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INTERFACING MIXIT TO THE BMS USING ANALOGUE SIGNALS

In the case of retrofit where no BACnet or Modbus interfaces are available MIXIT can be controlled via
analogue signals. The complete terminal overview is given in the MIXIT installation and operating instructions
that can be downloaded at

https://product-selection.grundfos.com/

, search for MIXIT, click on a MIXIT

product and browse to documentation. The most relevant are listed in Table 8.

Action

Input

Notes

Relevant MIXIT application

Set start

Pull DI5 low

Input has internal pull up

all applications

Set stop

Pull DI5 up

Input has internal pull up

all applications

Set setpoint

CI01

Configure range and type in
Grundfos GO

all applications

Temperature control
enabled

Relay 2

all applications

Fault

Relay 1

all applications

Boiler setpoint

CIO3

Voltage 0-10 corresponds to
0-100 deg. C.

all applications

Set overheat risk

Pull DI4 up

Input has internal pull down

underfloor heating

Remove overheat risk

Pull DI4
down

Input has internal pull down

underfloor heating

Set frost risk

Pull DI4 up

Input has internal pull down

heating coil

Remove frost risk

Pull DI4
down

Input has internal pull down

heating coil

Air sensor input

CI02

Configure range and type in
Grundfos GO

heating coil

Table 8: Most relevant datapoints associated with the underfloor and radiator heating applications.

Содержание MIXIT

Страница 1: ...MIXIT integration Guide Application guide JAN2022 ...

Страница 2: ...gration of MIXIT in AHU control with MIXIT configured for the heating coil application 8 4 3 1 AHU sequencing with safety functions for heating coil 8 4 3 2 Signal diagram of AHU 12 4 3 3 Signal diagram of AHU with MIXIT configured with the heating coil application 14 4 4 Integration of MIXIT in AHU control with MIXIT configured for the radiator heating application 16 5 MIXIT with radiators and un...

Страница 3: ...it can interface to MIXIT s fieldbus profile 3 Interface to a programmable controller that only supports analogue I O Use case 1 is the common situation for large systems Use case 2 is sometimes used in smaller buildings Use case 3 can be encountered if the integration task you face is for retrofit with an older BMS system If facing use case 1 sections 3 and 4 are of relevance if integrating with ...

Страница 4: ...eld level reflects the case for an air handling unit AHU 1 1 Alternative option for interfacing MIXIT to a dedicated controller If MIXIT cannot be connected at the automation level in use case 2 for example because no spare analogue outputs are available or there is no BACnet MS TP or Modbus RTU fieldbus master available at automation level there is one additional way of interfacing MIXIT to the d...

Страница 5: ...ture control loop of MIXIT The tuning of the dedicated control shall be slower than that of the MIXIT controller otherwise there is a risk that the overall control will oscillate and therefore the recommended option is to transfer the setpoints from the dedicated controller to MIXIT via the automation layer as shown in Figure 2 The source for the start stop signal that shall be given at a digital ...

Страница 6: ...or BUS control this is a persistent configuration and shall only be set once The configurations are described by Table 2 Action BACnet Modbus Persistent setting Object for setting Object for status Register for setting Register for status Config set point from fieldbus MV 0 3 MV 0 00117 2 00117 Yes Set setpoint from fieldbus AO 0 AI 0 00102 00311 No Set bus control state BO 0 1 BI 0 00101 0 1 0020...

Страница 7: ...s the fluid temperature flowing towards the coil The difference between the two are briefly described below In either case local setpoints sequencing and safety functions can be managed by the AHU controller The application selection is done via the Grundfos GO app 4 1 MIXIT AHU control of discharge air temperature heating coil application Figure 4 shows the simplified cascaded control loops assoc...

Страница 8: ...water temperature that is supplied to the coil MIXIT controls therefore the water temperature TF out of the mixing loop according to the setpoint The AHU controller is responsible for setting the appropriate water temperature setpoint such that the air temperature leaving the coil is at its appropriate setpoint for TA Figure 6 Alternative AHU control loops with MIXIT The drawbacks of this way of i...

Страница 9: ...r Figure 7 shows the state diagram of MIXIT with the integrated coil preheat and frost protection functions enabled The shown states are as follows READY If a start signal is not given MIXIT is in the READY state The pump is stopped and the valve is closed PREHEAT When a start signal is given the PREHEAT state is entered e g see section 4 3 1 2 TEMPERATURE CONTROL When the coil has been preheated ...

Страница 10: ...th the preheat function disabled Even simpler if the internal frost protection function has also been disabled the only thing that can bring MIXIT to the frost state is either a signal on the fieldbus BACnet BO 4 Modbus 00101 7 or a signal at a digital input from a frost thermostat Figure 9 shows how to interface to MIXIT when the coil preheat function in MIXIT is enabled The example in the figure...

