30
Ideal airtherm - Air Source Heat Pump -
Installation
HeAt PUMP BUFFeR InStALLAtIon ReqUIReMentS
There are a number of main points that affect the buffer sizing requirements as follows:
1. A constant water flow of +/- 10% of design must be maintained through the heat pump. This can be achieved using good system
design. Where TRV’s or underfloor heating are used special care must be taken to ensure the flow is maintained regardless of
system turn down.
2. The assumptions using combination cylinders in table1 assume that the buffer vessel is plumbed in series with the radiator circuitry
simply adding water volume to assist flow rates.
3. Table 2 shows the temperature drop in the water volume in the buffer and the heat distribution circuit as a result of providing energy
for the heat pump to perform defrost functions when necessary.
Heat Pump
System
type
TR
V’
s fitted
Flow rate
required l/m
System
water
volumes
Buffer tank
Minimum size
of buffer
Method
proposed
Minimum DHW
Cylinder
n
ormal DHW
Cylinder
Max DHW size
Minimum
Circulation
Pump Size
no of Pumps on
system
typical System
Design
4.5kW
radiators
no
7.5
above
45 litres
No
n/a
DHW cylinder
only
150
litre
150
litre
180
litre
15 - 50
1
S or W
Plan
4.5kW
radiators
no
7.5
below
45 litres
Yes
50 litres
combination
cylinder
150
litre
150
litre
180
litre
15 - 50
1
S or W
Plan
4.5kW
radiators
yes
7.5
n/a
Yes
50 litres
combination
cylinder
15
0 litre
150
litre
180
litre
15 - 50
1
S or W
Plan
4.5kW underfloor
n/a
7.5
n/a
Yes
50 litres
separate
cylinder /buffer
150
litre
150
litre
180
litre
15 - 50
2
2 pump
system
9.0kW
radiators
no
15
above
80 litres
No
n/a
DHW cylinder
only
150
litre
180
litre
250
litre
15 - 60
1
S or W
Plan
9.0kW
radiators
no
15
below
80 litres
Yes
50 litres
combination
cylinder
150
litre
180
litre
250
litre
15 - 60
1
S or W
Plan
9.0kW
radiators
Yes
15
n/a
Yes
50 litres
combination
cylinder
150
litre
180
litre
250
litre
15 - 60
1
S or W
Plan
9.0kW underfloor
n/a
15
n/a
Yes
95 litres
separate
cylinder /buffer
150
litre
180
litre
250
litre
15 - 60
2
2 pump
system
12kW
radiators
no
20
above
160 litres
No
n/a
combination
cylinder
150
litre
210
litre
250
litre
15 - 60
1
S or W
Plan
12kW
radiators
no
20
above
110 litres
Yes
50 litres
combination
cylinder
150
litre
210
litre
250
litre
15 - 60
1
S or W
Plan
12kW
radiators
no
20
below
110 litres
Yes
95 litres
combination
cylinder
150
litre
210
litre
250
litre
15 - 60
1
S or W
Plan
12kW
radiators
Yes
20
n/a
Yes
95 litres
combination
cylinder
150
litre
210
litre
250
litre
15 - 60
1
S or W
Plan
12kW
underfloor
n/a
20
n/a
Yes 150 litres
separate
cylinder /buffer
150 litre 210 litre
250
litre
15 - 60
2
2 pump
system
table 1
table 2 - Defrost times & temperature Drops
** Estimated from defrost tests carried out
Model
operation Condition
Defrost times - mins
System Volume - ltrs
System temp drop - ºC**
4.5
A5/W55
5
45
4.9
4.5
A0/W55
6
45
3.9
4.5
A-3/W55
7
45
3.8
9
A5/W55
5
80
5.5
9
A0/W55
6
80
4.4
9
A-3/W55
7
80
4.3
12
A5/W55
5
110
5.5
12
A0/W55
6
110
4.4
12
A-3/W55
7
110
4.2