Feature Notes
Light Commercial Boiler Controller
BLR / DIN / DHW / .../ ...
Main Features Ideal for small heating schemes Controls 1 or 2 Boilers & Pumps,1 Heating Zone Valve and 1 DHW Valve Self adapting Weather Compensated Control Boiler plant operates on demand from the building, not a fixed time programme Control of Additional Boilers, Pumps Sets or Heating Zones by using additional submodules Automatic Summer/Winter Changeover

Summary Features

General

The SeaChange combined boiler and HWS controller has been designed to cater for small scale boiler plants and is an alternative to our conventional boiler controller used is commercial heating plants. The controller is a cost effective solution for small heating schemes and provides all the energy saving features and functionality in line with other SeaChange heating controllers. The controller works in conjunction with the SeaChange zone controller to provide control of a heating and hot water circuit. The SeaChange zone controller is a feature packed user interface which has specifically been designed with the use in mind. The interface is intuitive and simple to use and enables the end user to have control over their own environment. Features such as optimum start/stop, time profile setting, holiday mode, extension timer, setpoint adjustment and fabric protection are provided as standard providing high levels of comfort and energy efficiency

Heating and DHW demand signals

The DHW Boiler Controller has built-in controls for 1 zone of Domestic Hot Water, with a locally wired temperature sensor to measure DHW temperature, an output for an On/Off valve and an internal setpoint (set on parameter HWSP). The Heating valve is controlled by one or more Zone Controllers (Consumer Modules); the Occupancy Status of all the Consumer Modules will be used to set Occupancy Times for the DHW service.

If no internal Domestic Hot Water demand exists, the Boiler Flow Temperature setpoint will equal the Heating setpoint which is generated by Zone Controller demand (see Weather Compensation and Trim, later).

If a DHW demand exists, the Boiler Flow Temperature setpoint will automatically be raised to 10 degC above the DHW setpoint (HWSP).This will normally exceed the setpoint required by the Heating circuit, so the Heating valve will be opened and closed on a time proportioned basis to control the temperature in the Heating circuit to the Heating setpoint. The minimum-on time constant for this feature, (which represents the shortest time that the Heating valve will open for) is set using the PERD parameter, or alternatively can be set using the SELECT pushbutton.

If multiple demands are being received from other modules requiring Primary CT water (for instance, another VT circuit controlled by a Secondary Circuit Controller, or another Domestic Hot Water load) the Boiler Flow Temperature setpoint will automatically be raised to the correct value to satisfy the Module with the highest demand. Modules that require Primary (CT) water send their Demand signals in the form of a setpoint, which is high enough to account for Primary losses.

Typical Application

Detailed Features

Registration

Registration is the simple process by which logical connections are made between Controllers in a SeaChange system; it is done at time of commissioning and involves pressing buttons on the Controllers in a specific sequence, see our 'Design Guide' publication.

Registration of Secondary Boiler Controllers (Boilers without Housekeeping)

Secondary Boiler Controllers must be registered with the Controller in the system which is performing System Housekeeping Functions, (usually a Boiler Controller). This part of the registration process will allocate a system address to the Secondary Boiler Controller. The Register button on the Secondary Boiler is pressed, and its Status lamp will flash to indicate its address (Heat Source) number, see 'Design Guide'.

Registration of Boiler Controller Submodules

If the Boiler Controller has Submodules to control pump sets, additional boiler stages etc, they must be Registered to the Boiler Controller. The Boiler Controller is put into Configuration Mode, and the Submodules are Registered to it, see 'Design Guide'.

Registration of Consumer or Distributor Modules - Demand Linking

The Boiler Controller must be provided with at least one demand signal from another module - otherwise it will not run (it is demand-driven). The Boiler Controller is put into Configuration Mode, and the Consumer and Distributor Modules that it feeds with heat energy are Registered to it, see 'Design Guide'.

This sets the HTSC parameter in each Consumer or Distributor Module to “point” their Heating Demand signals at the Boiler Controller.

Zone and Slave Zone Controllers Registered in this way will generate demands for the local Secondary (VT) circuit controlled by the Boiler Controller; other Modules (e.g. Secondary Circuit Controllers, AHU Controllers, DHW Controllers) will generate CT demands for the Primary circuit. These parameters could be manually set in each Controller as an alternative to this part of the Registration process, if desired.

