Mark MEGAFLEX, Technical Manual

Page: 15 / 58

EN
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4.2.5 Slow start
The boiler uses the “slow start” procedure to prevent the boiler from supplying excessive power in low
load situations.
After “zero check” APS and closure APS with pre purge ignition starts. Following, a stabilization period,
the boiler modulates down to low capacity and maintains this capacity for 1 minute. Subsequently the
boiler power increases at a target rate of 4°C/min until maximum capacity or set temperature has been
reached. Once heat demand has finished the burner will turn off following a set post purge period.
The graph below illustrates this;
4.2.6 Protection against insufficient flow through boiler
When the requirements of 6.3.2 are fulfilled the boiler will protect itself against insufficient flow. This is
done by checking the difference in temperature between flow and return (so called ΔT).
In a low flow scenario the ΔT will rise rapidly. The ΔT safe-guarding principle is as follows ;
At ΔT > 22 the boiler starts modulating
At ΔT between 22 and 27 the boiler continues modulating
At ΔT > 27 boiler the fan speed will reduce until ΔT < 25