Boiler Control - Toshiba ESTIA RUA-CP1701H Service Manual

Monobloc Outdoor Unit
8.2.7.

Boiler control

In the case of very low outdoor air temperature or unit failure, the control will allow a gas or oil boiler to be activated as
supplemental heating or heating replacement of the heat pump when the operating conditions are not suitable for
thermodynamic heating.
Please note that the heat pump and the boiler are not allowed to run at the same time when connected to the
same water loop.
i) Operation by boiler
The boiler can be started under the following conditions:
• If the unit is in Heating Mode, but has stopped due to a detected system failure.
• If the unit is running in heating mode with a very low outdoor temperature that causes the thermo-dynamical
heating to be inefficient. The minimum OAT for Heating is by default -20.0°C [P514], but this value can be
adjusted by the user.
The boiler operation is disabled when:
• No boiler is configured
• Unit is not in heating mode
• Capacity limit of 0% is applied (Demand Limit [P067]
• DHW mode is active
ii) Control Operation
Set minimum
OAT for heating
using [P514]
[P514] = -7°C
HTG Mode
DO#07 Boiler
O/P
HP ON/OFF
DHW Mode
System Alarm
• To use the boiler control function a control relay (locally sourced) must be used to turn the boiler ON / OFF.
The relay coil must be rated for 230VAC 50Hz. The relay operation is controlled by DO#07 (set to "back up by
oil or gas boiler" by setting [P601] = 90
• The boiler ON trigger temperature can be adjusted using [P514] (range -20.0°C ~ 10.0°C; default -20.0°C)
• When there is a heating demand AND TO > [P514] then the heat pump is used to heat up the water in the
heating circuit [(1)]
• The boiler output will switch ON when there is a heating demand AND TO < [P514]. At this point the heat
pump will stop and the boiler will heat up the water in the heating circuit [(2)]
• If, when the heating is supplied by the back-up boiler, there is a DHW demand then the boiler output will switch
OFF and the heat pump will start in DHW mode to produce DHW. On completion of the DHW operation the
heat pump will stop and the back-up boiler will switch ON to provide space heating [(3)]
• The boiler output will remain ON until TO > [P514] + [P410] (hw_hyst: heat hysteresis) [(4)]
Related Parameters for Boiler Operation:
Par.No
514 Minimum OAT for heating – (oat_min): [°C]
601 Backup type – (bck_type):
TO (1)
(2)
5.0
2.5
0.0
-2.5
-5.0
-7.0
-9.5
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
Description
(3)
Range
-20.0 ~ 10
0 ~ 10
41
Service Manual
(4) (5)
Default
-20.0
0