Toshiba sm800 cassette problem

[Andy AC]

Hello guys, I have been called to a site which has 4 toshiba sm800 cassettes, (individual systems) with one controller. The problem is that the controller shuts down at random intervals, and stops all the units, and sometimes its as if system has had a complete power cut. Apparently this has been going on for a few months now, the staff just keep restarting the system.
Because all the systems have there own power supply, and the controller wires are daisy chained, killing the power to any of the units does not affect the controller, and will carry on with whatever units still has power.
I think it is highly unlikely that there is intermittent power failure to all four condensers, I have checked the a/c distribution board, however have not been able to check where that has been fed from., I have also checked for any external timeclocks etc. I am starting to think the controller is faulty, anybody got any other ideas?

Andy

[marc5180]

Hi Andy,

Have you checked the cable from the master indoor to the remote controller to verify no voltage drop or even breaks in the cable?

If this is ok then would it not be worth swapping the master indoor board with another indoor just to confirm the board is ok.

If so then it can only be the remote controller as you suggest,

[assailant]

id be checking the cable down to the wall controller first.
we see intermittent issues like that when mice get in and start chewing wires..

[install monkey]

external condensate pumps with failsafe float switch disconnecting the power supply? loose connection on indoor spurs? controller should auto address on powering up, http://www.mediafire.com/view/?81o38t6whxylkip sm service manual- interrogate remote controller - is there a fire alarm relay that's weak, page 112 of manual refers to group control and retrieving error history

[Andy AC]

Thanks for the input guys.
Unfortunately I have been told that I cannot spend any more time there unless someone agrees to paying for further investigation time.
The last time I was there I think I managed to set them all as individual systems, but after looking at the manual Install Monkey posted, I'm gonna have to check that again. I hate it when they only use one controller to control multiple units, what wrong with four separate ones.
No sign of any condensate pumps anywhere, there is some sort of fire panel next to the a/c board, but I cannot see how that is linked into the system if at all, might have been for the old systems from years ago.
I have also checked the connections at every indoor unit - all ok, and no sign of additional wires from fire panels/time clocks etc.
The system did at one time have the proper toshiba timer control fitted next to the controller, but has been disconnected.
I am currently unable to check the wiring into the condensers as some joker decided to put them high on the wall in cages - 2 man job and possible scaffold tower - I work alone.

Cheers again for the help, I will let you know what I find if I am allowed to go back.

Andy

[refcon32]

My company looks after a lot of Toshiba and had this problem a few times, of a blank controller, not even the lines on it, even though it had 15vdc at it. controlling four split systems. Had to reset everything to get it back on and then it would happen a couple of days later. resolved by a new master indoor board and controller, was a RBC 21, changed to the new RBC 32 controller.

[Andy AC]

I've popped back in a couple of times to see what was happening, and since my original visit, it has been behaving. I had come across another timer, which was installed with the original hvac equipment when the shop was built. The toshibas are replacements for original hitachis. Anyway, the panel has been set to off and the units have not faulted since. I have mucked about with the timer but still could not get it to switch on and off so presumably it had something to do with it. The staff now know not to touch and are nice and warm.

[paddyaircon]

if the outdoors are sm801 units check condition of secondry pcb on each. these have the three dip switches and are prone to failure in colder weather and have changed quite a few in coastal locations. a quick fix is to power down indoors and give the dip switches a toggle up an down a few times as the switch perishes. this pcb is located just above interconnection terminals . Good Luck !