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1. 06:57 PM - Z14 with different bus voltages ? (bobbarrow)
2. 08:07 PM - Re: Z14 with different bus voltages ? (user9253)
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Subject: | Z14 with different bus voltages ? |
I have a Vans RV7A (finished but not yet flying) with the Z14 architecture (dual
buses with crossfeed contactor). The only deviation from Z14 is that the system
does not automatically crossfeed between buses at engine start).
Bus 1 has a B&C LR3C voltage regulator, a B&C L40 alternator and an Odyssey PC680
AGM battery (17 Amphours). The aircraft starts on Bus 1 and all heavy current
users are on this bus.
Bus 2 has a B&C LR3C voltage regulator, a B&C SD20 alternator and an Odyssey PC310
AGM battery (8 Amphours). This bus supports only the primary EFIS and one
LightSpeed EI (magneto on the other ignition side).
The LR3C regulators are both factory set to approx 14.4 volts but there is likely
to be a very small difference in the settings. In practical terms this means
that when the crossfeed contactor is activated one alternator will tend to hog
the load but the other alternator will tend to flicker on and off. I think
that this cannot be desirable.
Odyssey Batteries have advised me that the optimum bus voltage for charging either
the PC310 or PC680 is 14.4 volts but that the recommended min/max is 13.6
to 14.8 volts. The B&C installation manual for the LR3C regulator says that the
voltage can be manually adjusted up and down. So here are my questions:
1. Should I create a voltage spread between the LR3C regulators such that when
the crossfeed contactor is activated the L40 takes all the load and the SD20 justs
sit idle in the background as a true standby alternator. In other words Bus
1 and Bus 2 would run at different voltages when the crossfeed is NOT activated.
2. If the answer to question 1 is YES then what would be the optimum differential
voltages for the alternators to achieve a satisfactory outcome. Would say running
the L40 at 14.6 volts and the SD20 at 14.1 volts (thus creating a spread
of 0.5 volts) be desirable.
Bob Barrow
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=437794#437794
Message 2
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Subject: | Re: Z14 with different bus voltages ? |
Yes, adjust the regulators to achieve a 1/2 volt difference. Adjust L40 to 14.2
volts and SD20 to 13.7 volts. That is just an educated guess on my part. Bob
N is the expert. Since the small battery is not intended for starting, it
will not be discharged very much. 13.7 volts will keep the small battery charged
if the cross feed contactor is not energized. And 14.2 volts is optimum for
the big battery.
Joe
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Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=437799#437799
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