Is a TVS required when a TIU is present?

Some knowledgeable folks on the forum have stated the TVS in each TIU channel is adequate.  I use several between the transformer and the track because the TVS has a failure mode that is undetectable.

Also, the 33 volt TVS may not be sufficient if your transformer puts out more than 18 volts, or you are using an older transformer with whistle/bell buttons that adds volts to the circuit when pressed.  There was some discussion on this a while back that the 33 volt TVS works well with the PowerHouse bricks because they are limited to 18 volts, but the 36 volt TVS was better for other transformers.

This is just me, but I would put a 36 volt TVS at each track connection.  This is because other knowledgeable folks on this forum recommend putting the TVS as close to the engines as possible; inside each engine is even better. 

Cappilot offers good advice. Here are some part numbers if you want them. This list also states what Cappilot said above.

PTC and TVS - Some Commonly Used Sizes and Part Numbers (from other threads)

Thanks for the comments & information.

I am in agreement in using a 36v TVS in conditions where the transformer provides up to a 24-25 volt RMS range (with horn voltage).    25v rms X 1.414 = 35.4v Peak, requires a 36v TVS.    

As for redundant TVSs at the track connection, sounds like a good idea for smaller layouts. I am dealing with a LARGE layout with hundreds of multi level track connections, many of which are hard or impossible to get to. It is not a matter of cost or initial installation of the TVS, I see the problem of trouble shooting if and when a TVS fails in a shorted condition.  The TVS located in the Engine might be the way to go if people want to install it.

Thanks again,

Bob D

 Quote from Ron      This is because other knowledgeable folks on this forum recommend putting the TVS as close to the engines as possible; inside each engine is even better.

I'm guessing between the roller pick--ups and chassis. ?   Why don't the manufactures install these things?

Gregg posted:

 Quote from Ron      This is because other knowledgeable folks on this forum recommend putting the TVS as close to the engines as possible; inside each engine is even better.

I'm guessing between the roller pick--ups and chassis. ?   Why don't the manufactures install these things?

I agree, with the prices that are charged for an engine today, you would think the manufactures would add a < 20 cent TVS. 

A 32 volt bi-directional(for AC must be bi-directional) TVS would be better then the 33 or 34 volt model. However from what I am understanding about MTH DCS base it has the TVS unit already inside it so an additional TVS would be overkill. Don't know about TMCC or Legacy if they have a TVS unit or not.

Lee Fritz