Air Conditioning Failures

[kermit]

After the experience of travelling on a Pendolino with no, or minimal, air conditioning yesterday, I found myself wondering why it is that train AC units don't seem to default to ducted fresh air (blown through by the forward motion of the train) when in failure mode? Maybe not ideal, but a lot better than being stewed in an apparently sealed can!

 

[Russel]

Good question.

In my car, I'll often have the HVAC set to just draw in outside fresh air as that is all that is needed.

 

[frankmoh]

After the experience of travelling on a Pendolino with no, or minimal, air conditioning yesterday, I found myself wondering why it is that train AC units don't seem to default to ducted fresh air (blown through by the forward motion of the train) when in failure mode? Maybe not ideal, but a lot better than being stewed in an apparently sealed can!

You have to feel for the people on trains with no AC in the first place!

A month ago during the heatwave, I was on a 376. The train already is warm in summertime because of the tiny windows, but it was made even worse by the fact my train was stopped at a red signal for 5 minutes and the sun was low enough in the sky to come beaming directly through the windows. I was even sat in the front so I was forced to hear the AC in the driver's cab whirring.

 

[Krokodil]

I can't speak for Pendos but when 158 a/c fails we put it on "vent". Which may as well be made of chocolate for the good it does in the heat. Hopper windows open instead, and start throwing (containers of) water at passengers.

 

[vicbury]

I can't speak for Pendos but when 158 a/c fails we put it on "vent". Which may as well be made of chocolate for the good it does in the heat. Hopper windows open instead, and start throwing (containers of) water at passengers.

I don't think I've ever been on a 158 that's been able to blow sufficient fresh air through the vents, cooled or otherwise. They seem to have a very limited air flow capacity, which isn't a huge surprise when you look at the size of the equipment on the roof compared with any other air conditioned rolling stock.

 

[Flying Snail]

After the experience of travelling on a Pendolino with no, or minimal, air conditioning yesterday, I found myself wondering why it is that train AC units don't seem to default to ducted fresh air (blown through by the forward motion of the train) when in failure mode? Maybe not ideal, but a lot better than being stewed in an apparently sealed can!

The entire Pendolino had no AC, or just the coach you were in?

Most of the time when AC breaks it is the refrigeration system that fails and the air handling remains running. Unfortunately the air, even though it is fresh is also passed through the AC evaporator, fans and ducting. As well as there being heat sources in the equipment when the refrigeration cycle is not running this is all in the roof space of the train, being baked by the sun so the air that gets to the coach interior is significantly warmer than ambient air.

 

[Envoy]

Opening small vent windows on 158’s will bring in a bit of fresh air - but, that air is still hot air in a heatwave.

 

[Toby268]

The air conditioning on Pendos are a major problem and they are currently going through a HVAC overhaul to try and fix the issues but this will take some time - several years to get through all the units. They just can’t cope with temperatures over 21/22 degrees. Most trains are going about with at least 2 carriages overheating at the moment but over the weekend there was severe cases of all 9/11 coaches overheating and several trains being cancelled due to this. Hopefully the overhaul will fix the HVAC issues in due course.

 

[DarloRich]

After the experience of travelling on a Pendolino with no, or minimal, air conditioning yesterday, I found myself wondering why it is that train AC units don't seem to default to ducted fresh air (blown through by the forward motion of the train) when in failure mode?

how would that work? Can you explain it for me?

 

[Russel]

how would that work? Can you explain it for me?

The system should have been designed the same way as a cars HVAC system works, so you can just set it to pull in fresh air from outside, simple really.

 

[Snow1964]

Most of the time when AC breaks it is the refrigeration system that fails and the air handling remains running. Unfortunately the air, even though it is fresh is also passed through the AC evaporator, fans and ducting. As well as there being heat sources in the equipment when the refrigeration cycle is not running this is all in the roof space of the train, being baked by the sun so the air that gets to the coach interior is significantly warmer than ambient air.

Refridgerant shouldn't leak if all the seals are properly fitted and maintained with lubricant (normally in the gas).

Either the depot is not checking concentrations at intervals to spot potential depressurisations, or known leakage points are not being addressed and upgraded (and after 20+ years really ought to know the common failure points).

