Balancing the power requirements using an NCE EB1 cut-out

[RobinofLoxley]

I have just acquired one of these with a view to installing it in a typical location between a z21 and the track bus, while leaving a direct feed from the z21 to the accessory bus. Reading the associated paperwork I find that the relevant available trip current settings for the cut-out are 2.2A or 3.3A. I had an idea from previous threads on the subject that the cut-out current limit could be set more flexibly or at least that settings of for example 3A or 2.5A were mentioned, but this wasnt correct.

 

So now I have a slight quandary in that I will have to set 2.2A which in the future might be said to be 'wasting' 25% of the available power from the z21. However, when I have finished track laying I will have probably 8 Digikeijs DR4018's driving point motors (MTB-1's) so they will require some power and might well take quite a bit of the 0.8A that is 'available'. But that wasnt the plan, I was either going to fit a separate power supply for the accessories, or a booster, depending how things developed as I start to automate. I wont have massive loco numbers on the layout (i dont have massive loco numbers) and no intention to fit sound.

 

Comments welcome.

[WIMorrison]

You need to set it to the lower, 2.2A level as the EB1 must trip before the z21 trips. This means that you will still be able to operate the accessory bus when you have a track short. If you set it at a higher level the EB1 will not trip, and it will be the z21 that trips meaning you cannot operate the Accessories - which means that the EB1 is pointless and not doing anything.

[RobinofLoxley]

I understood that Iain. But that leaves me with a considerable amount of the z21 capacity not available to run locos. In view of the balance of power consumption between accessories and track is this ever going to be an issue or not?

[WIMorrison]

It is unlikely to be an issue, the Locos will draw around 200-400mA (depending on gauge)  when running which means you could have 6 running simultaneously with lights and sound and still leave power to operate accessories. When I used an EB1 to create power districts I never saw an issue with track power. 

 

The reality is that there is always a trade-off between available power and track bus power because, unless you are using a booster, the power cut out has to be lower than the main supply :(