler will be the same as the output temperature and the boiler thermostat will shut down the boiler.

With this sort of scheme I don't see the value of a separate room-based thermostat - or am I missing something?

The water in the boiler will cool relatively quickly and then it will switch on again, and then soon off again if none of the rads is calling for heat. Cycling in this way is detrimental to boiler life and fuel use.
Controlling the boiler by means of its thermostat seems to me akin to governing the speed of a car by holding the accelerator on the floor and switching the ignition on & off.
It's the sort of arrangement plumbers used to put in because they weren't capable of wiring up any meaningful control system. And perhaps still do :?

Ivor

 

[Flyfisher]

I see your point about short cycling (though only when every room is up to the TRV set temperature), but can't this be easily solved with suitable hysteresis in the boiler thermostat, i.e. turning off at (say) 80C but not turning back on until (say) 70C ?

Isn't the problem with a room thermostat that the selected room may get up to temperature before the other rooms and swicth off the boiler and, therefore, effectively cutting off heat to all the other rooms (well, not completely, but enough to prevent further temperature rises)?

Perhaps this is why system thermostats were typically located in hallways, as these could be the coldest areas of the house? Trouble is, if I do that here then the thermostat would probably never operate, in which case things would revert to the boiler thermostat anyway.

Hmm - tricky!


PS: Why should short cycling be particularly detrimental to boiler life - does boiler life really shorten slightly each time it is switched on? I can see the potential for using more fuel with condensing boilers not operating in their most efficient mode - but wouldn't boiler thermostat hysteresis help in this respect?

 

[Keithj]

I don't think I buy that "on and off" argument. My boiler has only one rate of heat production - let's call it "ON". Once all the rooms in the house are at the desired temperature, the boiler goes "OFF".

The only options are to keep it running all the time and dump the excess heat somewhere (maybe for collection later), or to turn it off when the house is up to temperature. Being a simple soul, I go for the latter. The boiler is 38 years old and still working. The local plumber services it once a year and sees no reason to change it. A neighbour opted to fit a condensing boiler, and tells me they last about seven years: I know which I prefer. Apparently if we fit a new boiler we can't put it where this one is, anyway.

I think the better car analogy is "start the engine when you want to go somewhere, turn it off when you get there."

 

[agbagb]

Turing the boiler on and off "cycling " will wear a modern boiler out quicker, valves, fan, pump, ignition, and thermal expansion/contraction of the all components. The hysteresis in the boiler will be pre-set but I don't know at what range. To avoid this boilers now modulate down try and match output to the heat load. e.g. 30kW max used when system is cold, when the rads heat up the burner turns down to try and keep the return temperature low enough to keep it in condensing mode, 30% of max = 10kW at its lowest.

When only one TVR is open on a radiator that is shedding 1kW the boiler will have to cycle 1:10. (time of this would depend on the boiler hysteresis). If that TVR then closes then the boiler will fire up just to heat water in the by-pass loop, burning for say .5 of second. So all your boilers parts switching on off hundreds of times more than with a balanced system with a room stat. (the room stat adds a large hysteresis to the system). The boiler will also spend less time at 90%+ efficiency and more at 75% non condensing, unless you have set the CHW temp really low (not very good for heating the house up when you need it to)

Its asking a lot of system to perform well in the extremes, from heating from cold in the depths of winter to just keeping the chill off in the spring. TVRs on an unbalance system throw more variables at the problem.

Old boilers only have a simple gas valve to operate when cycling and a large thermal mass that lengthens the on - off periods, hence they tend to last for years/decades. But they may only be around 60% efficient. The calculation to replace could be a 30% energy saving V. a new boiler every 5? 7? 10? years + parts.

 

[Keithj]

Interesting.

My heating has one loop (the hall downstairs which also serves the stairs and effectively the upstairs hall) which does not have a radiator thermostat. The house stat is in the hall. Our plumber insisted that it's important to have one "open loop" like that.

There is something like 3 degrees of hysteresis in the hall thermostat, and more than that in the water stat - the gauge shows anywhere between 60 and 70 degrees during the day when it's on. When the boiler fires up, it usually runs for several minutes before shutting down again. It's not a condensing boiler, I'm happy to say: I couldn't afford to replace it every few years. Even if it is a few percent less efficient, I doubt the better efficiency would pay for the new boiler before it needed replacing again. It's also very old, so seems not to mind how many cycles it goes through.

 

[88v8]

Ah yes, endless variations, each system is unique, and the usage and living patterns.

