# Trying to reduce my oil usage



## guernseyguy (2 Nov 2011)

Hi all, I have my oil heating set to come on for 2.5 hours every evening to heat 6 rooms. In order to reduce oil usage, I turned off a couple of rads in 2 of the rooms that are rarely occupied. My O/H says turning off rads makes no difference and that to reduce oil usage, I need to cut back on the length of time the burner is on. Surely turning off rads reduces oil usage? Any advice on this would be welcome.


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## onq (2 Nov 2011)

The burn time defines the oil usage.

The number of rads "on" defines where the resultant energy is located.

You should be reducing the time the burned comes "on" for as opposed to turning off rads.


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## SparkRite (2 Nov 2011)

guernseyguy said:


> Surely turning off rads reduces oil usage? Any advice on this would be welcome.



Absolutly, of course it does, the energy that would have gone into those rads will now go into the rads that are on and therefore those rooms will heat up quicker and therefore the boiler will be "called for heat" less often, thus saving fuel.


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## SparkRite (2 Nov 2011)

onq said:


> The burn time defines the oil usage.
> 
> The number of rads "on" defines where the resultant energy is located.
> 
> You should be reducing the time the burned comes "on" for as opposed to turning off rads.




Whilst true in as far as the statement goes "The burn time defines the oil usage." the "burn" time will obviously be shorter the less of a load is put on the boiler, ie. less rads turned on.


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## PaddyBloggit (2 Nov 2011)

So  .... taking all the above into account:


 Turn off unnecessary rads &
 Reduce the length of time you have your burner on.
  You'll definitely reduce your oil usage then!


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## lowCO2design (2 Nov 2011)

guernseyguy said:


> Hi all, I have my oil heating set to come on for 2.5 hours every evening to heat 6 rooms. In order to reduce oil usage, I turned off a couple of rads in 2 of the rooms that are rarely occupied. My O/H says turning off rads makes no difference and that to reduce oil usage, I need to cut back on the length of time the burner is on. Surely turning off rads reduces oil usage? Any advice on this would be welcome.


do you have a temputure sensor/ thermometer? 
and what is the house generally heated too? 
is the system zoned? 
is it also automatically heating a HW cylinder? 

at the moment many people are wondering about reducing their heating costs, but do not appreciate they need to deal with heat loss to achieve this.
what year was your home built? 
what windows, insulation (wall,Fl, ceilings) ?
and have you a lot of drafts/air-leakage? 
also what year is your boiler? 
and have you insulated the pipework?

we could go on, but you see my point


> In order to reduce oil usage


: you need to take a holistic view of your home and energy usage.

you might find by cutting down/turning off your electrical appliances or walking to the shop instead of driving you'll save more energy/money at a cheaper cost than doing all the measures above in order to save a little on your oil heating. 

but you haven't said what your yearly oil bill is either?


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## onq (2 Nov 2011)

SparkRite said:


> Whilst true in as far as the statement goes "The burn time defines the oil usage." the "burn" time will obviously be shorter the less of a load is put on the boiler, ie. less rads turned on.




Is the system demand driven by the rads at set temperatures, or supply driven by the heat produced by the boiler for a set time?


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## SparkRite (2 Nov 2011)

onq said:


> Is the system demand driven by the rads at set temperatures, or supply driven by the heat produced by the boiler for a set time?



IMHO, most, if not all, domestic heating systems are demand driven.


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## onq (2 Nov 2011)

That seems to be at variance with the OPs first post.


> Hi all, I have my oil heating set to come on for 2.5 hours every evening to heat 6 rooms.


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## SparkRite (2 Nov 2011)

onq said:


> That seems to be at variance with the OPs first post.



Not at all, I take that to mean that the OP has a simple timer that switches his heat on for a set time. 
In that time the boiler will try to reach whatever temp. (remember it will not be running constantly for the 2.5 hrs) he has set, either at the boiler itself or with a rad/s stat.
Either way that temp. will be arrived at earlier when the *demand* from the rads diminishes, whether from reaching a predetermined temp. or having less rads on.


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## onq (2 Nov 2011)

Okay, in one of those scenarios there is a local rad temperature setting which the boiler must satisfy.

The other is where the boiler has a temperature setting.

My point is that in both cases the duration for which the boiler is "on" plays a role.

Paddybloggit's advice at Post #5 above is still sound.

I would add a suggestion to also lower the set temp by 2 degrees.


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## Shane007 (2 Nov 2011)

SparkRite said:


> Absolutly, of course it does, the energy that would have gone into those rads will now go into the rads that are on and therefore those rooms will heat up quicker and therefore the boiler will be "called for heat" less often, thus saving fuel.


