• 25 •
Application Guide /NEOSYS-AGU-1801-E
eDrive™ VARIABLE WATER FLOW BY LENNOX
3 control modes available :
Constant speed
• Interest to set the right installation design fl ow (avoid setting valve).
Constant Delta P (setting to declare the required working pressure)
• Implementation and management adapted to systems with two-way valves and bypass of the installation to ensure a minimum
water fl ow back into the evaporator.
Constant Delta T (Setting to declare the required delta T)
• Need a good installation with well balanced circuits to ensure good fl ow distribution when the fl ow is reduced.
• Installation with terminal units fi tted with 3-way valves.
Operation for each mode:
• Constant speed : eDrive pilots the pump to the water fl ow desired when the compressors are in operation. When the compressors
are stopped (dead zone), control will automatically reduce the speed of the pump to the minimum water fl ow This minimum fl ow
is also adjustable within minimum 30Hz (60% fl ow).
• Constant delta P : the eDrive™ regulation is managing the pump to maintain the required delta P in order to keep constant the
customer available static pressure. When the terminals control valves close in response to decreased building loads, the pump
controller slows the pump speed to maintain the target delta P. In this mode the pump does not detect terminal capacity reduction
(fan speed staging)
• Constant Delta T : the eDrive™ regulation is managing the pump to maintain the required Delta T. When the Delta T is increasing
in response to the number of compressors running, the pump controller increases the speed of the pump. Conversely, when the
compressors are stopping in response to decreased building loads, the pump controller slows the pump speed to maintain the
target Delta T.
Safety parameters:
• If the evaporating pressure reaches the low limit (risk of evaporator frosting), the fl ow is increased.
• If the outlet evaporator temperature reaches the low limit, the fl ow is set to the maximum.
• When the pump speed varies and the fl ow switch trips, the fl ow is automatically increased.
• During defrost procedure (HP), the fl ow is set to the maximum.
• Pump motor supply range from 30 Hz minimum to 50Hz maximum. Minimum pump motor frequency set at 30 Hz. Below this value,
risk of pump motor failure due to overheat.
• For safe operation of the chiller, the unit is protected by the fl ow switch.
• Minimum and maximum admissible water fl ow per unit size: with constant delta T, the fl ow may vary from 60% to 100% of the
selected pump nominal fl ow.
• Maximum change in fl ow rate through the evaporator: a 10% per minute change in fl ow rate is admissible in most of air conditioning
applications.
HYDRAULIC EQUIPMENT
To Next Page
Loading...