Oil Consumption Query Please

Alfster

Hi,

We recently from a medium size modern house with a combi boiler to a much older house (200 years old) with oil boiler which the previous owners replaced brand new prior to us moving in. We had 600L delivered on 5th October and it has gone already! Just wondering if that is normal for a large old house. It's 5 bedrooms and has no cavity. Central heating is run off boiler. Most rooms have a large double panel radiator. We also run hot water off oil boiler. Finally we run roughly 40 square metres of downstairs flooring off wet underfloor heating which is heated by oil. Underfloor heating has 4-5 hour warm up time due to it being underneath thick natural stone flooring so advice was to leave it on continuously - 21 degrees when we are in and 17 degrees when we are out.  So I have a few questions if you would be so kind:

1) Is 300L per month reasonable given the above? Seems excessive and guy that delivered it in October said it will 'definitely do you until after Christmas'. 
2) The plumber who fitted the boiler said that because the hot water tank is well insulated it is roughly costs the same amount of fuel to leave the hot water on continuously than it does to boost it from cold a few times in the day. What are peoples thoughts on this? Seems fairly inconclusive whether or not this is a myth or not? 

Thanks in advance for any advice/insights offered!

canaldumidi

For comparison, I use around one tankful of 2500 ltrs a year. I run the heating from autumn to spring (so 6 months depending on weather?) on a 12 hour per day basis, but only heat hot water every other day or so as well-insulated tankful lasts that long (low usage).

You have a larger house and much greater hot water usage. I'm no expert on underfloor heating but have always imagined it's a more expensive way to heat, especially if there's insulation between the heat source and the room being heated (which sounds counter-effective). On top of that old houses are typically less well insulated than modern ones, though you give no detail of this.

1) So 600 ltrs in 2 months (and Oct/Nov were pretty cold) does not sound unreasonable.

2) Are you drawing off hot water 'a few times a day'? ie is the house occupied and people taking baths? There are endless debates about the run continuously Vs re-heat myth, but I believe constantly heating water so as to not use it and let it cool down is more wasteful than heating it to use. You can also never over-insulate. Yes, modern tanks are supplied with fitted insulation, but for around £10 you can fit an extra jacket.

(edit: if you're near MK I have one unused panel you can have for free as I bought 2 jackets and couldn't physically fit all the panels on!)

justwhat

5 bed and 2 living rooms.  end terrace rubble wall house. House over 200 years old 
All rooms with radiators no underfloor heating.

approx 2500-3000 litres per year. That was our usage 

1: Your  usage would be fairly normal in colder months for the above house we lived in.

2: We had a combi so hot water was heated on demand. 

Is you hot water tank a thermal store for the underfloor heating ?

dunstonh

We had 600L delivered on 5th October and it has gone already! 

We use around 2800 litres a year.  Typically that means filling up in  September, November,  January and March as our tank is too small for the size of the house at 1440 litres.

The weather has an impact.   It was mild quite late this year. So, usage is down.

1) Is 300L per month reasonable given the above? Seems excessive and guy that delivered it in October said it will 'definitely do you until after Christmas'. 

It won't be 300L a month.   You will use virtually nothing between late May to September.   You will use more than 300l a month between December to March.

With oil, you get to understand your usage better.  On the mains gas, you average your usage over the year and build summer credit that is used in winter.  With Oil, you dont get that averaging.  So, you see the heavy use in cold months and virtually nothing in the warm months.    The vast majority of your oil is used in just 6 months of the year.

2) The plumber who fitted the boiler said that because the hot water tank is well insulated it is roughly costs the same amount of fuel to leave the hot water on continuously than it does to boost it from cold a few times in the day. What are peoples thoughts on this? Seems fairly inconclusive whether or not this is a myth or not? 

There is no point keeping the tank topped up with heat if you are not using water in that period.   We heat the water in the morning.   There is a 15-minute heat at lunchtime (which we wouldn't need if the home was empty during the day) and another heat in the evening.   It should only take about 30 minutes from cold to hot and a well-insulated tank won't drop a lot of heat.  So, probably only needs 10 minutes, three times a day  (disregarding use) to bring it back to temp.   With showers and baths, you will need to heat the water longer to bring the replacement water up to temp.   But no more than 30 minutes should be fine.  Ours is currently sitting at 1 hour in the morning, 15 minutes at lunchtime and 30 minutes in the evening.

Every system is different and your usage will be different.   You need to learn and understand your system.     Plus, in my case, there are three women in the house.  So, water has to be hot and the air temp about 2 degrees more than I would like it.  Otherwise, my life would be misery and as someone said recently, divorce is more expensive than a few litres of oil.

lohr500

We live in a similar aged and by the sound of it similar sized house. An old converted farmhouse with thick walls but no cavity insulation.

We have the heating set at 16.5 C between 7am and 5pm during the week, rising to 19 C from 5pm to 10pm, then falling back to 13 C overnight. At the weekend, the daytime temperature is set slightly higher at 17.5 Deg.

We have the water heated by the boiler for a couple of hours, three times per day around the periods of highest demand. I put extra insulation around the hot water cylinder and I also wonder about the wisdom of running the hot water permanently, rather than boosting three times per day.

