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Intermittent Pump Operation
The MVB can control up to three pumps simultaneously depending on water heater type and system
configuration. The pumps will be energised and de-energised based on system parameters including
pump run-on at the end of a heating cycle. Refer to "Applications and Modes" on page 52. These
include:
W Models
1. Primary flow and return pump between water heater and storage tank. Where single phase pumps
with max current not exceeding 8 Amps are used, power for pump is supplied via the MVB and
pump is controlled directly via the MVB. Where three phase pumps, or single phase pumps with
current exceeding 8 Amps, are used, the pump contactor is controlled via the MVB.
H Models
1. Water Heater primary flow and return pump between heater and main system flow and return circuit.
Where single phase pumps with max current not exceeding 8 Amps are used, power for pump is
supplied via the MVB and pump is controlled directly via the MVB. Where three phase pumps, or
single phase pumps with max current exceeding 8 Amps, are used, the pump contactor is controlled
via the MVB.
2. Main system flow and return circuit pump. The MVB can be optionally used to control the main
system pump. Where single phase pumps with max current not exceeding 8 Amps are used, power
for pump may be supplied via the MVB and pump is controlled directly via the MVB. Where three
phase pumps, or single phase pumps with max current exceeding 8 Amps, are used, the pump
contactor is controlled via the MVB.
3. DHW primary flow and return pump between water heater and storage tank (calorifier), in systems
providing combined heating and DHW. Where single phase pumps with max current not exceeding
8 Amps are used, power for pump is supplied via the MVB and pump is controlled directly via the
MVB. Where three phase pumps, or single phase pumps with current exceeding 8 Amps, are used,
the pump contactor is controlled via the MVB.
Minimum Pump Inlet Pressure
Circulating pumps require a minimum inlet pressure in order to operate without cavitation. For the
minimum pressure requirements for Grundfos UPS and Magna 1 series pumps, refer to
page 31.
Pump
Up to 75
UPS32-80N
Magna 1 40-120
Magna 1 65-150
Note: the minimum relative inlet pressures apply to pumps installed up to 300m above sea level.
Increase the relative inlet pressure by 100mm for every 100m above 300m altitude up to 2000m.
Table 12: Minimum Pressure Requirements for Grundfos UPS and Magna 1 Series Pumps
Checking or Adjusting Pump Speed Setting – Magna1 Pump
Magna1 pumps have 3 speed settings and 3 control modes which must be set according to the
application. Refer to Tables 9 and 10 on page 29 for the correct speed setting.
1. Ensure a call for heat is present and that power is being supplied to the pump.
2. Press and release the speed selection (arrow) button on the pump fascia. Each press and release
of the button will advance the pump setting one position.
Minimum Inlet Head Required at Operating Temperature (m)
o
o
C
80
C
0.5
0.5
1.0
5.0
7.0
12.0
o
85
C
0.5
5.0
12.0
31
Table 12
o
o
90
C
95
C
3.0
5.0
5.0
5.0
12.0
12.0
on
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