Unless the depot has actively decided to do two tiers of repairs, treating them differently, critical and desirable, and only seeing one as worth doing. Then have to remember the depot maintaining the a/c is same one that checks the brakes. Not good practice to approve a train for service if know half the repairs/maintenance has been skipped over.

 

[Bletchleyite]

Opening small vent windows on 158’s will bring in a bit of fresh air - but, that air is still hot air in a heatwave.

It's easier to cope with moving air than static air - hence why I don't agree with people who tell you to close the windows when it's hot at home. Yes, you might get it down from 27 to 25 degrees, but 27 degrees with moving fresh air is to me much more tolerable than 25 with static stale air.

As for forced-air from vehicle motion, I've noticed recent cars don't really provide this either, you need the fan on. My present Kia certainly doesn't.

 

[43066]

The system should have been designed the same way as a cars HVAC system works, so you can just set it to pull in fresh air from outside, simple really.

Which won’t actually work effectively at all during extremely hot weather, especially with no opening windows.

Comparisons to your car aren't particularly illuminating, especially as many cars don’t actually work in the way you’ve described - mine needs the fan running or no air comes in at all.

 

[Howardh]

Rather ironic that in winter, Transpennine's 185's have their aircon on full blast so the carriage always feels uncomfortably cold, yet when you really needed it this week, it's failed!

On Saturday was on the Bolton - Blackburn route, steaming hot inside even with all the windows open, couldn't tell if that was just the ambient temperature or the heating system couldn't be switched off!!

Regarding cars, my aircon unit in my 9-yr-old Hyundai i10 failed a couple of years ago, but haven't had it fixes as I rarely use the car - prefer public transport!

 

[DarloRich]

The system should have been designed the same way as a cars HVAC system works, so you can just set it to pull in fresh air from outside, simple really.

I don't know how that works! Surely ducting the fresh air into the system will just heat it as it passes through the various pipes and heating/cooling elements?

Also wont the entry vent have to be quite large to provide fresh air to a whole train?

 

[Bletchleyite]

Also wont the entry vent have to be quite large to provide fresh air to a whole train?

Surely not that big - every road coach has pressure ventilation of that kind (though most also have aircon these days).

 

[Russel]

I don't know how that works! Surely ducting the fresh air into the system will just heat it as it passes through the various pipes and heating/cooling elements?

Also wont the entry vent have to be quite large to provide fresh air to a whole train?

It could just be routed through the existing AC vents.

Surely not that big - every road coach has pressure ventilation of that kind (though most also have aircon these days).

This is what I mean.

 

[Bletchleyite]

I think to be fair for pressure ventilation to have a decent cooling effect it needs to be via personal vents as per some Networkers (and most planes and basically all road coaches). If it's just blown in at ceiling level it probably doesn't move the air sufficiently to have much of an effect.

Notably in hot countries most trains that don't have aircon have actual fans.

 

[DarloRich]

Surely not that big - every road coach has pressure ventilation of that kind (though most also have aircon these days).

I didn't know that!

It could just be routed through the existing AC vents.

fair enough - I am not a technical person.

 

[43066]

I think to be fair for pressure ventilation to have a decent cooling effect it needs to be via personal vents as per some Networkers (and most planes and basically all road coaches). If it's just blown in at ceiling level it probably doesn't move the air sufficiently to have much of an effect.

Notably in hot countries most trains that don't have aircon have actual fans.

Class 376s being an example of example of how “forced air cooling” doesn’t really work - and they do have opening windows, albeit also ineffective because the Electrostar body was designed for aircon.

 

[The exile]

Opening small vent windows on 158’s will bring in a bit of fresh air - but, that air is still hot air in a heatwave.

Maybe, but the psychological (and indeed practical) effect of being able to feel moving air shouldn’t be forgotten. Otherwise there’d be no market for fans.

 

[ainsworth74]

Hopper windows open instead, and start throwing (containers of) water at passengers.

I mean depending on how hot is the passengers might actually start to appreciate just having straight water thrown at them!

 

[kermit]

The entire Pendolino had no AC, or just the coach you were in?

Most of the time when AC breaks it is the refrigeration system that fails and the air handling remains running. Unfortunately the air, even though it is fresh is also passed through the AC evaporator, fans and ducting. As well as there being heat sources in the equipment when the refrigeration cycle is not running this is all in the roof space of the train, being baked by the sun so the air that gets to the coach interior is significantly warmer than ambient air.

