Technical data

i-KI(R) MTD
19
HFC 410Ai-KI(R)_MTD_0011_0061_201307_EN
The control unit adjusts the speed of the primary circuit pump to
maintain the set domestic hot water temperature, adjustable
from 30°C to 65°C. If the domestic hot water temperature leav-
ing the heat exchanger reaches Tmax (between 60°C and
75°C) the primary circuit pump is switched off.
When the temperature falls below the threshold (Tmax) the
pump is started again.
For systems with supplementary solar heating, the primary
circuit temperature may exceed the maximum limit of 65°C
and pump speed modulation may not guarantee the DHW
set point.
In this case, a thermostatic valve should be used at the
instant domestic hot water production kit outlet to avoid
excessive domestic hot water temperatures.
The DHW recirculating pump can be managed (maximum pow-
er 185 W) by setting the water temperature in the recirculation
circuit.
When the temperature falls below the set point the recirculating
pump is activated, and vice-versa.
In addition, on and off times can be set for the recirculation cir-
cuit and a custom program created for each day of the week.
Selection guide
To choose the best system made up of storage tank and exter-
nal instant hot water production unit, the following three para-
meters need to be verified:
1. Tank volume is sufficient to produce the DHW required by
the system.
2. Instant flow-rate of the external unit is higher than peak deliv-
ery flow-rate.
3. Storage tank volume is higher than the minimum recom-
mended volume for correct heat pump operation (based on
heat output).
This condition is normally verified as the volume is quite low.
1.Storage tank volume
Tank volume and the characteristics of the primary source (heat
output and outlet temperature) are the parameters that deter-
mine the amount of water that can be delivered in a certain unit
of time. The following equation can be used to size the tank in
terms of volume.
V= [Wf*(Tout-Tin)/(T0-Tf)] - [(P*tm*1000)/(Cp*(T0-Tf)]
Where:
V: Required storage tank volume in litres
Wf: Amount of domestic hot water required in the peak peri-
od, in litres
Tm: Duration of the peak period in minutes
T0: Temperature inside the storage tank [°C]
Tf: Minimum usable storage tank temperature [°C]
Tin: Mains water inlet temperature [°C]
Tout: DHW delivery temperature [°C]
Cp: Specific heat of water 4.186 kJ/kg °K
P: Primary source heat output [kW]
2. Instant DHW production
The amount of domestic hot water required at the points of
delivery must be less than the amount produced by the unit.
The graphs on the previous pages illustrate the amount of water
produced by the units as the primary circuit temperature changes.
3. Thermal inertia
The storage tank, as well as accumulating energy to be used
when necessary, also acts as a buffer for the primary source of
energy, reducing the number of starts and stops.
The volume of the storage tank must therefore be greater than
the value recommended by the manufacturer of the primary
source (heat pump or other appliance).
Typical combinations
Below are some combinations for typical residential applications
with heat pumps.
* Domestic hot water flow-rate (l/min)
Tin = cold water from mains
Tout = domestic hot water
Primary inlet temperature [°C]
DOMH20 15 heating performance
* Domestic hot water flow-rate (l/min)
Tin = cold water from mains
Tout = domestic hot water
DOMH20 24 heating performance
* The domestic hot water flow-rate shown on the performance curves remains constant for a variable time, depending on the volume of the storage
tank. Also see the instructions in the "Selection guide”.
The combinations are calculated based on the following peak consumption:
- 60 l per person in single homes,
- 250 l per apartment with one bathroom,
- 350 l per apartment with two bathrooms,
- Simultaneous use factor
Type of home
no. of
people
no. of
bathrooms
Heat pump
heat output
Storage tank
volume
DOMH20
model
Single home <3 1 4 - 6 kW 300 15
Single home 4 - 5 2 6 - 8 kW 500 15
Single home 5 - 6 2 10 - 13 kW 1000 24
Single home 6 - 7 3 15 - 18 kW 1000 24
2 apartments 4 - 5 2 6 - 8 kW 500 15
2 apartments 7 - 8 5 15 - 18 kW 1000 24
3 apartments 7 - 8 3 15 - 18 kW 1000 24
3 apartments 9 - 12 6 20 - 22 kW 1000 24