Alarms

The Boiler Controller may be set to generate Alarms, which may be sent to a Doorway Supervisor or other Network Alarm device. Alarms may be enabled by setting the ALRM parameter. The text strings generated at Doorway are as follows;

Danger of Freezing

This Alarm is generated when any of the connected water temperature sensors (Flow, Return or DHW sensor) shows a reading below 3 deg C; implying the Frost Protection strategy has failed.

Outside Sensor Failed

This Alarm is generated when either the locally wired thermistor sensor fails (to open or short circuit), or if a Networked Outside Sensor is used, the alarm will be sent if this device fails.

External Alarm Inputs

The 2 external inputs ‘a’ and ‘b’ may be used for monitoring purposes only, or alarm generation, or alarm generation with plant shutdown. The ALRM parameter is used to set the desired action, and the ALST parameter is used to set the sense (ie. whether a closing or opening contact generates an alarm) of the inputs.

Status Monitoring only may be selected by setting ALRM to O; the status of inputs can be read on parameters INPA and INPB.

Status Monitoring with Alarms is selected with ALRM set to 3; this generates a GENA/B Alarm, but takes no Control action.

Boiler Stage Shutdown, no Alarms is often used for Maintenance switches, or Summer/Winter Boiler changeover switches. Set ALRM to 1.

Boiler Stage Shutdown, Lockout Alarm is often used for Lockout signals; set ALRM to 2 (generates LOKA, LOKB alarms).

General Plant Shutdown, Stop Alarm; this uses the critical alarm signal wired to input ‘a’ (input ‘b’ is available for another signal). An event on input ‘a’ (e.g. a Fire Alarm) will shut down all Controller outputs and all other plant which is set to respond to a STOP Alarm. Set ALRM to 4

DHW Priority

The DHWP parameter may be set to give priority to DHW where the plant is sized for Heating or DHW, but not both, or where a fast DHW recovery is required; if this is used, the heating will be disabled until all DHW services are up to temperature.

Flow & Return Temperature Control

The Boiler Controller is capable of several different methods of controlling Flow and Return Temperatures. All of them are based on the principle of controlling to the lowest possible water temperature in order to minimise circulation losses; the Controller decides which method to use depending on which sensors are connected to it.

If just a Flow Temperature sensor is connected, the Controller will control using a Flow Temperature setpoint. If just a Return Temperature sensor is fitted, it will control using a Return Temperature setpoint. If both are fitted, an average value is used, which is usually the best method. However, parameter SACT may be used to force the controller to use Flow or Return control if desired.

MAXF and MINR are used to set the Maximum Flow and Minimum Return Temperatures; the Minimum Return Temperature is important for protecting some boilers against back-end corrosion.

Boiler Sequencing and Duty Rotation

Multiple Boilers will be automatically rotated in their sequence on the basis of “longest running boiler goes off first”. This equalises running hours of the boilers, and also gives good controllability under part load conditions. A Fixed sequence version of the Boiler Controller is available if required (See last page for order code). This is useful where modular boilers must be brought on in a fixed sequence, or where single and two stage boilers are mixed.

Pump Control and Demand

To maximise energy efficiency,normally the heating will run only when a heating demand exists; when the Zones are satisfied, the valve will close. If, however, the Zone Controllers are not optimally located to give a comprehensive indication of demand from all areas, the MIND parameter can be set to zero, i.e.. no demand is necessary to run the heating. This will mean that the heating will run, controlling to the heating setpoint, for the whole of the Occupation period. Alternatively, Parameters in the Zone Controllers may be set to achieve a similar result while minimising the overheating effect that may otherwise occur (see Zone Controller Data Sheet for further details).

Pumps are started as each Boiler is fired or if only one pump is present, when either Boiler is fired, (parameter NPMP sets the number of Primary Pumps) and continue to run-on after the Boiler(s) have shut down.The BRON parameter sets the run-on time for the pumps.

When Heating or DHW is demanding heat, the appropriate valve opens before any boilers or pumps run, to ensure an open hydraulic path for the water. When demand reduces to zero, the valve stays open for the run-on time of the pump(s).

If Actuator Controllers are used in the heating system to control multiple On/Off Zone valves, the MODE parameter should be set to 1; this will ensure that at least one Zone valve will be fully open during a period of demand or run-on.

