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TCW IBBS Pass-thru inputs

Can someone explain why this is recommended? Pros and cons?

Thanks in advance!
They provide power output power if the IBBS master switch is off. They also provide power when the voltage sensed by the IBBS is above 11 volts. From the IBBS manual:
Pins 6,7,8 receive power that is passed-thru the IBBS unit to the loads connected to the output pins. These pass-thru power connections are optional and are only required for systems that do not have multiple power inputs. These pins can also be used if it is desired to have redundant power paths feeding the connected loads. These pins are internally wired in parallel, it is recommended to populate all three pins and join the wires together at the pass thru power breaker. Note: these pins do not individually correspond to any particular output pin (12-15). The pass-thru breaker must be sized for whatever load is connected to the IBBS outputs. The maximum combined load is 12 amps peak, 8 amps continuous. If Pins 6,7,8 are used they MUST be connected to the same power bus as Pin
 
If you don't use the pass thru then the master will turn off the outputs when voltage is sensed on the charge line, which means if you have the charge line on the main bus the output will turn off when you flip on the master (not what you want for avionics back up)

If you do wire the pass thru then you can't shut off the back up items unless you turn off the master (unless you wire the pass thru from the avionics bus).

I usually wire the charge input from the avionics bus that way the outputs will not shut off until the avionics bus is turned on and just forgo the pass thru.

Part of the reason I like breakers on the glass is to be able to reboot in flight, with the pass thru on the main bus you can't do that unless you turn off the master.

I've actually done it both ways, pick your poison.

Personally I wish the outputs would just stay on when the charge line is turned on.
 
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Personally I wish the outputs would just stay on when the charge line is turned on.
I wish there was some way of isolating the individual pass through output lines from the input side. As it is now if you pull the breaker or fuse on the pass through input, you lose power on all 4 of the pass through output lines.
 
I have done that. I created a buss for all my passthrus and put the main power to that bus thru a switch.

I find this very useful as it gives me the ability, both in the air or on the ground, to isolate and shut down any of the devices/avionics that has dual input power.
 
I have done that. I created a buss for all my passthrus and put the main power to that bus thru a switch.

I find this very useful as it gives me the ability, both in the air or on the ground, to isolate and shut down any of the devices/avionics that has dual input power.

I have thought that the best solution would be use a DPDT switch, that way you could switch the pass thru and the on/off function with the single back up switch. I may do this on my next install which is in the shop now.
 
If you don't use the pass thru then the master will turn off the outputs when voltage is sensed on the charge line, which means if you have the charge line on the main bus the output will turn off when you flip on the master (not what you want for avionics back up)


Walt-

So since I don’t have an avionics buss and everything is on the main. Is what you mention above not an issue for my setup.

If ibbs is on first, then you bring on main battery, shouldn’t the change in power source (ibbs off, main on) be so quick it’s irrelevant?

Thanks
 
If you don't use the pass thru then the master will turn off the outputs when voltage is sensed on the charge line, which means if you have the charge line on the main bus the output will turn off when you flip on the master (not what you want for avionics back up)


Walt-

So since I don’t have an avionics buss and everything is on the main. Is what you mention above not an issue for my setup.

If ibbs is on first, then you bring on main battery, shouldn’t the change in power source (ibbs off, main on) be so quick it’s irrelevant?

Thanks

Part of the reason to have a backup is so you don't get a reboot on start.
I'm not sure how your setup will handle that as the voltage will sag when you hit the start button.
 
I have thought that the best solution would be use a DPDT switch, that way you could switch the pass thru and the on/off function with the single back up switch. I may do this on my next install which is in the shop now.

I had thought about that but I had already installed my switches and not as easy to change it with the type of switch I have.
 
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