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Unit 2 Block 4
Castlehill Ind. Est., Carluke
Scotland ML8 5UF

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LSC2A Staging / Load Sequencing Controller

LSC2A Staging / Load Sequencing Controller
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  • Up to 6 Stages in one unit
  • Up to 11 stages with slave unit
  • Directly interfaces to low cost logic input thyristor stacks or to contactors
  • Built in Burst fire and Single Cycle Control Algorithms
  • Allows modulating stage oversizing for stable control
  • Stage rotation facility to balance heater usage
  • Algorithms for heaters installed in-line or distributed around a vessel
  • Galvanically isolated digital inputs and outputs


The LSC2A load sequencing controller is designed for use with a large process heating system which is split into several banks of heaters, all of which apply heat input to the same heating load. The staging controller balances the required heating demand by switching on the number of stages (heater banks) which most nearly match the demand, and modulating one additional stage to make up the difference. Versions are available with combined relay + logic outputs and all logic outputs. A single analogue output is also provided. Relay + logic types are used with contactor stages + 1 modulating thyristor stage; all logic outputs are used when all the stages are controlled by thyristors. The analogue output may be used to drive one modulating thyristor which accepts a standard analogue input signal if preferred.

The staging technique provides the following advantages:-

1. On large electric heating systems the load is broken into banks of a smaller kilowatt rating, and the maximum size of load being switched on or off at any one time is reduced. This reduces the magnitude of switching disturbances on supply lines, and is particularly useful where the load represents a significant proportion of the supply capacity.

2. On systems where the load demand does not frequently vary over a wide range the non-modulating stages may be contactor controlled, and the modulating stage thyristor controlled.

The LSC2A controller is based on our successful LSC2 controller. It includes additional features which have been incorporated over time in various versions of the LSC2 controller; in particular a digital enable input and the ability to change operating modes between standard burst fire and single cycle burst fire using a digital input.

More detailed product information is available on our downloads page

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