Transport for Wales Class 231 / 756 Stadler FLIRTs

[MikePJ]

No need, the batteries are 140kWh which will be enough to have them off wire for 45-60 minutes easily given their duty cycle - longer for low speed / frequent stop routes. It would be relatively easy to put in opportunity charging at the end of any new line in the event that an onstreet section was more than (say) 20 minutes run time from an existing wired section.

Out of interest the 756s have been running in OLE + Battery format for a while now, with automatic pan up / pan down / charging etc. How many incidents have there been of trains losing pantograhs or failing having run out of charge?

One of the traincrew had said a few months ago that the automatic power changeover system was the main source of problems on the 756s, but I’m not aware of any units taking physical damage or needing rescuing.

 

[Adlee Turner]

No need, the batteries are 140kWh which will be enough to have them off wire for 45-60 minutes easily given their duty cycle - longer for low speed / frequent stop routes. It would be relatively easy to put in opportunity charging at the end of any new line in the event that an onstreet section was more than (say) 20 minutes run time from an existing wired section.

Out of interest the 756s have been running in OLE + Battery format for a while now, with automatic pan up / pan down / charging etc. How many incidents have there been of trains losing pantograhs or failing having run out of charge?

Thankfully, we haven’t had any incidents involving a 756 losing their pantographs or failing having run out of charge. Like someone else said, most of the time we have issues with them is when they’re reading the beacons on the tracks. Although we did obviously have recent incidents at Pontypridd when the pantograph raised when it wasn’t meant to and one of the 756/0 suffering a badly damaged pantograph on inspection when it returned to depot due to a fault.

 

[AdamWW]

Thankfully, we haven’t had any incidents involving a 756 losing their pantographs or failing having run out of charge.

Presumably they'd also have to run out of diesel as well as charge to get stuck.

Unless they're currently running round with empty tanks.

 

[Adlee Turner]

Presumably they'd also have to run out of diesel as well as charge to get stuck.

Unless they're currently running round with empty tanks.

Yes, they would unless the unit has a complete electrical failure and it can not move then it would need to be rescued. To my knowledge, I do believe the 756s tanks are filled as backup just in case.

 

[Cardiff123]

This looks like the first ECS of a 4 car 756 on Barry to Cardiff today, making several all stops runs

Realtime Trains | 5Q01 1005 Barry to Cardiff Central | 12/10/2025

Real-time train running information for 5Q01 1005 departure from Barry to Cardiff Central on 12/10/2025. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

 

[MikePJ]

I’m on 756001, just heading to Penarth. It came into Queen St with the diesel engine running, which is the first time I’ve seen one in diesel mode. I took a walk through the power pack car - here’s a video:

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[tfw756rider]

I’m on 756001, just heading to Penarth. It came into Queen St with the diesel engine running, which is the first time I’ve seen one in diesel mode. I took a walk through the power pack car - here’s a video:

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Thanks for sharing - I wonder why it was in diesel mode? It's surprising how much engine sound there still is, considering that a 756 only has one engine (rather than the four of a 231).

 

[MikePJ]

Thanks for sharing - I wonder why it was in diesel mode? It's surprising how much engine sound there still is, considering that a 756 only has one engine (rather than the four of a 231).

It was definitely quieter than a 231 when pulling into the station, but still very noticeable as a diesel rather than the usual electric whine. The diesel had shut down by the time we reached Penarth, so it's possible that it ran for a top-up?

 

[AdamWW]

It was definitely quieter than a 231 when pulling into the station, but still very noticeable as a diesel rather than the usual electric whine. The diesel had shut down by the time we reached Penarth, so it's possible that it ran for a top-up?

I've heard 756s make quite a lot of noise from the power module but it didn't sound like a diesel engine running.

My guess was that it was a cooling system running to prevent the batteries from overheating - it only seemed to happen on particularly hot days.

 

[MikePJ]

I've heard 756s make quite a lot of noise from the power module but it didn't sound like a diesel engine running.

My guess was that it was a cooling system running to prevent the batteries from overheating - it only seemed to happen on particularly hot days.

I've heard battery cooling fans in the past, but this definitely had the beat of a diesel engine and I could hear it coming from just one side in the corridor through the power pack, so I'm pretty sure it was on diesel.

 

[AdamWW]

I've heard battery cooling fans in the past, but this definitely had the beat of a diesel engine and I could hear it coming from just one side in the corridor through the power pack, so I'm pretty sure it was on diesel.

That does sound convincing.

I'm less sure that what I heard was cooling fans not a diesel engine, though it didn't sound much like a 231.

 

[tfw756rider]

That does sound convincing.

I'm less sure that what I heard was cooling fans not a diesel engine, though it didn't sound much like a 231.

I do recognise the sound in the video as a FLIRT turbo-diesel engine (16-litre Deutz V8) used in classes 231, 755 and 756. Just that 756/0/1s have one engine, 755/3s two, and 231s/755/4s four.

 

[nigelsporne]

Now that the section to Rhymney is open is there any news on when 756s will be tested north of Caerphilly?

 

[MikePJ]

Now that the section to Rhymney is open is there any news on when 756s will be tested north of Caerphilly?

The wires aren't yet energised - they're due to go live on 8th December (according to a consultation document that's currently awaiting responses). TfW don't have a very good record of getting overhead line energised on time, so don't hold your breath.

 

[nigelsporne]

Thanks for this. So not much chance for the new Timetable then.

 

[MikePJ]

Thanks for this. So not much chance for the new Timetable then.

No - TfW are currently talking about "early 2026" for the first 398s to come into service, and then ramping up through the spring with 398s displacing 756s.

