767 Pack Standby Modes

[NSEU]

Hope someone has an answer to the following:

In STBY NORM, C and W what happens to the Master and Cabin zone trim air valves?

Do they remain in the last commanded position?
Do they close?
Do they continue modulating?

In theory, what would happen, say, if the zone temps were selected to high and you selected STBY "C".

Thanks.
Rgds.
NSEU.

[None]

OFF closes the pack valve
AUTO is normal position for automatic pack control - according to selector
STBY N sets the pack control to produce normal temperature air continuously
STBY C is cooler than N - trim valve opens less
STBY W is warmer than - trim valve opens more

[NSEU]

Thanks, None, but I already knew what the pack does in this situation. What I really wanted to know was what the Trim Air system components did in this situation (i.e the main and individual Zone trim valves). Closed, open, remain in last position?

Thanks.

Rgds.
NSEU

[Joetom]

The packs make the air temp about right for lowest selected zone temp, the other zone valves open more to allow warmer air into said zones so as they can reach selected temp.

If one pack is in auto and other is in a stby mode, the auto pack will work out the best temp to provide.

[NSEU]

Thanks Joetom.

I probably should add a little more detail, so you know where I'm headed. A question was asked on another forum "What would happen if both packs were in Stby C?"

To know this, I would need to know if the Zone Temp Control system was completely shut off or frozen in the last position prior to the packs being selected to Stby C... or even still operating as best it could with the pack forced into cold mode.

Rgds.
NSEU.

[Terraplaneblues]

I had a look for this, it's not blindingly obvious at all, it seems that only the overheat relays can switch off the trim air system either by a genuine overheat or turning out of auto or trim reg off.

It appears that the ZTC would attempt to control whatever it is dealt with. Although the references to "backup" modes are really confusing i.e. not differentiated between PTC & ZTC.

Any one pack in stby appears go to relay control of it's components and also into a 40°F protection mode via a standby card which doesn't appear to talk to the ZTC.

However there is one annoying statement that the ops of the ZTC rely on packs being selected to auto and then is simply never refferred to again.....

Will continue looking. :confused:

[Joetom]

Think if both packs to stby c, they will both suppy cool temp air.

Zone contoller with need to keep zone valves more open that normal so as to supply suitable temps in zone.

In the above case, it may be that during flt zones may get to cold because volume of trim zone air will not raise duct temp enough.

If the above case and if both packs will only run stby c, may be switch off one pack to reduce cool air supply, think other pack will then supply 120% flow, but still cutting total flow by 80% and would guess the zone temps will be ok then may be.

Is this the question you asking.......???

[NSEU]

However there is one annoying statement that the ops of the ZTC rely on packs being selected to auto and then is simply never referred to again.....

&

Think if both packs to stby c, they will both suppy cool temp air. Zone contoller with need to keep zone valves more open that normal so as to supply suitable temps in zone.

Somehow, I will have to find a way to integrate these two statements. Perhaps the first statement is saying that for the optimum operation of the Zone Temp system, the Packs must be selected to AUTO?

Anyway, I'll keep digging.

Thanks, gentlemen.

Rgds.
NSEU.