Bus wires for three separate controllers

[FattishBoy]

As someone from an electrical background am rather embarrassed to ask this question, the layout I am currently building needs three controllers as there will be three circuits, do I need to run three sets of bus wires ie. three positives and three negatives so that the controllers are not connected electrically or can the three controllers feed on to the one set of wires and the appropriate droppers attached. I know I will need IRJ's at the crossovers. Currently have an H&M 'clipper' single track controller and looking to get another two or a twin track one like a 'duette' or Gaugemaster model D.
Any advice appreciated.

J.

[Walkingthedog]

Yes three separate bus. If the three circuits are linked with points you will need insulated rail joiners where the points join..

[Brian]

Hmm... You can use Common Return for all track feeds which then reduces the wiring to four - Three track feeds and one common return. All one side rails are connected together and then connect to the common return wire. e.g. All Inner rails on all loops connect to the Common Return wire. Note as this one return wire has to carry all current from all locos running it needs to be of a larger wire size than the feeds i.e. feeds are 7/0,2mm while the common return wire is 16/0.2mm or better if larger.
But the main issue is that each controller has to be feed from a totally separate power source or multi wound transformers. You cannot use one power supply to feed two or more controllers when using Common Return wiring. See here for the basic idea.. https://www.brian-lambert.co.uk/Electri ... mmonReturn

[FattishBoy]

Guy's, thanks for the replies, I suspected that would be the case, Brian it makes sense to use the common return system I assume the common is the negative and as I have a lot of very old loco's I wont use the IRJ on the negative at the crossovers as recommended in your link. Is the Gaugemaster Model D twin track controller okay to use for common return, I know the H&M 'duette' is double wound so assume that's fine, still to get a controller but likely to be either of these.
Just to throw another spanner in the works do I need to use IRJ's at the diamond crossings and then run a separate feed to power them up. I appreciate I am asking a lot of questions here but don't want to have it all pinned down and realise I have missed something and then have to start again.

J.

[Brian]

Hi

There technically is no Negative where Track outputs are concerned as the polarity is reversible depending on direction set. But for simplicity you can indeed call one the Positive and the other Negative, but remember they swap. When using Common return keep all the same and the same handed rails too to the common connection.
The Gaugemaster Model D Track outputs are fine to use with Common return, but the auxiliary outputs are not, so the 12v DC and 16v AC accessory outputs have to have their own returns and cannot share the common return. Reason is these share the same windings on the internal dual wound transformer as the Track outputs. The H&M Duette is the same - Both Track feeds are ok for common return but the uncontrolled 12v DC and 16v AC are not suitable for the same reason of sharing a transformer output with the Track output.

Your Diamond crossing if Insulated Frog type does not need IRJs fitted, only the Electrofrog needs IRJs.

[FattishBoy]

Thank you Brian.