Our boiler is also new this year. A Grant Vortex Blue External, nozzled to output at 30kW. It isn't a system or combi type. Just a conventional boiler.

Over the past 14 days, which have been pretty cold in North Yorkshire, we have used a whopping 240 litres of kerosene, so 17.1 litres a day! That's the highest consumption I have seen since monitoring the usage, but it has been very cold and windy for most of that period. On this basis, your 300 litres per month doesn't seem unreasonable.

Between May and September when the heating was hardly ever kicking in, the boiler was averaging just 1.8 litres per day to supply the hot water. So clearly the cold weather and needing lots of heating is the main contributor to high oil consumption. 

It would be worth checking your boiler flow and return temperatures to make sure the new boiler is condensing efficiently. For this to happen, the return temperature needs to be below 50 C and the flow should be 20 deg higher than the return. If you can get the return down to 40 deg or less, with say a 15 deg difference on the flow, then the condensing function will be even more efficient. After messing around with the boiler temperature, circulation pump speed and flow valves on the radiators, I've got mine to around 40/60 which I am happy with. The fitter should have done this as part of the original installation, as mine did, but I found it needed a bit of tweaking to improve it. You can buy analogue dial type thermometers that just clip on to the flow and return pipes to monitor the temperature.

If the radiators in the house don't have individual thermostatic valves, consider fitting these as well so you aren't overly heating rooms in the house that don't need it when the boiler is running through the day to maintain the underfloor heating temperature.

Hope this helps.  

comeandgo

You will be using more than 300 l per month for December and January as October and November have been quite mild but you will use a lot less April to September.  Do you have any opportunity to fit a stove?  Positioned in a decent place it may help heat a few rooms.  Oil is a very expensive fuel again .  Are you able to order more than 600 litres at a time?  Some of the distributors give a cheaper rate if you buy in the thousands.

Alfster

justwhat said:

5 bed and 2 living rooms.  end terrace rubble wall house. House over 200 years old 
All rooms with radiators no underfloor heating.

approx 2500-3000 litres per year. That was our usage 

1: Your  usage would be fairly normal in colder months for the above house we lived in.

2: We had a combi so hot water was heated on demand. 

Is you hot water tank a thermal store for the underfloor heating ?

Thanks for all of the advice guys. Such great, detailed responses! I'm not sure about the thermal store - I wouldn't have thought so as our hot water tank is small. I don't really know and it's something I want to find out. Sometimes the underfloor heating is on and the CH is off yet the boiler is also off so it must be using some reserve to heat the floor whilst the boiler is off?

Alfster

comeandgo said:

You will be using more than 300 l per month for December and January as October and November have been quite mild but you will use a lot less April to September.  Do you have any opportunity to fit a stove?  Positioned in a decent place it may help heat a few rooms.  Oil is a very expensive fuel again .  Are you able to order more than 600 litres at a time?  Some of the distributors give a cheaper rate if you buy in the thousands.

Not sure if we can fit a stove. We are currently getting quotes for a new tank as ours is only 1000L and using 300+L a month in winter is a nightmare with a tank this small. The house next door has a 3500L tank and buys all his oil in bulk in June! 

Alfster

lohr500 said:

We live in a similar aged and by the sound of it similar sized house. An old converted farmhouse with thick walls but no cavity insulation.

We have the heating set at 16.5 C between 7am and 5pm during the week, rising to 19 C from 5pm to 10pm, then falling back to 13 C overnight. At the weekend, the daytime temperature is set slightly higher at 17.5 Deg.

We have the water heated by the boiler for a couple of hours, three times per day around the periods of highest demand. I put extra insulation around the hot water cylinder and I also wonder about the wisdom of running the hot water permanently, rather than boosting three times per day.

Our boiler is also new this year. A Grant Vortex Blue External, nozzled to output at 30kW. It isn't a system or combi type. Just a conventional boiler.

Over the past 14 days, which have been pretty cold in North Yorkshire, we have used a whopping 240 litres of kerosene, so 17.1 litres a day! That's the highest consumption I have seen since monitoring the usage, but it has been very cold and windy for most of that period. On this basis, your 300 litres per month doesn't seem unreasonable.

Between May and September when the heating was hardly ever kicking in, the boiler was averaging just 1.8 litres per day to supply the hot water. So clearly the cold weather and needing lots of heating is the main contributor to high oil consumption. 

It would be worth checking your boiler flow and return temperatures to make sure the new boiler is condensing efficiently. For this to happen, the return temperature needs to be below 50 C and the flow should be 20 deg higher than the return. If you can get the return down to 40 deg or less, with say a 15 deg difference on the flow, then the condensing function will be even more efficient. After messing around with the boiler temperature, circulation pump speed and flow valves on the radiators, I've got mine to around 40/60 which I am happy with. The fitter should have done this as part of the original installation, as mine did, but I found it needed a bit of tweaking to improve it. You can buy analogue dial type thermometers that just clip on to the flow and return pipes to monitor the temperature.