I believe there were problems throughout the train, though I couldn't move, as it was rammed!
On the second point, this suggests very poor design to me. Any stock that is effectively sealed, without opening windows, needs to have a failsafe system, either manual or automatic, to divert fresh air straight in to the cabins, without passing through or over hot metal parts on the roof.

The fact that trains are cancelled because of inoperative AC is horrific in itself, as cancellations lead to passenger misery through hot overcrowded trains as well as delays. AC systems will always fail, assuming they will not is carelessness in design at best.

 

[ainsworth74]

Must admit I do think all stock should be specified with a small number of lockable (to prevent people just opening them and causing the AC to knacker itself trying to cool the outside) hopper style windows. They're not brilliant but it's a heck of a lot better, at least when the train is moving, compared to there being no ventilation at all.

I recall being on an HST once on a hot day with failed aircon in the carriage I was sitting in. The crew had locked the saloon doors open and had the drop-lights in all the doors open in the adjoining vestibules and whilst the train was in motion it was warm but not unbearably so. Admittedly every station stop seemed to last an eon as the temperature soon rose

These days, in that situation, you'd just slowly cook as there wouldn't be any fresh air entering the carriage at all anymore. Of course in an ideal world the AC would just be 100% reliable but we don't live in an ideal world so it seems barmy to me that we seemingly have no back up plan to just allow fresh air from outside into the saloon without any conditioning.

 

[Sorcerer]

I must admit it is somewhat concerning to me hearing about Pendolino air conditioning being poor because I'm due to travel on one soon, and even though I like hot weather I still prefer my air to feel fresh rather than stuffy. I always thought they had excellent air conditioning but apparently not so based on stories I've heard in recent years.

 

[meld3]

And yet the class 345 I caught on Saturday was like a fridge, despite many doors being opened every few mins and a big open interior space to cool. So it can be made to work fine.

 

[Welly]

Ugh! I remember the unreliable air-con of the Mark 4s in the early 1990s.

 

[Pyewipecarshed]

Opening small vent windows on 158’s will bring in a bit of fresh air - but, that air is still hot air in a heatwave.

There aren't really sufficient opening windows on a 158, so you get some seats whose occupants are not able to feel the air coming in. However it's still better than nothing.

I can't speak for Pendos but when 158 a/c fails we put it on "vent". Which may as well be made of chocolate for the good it does in the heat. Hopper windows open instead, and start throwing (containers of) water at passengers.

The old "EBAC" system on the 158s (that they had when new) allowed the guard to override the automatic settings and put it onto cooling or heating as required.
Unfortunately the later replacement systems didn't allow that. I used to just turn them off if they failed rather than using the ineffective "vent" function, and open the windows of course!

 

[Skie]

Problem with using the trains movement to force some fresh air in is that unlike cars, trains go in two directions . So any directional forcing of air needs to be duplicated to handle both directions which increases the cost. So most systems just have an intake as part of an existing circulation system and use the blower fans for that to draw the combined recirculated and fresh air into the carriage. This takes from the side to allow the blower and any baffles to control the flow, rather than relying on the trains movement. Plus you absolutely do not want air moving at 125mph being forced into your train and over delicate fans that might be powered off due to a fault. It would generate a voltage that could damage components, not to mention pump high speed air into the saloon.*

Generally when one component of a HVAC system fails other bits of it will still work, but might not help too much. So if the compressor fails the blower may still work, you’ll get fresh air but as others have said that air will be coming in warmer than ambient and is mixed with warm air already from the carriage.

The units are modular packages on modern trains, including the 390s, so they can be lifted off and swapped for working units relatively quickly. But if the design is flawed and prone to regular failure at high temperatures then you inevitably end up with a bunch of toasty trains and a backlog of repairs.

*reminds me of 142 drivers nicknaming the cab air vents as Wasp Dispensers because of this “design innovation”

 

[Trackman]

On Saturday was on the Bolton - Blackburn route, steaming hot inside even with all the windows open, couldn't tell if that was just the ambient temperature or the heating system couldn't be switched off!!

Not a 150 by any chance?