Standing Losses

Published February 28, 2013 by Sean

Daily heating load is about 16kWh for a day with night-time temp 4/daytime 6. From a breakdown of temperatures in the system, a quick analysis of where the energy goes, with an aim to asess where best to make savings. Thermal standing losses from Tank and DHW pipework come to 2kWh. Probably a little more for the full set of pipework. Compressor heater would take 2kWh if it runs 24/7.  Based on nightime load, heating load is roughly 12kWh (i.e. 24kWh heat). This is slightly variable depending on how heat is spread across the rooms. Using DHW is the largest complication in trying to make measurements, and I have set the immersion to cycle on daily to add more data.


Heat pump compressor heater

0.612 kwH in 7h13 = 85 watts

180 L Gledhill indirect solar cylinder1

1.4 kWh/day = 58 watts

Measured 6° drop per day.

DHW pipework (22mm).

6 degree/hour @ 25° above ambient

2 degree/hour @ 23° above ambient

stable @ 19° above ambient (improved to 21° with more insulation)

Assume 2m pipe, heat capacity 2800J/K

5W @ 25° cooling

1.5W @ 23° cooling

~20-30W loss.

System losses =160-170 W = 4kWh./day

House steady state:

Room with no heating input – balanced to outdoors @ +11° (150W electrical load + solar gain)

Overnight ~500W @ 15° differential (12 kWh/day)

Filed under Heating

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