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C. OPERATING DESCRIPTION
The
Dorchester DR-SG
is coupled to a DHW tank, the customer regulates the DHW setpoint
he wishes to obtain at the product outlet, which will be the same setpoint for the tank and the
Dorchester DR-SG
.
A pump is installed between the tank and the
Dorchester DR-SG
that can reactivate the tank
loading when the water it contains is lower than the setpoint minus the recovery hysteresis.
The control mechanism of the variable flow pump means that the water leaving the
Dorchester
DR-SG
rises in temperature more quickly (outflow close to the bottom heel of the pump). The flow
is then gradually increased to maintain the burner in operation throughout the DHW loading.
IMPORTANT:
When you are in DHW comfort mode (2 cursor on the HMI) the DHW
tank loading pump operates permanently, the pump restarts in reduced
mode (1 cursor on the HMI) when the temperature in the tank is not
satisfactory.
You can choose to operate in permanent comfort mode (2 cursors on the HMI), permanent reduced
mode (1 cursor on the HMI), or a timer program to alternate comfort and reduced modes (2 cursors
on the HMI + timer program ).
This pump operates during anti-legionella cycles to obtain a uniform water temperature in the
storage tank.
A timer program can be used to perform loading at either the comfort DHW setpoint or at the
reduced DHW setpoint.
IMPORTANT:
Check that the loop flow rate and temperatures comply with the
regulations; if necessary, adjust the loop circulator adjustment valve
and/or the mixing tap setpoint.
In principle, the circulator between the tank and the Dorchester DR-SG is dimensioned to ensure
a flow rate equal to P / (1.16 x ∆T)
- with P being the nominal power of the Dorchester DR-SG (in kW) and
- ∆T = setpoint T – cold water T considering the temperature of cold water in summer.
However, it is imperative that this flow rate is higher than the loop return flow rate in the tank, once
you are sure of compliance with distribution loop regulations.
It should be remembered that the power of the Dorchester DR-SG must be determined on the
basis of DHW consumption but also taking into account the heat losses of the distribution loop.
The Dorchester DR-SG's regulator will control the speed of the circulator; based particularly on the
return temperature and the instantaneous partial power, the circulator's flow rate will be adjusted
to maintain a flow temperature equal to the setpoint temperature, meaning that the electrical
power absorbed by the circulator will be minimised.
In summary, the circulator's maximum speed must be set to ensure a flow rate that is at least equal
to the loop return flow rate in the tank, so that the minimum speed setting can correspond to the
low limit speed of the circulator.
Diagram: DR-
SG120 bis
page 2 / 7
Page 60 / 104
00U07337760-A
DORCHESTER DR-SG -
Installation, Operation and Maintenance