TB3188 - 3 MINUTE TIMER/LP BYPASS
7th January 2005
3 MINUTE TIMER/LP BYPASS on MCU+ & MHPUL serial numbers 0929785 - 0941044
A potential problem has been identified on the operation of the 3-minute timer/LP bypass that has been fitted to all MCU+ and MHPUL units since 10th June 2002. During the same period a number of kits and spares have been produced using the same timer.
Nature of the problem: the LP bypass function may only operate during the first cooling cycle following application of power to the unit.
Solution: a simple wiring modification will ensure the LP bypass function operates at every start of the cooling mode as designed.
Kits and spares you may have in stock, that were manufactured during this period, will be reworked by IMI.
Actions: the following actions are proposed which, with your assistance, will minimise any inconvenience: -
1. IMI Air Conditioning Ltd. will issue a kit , part number 55021250, comprising a link wire and instruction sheet, for every MCU+ unit supplied between 10th June 2002 and 9th July 2002.
2. The Distributor will secure one of the 55021250 kits to each MCU+ unit sold.
3. IMI Air Conditioning Ltd. will arrange the collection and checking of your stocks of:
55000490 KIT 28PSI LP & BYPASS TIMER
5500043 KIT 3MIN START DELAY TIMER and
04000499S PCBA TIMER/LP BYPASS 230V
Should a problem arise on site with an MCU+ unit that has already been installed, the solution may be explained using the 55021250 kit instruction, of which a copy is attached to this bulletin.
We apologise for any inconvenience caused.
For further information, please contact:
Technical Services Department
IMI Air Conditioning Limited
Brighouse Tel: 01484 405600
West Yorkshire Fax: 01484 400543
HD6 1QF Email:firstname.lastname@example.org TB3188 12/07/02
ADAPTOR KIT 55021250. Modification to MCU+ and MHPUL to ensure LP bypass operation.
Unit serial numbers between 0929785 and 0941044
1. Isolate the unit electrically: remove the access panel
2. Remove and discard the black wire between
1 Ph: Timer pcb terminal L.and contactor L1
3 Ph: Timer pcb terminal L. and contactor 13
3. Fit the link wire between timer pcb terminals 3 and L
4. Fit the wiring diagram next to the existing wiring diagram, inside the access panel.
5. Refit the access panel then return power to the system.