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Question on Z-13 and E-Buss (Lengthy)

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piavis(at)comcast.net
Guest

Posted: Tue Oct 10, 2006 8:29 pm Post subject: Question on Z-13 and E-Buss (Lengthy)

I’m approaching the time where I need to spend some time on this board but forgive the somewhat basic nature of the questions.  

   

I’m starting to work on installation of the Z-13 architecture in an RV-7, IFR with dual GRT EFIS, and Garmin stack (SL-30/480/327), P800B audio panel, and TT DigiFlight II AP.  

   

I’ve done the load analysis and have come up with the following ( do have a full spreadsheet with each phase of flight listed against Normal Ops, Main Alt Fail, and Battery only):  

   

Main Buss: Total 26.5A  

   

Alt Field  

Lights - Taxi  

Lights - Nav  

Lights - Strobe  

Pitot Heat  

Flap Motor  

Auto Pilot - Pitch  

Auto Pilot - Roll  

Auto Pilot - Control Head  

   

E-Buss: 6.4A  

   

Alt Field  

EFIS 2 HIS  

Magnatometer/ AHRS  

Trim - Roll  

Trim - Pitch  

Turn Coordinator  

GNS-480 (Nav)  

GNS-480 (General)  

GNS-480 (Com)  

GTX-327 (Xpondr)  

   

Battery: Average 4A  

   

EFIS 1 ADI  

Fuel Pump  

Starter  

EDI 4000 (Eng Monitor)  

GMA-340 (Audio)  

SL-30 (Nav)  

SL-30 (Com-Rec)  

SL-30 (Com-Tx)  

EI #1 (P-Mag)  

EI #2 (P-Mag)  

Lights - Lnd  

"Lights - Flood/Cargo -.1  

     Cargo - .1  

     Panel- .5A  

     Cockpit - .2"  

Main Battery Contactor  

Starter Contactor  

Clock  

   

The list for the Battery buss seems extensive but my thoughts were that if stuck on top IFR, these items are potentially needed. Yes, that assumes both main and SD-8 alternator went south. The question is, using an SD-8, can run over 8A on the buss? Is this a valid distribution of components? Some of these on the Batt buss are also used for start (EIS) or ground ops (lights, clock). The other question is can I split the power leads on the SL-30 without making the radio inop for receive- only?  

       [quote][b]

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Jekyll

Joined: 22 Feb 2006
Posts: 44

Posted: Wed Oct 11, 2006 8:55 am Post subject: Re: Question on Z-13 and E-Buss (Lengthy)

Look more closely at the Z-13/8 schematic. Notice that the E-bus bypasses the battery contactor by running through the B-bus path. Therefore, the battery contactor draw is only on the M-bus.



Next, most of the loads on your B-bus are more appropriate for the other busses. Your B-bus should most likely contain only the items you want hot at all times, IE: those items you always want on, even when not operating such as your clock, hobbs, dome light (In your case, the cockpit light) or an accessory plug.



Remember the purpose of your E-bus: to provide an uneventful transition from normal operations to an endurance method to safely get you where you are going with the movement of 2 switches (turn off the master/battery and turn on the alternate feed). Once you arrive, you can turn the master/battery back on and use your other systems for approach and landing with a full battery to provide the extra load capacity. 



Here are some specific things to consider:



The chance of both alternators failing the same bag of gas is very, very remote.



You will probably be starting with both the M-bus and E-bus on; no real reason to start on just the B-bus that I know of, adding that capability clutters up your B-bus (remember, there is no way to turn off your B-bus other than disconnecting the battery. If you introduce a switch, then you really don't have a B-bus.



The EIS-4000 may be on the E-bus and be on for start and during the endurance flight. Some folks say the engine info is not needed for endurance flight and they are probably correct. My view is that it is a GOOD thing to have in endurance mode IF YOU CAN AFFORD IT.



Wire 1 DU, the AHARS and the magnetometer to the E-bus, make sure you have an on/off switch for the EFIS per GRT recommendations. The EIS-4000 doesn't need a switch.



From the B-bus: Move the fuel pump, starter, starter contactor, second com/nav, battery contactor, EFIS 1 ADI, GMA-340, landing light, flood/cargo lights to the M-bus.