 

[Adlee Turner]

Now that the section to Rhymney is open is there any news on when 756s will be tested north of Caerphilly?

As far as we know, it was going to be early December for 756 testing up to Rhymney

 

[nigelsporne]

Thank you.

 

[MikePJ]

Just having my periodic dig around in TfW's board meeting minutes, and found this quote from the July meeting of TfW Rail Ltd's board:

Class 756 units are experiencing compressor overheating near 50°C due to ineffective cooling fans, with
only partial visibility of the suspected damaged fan, noting full removal takes six hours. Additionally,
OLE faults are affecting pantograph performance and require further investigation.

This perhaps explains the slow introduction of the units over the summer - if a compressor fault takes the unit out for several days, that would have a big knock-on into fleet availability. The issue isn't discussed at the August meeting (the most recent one to have been published) so clearly it was either resolved or making sufficient progress that it needed no further update to the board a month later.

 

[AdamWW]

This perhaps explains the slow introduction of the units over the summer - if a compressor fault takes the unit out for several days, that would have a big knock-on into fleet availability. The issue isn't discussed at the August meeting (the most recent one to have been published) so clearly it was either resolved or making sufficient progress that it needed no further update to the board a month later.

That's interesting.

Yesterday I saw a 150 running to Coryton. Today there are cancellations on the Caerphilly/Penarth/Coryton services due to too many trains needing repair, which is a bit disappointing.

 

[tfw756rider]

Today (18/11/25) is 1 year since Class 756 "officially" entered service on the 18/11/24, and for consecutive days (and 1 year and 3 days since Class 756 was in service on one previous day of the 15/11/24).

 

[BillStampy]

I know that the units have been to Barry Island already - but tonight 3 756s are going for a visit, which I think makes it clear that the units are now fully cleared past just the one booked diagram. Units are 756101, 756002 and 756114.

 

[XCTurbostar]

This has probably been asked loads of times but - what do the boxes on either side of the front desination display indicate?
I also hadn't realised that the CDL lights do not illuminate on the opposite (non platform) side either but this appears to be a STADLER feature as the 398s appear to be the same - not a fan.

 

[BillStampy]

Some very sneaky runs for what I assume will be a Class 231 down to Maesteg and Ebbw Vale overnight today. Shame it's at such a dead hour!

Realtime Trains | 5Q10 0027 Cardiff Canton Sidings to Maesteg | 09/12/2025

Real-time train running information for 5Q10 0027 departure from Cardiff Canton Sidings to Maesteg on 09/12/2025. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 5Q11 0131 Maesteg to Ebbw Vale Town | 09/12/2025

Real-time train running information for 5Q11 0131 departure from Maesteg to Ebbw Vale Town on 09/12/2025. From Realtime Trains, an independent source of train running info for Great Britain.

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Realtime Trains | 5Q12 0320 Ebbw Vale Town to Cardiff Canton Sidings | 09/12/2025

Real-time train running information for 5Q12 0320 departure from Ebbw Vale Town to Cardiff Canton Sidings on 09/12/2025. From Realtime Trains, an independent source of train running info for Great Britain.

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Does prove that Mainline stuff is still be prepared!

 

[Jez]

Some very sneaky runs for what I assume will be a Class 231 down to Maesteg and Ebbw Vale overnight today. Shame it's at such a dead hour!

Realtime Trains | 5Q10 0027 Cardiff Canton Sidings to Maesteg | 09/12/2025

Real-time train running information for 5Q10 0027 departure from Cardiff Canton Sidings to Maesteg on 09/12/2025. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 5Q11 0131 Maesteg to Ebbw Vale Town | 09/12/2025

Real-time train running information for 5Q11 0131 departure from Maesteg to Ebbw Vale Town on 09/12/2025. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 5Q12 0320 Ebbw Vale Town to Cardiff Canton Sidings | 09/12/2025

Real-time train running information for 5Q12 0320 departure from Ebbw Vale Town to Cardiff Canton Sidings on 09/12/2025. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Does prove that Mainline stuff is still be prepared!

This is a good sign we wont have to wait too much longer for the 231's to take over the Maesteg and Ebbw Vale line. Things are finally starting to progress.

 

[BillStampy]

This is a good sign we wont have to wait too much longer for the 231's to take over the Maesteg and Ebbw Vale line. Things are finally starting to progress.

One can hope

 

[Jez]

One can hope

I wont be going to see them in the middle of the night! Will just wait until they are in service and then have a ride!

 

[BillStampy]

I wont be going to see them in the middle of the night! Will just wait until they are in service and then have a ride!

I'll wait until the next Sunday runs happen, I do like rare moves but I feel being up at stupid o' clock in the morning isn't worth it for a 231

 

[Adlee Turner]

231005 aka Gavin and Stacey is back in service today

 

[BillStampy]

231005 aka Gavin and Stacey is back in service today

Saw they were moving it around over the last week or two, good to see!

== Doublepost prevention - post automatically merged: 11 Dec 2025 ==

Realtime Trains | 5Q20 0048 Cardiff Canton Sidings to Cheltenham Spa | 16/12/2025

Real-time train running information for 5Q20 0048 departure from Cardiff Canton Sidings to Cheltenham Spa on 16/12/2025. From Realtime Trains, an independent source of train running info for Great Britain.

www.realtimetrains.co.uk

Realtime Trains | 5Q21 0255 Cheltenham Spa to Cardiff Canton Sidings | 16/12/2025

Real-time train running information for 5Q21 0255 departure from Cheltenham Spa to Cardiff Canton Sidings on 16/12/2025. From Realtime Trains, an independent source of train running info for Great Britain.

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They're getting on with it!