Note - this feature is only available in Boiler Controllers with Housekeeping function; the MODE parameter in non-Housekeeping Boiler Controllers is fixed MODE=0.

Maintenance mode

In Maintenance mode, the Boiler Controller simulates a 50% demand signal from Zone Controllers, so the heating will control to the Weather Compensated setpoint. DHW will control to its normal Occupied setpoint. This is useful for commissioning during the summer months, when no heating demand exists.

The Controller is put into Maintenance Mode by holding down the Override button until the status light flashes rapidly; the Controller will stay in this mode until the button is pressed again.

Heating Valve - setting the minimum-on time

The Heating valve output will automatically switch into a Time-Proportioning mode of operation if the Primary Flow Temperature is much higher than the heating setpoint. This may occur when heating demands are relatively small, resulting in a low heating setpoint, but an internal demand for DHW exists, which will drive the Primary Setpoint to a high value. In order to maintain an average heating flow temperature which is approximately the same as the heating setpoint, the heating valve will open and close (or, if a pump, will turn on and off) on a Time-Proportioning basis.

To prevent damage to the valve or pump from excessive cycling ,the Minimum-On time of the Heating output is set by the PERD parameter or alternatively can be set using the SELECT pushbutton.

Hold down the Select Button until the Temperature lamp flashes red slowly; the Heating output relay will now energise. Wait until the valve or pump has been energised for the desired Minimum-On time before proceeding, the relay will stay energised indefinitely, (until the button is pressed again - this gives an opportunity to correct any faulty wiring).

Now press and release the Select button; the lamp will now stop flashing, and the relay will de-energise. The Minimum-On time will have been stored (in non-volatile memory-unaffected by powering-down the Controller).

Weather Compensation and Trim

The Boiler Controller runs the Boiler Plant on the basis of demand signals that it receives from other SeaChange Controllers. For the heating circuit, the demand is received from one or more Zone Controllers, which provide Optimum Stop/Start control of the occupied space.

The Boiler Controller controls water temperature for the VT circuit according to a Weather Compensated setpoint; this is further modified by demand signals from the Zone Controllers to produce the Heating setpoint. Any Zone or Slave Zone Controllers which are registered to the Boiler Controller for the purposes of Heating Demand (i.e. their HTSC parameter is set to point to the Boiler Controller) will be used in the calculation.

Zone Controllers produce demand signals varying between -100% (full cooling) and +100% (full heating). The Boiler Controller adapts the Weather Compensation to “learn” the building’s characteristic by keeping the highest-demanding Zone device at a +50% demand level during occupancy.

Trim and Adaption

If the demand level is above or below 50%, the Weather Compensated setpoint is modified by two effects in the Fuzzy Logic Control loop; the trim effect will rapidly raise or lower the setpoint to take care of short-term changes in load.

The adaptive effect will additionally raise or lower the setpoint if the “error” from the 50% level is sustained over a long period, which represents the control system “learning” the thermal characteristic of the building.

The effects of these adaptations can be limited; the maximum excursion from the Weather Compensated setpoint caused by the effects can be set on two Configuration Parameters: TRNG sets the maximum trim effect, and CRNG sets the maximum influence of the adaptive effect.

Other Parameters

MXVT is a limit to heating flow temperature, and also defines the Weather Compensated setpoint at 0 degC Outside temperature.

FLAV defines another point on the Compensator curve (at 10 degC Outside Temperature).

SMRT is the Outside Temperature beyond which the Heating will be prevented from running.

Boost Mode

When any of the participating Zones are more than 1.5 degC below their setpoint, they will drive the Heating setpoint into a Boost condition; it will temporarily leave the Compensation Curve with its adapation, and be set to the maximum permissable temperature, MXVT. Only when all Zones are within 1.5 deg C of their respective setpoints will the Heating setpoint return to the adapted Compensation curve. This is done in order to perform the fastest possible Optimum Start, and also to provide a predictable heat input to the Zone in order that the Zone Controller’s Optimum Start self-adaption will work properly.

It is possible to disable the Boost feature; this may be necessary if none of the participating Zones are reading a representative temperature (for instance, a Hotel heating system where it is impractical to put sensing in all of the rooms, and a simple Weather Compensated scheme will suffice). In this case, ZBST may be adjusted to disable Boost. Be aware that doing this will almost certainly disrupt the Optimum Start abilities of the system.