Leave the clock, cockpit lights and both mags on the B-bus (P-mags are optional here because they will generate internal power over approximately 700 rpm).



Check the GMA-340 to see if it has a power off default to direct feed for #1 COM/NAV. I bet it does and therefore, no power to the audio panel is needed to operate #1 com/nav on the E-bus.



Consider placing the A/P on the E-bus. If you are IFR, you'll want this for safety and peace of mind.



You can have "normally-off" items on your E-bus with no penalty. I have a windscreen fan on mine. It only draws .45 amps and it is a transient load, not continuous so it doesn't add into my E-bus load. I'll turn it on for short periods if my glass fogs.



You didn't provide your load analysis so I don't know how you calcuated the trim. I assume you understand the trims are transient loads and don't effect your E-bus load. 



I'm not a GNS-480 user but I believe they have com/nav/GPS/WAAS. Look over your load numbers and see if the extra load over and above that of just the SL-30 is worth the allocation. You may decide the SL-30 is enough. It meets the FAA requirements and is an extremely powerful device. I bet you will have a backup handheld GPS when you are IFR. You can easily wire your panel to allow you to plug the handheld into the EFIS and AP through an isolator switch. In this way, you save some of your load for other items and still have your GPS and com/nav. You will lose the WAAS enabled IFR GPS but you will have VOR/LOC/GS and the EFIS enhancements of your handheld GPS to include full capability of the AP.



The GTX-327 should go on the M-bus. It is not required for safe continuance of flight. The FAA has transponder-inoperative procedures. Should you really need to ident, you can turn the M-bus on for a minute to make contact. The transponder takes 1.5 amps and is almost 20% of the output from the SD-8. Save that power for more important things such as the AP.



Finally, you are not limited to a total of 8 amps on your B and E-busses. Your battery will make up for any deficiencies. Say your total endurance load is 9 amps, the SD-8 will provide 8 amps and the battery will make up the extra 1 amp. Even a poor battery should be able to provide 1 amp for a tank's worth of fuel; it did start your engine after all. If you notice some problems developing down the road, you can start to remove loads from the E-bus as the need arises. Remember, the E-bus is there to provide you a no-brainer, no-sweat method to safely and quickly reconfigure your electrical system to an endurance mode with the movement of 2 switches – no thinking, no troubleshooting and no calculations. 



I don't know the answer about configuring the SL-30 to power only receive mode. I think it has 2 power feeds, 1 for com and 1 for nav.



I don't make any assertions that my observations are complete or even accurate. Just provideing another perspective that might help you.  I found this part of building to be very fun and informative. It's where the learning and operational planning merge. Your methods and results may vary.



Jekyll

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nuckollsr(at)cox.net
Guest

Posted: Thu Oct 12, 2006 3:42 am Post subject: Question on Z-13 and E-Buss (Lengthy)

At 09:27 PM 10/10/2006 -0700, you wrote:



 	  Quote: 	
		  I m approaching the time where I need to spend some time on this board but 

forgive the somewhat basic nature of the questions.



I m starting to work on installation of the Z-13 architecture in an RV-7, 

IFR with dual GRT EFIS, and Garmin stack (SL-30/480/327), P800B audio 

panel, and TT DigiFlight II AP.



I ve done the load analysis and have come up with the following ( do have 

a full spreadsheet with each phase of flight listed against Normal Ops, 

Main Alt Fail, and Battery only):



Main Buss: Total 26.5A



Alt Field

Lights - Taxi

Lights - Nav

Lights - Strobe

Pitot Heat

Flap Motor

Auto Pilot - Pitch

Auto Pilot - Roll

Auto Pilot - Control Head



E-Buss: 6.4A



Alt Field

EFIS 2 HIS

Magnatometer/ AHRS

Trim - Roll

Trim - Pitch

Turn Coordinator

GNS-480 (Nav)

GNS-480 (General)

GNS-480 (Com)

GTX-327 (Xpondr)


	


 	  Quote: 	
		  Battery: Average 4A

EFIS 1 ADI

Fuel Pump

Starter

EDI 4000 (Eng Monitor)

