Mitsubishi Electric PUHZ-W50VHA Technical Manual page 2

1 What is ATW heat pump?
1-1. Compare with conventional fossil fuel boiler
• Heat pumps produce water at 30°C – 60°C
• Ideal for underfl oor heating
• Average underfl oor heating circuit 35°C
• Fossil fuel boilers heat water to 80°C
• Flow temp in rads design temp approx 70°C
• Heat pumps can still be used with radiators
• Larger surface area to emit heat from lower temp water
1-2. Points to notice
1-2-1. Design (Radiator sizing)
• Careful consideration must be given to appropriate application of this technology to maximise its benefi ts – it will not suit all
properties, especially many retrofi ts
• Heat emitters may need to be larger
• Lower fl ow temperatures maximise COP
• Various regulations apply to the design and installation of such systems
• Because the fl ow temp. of heat pump is low compare to fossile fuel boiler, the temperature difference between the primary (fl ow
water) and secondary (room air) becomes little, it makes the heat emission little.
To emit the same amount of heat energy, it is needed to select the radiator that has a larger surface area.
Be especially careful of the surface area when you design the radiator.
1-2-2. Defrost
Note: Occasionally, vapor that is made by the defrost operation may seem as if smoke come up from the outdoor unit.
1-2-3. Water Pressure loss (for packaged type outdoor unit)
• Water pressure lose of the heat exchangers are as follows.
Be aware of the infl uence when you design total pipng system.
Hex for PUHZ-W50VHA (ACH30-30Plates)
Flow rate (L/min)
Pressure Loss (kPa)
Pressure loss (kPa)
50
45
40
35
30
25
20
15
10
5
0
5
Secondary (Water - side)
5 10
1.7 6.0
10 15
Flow rate (L/min)
15 20
12.4 20.9
20 25
2
25 30
31.4 43.8
30