Oil burner efficieny

G

gilboy

Registered User
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Hi

I have a Firebird Oil burner. My house is 3000 sq feet and I have underfloor heating. I leave the heating on 24 * 7 and the boiler kicks in and out as needed.

I find with the underfloor heating there is many different settings which can result in how efficient the system runs, i.e. various different thermostats, manifold settings etc.

Ideally I would like to have something which could tell me how much oil I used during a particular period(e.g. a week) or how long the burner as being running during a particular period.

This would allow me to then tweak some of the settings and run for the same period and determine which was more efficient.

Just wondering what people would recommend?

Thanks
Joe
 
gilboy said:
I leave the heating on 24 * 7 and the boiler kicks in and out as needed.
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That is the worst possible way of running your heating system. It will absolutely love kerosene and you will require 2 -3 services per year at that rate. You are keeping the boiler in short cycling mode at all times thus keeping it at its most inefficient level.

How many fills of oil are you using per year? I have 3,000sqft house with UFH both upstairs and downstairs and I used over the last year, hard winter included 2.5 fills. My attic insulation was very poor with only 4" and last month I laid a further 12" of earth wool insulation bringing it to 16". I am hoping to get my usage down to under 2 fills per year.
 
This is the way I have run my heating for a number of years now. I average about 3 fills a year and each room is at a steady 21 C. Also - from what I read this is the most efficient way to run underfloor heating. I find if I were to run the UFH for a couple of hours in the morning and a couple of hours in the evening the burner runs more.
 
this is not the most effiecent way of running underfloor heating. EG. We have an air source 8kw heatpump running ours. Our total lecky bill for 2010 was e1400. This includes heating/cooking/water/showers. We have no oil. This is for a bungalow of 2400sq ft. Oil is the most inefficent
 
nediaaa said:
this is not the most effiecent way of running underfloor heating. EG. We have an air source 8kw heatpump running ours. Our total lecky bill for 2010 was e1400. This includes heating/cooking/water/showers. We have no oil. This is for a bungalow of 2400sq ft. Oil is the most inefficent
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Running the risk of taking the thread off topic - but could I just quickly ask you for the make/model of a.s. heat pump? I looked into this last year -and came to the conclusion that they simply were not viable. Are you confident that your spend is €1400 total?
 
i think the heating source and use of the system should be quantified here by what the building fabric of the house is like. thermal insulation/ bridging, air-tightness and means of ventilation must be discussed along with heating..
OP your have an an UFH system with oil, this is not ideal BUT before you going changing to sightly lower rate of kwh deal with the actual problem your house is more than likely not built tight enough for UFH!

what is the insulation levels around the UFH and through-out the house

  1. walls,
  2. floors
  3. ceilings/attic,
  4. perimeter around the UFH.
  5. windows U-value
  6. what the draft seals are like
  7. what is the air-change rate in the house? ie is your house leaking like a sieve
 
I think you will find that you have a built in timeclock in the ufh control system that will include a "setback" mode. This will give a 4C less reading on the thermostats so that the stats when in set back will demand a 16C temperature instead of a 20C temperature that is set on the stat itself.

Any ufh system that I have corrected that was running 24/7/365 were using 6 to 7 fills of oil per annum.
 
Hi Shane

How do you recommend people should be running there ufh, i.e. how many hours per day etc

Thanks
Joe
 
gilboy said:
Hi Shane

How do you recommend people should be running there ufh, i.e. how many hours per day etc

Thanks
Joe
Click to expand...

It really depends on the parameters that affect the individual installation and the heat requirement of the occupants of the home. For example, the thickness of the floor screed plays an important part. In my own house, I have 3" thick concrete downstairs and 2" thick upstairs. The downstairs takes longer to heat up but it stays warmer longer. Upstairs heats up quicker but cools down quicker also. I only put upstairs on for about 3 hours before we use upstairs as being thinner, it reacts more like a radiator system.

Downstairs we have on for about 5 hours and it is still warm for the following day. Insulation underneath the concrete is very important. It should be minimum 125mm thick but I would tend to install 150mm thick.