If the radiators in the house don't have individual thermostatic valves, consider fitting these as well so you aren't overly heating rooms in the house that don't need it when the boiler is running through the day to maintain the underfloor heating temperature.

Hope this helps.  

This sounds excellent thanks. I have never checked the flow rates nor do I know how but will look into this for sure. We do have thermostatic valves and I am using those to ensure the rooms don't get too hot. 

Alfster

dunstonh said:

We had 600L delivered on 5th October and it has gone already! 

We use around 2800 litres a year.  Typically that means filling up in  September, November,  January and March as our tank is too small for the size of the house at 1440 litres.

The weather has an impact.   It was mild quite late this year. So, usage is down.

1) Is 300L per month reasonable given the above? Seems excessive and guy that delivered it in October said it will 'definitely do you until after Christmas'. 

It won't be 300L a month.   You will use virtually nothing between late May to September.   You will use more than 300l a month between December to March.

With oil, you get to understand your usage better.  On the mains gas, you average your usage over the year and build summer credit that is used in winter.  With Oil, you dont get that averaging.  So, you see the heavy use in cold months and virtually nothing in the warm months.    The vast majority of your oil is used in just 6 months of the year.

2) The plumber who fitted the boiler said that because the hot water tank is well insulated it is roughly costs the same amount of fuel to leave the hot water on continuously than it does to boost it from cold a few times in the day. What are peoples thoughts on this? Seems fairly inconclusive whether or not this is a myth or not? 

There is no point keeping the tank topped up with heat if you are not using water in that period.   We heat the water in the morning.   There is a 15-minute heat at lunchtime (which we wouldn't need if the home was empty during the day) and another heat in the evening.   It should only take about 30 minutes from cold to hot and a well-insulated tank won't drop a lot of heat.  So, probably only needs 10 minutes, three times a day  (disregarding use) to bring it back to temp.   With showers and baths, you will need to heat the water longer to bring the replacement water up to temp.   But no more than 30 minutes should be fine.  Ours is currently sitting at 1 hour in the morning, 15 minutes at lunchtime and 30 minutes in the evening.

Every system is different and your usage will be different.   You need to learn and understand your system.     Plus, in my case, there are three women in the house.  So, water has to be hot and the air temp about 2 degrees more than I would like it.  Otherwise, my life would be misery and as someone said recently, divorce is more expensive than a few litres of oil.

Thanks for such an informative post! That last sentence made me laugh so hard I spat out my drink 😂

We have one shower (me), a small bath (little one) and a big bath (wife) which is all in the evening so maybe I will take the hot water off the continuous cycle. 

Alfster

lohr500 said:

We live in a similar aged and by the sound of it similar sized house. An old converted farmhouse with thick walls but no cavity insulation.

We have the heating set at 16.5 C between 7am and 5pm during the week, rising to 19 C from 5pm to 10pm, then falling back to 13 C overnight. At the weekend, the daytime temperature is set slightly higher at 17.5 Deg.

We have the water heated by the boiler for a couple of hours, three times per day around the periods of highest demand. I put extra insulation around the hot water cylinder and I also wonder about the wisdom of running the hot water permanently, rather than boosting three times per day.

Our boiler is also new this year. A Grant Vortex Blue External, nozzled to output at 30kW. It isn't a system or combi type. Just a conventional boiler.

Over the past 14 days, which have been pretty cold in North Yorkshire, we have used a whopping 240 litres of kerosene, so 17.1 litres a day! That's the highest consumption I have seen since monitoring the usage, but it has been very cold and windy for most of that period. On this basis, your 300 litres per month doesn't seem unreasonable.

Between May and September when the heating was hardly ever kicking in, the boiler was averaging just 1.8 litres per day to supply the hot water. So clearly the cold weather and needing lots of heating is the main contributor to high oil consumption. 

It would be worth checking your boiler flow and return temperatures to make sure the new boiler is condensing efficiently. For this to happen, the return temperature needs to be below 50 C and the flow should be 20 deg higher than the return. If you can get the return down to 40 deg or less, with say a 15 deg difference on the flow, then the condensing function will be even more efficient. After messing around with the boiler temperature, circulation pump speed and flow valves on the radiators, I've got mine to around 40/60 which I am happy with. The fitter should have done this as part of the original installation, as mine did, but I found it needed a bit of tweaking to improve it. You can buy analogue dial type thermometers that just clip on to the flow and return pipes to monitor the temperature.

If the radiators in the house don't have individual thermostatic valves, consider fitting these as well so you aren't overly heating rooms in the house that don't need it when the boiler is running through the day to maintain the underfloor heating temperature.

Hope this helps.  

Thanks for such a great post. Since you also have an old house what do you think to this thermal plasterboard insulation you can get? This guy has done this and says it has worked wonders in his old cottage which has no cavity wall insulation:

type this into YouTube: How to Dot & Dab Insulated Plasterboard - a DIY Guide (won't let me copy links)

Only reason I ask is that we had a heritage survey done on our property prior to purchasing and they harp on about using breathable materials e.g. lime plaster on internal outside walls, no gypsum etc so you don't damage the fabric of the house so I wanted if something like the above is ok to do on older houses?