Carrier 30RQ Operation And Maintenance Instructions

Also see for AQUASnap 30RB: Manual Installation, operation & maintenance instructions Installation instructions Installation, operation and maintenance instructions Controls and Troubleshooting

Contents

Carrier 30RQ Operation And Maintenance Instructions Manual pdf 31 page image

315.7 - Demand limitThe demand limit is used to restrict the unit power consump-tion. The Pro-Dialog control system allows limitation ofthe unit capacity, using one of two methods:• by means of user-controlled volt-free contacts. Theunits without energy management option only have onedemand limit level (only one contact: control contact 3).The units equipped with energy management optionpermit three demand limit levels (2 contacts). The unitcapacity can never exceed the limit setpoint activatedby these contacts. The limit setpoints can be modifiedin the setpoint menu.• by means of a 4-20 mA input type on the energy manage-ment board. The limit is now based on a linear interpo-lation from 0 to 100%, based on the input signal. Thedemand limit in night mode is selectable (if the valueis below the one controlled by the external signal).5.8 - Night modeThe night period is defined (see User configuration) by astart time and an end time that are the same for each dayof the week. During the night period, the number of fansoperating can be reduced, and the unit capacity may belimited (but a minimum capacity value can be configured).5.9 - Capacity controlThis function adjusts the number of active compressors tokeep the heat exchanger water temperature at its setpoint.The precision with which this is achieved depends on thecapacity of the water loop, the flow rate, the load, and thenumber of stages available on the unit. The control systemcontinuously takes account of the temperature error withrespect to the setpoint, as well as the rate of change in thiserror and the difference between entering and leavingwater temperatures, in order to determine the optimummoment at which to add or withdraw a capacity stage. If thesame compressor undergoes too many starts (per hour) orruns below one minute each time it is started this automa-tically brings about reduction of compressor starts, whichmakes leaving water temperature control less precise. Inaddition, the high pressure, low pressure or defrost unloadingfunctions can also affect the temperature control accuracy.Compressors are started and stopped in a sequence designedto equalise the number of start-ups (value weighted bytheir operating time).5.10 - Head pressure controlThe head pressure is controlled by a maximum of six fans.As an option, a variable-speed controller can control one orall of the fans. The head pressure is independently controlledfor each circuit, based on the saturated condensing tempe-rature value.Fan start-up:ATTENTION: The fans can be started periodically (forcleaning), even if the unit is switched off.5.11 - Defrost functionDefrost is activated, when the unit is in heating mode, inorder to reduce frost build-up on the air heat exchanger.The defrost cycle can only be applied to one circuit at atime. During the defrost cycle the fans of that circuit arestopped, and the four-way refrigerant valve is reversed,forcing the circuit to cooling mode. The fan can temporarilybe restarted during the defrost cycle. The defrost cycle isfully automatic and does not require any setting.5.12 - Additional electric heater stage controlThe heat pump units can control up to four additionalelectric heating stages.The electric heating stages are activated to complement theheating capacity when the following conditions are satisfied:• The unit uses 100% of the available heating capacity,or the unit is limited in its operation by a protectionmode (low suction temperature, hot gas or defrostsequence in progress protection), and in all casescannot satisfy the heating load.• The outdoor temperature is below a configured threshold(see User 1 configuration).• The unit demand limit is not active.The user may configure the last available electric heatingstages as a safety stage. In this case, the safety stage is onlyactivated in addition to the other stages if there is a machinefault, preventing the use of the heating capacity. The otherelectric heating stages will continue to operate as describedabove.5.13 - Control of a boilerNOTE: The control of the electric heating stages or of aboiler is not authorised for slave units.The unit can control the start-up of a boiler, if it is in heatingmode. When the boiler is operating, the unit water pump isstopped.A heat pump unit and a boiler cannot operate together. Inthis case the boiler output is activated in the followingconditions:• The unit is in heating mode, but a fault prevents theuse of the heat pump capacity.• The unit is in heating mode, but works at a very lowoutdoor temperature, making the heat pump capacityinsufficient. The outdoor air temperature thresholdfor use of the boiler is fixed at -10°C, but this valuecan be adjusted in the User 1 menu.5.14 - Master/slave assemblyTwo PRO-DIALOG Plus units can be linked to produce amaster/slave assembly. The two machines are interconnectedover the CCN bus. All parameters required for the master/slave function must be configured through the Serviceconfiguration menu. Master/slave operation requires theconnection of a temperature probe at the common manifoldon each machine, if the heat exchanger leaving watertemperature is controlled.