Great Western Coffee Shop

When I got on the 0618 IEP from Pewsey on Tue 27th Nov, it felt very cold. This was the 1K71 0515 Bristol Temple Meads to Padd service.

One of my fellow passengers complained about it to the train manager who said that the heating was not working on the entire train and he advised us to get off and catch the next train 15mins later, which was a good old HST (the 1A70 0605 Frome to Padd)

When the IEP got to Hungerford there was a 10 minute delay due to a problem with the doors "probably caused by the cold" according to the train manager.

These IEPs don't seem very resilient. At least on the HSTs, if the heating or air conditioning was not working it was usually just one carriage which was affected one and you could always move to the next one!

Auxiliary power in an HST comes from the power cars, obviously, and I've always understood that the rear power car (if fit) supplies the whole train. If that fails there is only battery backup available, so the train is out of service.

IETs, on the other hand, have auxiliary power supplied from the traction/APS in each motor carriage (true in diesel or electric mode), so should be more resilient. There is 110V DC battery power again, but how it is used (directly or via an inverter) is unclear. The one thing that Hitachi do say is that "the on-board APSs operate in parallel to provide redundancy", and of course they have to provide power to the trailer carriages too.

There are several ways that "in parallel" could be implemented, but literally attaching them all to a single train-wide bus (at 400V 3-phase) is not a very likely one. Any fault on that would be a single point of failure, which would be a clear case of target-painted-on-foot syndrome. I would have thought that any train-wide failure of auxiliary power would take out not just the heating but most other systems too, and you'd not have been on that train.

So that leaves a failure of the heating controls - which might be human, software, or the two not getting on with each other.