The best installation will always incorporate a buffer tank as an additional energy store but maxmum volume of 500L. For example, a 35kW boiler will heat a 500L buffer tank tp 70°C in approx 35 minutes but using a ΔT of 30 - 35°C this will last for minimum 90 minutes will all heat demands on. In reality warmer rooms will have less demand and I usually find that the buffer tank lasts upto 180 minutes. Basically, for every 35 minutes of oil usage you will get approx 150 back out. It will take a 26kw boiler to heat the same volume in approx 55 minutes.

Therefore, you can see that having the boiler on for say 2 to 3 times per day for 35 - 55 minutes a time (depending on output of boiler) you can have a return of upto 9 hours of heating for 105 - 165 mintues of oil usage.

Other variables have an effect also such as obvious ones, building orientation, insulation levels, windows, etc. but the figures I give above are average.

You must look at UFH as an energy store rather than a radiator. The thicker the concrete the longer the heat will last but equally the longer it takes to heat up. If it is well insulated below but as importantly around the parameter of the screed it should give good results.

Room thermostats in every room are a must and not just one for downstairs and one for upstairs. Motorized valves on each zone, i.e. upstairs, downstairs and hot water circuits are also a must but are rarely fitted. When they are not fitted if one actuator is open and another zone is active, it will dispense heat to unwanted rooms, wasting energy. Hot water circuit must be isolated until it is required.

Hope this helps!
 
Thanks for the detailed response Shane.

In terms of the boiler, I have mine set on its lowest settings. I have a thermostatic valve controlling the entry of the hot water from the boiler in to the ufh system. The thermostatic value only goes up to 47°C - I have it set at this value. I also have a temperature gauge on the pipe just before the thermostatic valve - this normally reads between 60 - 70°C.

I do wonder if I put the boiler on a higher setting would the boiler kick in less often. However, putting the boiler on a higher setting confuses me because the thermostatic value on the entry to the ufh system will only allow water up to 47°C. Hence - seems a waste producing also this hot water if the ufh will not take it.

Would be interested to know what setting you put your boiler on? Do you have a thermostatic value on entry to the ufh and if so what setting do you put it on? Finally, I have a temperate reading on the water flowing through the ufh - I rarely see if over 40°C - what temperate would you ideally see this at. Sometimes mine reads just over 30°C and I do think its going to take much longer to heat things if the water being circulated is not particularly warm

Thanks again

Joe


 
The thermostat on the boiler should always be set to 70 - 75C. Especially with UFH as you want a ΔT of 11C. My boiler is a condensing HE boiler so it is also more critical to keep at this temperature is ensure that it is in condensing mode as much as possible.

A very good option is to install a modulating circulating pump such as the Grundfos Alpha pump. Once installed, you open all circuits including the hw, set this to be the template setting and as circuits close, the pump will modulate back to suit. It ensures a ΔT is maintained which is critical with ufh.

The pipe stat on the UFH is only there to protect the concrete slab from overheating and cracking. This should be set to approx 55C and certainly no more than 60C. This stat will turn off the UFH pump at temperatures above this so not to pump higher temps through the slab which could lead to cracking. The UFH heating circuit should generally be at a temperature of 45C with a return temp of 34C. If you have very different temps, then your flow regulators are incorrectly set. If you have lower temps then you need to increase the flow rate on each circuit. This is not a job for the untrained.

If you have your system zoned, and I mean with motorized valves on each circuit including the hw, then I would try to put on the hw circuit on the different time to the ufh. It will heat up quicker and take nothing from the ufh. If it is not zoned, do so but get somebody who is able to do so correctly. UFH often operates at 24v and relays, etc. must be used to link the various controls. Depending on when you home was built, you should qualify for the SEAI Heating Control Upgrade grant as you will probably not have time and temperature control on your hw circuit and each zone probably cannot be completely isolated in that if downstairs is on and one room upstairs wants heat, it will get it even though upstairs is in set back.

You may also have an ICV (Injector Control Valve) and this will be set to the desired flow temperature. This allows higher flow temps to be added to the return temps. An ICV looks similar to a TRV but on a pipe.
 
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