 
Well not really as this will only happen if there is a room thermostat installed. If not, by relying on the boiler thermostat will use more fuel. A domestic oil boiler is not modulating. By turning off radiators, it will just put the boiler in short cycling mode, turning itself off and on more frequently and thus using more oil. I suppose it's like driving a large engined Mercedes in stop start traffic, compared to driving at 100kph on a motorway.

To reduce oil consumption, the best and most effective way is to downsize the output of the boiler. For example, if the boiler is a 15 - 26kw (50 - 90,000Btu) it will have been installed with factory settings of either 20.5kw or 23kW output. You could downsize this boiler to 15kW or 17.5kW by installing a smaller nozzle and adjusting the oil pump pressure. This, of course, should be carried out with flue gas analysis.

Make sure the boiler is properly serviced to maximize it's efficiency also and by installing a simple room thermostat located in an average heated area such as the hallway, will be better than using the boiler thermostat to control the boiler. Once the house has reached it's pre-determined temperature, it will turn off the boiler completely until the temperature drops again. Of course, a full time & temperature control zoning is preferable but this is cost significantly more.


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## SparkRite (2 Nov 2011)

Shane007 said:


> Well not really as this will only happen if there is a room thermostat installed. If not, by relying on the boiler thermostat will use more fuel. A domestic oil boiler is not modulating. By turning off radiators, it will just put the boiler in short cycling mode, turning itself off and on more frequently and thus using more oil. I suppose it's like driving a large engined Mercedes in stop start traffic, compared to driving at 100kph on a motorway.



Well, yes really, I never said it was the best way to reduce fuel usage, but it WILL reduce fuel usage.

It makes sense..... that if I have 10 rads drawing energy from a boiler for 1 hour and then have 5 (same size) rads for the next hour (excluding ambient changes) my fuel usage will be less in the second hour. Not quite half, and I never claimed it would be, but less nonetheless.

And I still maintain, that to answer the OP's question, turning off rads (cheapest method...costs nothing) DOES save fuel.


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## Shane007 (2 Nov 2011)

I would disagree. A boiler that is oversized as radiators are turned off will cause the boiler to turn on and off much frequently. If a boiler is correctly sized for the heat demand that is required, it will stay on longer, however, the ΔT will be maintained at a more consistent rate. This will lead to the boiler being on for longer, but also being off for longer. The overall result is less energy is used and therefore less oil is consumed.

For years, installers normally over-size boilers on the understanding that being over-sized it will do less work. Boilers work more efficiently when they are chasing heat rather than being on top of it. Especially with high efficiency condensing boilers. By slightly undersizing them, it will keep a more consistent ΔT and thus keeping the boiler in condensing mode and pluming.

This is another reason why gas boilers can be more efficient. The reason is that they are modulating. The only use the power that they require so if 3 zones are open, it is on full power but it modulates down when only 2 or 1 zone is open.

A modulating circulating pump will greatly help the efficiency of an oil boiler but not as well as a modulating boiler. I have many indepth talks with manufacturers regarding the design of a modulating oil boiler but the nearest thing to it is in commerical 2 and 3 stage burners. Not economically viable in a domestic situation but hopefully watch this space!


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## burmo (2 Nov 2011)

Hi,

A dirty burner / boiler, incorrect boiler jet size, air flow and oil pressure settings will also consume more fuel. If you haven't serviced it in years now could be a good time.

Burmo


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## guernseyguy (2 Nov 2011)

Hi all, thanks for the replies so far. To answer some of the questions raised, our boiler is a Firebird Popular 120 model, thermostats are installed in each room and the house which was built in 2006 is well insulated. Our oil bill for 2010 was €1500 approx. I was hoping to benefit from lower oil bills by turning off a few of the rads in the rooms not used much as I assumed this would be a more efficient approach. Thanks again.


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## SparkRite (2 Nov 2011)

Shane, forget about modulating pumps/boilers and so forth, in most situations if the load on a boiler is reduced from say, 25KW to 15KW then (as enegy cannot be destroyed/created) the amount of fuel used to produce 15KW of heat for 2.5 hours will be less than producing 25KW of heat for the same time. 
I fully accept that effieciency may suffer if loads are not balanced.
I KNOW for a fact that if I have ALL rads on in my house I use more fuel over any given time as opposed to having some turned off.

PS I suspect that the OP does not have a condensing boiler so efficiency is probably not rate/load dependant.


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## Shane007 (2 Nov 2011)

When you say thermostats in each room, do you mean thermostatic radiators valves or a wall mounted electric room thermostat?

A TRV will not turn off the boiler but add to the short cycling problem when it switches off the radiator, whilst an wired room thermostat will.

How big is the house? A Firebird Popular 120 is far too big to heat your originally quoted 6 rooms. Downsizing the nozzle should very much benefit your oil consumption without losing heat.


