Natural Cooling Function; Function Description; Nc-Box; Natural Cooling With The Nc-Box - Viessmann VITOCAL 222-G Technical Manual

Design information
(cont.)
Storing 100 % of heating energy for the duration of the power-OFF
periods is feasible, but not recommended, otherwise cylinders would
become too large.
Example:
Φ = 10 kW = 10000 W
HL
t = 2 h (max. 3 x per day)
Sz
=10 K
Δϑ
c
= 1.163 Wh/(kg∙K) for water
P
Spec. thermal capacity in kWh/(kg ∙ K)
c
P
Φ Heat load of the building in kW
HL
t Period in h during which the supply is blocked
Sz
V Heating water buffer cylinder volume in litres
HP
System cool-down in K
Δϑ
100 % sizing
(subject to the existing heating surfaces)
Φ · t
HL SZ
V =
HP c · Δ
P

12.9 Natural cooling function

Function description

With natural cooling, the heat pump control unit regulates the following
functions:
■ Switching all necessary circulation pumps, diverter valves and mix-
ers
■ Recording all essential temperatures
■ Dew point monitoring

NC-Box

■ The installation room must be dry and free from the risk of frost.
■ Vitocal 200-G/300-G: Install the NC-Box inside the installation room
above the heat pump and connect with the corrugated pipes sup-
plied.
■ Compact heat pumps: Install the NC-Box near the compact heat
pump and use on-site pipes for the hydraulic connection.
■ Carry out the diffusion-proof thermal insulation of all brine and cold
water lines in accordance with standard practice to prevent conden-
sation.

Natural cooling with the NC-Box

Subject to the probe/collector system and the temperatures under
ground, the NC-Box can transfer a refrigerating capacity of up to
5 kW.
For cooling, it is possible to connect either a heating/cooling circuit,
e.g. underfloor heating circuit or a separate cooling circuit, e.g. a fan
convector.
The NC-Box is equipped with all necessary circulation pumps, diverter
valves, mixer and sensors as well as the essential KM BUS interface
to the heat pump control unit.
The heat that is extracted from the heating/cooling circuit is transferred
to the ground by the NC-Box. This heat exchanger is connected in
series and enables a system separation between the primary and the
heating circuit.
Note
Thermally insulate all lines on site with vapour diffusion-proof mate-
rial.
VITOCAL
10000 W · 2 h
V = =1720 kg
HP
Wh
1.163 · 10 k
kg · k
1720 kg water represent a cylinder capacity of approx. 1720 l.
Selection: 2 Vitocell 100-E each with 1000 l capacity.
Rough sizing
(subject to the utilisation of the delayed building heat loss)
∙ (60 to 80 l)
V
= Φ
HP
HL
= 10 ∙ 60 l
V
HP
V = 600 litre cylinder capacity
HP
Selection: 1 Vitocell 100-E with 750 litre cylinder capacity.
The control unit enables the natural cooling function as soon as the
outside temperature exceeds the cooling limit (adjustable). Control
operated in weather-compensated mode when cooling via heating cir-
cuit (underfloor heating circuit). When a separate cooling circuit is
used, e.g. a fan convector, then the control is room temperature-
dependent.
DHW heating by the heat pump is possible during the cooling opera-
tion.
■ Power supply (1/N/PE, 230 V/50 Hz) is required.
Recommendation: Utilise the heat pump power supply from an on-
site power distribution board.
■ If the NC-Box is used with a separate cooling circuit (exclusively
used for cooling), protect that circuit via an additional expansion
vessel and safety valve.
■ Use only Teflon and EPDM seals for the connections on the NC-Box.
Arrangement of the NC-Box adjacent to the heat pump
■ For compact heat pumps Vitocal 222-G/242-G/333-G/343-G.
■ With the Vitocal 200-G/300-G, if the installation room above the heat
pump is not high enough.
■ Hydraulic connection with on-site pipes.
Arrangement of the NC-Box above the heat pump
■ With the Vitocal 200-G/300-G.
■ Hydraulic connection with corrugated pipe set.
12
VIESMANN
69