Frost and Fabric Protection

Frost Protection is arranged as a 3-Stage sequence, which operates from a Frost Protection setpoint relating to Outside Air Temperature.

Stage 1 is invoked if the Outside Temperature falls below the Frost Protection setpoint. The heating valve will open and the primary pump will run for 10 mins every hour.

Stage 2 is invoked as temperature in the primary circuit or the DHW Calorifier falls close to the Frost Protection setpoint. The primary pump now runs continuously, the heating valve will open, and the DHW valve will open if the DHW temperature is low.

Stage 3 is invoked as the temperature in the primary circuit or DHW Calorifier reaches the Frost Protection setpoint. The Boilers will now fire, until all water temperatures reach 35 degC.

Disabling Frost Protection

Stages 1&2 Frost protection may be disabled; this may be useful in a Domestic installation, where the noise of pumps running during the night is intrusive, and pipework is all contained in occupied parts of the building, and is hence unlikely to freeze. The procedure is deliberately made complex, in order to avoid inadvertant use:

Access the FRST parameter using a Zone Controller, and reduce it to its lowest allowable setting of 2°C. Now put the Boiler Controller into Maintenance Mode and temporarily “short” the Outside Sensor connection using a wire shorting link. Refresh the FRST variable (by pressing Select on the Zone Controller); it will now display as 0°C, this value can now be “written” (i.e. pressing the Override button on the Zone Controller) to the Boiler Controller.

Take the Boiler Controller out of Maintenance Mode and remove the shorting link, confirm the FRST setting is 0°C, the variable is now fixed at 0°C and cannot be adjusted by normal methods.

To re-enable frost protection, select the 'FRST' variable and put the Boiler Controller into Maintenance Mode. Press the Override button on the Zone Controller ( to “write” the parameter to the Boiler Controller); the 'FRST' variable will default back to 2°C. Take the Boiler Controller out of manual operation, the 'FRST' variable can now be set as normal to any permissible value.

Fabric Protection

Fabric Protection is an independent process operating in Zone and Slave Zone Controllers, with the purpose of protecting the building fabric against damage due to condensation. If the temperature in the space falls below the Non-Occupied setpoint (usually set to 10 degC) the Zone Controller will send a demand signal to the Boiler Controller, which will start the plant in the usual manner.

System Housekeeping Functions

In a conventional Wet Heating environment, the Boiler Controller performs several important housekeeping functions for the rest of the system.

Firstly, it contains the real-time clock, which broadcasts time-of-day and day-of-week information to any modules that may need it. The clock may be set from any Zone Controller, and the time information is backed up by a Capacitor, which means that the correct time is retained for a minimum of 8 hours in the event of power failure (providing that power has been applied for at least 1 hour).

Secondly, it broadcasts Outside Temperature to any other modules that may need it; it acquires the temperature either from a sensor directly connected to its input terminals 15 and 16, or from a Networked Outside Temperature Sensor. In the absence of both sensors, it will transmit a default value of 0.1 degC lower than the Frost Setpoint (FRST).

Thirdly, it performs an important role in the unique SeaChange Registration process; it is responsible for the automatic allocation of system addresses during registration. It also keeps track of all Registered Controllers, so that if one of them fails, a replacement will be automatically allocated with an address. This automatic feature may prove troublesome when commissioning large sites, so it can be disabled using parameter RPLN. When Commissioning is complete, the automatic mode can be re-instated. For further details, see our Commissioning Guide document.

DHW Times and run-on feature

The operating times for the internal DHW Control is set by the Zone Controllers registered to the Boiler Controller. If any of the registered Zones are in Occupancy, the DHW control will be enabled. Sometimes it is useful to be able to extend the DHW operating times beyond the normal Zone times (for instance, if cleaners require hot water out of hours). The parameter HWRO may be used to make the DHW run-on after the last Zone has finished its Occupied period.

Submodules

The Boiler Controller may have a number of Submodules to extend its control capabilities;

Options and Product Codes

Light Commercial Boiler Controller

BLR / DIN / DHW /

SC Controls Ltd

PO Box313
Wadhurst
East Sussex
TN5 6JL

phone 08707 606040
fax 08707 606041
e-mail seachange@sccontrols.co.uk
http:// www.seachange.co.uk