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Knights Place Winter MVHR Operation & Efficiency The main objectives : To assess MVHR system operation in winter when conditions fall below zero 0C To determine if MVHR below zero 0C modulates down the supply air and affects air quality




MVHR System

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Model: Zehnder comfoair CA200 PHI efficiency 92% Frost protection operation: Below -1째C frost protection enables. When the efficiency between the supply air temperature (T2) and the extract air temperature (T3) drops below 85% supply motor will decrease 1% every minute until efficiency increases.

Weather file: Exeter university provide a DSY & TRY detailing a winter design figure of - 4.7째C for the Exeter region


Knights Place Flat Details

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1 bed mid floor, south west facing elevation good solar gain in afternoon. Occupied by 2 adults. Flat 15: 2 bedroom mid floor gable end flat, south facing. Very good solar orientation, faรงade glazing picks up morning afternoon & evening sun Occupied by 2 adults.

Flat 18: 2 bedroom roof space gable end flat, south facing. Exceptional solar orientation, faรงade glazing & roof lights picks up morning afternoon & evening sun Occupied by 2 adults.


Knights Place External Air Temperatures

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Coldest Winter Day 12th March 2013 External minimum temperature = - 3.190C


Knights Place External Air Temperatures

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Milder Winter Day 19th March Above 0 0C External minimum temperature = 0.760C


Flat 14 C02 Levels

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Cold Winter Day 12th March minimum External temperature = - 3.19

0C

Peak CO2 levels 1200 – 1400 ppm


Flat 14 C02 Levels

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Mild Winter Day 12th March minimum External temperature = 0.76

0C

Peak CO2 levels 1200 – 1400 ppm There is not much difference between coldest winter day below zero and a mild winter day above zero Low CO2 levels in the afternoon could represent an empty flat or window open


Flat 14 C02 Levels

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Cold Winter Day 12th March minimum External temperature = - 3.19

0C

Peak CO2 levels 1200 – 1400 ppm


Flat 14 C02 Levels

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Mild Winter Day 12th March minimum External temperature = 0.76

0C

Peak CO2 levels 1200 – 1400 ppm There is not much difference between coldest winter day below zero and a mild winter day above zero Low CO2 levels in the afternoon could represent an empty flat or window open


Flat 15 C02 Levels

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Cold Winter Day 21st Jan minimum External temperature = - 2.2

0C

Peak CO2 levels 1400 – 1500 ppm


Flat 14 C02 Levels

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Mild Winter Day 15th March minimum External temperature = 1.26

0C

Peak CO2 levels 1400 – 1600 ppm There is not much difference in peak C02 levels between cold winter day below zero and a mild winter day above zero


Flat 14 C02 Levels

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Mild Winter Day 23rd March minimum External temperature = -0.1

0C

Peak CO2 levels 1400 – 1600 ppm There is not much difference in peak C02 levels between cold winter day below zero and a mild winter day above zero


Key Conclusions The coldest temperature observed was found to be -3.19 0C which is not as cold as the weather file data of -4.7 0C for the Exeter region. Nevertheless a comparison can still be made to see if there is any noticeable change in air quality between conditions above 0 0C and 0 those below 0 C.

0 No drop in air quality was observed when conditions fell below 0 C This suggests that the unit is not entering frost protection mode to significantly alter the supply air during these cold conditions as the efficiency between T2 (supply) and T3 (extract) is being maintained.


Knights Place Winter MVHR Efficiency Analysis