Страница 11: ... Figure 9 MIXIT detects frost by the build in frost detection function It could also be signaled from the AHU control to MIXIT to go into FROST state This is done by setting frost risk BACnet BO 4 Modbus 00101 7 In that case MIXIT sets frost risk detected BACnet BI 7 1 Modbus 00204 4 1 as would happen when frost was detected by the build in frost detection function ...

Страница 12: ...4 3 1 2 The build in preheat function The preheat function will warm up the coil until the water return temperature is above a certain threshold The threshold can only be set from Grundfos GO e g see Figure 10 The preheat function makes sure there is a flow in the shunt such that the return temperature sensor can be trusted That is it exists into the TEMPERATURE CONTROL state shown in Figure 9 whe...

Страница 13: ...n for all is that heat recovery is needed and there are coils to control the temperature leaving the AHU It is for this temperature control MIXIT can be used In Europe air handling units often have a structure like the one shown in Figure 11 In the figure sensors and control loops relevant for control of the air temperature leaving the AHU are shown and sensors and control loops relevant for contr...

Страница 14: ...controller have the following functions zone temp controller Calculates the reference for supply air temperature bases on the discharged air stream temperature and the outdoor temperature sequencing and defrost Decides which control loop runs and by which setpoint Priority for air heating is via the heat recovery system if such is present It also controls defrosting of the heat recovery system pre...

Страница 15: ...st protection in the figure happens by a temperature switch with manual reset This can be used exclusively or alongside the build in frost protection function in MIXIT Figure 13 shows the same system but where setpoints and on off signals are read back and the flags for finished preheating of the coil BI 1 and frost risk detected BI 7 are used for appropriate sequencing with the rest of the AHU co...

Страница 16: ...on fieldbus analogue signal internal variable Temperature control enabled BI 1 q air temp heating coil preheat and frost TF TS TR Valve opening AI 1 9 MI XI T AI 2 1 AI 1 7 AI 1 6 AI 2 7 AI 2 0 _ q ZONE TA Outdoor air Discharge air preheat temp controller air temp heating zone temp controller coil preheat and frost sequencing and defrost TZ TO TF TS TR Set start stop BO 1 Start stop read back BI 2...

Страница 17: ...erature control loop Air inlet temperature control loops via heat recovery Setpoint for air inlet temperature control with coil Coordinating balance between heat regeneration and heat injection with mixing loop Defrosting of heat recovery system Controlled by MIXIT Direct control of the air temperature at the coils according to setpoint from AHU controller Safety functions o Heating coil preheat o...

Страница 18: ...sor is integrated in the shunt so if using this datapoint from MIXIT to detect the preheat the water temperature towards the coil must be less than the water supply temperature to MIXIT otherwise there is no shunt flow and the instantaneous return temperature measured at the sensor in shunt is not correct in this case If using the heating coil application with the build in preheat function this pr...

Страница 19: ...controller interaction with MIXIT when configured with the radiator heating application Figure 16 shows a signal diagram of MIXIT configured for the radiator heating application Table 5 list the associated control and status registers ...

Страница 20: ...controller water temp control zone temp controller sequencing and defrost TZ TO TF TS TR on off BO 1 on off read back BI 2 setpoint AO 0 setpoint read back AI 0 damper ratio on off setpoint defrost TA valve opening AI 19 TZ TA reference AHU controller TZ reference AHU MI XI T signal available on fieldbus other signal internal variable AI 21 AI 17 AI 16 AI 20 _ ZONE 1 TA Outdoor air Discharge air T...

Страница 21: ...aximum level This is to avoid triggering the overheat protection function in case of a small overshoot The control loop carried out by MIXIT is shown simplified in Figure 18 Figure 18 MIXIT control loop with setpoint limitation due to overheat protection function For example if the overheat protection function is set with a maximum level of 50 deg C and the given setpoint is above the 45 deg C MIX...

Страница 22: ...s are listed in Table 7 Figure 20 MIXIT used with floor heating application Action BACnet Modbus Persistent setting Object for setting Object for status Register for setting Register for status Set start BO 1 1 BI 2 00101 1 1 00201 3 No Set stop BO 1 0 BI 2 00101 1 0 00201 3 No Set overheat risk Overheat risk detected BO 3 1 BI 6 00101 4 00212 6 No Set setpoint from fieldbus AO 0 AI 0 00102 00311 ...

Страница 23: ... Pull DI5 up Input has internal pull up all applications Set setpoint CI01 Configure range and type in Grundfos GO all applications Temperature control enabled Relay 2 all applications Fault Relay 1 all applications Boiler setpoint CIO3 Voltage 0 10 corresponds to 0 100 deg C all applications Set overheat risk Pull DI4 up Input has internal pull down underfloor heating Remove overheat risk Pull DI...

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