In the average house - not perhaps what PPFers inhabit - if the system is properly designed in terms of the rad sizes in each room - and of course the rad positions; under or near with windows, not behind furniture, and no curtains covering them - then the single room stat, usually in the hall so it's not influenced by open fires, will adequately control the temp so that when the stat switches each room will be at its designed temp.

This needs the heat requirement for each room to have been calculated, not just vaguely guessed, which take time. So, installers make an estimate, perhaps based on experience, and then use TRVs as a prop to correct their errors. Some regard TRVs as a cop-out and a poor substitute for designing the system properly, I couldn't possibly comment
In the system I designed and installed in 1982 - still in use in 2012 and now for all I know - the hall and all rooms had a target temp of 65F, with the exception of box room 60F, sitting room and bathroom 70F. All rooms had doors, which were usually closed, and those temps were achieved although in practice we ran it nearer 60F and wore a wooly.

As an aside, it was jolly difficult in the early 1980s to find second-hand cast-iron rads of the correct relative sizes so that each room had the correct output. There is only so much one can do to balance an oversized rad with the lockshield valve.

The heating and water were separately controlled, and the water fully pumped. In the bathroom there was an open loop which fed the heated towel rail and one rad so the towels dried even in spring & autumn when the heating wasn't on.

On weekdays, we set the Landis programmer so that only the heating came on the morning, this gave a quicker warm-up. The water coil takes about 15,000 btu which is a large chunk of boiler output and there is no point in heating the water if you're going to be out all day. The water heated up in the evening and stayed hot through next morning.
On the water cylinder we had two stats, one a third up from the bottom, one a third down from the top. In the kitchen there was a changeover switch to select the stat, and the effect was that we could heat half a tank, which in practice was plenty 99% of the time, or a whole tank if we were both going to want a bath. Not heating a whole tank unnecessarily saves a good deal of money.

The boiler was a simple non-condensing non-computerised design and completely reliable. It was replaced with a larger one, also simple design, when we extended the house in 1991, and that was fine when we sold it (boohoo) despite never being professionally serviced in 21 years. In a simple balanced flue boiler, there's nothing to service. Thankyou to agbagb for so eloquently describing all the superfluous junk that forms part of a modern boiler, rather like a modern car
Fitting a new boiler for the sole purpose of efficiency/saving money is a dead loss - a new boiler is going to be £3k+ plus all the H&S b***x, that could be invested at 5% so that's £150 per annum lost and all the capital, when one works it out the payback time on a new boiler is never.

Now we have woodburners, and storage rads which of course are on 24/7 :shock:

Ivor

 

[Flyfisher]

It seems to me that the more detail I go into the more confusing it all becomes. No wonder people just go with rules-of-thumb and then just live with the results.

I'm beginning to think that simple fires have a lot going for them. If you're cold, just light a fire!


Incidentally, 'PPFers' is an interesting acronym I've not seen before . . . . . . :lol:

 

[Keith Bowman]

....... a new boiler is going to be £3k+ plus all the H&S b***x, that could be invested at 5%......

Ivor

URGENT. PLEASE SUPPLY DETAILS OF INVESTMENTS YIELDING 5% ON £3K

 

[88v8]

....... a new boiler is going to be £3k+ plus all the H&S b***x, that could be invested at 5%......

Ivor

URGENT. PLEASE SUPPLY DETAILS OF INVESTMENTS YIELDING 5% ON £3K

Example shares...
Admiral (ADM) current dividend yield c7% tax paid.
Catlin (CGL) 6.3%
Amlin (AML) 6.2%
Astra Zeneca (AZN) 5.7%
National Grid (NG.) 5.5%
SSE 5.4%
ICAP (IAP) 5.4%
etc etc

And then there's bank preference shares
Aviva (AV.B or AV.A) 7.1%
Bristol & West (BWSA) 7.9%
Ecclesiastical (ELLA) 7.5%
General Accident (GACA or GACB) 7.3%
Lloyds (LLPC or LLPD) 7.6%
Natwest (NWBD) 7.6%
RSA (RSAB) 6.6%
Standard Chartered (STAB or STAC) 6.6%.
etc etc
all tax paid for a basic rate taxpayer.

In an entirely amateur capacity, I hold many of these.
Your capital is at risk with this type of investment.

Ivor

 

[worms]

....... a new boiler is going to be £3k+ plus all the H&S b***x, that could be invested at 5%......

Ivor

URGENT. PLEASE SUPPLY DETAILS OF INVESTMENTS YIELDING 5% ON £3K

Example shares...

But that ignores broker's charges. The switch to nominee holdings was such a bad move!