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98
MERLIN
Smart Speed Controller
Description:
Merlin
SSC is a plug on printed circuit board (PCB) that can be installed on any system incorporating
the Danfoss BD35 or BD50 compressor.* The
Merlin
SSC PCB measures 1.75”w x 1.5”h and plugs on to the “C” and
“T” thermostat pins on the standard 101N0210 Danfoss electronic controller. The “C” and “T” pins are replicated on the
front of
Merlin
SSC to enable the thermostat wires to be connected. Not for use with the 101N0300 AEO controller.
12v or 24v DC power connection is made simple with “piggy back” slip on electrical connectors. A steady green LED
shows that thermostat circuit is open circuit; while a flashing LED shows speed compressor is currently running at.
*
Not recommended for pumped water cooled systems, or those utilizing a holding plate
Operation:
Merlin
SSC performs three functions:
1. Uses cold start ramp up speed routine for protection of electronics.
2. Automatically controls compressor speed for highest possible efficiency.
3. Gives visual indication of thermostat status or compressor speed.
(1)
Cold Start Ramp Up Sequence:
When a refrigeration system is first powered up (cold start), the loads
on the electronic controller are extremely high compared to normal cycling loads. This condition exists for only the first
few minutes of operation, then as the refrigeration process starts to work and begins to lower the temperature of the
evaporator, the loads on the electronics decrease accordingly. To protect the electronics from these potentially
damaging loads on a cold start,
Merlin
SSC will start the compressor in a medium speed and then ramp up gradually
until full speed is engaged after fifteen minutes of system operation.
(2)
Automatic Compressor Speed Selection:
Merlin
SSC will decide which of the six available
compressor speeds is appropriate, determined by the run time of the previous thermostat cycle and with reference to
the algorithm stored in memory. After the initial cold start ramp up sequence and over the course of the next few
cycles, the compressor speed choice will settle down to one that will give the longest possible run time and hence the
highest efficiency. As operating conditions and usage change, the compressor speed will be adjusted by
Merlin
SSC to
maintain the highest possible efficiency while ensuring that the box is kept at the desired temperature. The principle
behind controlling compressor speed being that the longer and slower a compressor can be run, the more efficient it will
be, and the less energy it will consume overall.
(3)
Status LED
: A green LED is provided on
Merlin
SSC to give visual indication of compressor status. When the
thermostat is open circuit and not calling for the compressor to run, the LED will be steady. When the compressor is
operating, the LED will flash corresponding to the speed at which the compressor is being operated. This is an
indispensible tool for troubleshooting thermostat issues, as well as for periodic system operational checks.
Prototype shown
#VE-E52151
