Feb 2015: TB 3211 Fan Speed Controller Change

Technical bulletin:TB/2015/3211
Title:Marstair condensing units fan speed controller change
Product:Condensing units fitted with Saginomya fan speed controllers
Models:MCU+, CKC and MRC
Date:16 February 2015

With immediate effect, the Saginomiya condenser fan speed controller has been changed to an Alco model.

All MCU+, CKC and MRC condensing units are now supplied with an Orange link between terminal 40 and 41.  The fan will run at full speed for commissioning when the link is fitted.

Simply remove the link for the condensing unit to run with fan speed control. Details for adjusting the controller and an example of a wiring diagram are shown below:

The new spare for this fan speed controller is 04401288 and is backwards compatible for replacing the previous controller. The previous fan speed control spare 55000487 is now obsolete.

The head pressure controller is factory set to suit the refrigerant. It may be necessary to adjust this to suit site conditions, to raise or lower the nominal head pressure.

1. With the system switched off, connect a high-pressure gauge to the liquid line service valve.
2. Switch on the system, and run for a few minutes to stabilise.
3. The head pressure should be approximately: R407C: 18.9-19.6 Barg, to achieve this remove sealing plug and insert 2mm Allen key into setting screw. Turn the Allen key clockwise (+) or counterclockwise (-) to readjust the setting. Do not turn setting screw more than three turns clockwise (+3). Use the following table as a quick guideline for setting:

Pressure changes per turn of adjusting screw:

Pressure change 1: 4.0 … 12.5 bar: Clockwise ~ +1.2 bar, counterclockwise ~ -1.2 bar

Pressure change 2: 9.2 … 21.2 bar: Clockwise ~ +2.5 bar, counterclockwise ~ -2.5 bar

Pressure change 3: 12.4 … 28.4 bar: Clockwise ~ +3.3 bar, counterclockwise ~ -3.3 bar

After adjustment, re-insert sealing plug and make sure that it is properly fitted. IP65 protection requires a firmly sealed plug.


Tolerances for condensing temperatures setpoint: ±2K

Minimum fan speed (0 rpm) and fan cut in pressure 13.8 Barg are factory set and not adjustable.

NOTE: The condenser fan may stop if the operating pressure drops below 13.8 Barg.