ModvFresh 2

Pump unit to deliver fresh hot domestic water (HDW) with electronic control and high efficiency pump

Employment: on inertial cylinders (buffer tanks) connected to standard thermal heating systems, heat pumps, thermal solar and biomass systems. It provides fresh hot domestic water, avoiding phenomena of bacterial pollution, such as the legionnaire’s disease, due to the stagnation of the hot water. The compact size allows an easy installation even on small cylinders.

The unit, by a special electronics, modulates the speed of the primary high efficiency circulating pump, from a minimum speed of 10% up to 100%, in order to provide always a precise temperature of exploitation (f.i. 45°C). The variation of the requested flow is suddenly recorded by a digital sensor that gives the inputs of flow and temperature.

Two models are available, fully assembled and pre-wired:

50 kW, with flow up to 20 l/min, for domestic use installations;
70 kW, with flow up to 30 l/min, for heat pumps up to 18 l/min;

Selction chart to deliver HDW at 45°C with cold water at 10°C:

Heat source	Buffer tank temperature	Flow	Return temperature	Code
Heat pump	52 °C	15 l/min	33 °C	031300-70-30
Heat pump	55 °C	18 l/min	31 °C	031300-70-30
Gas, biomass, boiler, thermal	60 °C	20 l/min	33 °C	031300-50-20
Gas, biomass, boiler, thermal	68 °C	30 l/min	29 °C	031300-70-30

Features:

High Efficiency circulating pump;
Delivered hot water temperature: 45°C with supply water temperature at 10°C.
The HDW temperature is adjustable every single degree from 30°C up to 70°C;
A big surface heat exchanger weld-braised made of stainless steel AISI 316 guarantees a remarkable thermal exchange that allows a water return to the buffer tank at a temperature up to 25°C;
The heat exchanger can be easily removed in case of maintenance and/or cleaning;
Counting of used energy by means of the digital sensor (cold water temperature fixed at 10°C);
PPE insulation box (277 x 417 x 137 mm). A special back plate fixes the unit to the insulation box and it allows a quick fitting to the wall or to the cylinder;
The pump unit is supplied with 3/4” Male connections (pipe-union).

A special ball valves kit, on request (to be ordered), completes the installation.

FIELD OF UTILIZATION:
For a maximum power of 70 kW and flow up to 30 l/min.
Nominal supply temperature of the storage tank: 60°C.
Nominal temperature of the water supply: 10°C.
Nominal temperature of HDW production: 45°C, adjustable from 30°C up to 70°C.

Technical features

Maximum allowed pressure (without water hammer):	6 bar
Working temperature:	2 ÷ 95 °C
Headloss in the secondary circuit at the flow of 20 l/min (50 kW model):	3 mH₂O
Headloss in the secondary circuit at the flow of 30 l/min (70 kW model):	6,5 mH₂O

Connections size: min. DN20 (Cu 22x1) near the cilynder.

On demand, a test report of the VFS is available. It shows the result of the tests made directly in the Grundfos Lab.

Pump unit assembled with optional ball valves kit

Diagrams of the pump unit performances

The following diagrams relate the user’s flow rate and the supply temperature to the buffer storage tank, according to the requested temperature of HDW. This allows to identify the minimum supply temperature needed to supply HDW at a required temperature and flow. Vice versa it is also possible to fix which is the maximum usable flow at the selected HDW temperature, at the available supply temperature.

HDW pump unit ModvFresh 2 - 50 kW

HDW pump unit ModvFresh 2 - 70 kW

The buffer temperature must be almost 5 K higher than the desired temperature of the domestic water. Bigger temperature differences allow to extend the tapping time.

DANGER OF SCALDS: To avoid scalds to the users, the temperature of hot water supplied must never be more than 60°C. This temperature limits is preselected into the controller, anyway it can be reduced.

Code 50 kW, 3/4”: 031300-50-20
Code 70 kW, 3/4”: 031300-70-30