Reference calculations, Pressure drop, Operating limits – WaterFurnace Envision Hydronic User Manual
Page 36
36
NSKW INSTALLATION MANUAL
HE
L/s x 4.2*
Reference Calculations
Heating Calculations:
Cooling Calculations:
LWT = EWT +
HR
L/s x 4.2*
LWT = EWT -
NOTE: * When using water. Use 4.1 for 15% methanol/water
or Environol solution.
Operating Limits
Heating with High Source Temperatures
Heating water with a water to water unit using high source
temperatures can lead to operating conditions that fall
outside of the system operating range. The condition occurs
when the loop (source) temperature exceeds 21.1°C with
a full flow of 0.054 L/s per kW. Under this scenario, the
evaporating temperature can fall outside of the compressor
operating window.
To allow the system to operate correctly, restricting the
source side flow when the evaporating temperature exceeds
12.7°C is recommended. One way of accomplishing this is to
use a flow-restricting valve on the source loop circuit that
is controlled by the evaporating temperature. Locate the
sensing device on the refrigerant inlet of the evaporator.
As an alternative to the evaporating temperature, the
suction line temperature can be monitored with the same
control capability. In this control, temperature should be a
maximum of 18.3°C.
Operating Limits
Cooling
Heating
°C
°C
Source Side Water Limits
Minimum Entering Water
-1.1
-6.7
Normal Entering Water
29.4
15.6
Maximum Entering Water
43.3
32.2
Load Side Water Limits
Minimum Entering Water
10.0
15.6
Normal Entering Water
15.6
37.8
Maximum Entering Water
32.2
48.9
NOTES: Minimum/maximum limits are only for startup
conditions, and are meant for bringing the space up to
occupancy temperature. Units are not designed to operate
at the minimum/maximum conditions on a regular basis.
The operating limits are dependent upon three primary
factors: 1) entering source temperature, 2) entering load
temperature, and 3) flow rate L/s. When any of the factors
are at the minimum or maximum levels, the other two
factors must be at the normal level for proper and reliable
unit operation. Consult the Performance Tables for each
model to determine allowable normal operating conditions.
Units are not designed for outdoor installation.
Pressure Drop
NOTE: Temperatures are Entering Water Temperatures
Model
L/s
Pressure Drop (kPa)
0°C
15°C
25°C
35°C
50°C
06
0.25
6.2
4.8
4.1
3.4
2.8
0.35
13.8
13.1
12.4
11.7
10.3
0.45
22.1
20.7
20.0
19.3
17.9
0.55
30.3
29.0
27.6
26.2
25.5
08
0.30
6.2
4.1
3.9
3.7
3.4
0.45
15.9
14.1
13.4
12.8
12.1
0.65
25.5
24.1
23.0
21.9
20.7
0.80
34.5
32.4
30.3
29.0
27.6
12
0.50
11.7
9.7
9.4
9.2
9.0
0.75
24.8
23.4
22.0
20.5
19.0
1.00
38.6
37.2
34.5
31.7
29.0
1.20
57.2
55.8
52.4
49.6
46.9
17
0.60
22.1
20.7
19.5
18.3
17.2
0.90
37.9
36.5
35.2
33.5
32.1
1.20
54.5
52.4
50.3
48.7
46.9
1.50
79.3
77.9
75.8
74.5
72.4
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