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## Shane007 (2 Nov 2011)

SparkRite said:


> Shane, forget about modulating pumps/boilers and so forth, in most situations if the load on a boiler is reduced from say, 25KW to 15KW then (as enegy cannot be destroyed/created) the amount of fuel used to produce 15KW of heat for 2.5 hours will be less than producing 25KW of heat for the same time.
> I fully accept that effieciency may suffer if loads are not balanced.
> I KNOW for a fact that if I have ALL rads on in my house I use more fuel over any given time as opposed to having some turned off.


 
My point is, using Guernseyguy's boiler as an example, this boiler has a 0.85 80 S nozzle. This will be using at 7.0 bar pressure 0.85 US gallons/hour. The probable pump pressure is somewhere between 8 and 9bar therefore more fuel used. By not requiring the extra demand, this boiler could be downsized to use 0.65 outputting 26kW. This will give a 25% saving in fuel with no loss of heat.

With regard to your situation, having an oversized boiler will use more fuel than an undersized one and it will keep the boiler in short cycyling mode. It will also have the keep the boiler/burner components at an excessively high temperature leading to more failures as the heat is not being transferred from the boiler into the heating system.


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## SparkRite (2 Nov 2011)

Shane007 said:


> My point is, using Guernseyguy's boiler as an example, this boiler has a 0.85 80 S nozzle. This will be using at 7.0 bar pressure 0.85 US gallons/hour. The probable pump pressure is somewhere between 8 and 9bar therefore more fuel used. By not requiring the extra demand, this boiler could be downsized to use 0.65 outputting 26kW. This will give a 25% saving in fuel with no loss of heat.
> 
> With regard to your situation, having an oversized boiler will use more fuel than an undersized one and it will keep the boiler in short cycyling mode. It will also have the keep the boiler/burner components at an excessively high temperature leading to more failures as the heat is not being transferred from the boiler into the heating system.



I fully accept your point and indeed on its own it makes perfect sense.

However I still maintain, that in the normal run of things, if the OP reduces his demand for heat by 33% (as stated, re: his first post) then there will be a saving of fuel.

His boiler may or may not be short cycling but it still will burn less fuel if the demand is reduced by 33%, unless that total amount of energy is lost to the flue, which I doubt.

What gets me about this thread is that the OP asked a simple question, "If I turn off rads will I save fuel?" and basically the answer is yes. But between us all we have complicated it beyond reason.

The bottom line is....If I turn off all my rads and run my boiler for 1hr and then run it for 1hr with all my rads on....which scenario will use more fuel?

I think the answer is obvious.


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## Shane007 (2 Nov 2011)

It may seem obvious but it is still incorrect. In a sense you have touched on the answer in relation to the flue.

Short cycling directly increases the boiler temperature (in that the heat is not been dispersed from the boiler quick enough), thus increasing the flame chamber temperature thus increasing the flue temperature. Flue temperature is directly proportional to efficiency, which is turn is directly proportional to fuel consumption. The higher the flue temperature the lower the efficiency of a boiler and thus more fuel will be wasted to the atmosphere and not into your home where it should be going. For example a standard efficiency boiler will have on average 200C flue temperatures. A high efficiency condensing boiler will have a flue temperature of approx 50C. The extra heat is being transferred into the heating system and thus being more efficient.

To check this have the boiler running with all radiators open and check the flue gas temperature with a FGA and then close down most of the radiators. An distinct increase in FG temperature will occur.

As I previously stated, another directly proportional side effect of consistent high boiler temperature is component failure. Metal expands as we know when heated. It generally reverts back to it designed state when cooled. Heat excessively and it does not, leading to undesired performances and eventual failure. This brings unnecessary cost to the homeowner.


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## SparkRite (3 Nov 2011)

Shane007 said:


> It may seem obvious but it is still incorrect. In a sense you have touched on the answer in relation to the flue.



No Shane007 what I advocate is correct, it may not be efficient or the best way to run a heat source but nevertheless is correct.

As stated, assuming all uncalled for energy is not lost/dissipated through the flue, or indeed through other losses, then that energy will be sent to existing loads, and not withstanding boiler short cycling it still remains that if I reduce the load put on an energy source by 33% then if above is accepted it follows that input is also reduced.

As I already said input may or may not be reduced accordingly but it will be reduced.

It would need to be a very *in*efficient system if the load is reduced by the tune of 33% and no corresponding reduction in input is measured.


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## Shane007 (3 Nov 2011)

So at what point does your theory not work? Should I fit a 100kW boiler to heat one radiator. Would this use less oil? So if you are correct and a 100kW boiler uses more oil to heat one rad then at what point does the balance tip? 

I think you are getting too hung up on the demand rather than the whole picture. It is more to do with how a domestic oil boiler behaves and how it is designed for the job in hand. Over-sizing is an incorrect practice. It will heat the system quicker than a smaller sized boiler but it will use more once heated.


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