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Z14 regulator voltages

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Bob Barrow

Joined: 11 Jan 2006
Posts: 29

Posted: Sun Aug 08, 2010 3:26 am Post subject: Z14 regulator voltages

I have installed a Z14 split bus architecture with 2 B&C LR3 regulators. I have a couple of avionics devices that can draw power from both buses. They will draw power from whichever bus providing the greater voltage.



In order to ensure that a particular bus normally provides the power to these devices I will presumably have to have that bus running at a slightly higher voltage than the other. As provided by B&C the LR3 generates 14.2 volts. I presume that I will have to set the secondary bus(non preferred current supplier)  to a lower voltage. 



My question is what voltage should I set the secondary bus to: would 14.0 volts do the trick.



My second question is how do I determine the actual voltage of the adjusted secondary regulator without actually running the alternator (I'm probably 12 months away from running the engine). In other words I know how to make the adjustment but I'm not sure how to determine if the voltage adjustment is accurate.



Regards Bob Barrow

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nuckolls.bob(at)aeroelect
Guest

Posted: Sun Aug 08, 2010 8:49 am Post subject: Z14 regulator voltages

At 06:26 AM 8/8/2010, you wrote:




I have installed a Z14 split bus architecture with 2 B&C LR3 

regulators. I have a couple of avionics devices that can draw power 

from both buses. They will draw power from whichever bus providing 

the greater voltage.



In order to ensure that a particular bus normally provides the power 

to these devices I will presumably have to have that bus running at a 

slightly higher voltage than the other. As provided by B&C the LR3 

generates 14.2 volts. I presume that I will have to set the secondary 

bus(non preferred current supplier)  to a lower voltage.



My question is what voltage should I set the secondary bus to: would 

14.0 volts do the trick.

   Why are you doing this? The whole idea behind

   Z-14 was to cover any single point of failure

   with a robust plan-b. What kind of event do you

   anticipate that takes down an entire bus structure

   such that "dual sources" for some appliances is

   called for? The whole architecture of Z-14 is already

   set up to offer 4 sources of power for everything

   in the airplane no matter what bus the device is

   fed from.



My second question is how do I determine the actual voltage of the 

adjusted secondary regulator without actually running the alternator 

(I'm probably 12 months away from running the engine). In other words 

I know how to make the adjustment but I'm not sure how to determine 

if the voltage adjustment is accurate.



   You can't. All operating adjustments are made

   with the alternator turning and anticipated

   loads turned on.

   Bob . . .

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Bob Barrow

Joined: 11 Jan 2006
Posts: 29

Posted: Tue Aug 10, 2010 12:23 am Post subject: Re: Z14 regulator voltages

Yep, I take your point Bob. However the engine management system on my EFIS of choice will only provide me with a voltage reading on both buses if I actually source power from both buses via a primary and secondary power input. And I really want a voltage reading for both buses.



My ignorance was in thinking that the EFIS would source power from the bus of higher voltage...and that it would oscillate constantly between the two buses if they had similar voltages. But the EFIS manufacturer now advises me that this is not how it works.  



In fact the EFIS always draws power from the primary bus, and only switches to the secondary bus if the voltage on the primary bus drops below approx 8 volts. 



Of course having a seamless transition to the secondary bus in the event of a catastrophic failure of the primary bus ensures that there is no reboot and therefore no loss of potentially crucial flight information.



Six years of building and I'm still learning something new virtually every day. It's great. And the "Connection" is the most fabulous of resources.



Cheers Bob Barrow



My question is what voltage should I set the secondary bus to: would 

14.0 volts do the trick. 



Why are you doing this? The whole idea behind 

Z-14 was to cover any single point of failure 

with a robust plan-b. What kind of event do you 

anticipate that takes down an entire bus structure 

such that "dual sources" for some appliances is 

called for? The whole architecture of Z-14 is already 

set up to offer 4 sources of power for everything 

in the airplane no matter what bus the device is 

fed from.

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue Aug 10, 2010 6:44 am Post subject: Z14 regulator voltages

At 03:23 AM 8/10/2010, you wrote:

 	  Quote: 	
		  

<bobbarrow10(at)hotmail.com>



Yep, I take your point Bob. However the engine management system on 

my EFIS of choice will only provide me with a voltage reading on 

both buses if I actually source power from both buses via a primary 

and secondary power input. And I really want a voltage reading for both buses.


	


   These are independent electrical systems and

   would normally be fitted with separate voltmeters.

   They certainly need to be fitted with their

   own active notification of low voltage.

 	  Quote: 	
		  My ignorance was in thinking that the EFIS would source power from 

the bus of higher voltage...and that it would oscillate constantly 

between the two buses if they had similar voltages. But the EFIS 

manufacturer now advises me that this is not how it works.



In fact the EFIS always draws power from the primary bus, and only 

switches to the secondary bus if the voltage on the primary bus 

drops below approx 8 volts.



Of course having a seamless transition to the secondary bus in the 

event of a catastrophic failure of the primary bus ensures that 

there is no reboot and therefore no loss of potentially crucial 

flight information.


	


    We've had a lot of builders investing intellectual

    and emotional capital in devising golden power sources

    for devices that are not themselves golden. Failure

    TOLERANT design assumes that EVERY installed item

    is subject to failure from defect, wear-out or

    improper installation. The elegant design uses

    the minimum of components and operating procedures

    to detect and react to any single failure for

    any reason.



    With a cross-feed contactor closed, All the busses

    in Z-14 enjoy (count 'em) FOUR separate sources

    of electrical energy. Detecting and reacting to loss

    of an alternator requires nothing more than active

    notification of low voltage for each bus. All contactors

    are pre-flight tested and the cross feed contactor

    is normally left off in flight. The layers of capability

    to react to a failure in this system are many and

    robust.



    Catastrophic failures don't happen. Some single

    component fails which MIGHT produce a reduced bus

    voltage . . . but doesn't take it to zero. Do

    you plan to spend a lot of time boring pathways

    through clouds? If your EFIS suffers its own failure,

    what is your plan for dealing with it? It is many

    times more likely that your EFIS wanders off into

    the weeds than it is to loose power.



    We'll have several options available for monitoring

    the health of a multi-source electrical system.

    One interesting device is the 9011 multi-channel

    monitor. Two such devices installed on Z-14 would

    provide real time monitoring of both alternators and

    battery contactors.

 	  Quote: 	
		  Six years of building and I'm still learning something new virtually 

every day. It's great. And the "Connection" is the most fabulous of resources.


	


    I'm pleased that you find the work useful. It's

    been a great project for me in that much of

    what I've been able to share with the OBAM

    aircraft community is not understood/practiced

    by segments of the TC aircraft community.

    Attempts to help them understand and react to

    this condition have thus far been un-successful.

    They don't know what they don't know and

    cannot appreciate the increased risks, costs of

    certification, manufacturing and ownership that

    accompanies such ignorance.



    You folks are building some of the most utilitarian,

    low cost and lowest risk airplanes in the world.

    I am pleased to be a participant in that endeavor.



   Bob . . .

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