City Multi Headache

[garytreez]

Today i had the pleasure of looking at a non working city multi PURY-P200-YGMA (R410A).
Compressor does not fire up despite the following checks -
6 indoor units run from this condensor, all running fan only with no fault code from each PAR 27 controller. All set to heat 24 degrees and all units go into standby permanently.
No fault codes on outdoor PCB and no visible faults on BC Box. A restart generates the correct sequence but then the outdoor unit read "1" (awaiting command). The compressor does not respond to any command but audible relay clicks are heard. The comms voltage is a steady 30 volts (OK). I have checked sw switch 1 and the outdoor unit can see all 6 indoor units. I have tried sw3 1&2 to test run and the indoor PAR 27 read test run as they should but still no firing up of compressor. and the outdoor unit read 1 at flags 2, 5 & 8. I have also put system into test, inverter board sw1 no 1 to "on", disconnected the cables from the compressor, powered back up and checked the voltage at these cables - 40v balanced....but thats all. I know that i should be getting this voltage as a start up to the compressor but i expected to get the mains voltage to this cable eventually but nothing.
The system was left in test for 90 minutes this morning whilst i fed my fat face & when i returned i recieved a fault code 6603 Communication error - Transmission line busy. This error has only appeared once .

sorry its long winded but i could really use some input please :) ps - gas is good.

[Thermatech]

Compressor warm up function
If the 3ph power was switched off at outdoor unit it will be warming the compressor for up to 30 mins if the outside air temp sensor is reading -5 or colder.

6603 is a worry because it is reporting external electrical noise has entered the 30vdc Mnet comms & scrambled the communications signal for more than 4 mins.
If the outdoor unit makes a constant ticking noise from the relay board then its usually a dead short on the comms 30vdc Mnet.
Make sure the comms cable is seperated from any 3 ph power cables & be sure the screen is daisey chain connected at BC & all indoor units.
Make sure the screen is connected to ground at the outdoor unit.

If comms cable with screen is correct then perhaps a faulty circuit board in the system.
Perhaps try disconnect 5 indoor units from Mnet daisey chain & just make the system outdoor / BC / one indoor.
Virgin start procedure to make the outdoor unit communicate with just one indoor unit & If the outdoor unit runs then suspect problem with comms cable / indoor circuit board / remote controller further down the daisey chain.

[garytreez]

Compressor warm up function
If the 3ph power was switched off at outdoor unit it will be warming the compressor for up to 30 mins if the outside air temp sensor is reading -5 or colder.

6603 is a worry because it is reporting external electrical noise has entered the 30vdc Mnet comms & scrambled the communications signal for more than 4 mins.
If the outdoor unit makes a constant ticking noise from the relay board then its usually a dead short on the comms 30vdc Mnet.
Make sure the comms cable is seperated from any 3 ph power cables & be sure the screen is daisey chain connected at BC & all indoor units.
Make sure the screen is connected to ground at the outdoor unit.

If comms cable with screen is correct then perhaps a faulty circuit board in the system.
Perhaps try disconnect 5 indoor units from Mnet daisey chain & just make the system outdoor / BC / one indoor.
Virgin start procedure to make the outdoor unit communicate with just one indoor unit & If the outdoor unit runs then suspect problem with comms cable / indoor circuit board / remote controller further down the daisey chain.
thanks thermatech, the relay ticking is only the initial on power up and a fan/very quiet compressor noise is heard but the compressor doesnt fire up. The compressor gets warm ok past 30 mins after power up. I will try each indoor unit in turn as you have suggested. I have also thought that it may be an outdoor board but its a lot of money if im not sure.

[garytreez]

Compressor warm up function
If the 3ph power was switched off at outdoor unit it will be warming the compressor for up to 30 mins if the outside air temp sensor is reading -5 or colder.

6603 is a worry because it is reporting external electrical noise has entered the 30vdc Mnet comms & scrambled the communications signal for more than 4 mins.
If the outdoor unit makes a constant ticking noise from the relay board then its usually a dead short on the comms 30vdc Mnet.
Make sure the comms cable is seperated from any 3 ph power cables & be sure the screen is daisey chain connected at BC & all indoor units.
Make sure the screen is connected to ground at the outdoor unit.

If comms cable with screen is correct then perhaps a faulty circuit board in the system.
Perhaps try disconnect 5 indoor units from Mnet daisey chain & just make the system outdoor / BC / one indoor.
Virgin start procedure to make the outdoor unit communicate with just one indoor unit & If the outdoor unit runs then suspect problem with comms cable / indoor circuit board / remote controller further down the daisey chain.

Thermatech - please excuse my lack of experience but what do you mean by the "screen" and could it also be a faulty circuit board on the outdoor unit ?, if so; would it be the power main board. I am back to this on Monday & ill carry out your reccomendations. Thanks :o

[Brian_UK]

The screen is the outer electrical shield of the data cable.

Inner two cores are connected to the respective terminals.

The screen must not be connected to a ground point or anywhere else in the terminal units or BC boxes etc.

It must however be cross connected where the data cables link at terminal units.

The screen is then grounded at the outdoor unit, only. This should then provide a shield circuit from the outdoor unit along all of the data cables but without touching anything else.

Its purpose is to carry any stray electrical signals from the data cables back to earth at the outdoor unit.

[garytreez]

thanks brian

[garytreez]

went back to this after a week, system isolated, sw2 1&2 virgin restart.....power off again....dips off....sw3 1&2 test......ran the test completely, no faults.......system working fine !!!!????
The difference in outside temp....at fault was -6 ,...working ok +2.
Im baffeled but its all working ok now !