GMA-340 (Audio)

SL-30 (Nav)

SL-30 (Com-Rec)

SL-30 (Com-Tx)

EI #1 (P-Mag)

EI #2 (P-Mag)

Lights - Lnd

"Lights - Flood/Cargo -.1

      Cargo - .1

      Panel- .5A

      Cockpit - .2"

Main Battery Contactor

Starter Contactor

Clock


	




   It's not clear from your narration that you've categorized this

   list of loads for modes of operation. Not all loads are on

   for all modes of operation. The battery bus has things on

   it that are (1) not necessary for keeping an engine running

   or (2) need to be operable on the ground with the rest of

   the airplane powered down.



   Suggest you use this form as a guide:



http://www.aeroelectric.com/PPS/Load_Analysis/Blank_Form.pdf



   prepare one page for each of the three busses. Decide

   which load item will feed from which bus, what CONTINUOUS

   loads they present to the bus and under what conditions

   those loads would be present.





 	  Quote: 	
		  



The list for the Battery buss seems extensive but my thoughts were that if 

stuck on top IFR, these items are potentially needed. Yes, that assumes 

both main and SD-8 alternator went south. The question is, using an SD-8, 

can run over 8A on the buss? Is this a valid distribution of components? 

Some of these on the Batt buss are also used for start (EIS) or ground ops 

(lights, clock). The other question is can I split the power leads on the 

SL-30 without making the radio inop for receive- only?


	


   Don't understand the "receive only" mode . . . if you

   don't punch the mic button, then you're in a receive

   only mode no matter how power is wired to the transceiver.

   All SL-30 loads would be supplied by the e-bus which

   needs to be pre-flighted anyhow by closing the e-bus

   alternate feed switch before closing the master contactor.

   Get your ATIS and Clearance before bringing the main bus

   up and starting the engine.

   Bob . . .

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N6030X(at)DaveMorris.com
Guest

Posted: Sun Oct 15, 2006 6:33 am Post subject: Question on Z-13 and E-Buss (Lengthy)

One thing I find useful when you get bogged down in M-bus vs E-bus vs 

B-bus divisions is to go flying and start turning off everything 

electrical.  Eventually you realize just how little you really need 

to have, unless you're in IMC with ice.  For instance, the turn 

coordinator is sometimes presumed to be important, but in VFR, it's 

just not needed at all, so it doesn't have to be sitting there on the 

e-bus drawing all that current.



Also, remember in the event of an off-field emergency landing, you 

want to be able to shut off your fuel pump and some other things 

you've currently got wired to your battery.



Dave Morris



At 11:27 PM 10/10/2006, you wrote:

 	  Quote: 	
		  I'm approaching the time where I need to spend some time on this 

board but forgive the somewhat basic nature of the questions.



I'm starting to work on installation of the Z-13 architecture in an 

RV-7, IFR with dual GRT EFIS, and Garmin stack (SL-30/480/327), 

P800B audio panel, and TT DigiFlight II AP.



I've done the load analysis and have come up with the following ( do 

have a full spreadsheet with each phase of flight listed against 

Normal Ops, Main Alt Fail, and Battery only):


	


.. snip ...



 	  Quote: 	
		  

Battery: Average 4A



EFIS 1 ADI

Fuel Pump

Starter

EDI 4000 (Eng Monitor)

GMA-340 (Audio)

SL-30 (Nav)

SL-30 (Com-Rec)

SL-30 (Com-Tx)

EI #1 (P-Mag)

EI #2 (P-Mag)

Lights - Lnd

"Lights - Flood/Cargo -.1

      Cargo - .1

      Panel- .5A

      Cockpit - .2"

Main Battery Contactor

Starter Contactor

Clock



The list for the Battery buss seems extensive but my thoughts were 

that if stuck on top IFR, these items are potentially needed. Yes, 

that assumes both main and SD-8 alternator went south. The question 

is, using an SD-8, can run over 8A on the buss? Is this a valid 

distribution of components? Some of these on the Batt buss are also 

used for start (EIS) or ground ops (lights, clock). The other 

question is can I split the power leads on the SL-30 without making 

the radio inop for receive- only?

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