60
PMML0600 rev.0 - 06/2022
5
MINIMUM WA
TER V
OL
UME DESCRIP
TION
DRAIN AND WA
TER PIPING
5.6 Minimum water volume description
The following part shows how to calculate the minimum water volume in the system for product
protection (anti-hunting) and temperature drop at defrosting.
MODEL
4HP
5HP
6HP
7HP
Minimum Volume *
L
55
55
55
55
NOTE
(*) Minimum volume is applicable for usual working conditions. If T
wi
temperature during normal
operation is below 25ºC, the following steps must be applied to consider the defrost effect.
1 Minimum required water volume during defrosting
The following formula is used to make the calculation:
Where:
V =
360 x Q
DEF
; Q
DEF
=Q
I
+ Q
Y
ΔT x 4168.8
V =
Required water volume (m
3
)
The minimum volume of water needed in the installation to cover the heat loss caused by a
reduction in the delivery water temperature during defrosting.
ΔT =
Permissible water temperature drop (ºC)
Drop in the delivery water temperature that the client is willing to allow in the installation.
Q
DEF
= Heat loss during defrosting (kW)
Heat loss caused in the system by reducing the delivery water temperature, which may
affect the user’s comfort level of warmth. This value is the sum of the two following items:
Q
I
= Heat demand from the installation (kW)
While defrosting is taking place, the unit is not providing the heat required to cover the
heat demand from the installation. This value can be obtained in 2 ways:
1. By using the value of the energy demand from the installation, if known.
2. If this value is not known, it can be estimated by using the heating capacity of the unit at
an air temperature of 0ºC WB and a delivery water temperature at, for example, 45ºC.
Q
Y
= Cooling load on the YUTAKI M / YUTAKI Hydrosplit unit (kW)
In addition to not providing the heat required to cover the heat demanded by the
installation during defrosting, the unit is also producing cold. It can be estimated that this
