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The Efficiency Of A Lounge Installation
The efficiency Of A FAHRenergy With A Heat Pump

Measuring And Understanding efficiency

The Efficiency Of FAHRenergy HRV Solar In A Kitchen

One ‘FAHRenergy HRV-Solar’ unit is installed in the kitchen. 
Next to the kitchen is a small utility room with a door which leads to the garden. 
A door connects the kitchen and a medium sized lounge.
 The total space is 70m3

The ‘FAHRenergy Solar’ unit delivers 60m3 of heat recovered fresh air every hour. 
Governments generally specifies an exchange of the air every 2 hours as minimum.


The kitchen and associated rooms

The Value Of The Installation

The kitchen FAHRenergy system discussed to the left
gives optimal value on several levels:

  1. Recovers energy produced in the kitchen from the cooker, the boiler and the kitchen air
  2. Extracts cooking smell and vapour
  3. Extracts carbon monoxide (poisonous CO) and carbon dioxide
  4. Injects fresh heated air to the kitchen
  5. Injects fresh air to the lounge
  6. Removes cold draft from the floor
  7. Removes damp air from the utility room

The old kitchen has been transformed from a cold, smelly 
place with draft and potential 
poisonous carbon monoxide to a pleasant and healthy work 
The adjacent lounge has become a fresh healthy room at 
reduced energy need and no other cost than a 2m 
concealed duct.

This has all been achieved without extra energy!


The Efficiency

The chart below shows the energy collected over 24 hours on two different days 
and under two conditions:

1: The cooker is off and thus the cooker hood. The result, in kilowatt hours (Kwh), 
    is shown in yellow colours.

2: The cooker is on and thus the cooker hood. The result is shown in red colours.

The 5.3Kwh and 5.6Kwh are actually recovered as the FAHRenergy system was 
active all 24 hours.

The result with the Cooker On would have recovered the shown energy if the cooker 
was on 24 hours. This is obviously not the case. How much energy that is actually 
recovered depends on how many hours the cooker is on.

The 15th of November 2006 was a normal day with no excessive cooking. 
Outdoor temperature = 3.2°C.

The 17th of December 2006 was a party day with extra cooking. 
Outdoor temperature = 2.5°C.

Depending on the cooking habits it is likely that the recovery of cooking energy 
improves the actually collected energy by more than 20% . A valuable addition over 
the years as the added installation effort and price normally is minimal.

The calculated efficiency from the two days is shown below:

The efficiency of the installed FAHRenergy system with the cooker off is 78% and 
84% respectively on the days the measurements were collected. This is expected for 
a sensibly installed system. The efficiency will vary from day to day due to variables 
as open/closed doors and windows, moisture in the air, in/out temperature
differences, duct insulation quality and general measurement errors.

The efficiency with the cooker on shows the added value the recovery of the cooker 
energy gives. The actual efficiency of the system does not change whether the cooker 
is on or off. If the cooker energy were added to the calculation on the ‘old air’ side the 
result would be the same as with the cooker off.

‘FAHRenergy Medium’ unit consumes 10w which becomes 240wh per day or 5% 
of the recovered energy. 

The energy recovered is 20 times larger than the energy consumed. 


The Efficiency Of A 
FAHRenergy System In A Lounge

One ‘FAHRenergy Room’ unit is installed in a lounge. A ‘FAHRenergy Room’ unit delivers 30m3 of fresh heat recovered air every hour in quiet mode. 

The room unit is fitted with rectangular connections and is small enough to hide behind a standard curtain. This allows for having the entire system in the room in which it must exchange the old air with fresh heat recovered air.

The installation uses an existing draft window for expelling old air and drawing in fresh air. In this way holes for ducts are avoided.

The Value Of The Installation

The lounge FAHRenergy system discussed above gives optimal value on several levels:

  1. Odours are removed
  2. Dust mites are killed over time
  3. Dampness eliminated
  4. Smokers may associate with the family (Smokers Corner)
  5. Draft from trickle ventilation and draft windows is reduced (or eliminated)
  6. Security improved (no open windows)
  7. Carbon monoxide (poisonous CO) from fireplace is removed
  8. General improved health of persons and house

The Efficiency

The chart shown below shows the energy collected on 4 specific days:

The energy collected on any given day depends on several factors. The most pronounced factor is the temperature difference between the indoor temperature
and the outdoor temperature. The larger the difference between these two temperatures, the larger the collected energy will be. 

From collected data the system efficiency has been calculated and is shown in the chart below:

The general energy efficiency for this system is over 80%.

As this installation is balanced, that is the volume of old heated air entering the FAHRenergy unit is the same as the volume of cold fresh air entering the system, energy efficiency and temperature returned in % are the same.

The temperature returned is over 80% of the temperature of the old air. This means that the incoming fresh air is pleasantly heated and no extra heating of the incoming fresh air is needed.

The actually recovered energy is reduced by the energy the FAHRenergy uses to function. For ‘FAHRenergy Room’ this is approximately 6w or 144watt hours per day. A negligible amount compared to 3500watt hours collected per day.

The above heat recovery system collec ts 24 times more energy than it uses.

Efficiency Difference From Day To Day

The measured efficiency depends on many factors such as:

  1. Indoor and outdoor temperature difference
  2. Sources such as sunlight adding energy
  3. Sources such as moisture changing air energy content and conductivity
  4. Precision of used instruments
  5. Open doors and windows

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