mCq pCO - Standard + Heat Pump - McQuay

Conditioning: pCO Standard chiller + heat pump User Guide ver. 2.9 02/11/99It is also possible to set a dead (neutral) zone around the set-point permitting the compressors -as well as the fans when working in freecooling mode - to remain off.In this way the steps of both fans and compressors will be moved on the right with respect tothe selected dead zone. The example below shows the position of the steps after havingselected a neutral zone around the set-point.dead zoneC = compressorP = parzializationC1P1C2P2setpointdifferentialwatertemperatureNote: the range of the dead zone must be inferior to the selected differential otherwisethe connected devices will not activate.Compressors start-up (with and without capacitycontrolled)Any time the compressor is instructed to start, the relative contactor will energize and -depending on the value of the water temperature at evaporator inlet or outlet - the controllerwill:- instruct the compressor to start;- energize the LIQUID SOLENOID valve.- the compressor will start.Compressors shiftSelecting the compressors shift ensures longer life to the compressors.This procedure, in fact, makes them work in a very balanced way and compensates the numberof their on/off routines as well as their working hours.The shift is based on a F.I.F.O. logic: the first compressor that starts will be the first to bestopped.At the very beginning this logic might cause an unbalanced compressors management but thesystem will gradually settle.Upon a call for compressor start-up, the logic will be as follows:- the compressor that has been Off for the longest time-interval will be the first to start;- the first compressor that starts will be the first to be stopped;- any compressor will start again only after all the other compressors have started once.Capacity-controlled routines do not undergo shifts.Pag.27/61