Air conditioning failures on Mk3 coaches

[Drsatan]

On Twitter, one recent subject of discussion has been air conditioning failures on FGW's HSTs, as seen from Twitter users complaining about failed air conditioning on peak time departures.

However, I want to clarify whether air conditioning failures during this heatwave on Mk3s are either due to poor maintenance, or a design flaw which means the air conditioning fails when the outside temperature exceeds a certain amount.

If it's a maintenance issue, I won't be surprised.

 

[ainsworth74]

Had a XC HST a couple of weeks ago with failed aircon and it appeared to be a most of the set that had failed.

 

[Bushy]

It was certainly b***** hot on an HST from Swindon to Paddington yesterday lunchtime. Makes me appreciate the A/C on 375s on my normal commuting route.

Regards

Bushy

 

[38Cto15E]

Coach C on the 0755 Inverness to Kings Cross also had no air con today, I think the down service yesterday may also have had problems which couldn't be fixed at Inverness, as I noticed several packs of water in the baggage area.

 

[The Ham]

On Twitter, one recent subject of discussion has been air conditioning failures on FGW's HSTs, as seen from Twitter users complaining about failed air conditioning on peak time departures.

However, I want to clarify whether air conditioning failures during this heatwave on Mk3s are either due to poor maintenance, or a design flaw which means the air conditioning fails when the outside temperature exceeds a certain amount.

If it's a maintenance issue, I won't be surprised.

...and people think that the mark 3's are wonderful and can keep going forever with no problems!

It's not only a recent thing, I can remember sevral years back (maybe about 8 years) being offered free water because the AC had broken whislt traveling on a HST.

 

[TDK]

A Mk3 coach has 2 x MA (Motor Alternators) and one of these powers the aircon. They are old now and do fail on a regular basis.

 

[TheEdge]

My understanding of one of the problems with the Mk3 heating is the thermostats that automatically control the heating are in the vestibules.

People get on and off, leave windows open, the vestibule gets cold, heating comes on in the saloon. People think its too warm, open more of the vestibule windows, they get colder, heating gets hotter. And so on.

 

[RPM]

The air-con fails fairly often on the Chiltern refurbished Mk3s, which have plug doors so it isn't down to the opening windows. I know the MA sets are a constant source of problems in general (Chiltern have been looking at the feasibility of replacing them with static inverters). Whether it is the MA sets causing the air-con problems or faults with the air-con units themselves I don't know.

 

[Flying Snail]

My understanding of one of the problems with the Mk3 heating is the thermostats that automatically control the heating are in the vestibules.

People get on and off, leave windows open, the vestibule gets cold, heating comes on in the saloon. People think its too warm, open more of the vestibule windows, they get colder, heating gets hotter. And so on.

That wouldn't happen in the sort of weather we are having at present seeing as the air entering through any open droplights will be in the mid to high 20s.

It is not just Mk3s, there have been plenty of failures in other stock as well. The Mk4 set I was on earlier had 2 coaches down and out of the dozen ATW, Northern and Scotrail 158s I have passed in the last few days only one had it's emergency windows closed.

Have any of the numerous Mk3 refurbishment programmes included replacement AC units or are they all still fitted with their original ones?

 

[DarloRich]

at least with a MKiii you can stick your head out f it gets to hot

 

[Goatboy]

...and people think that the mark 3's are wonderful and can keep going forever with no problems!

It's not only a recent thing, I can remember sevral years back (maybe about 8 years) being offered free water because the AC had broken whislt traveling on a HST.

I somehow doubt its all down to the age, I remember once getting a huge pile of RTV's from what was either IC EC or GNER (This would have been about 1996) because the AC in a 4 year old Mk4 was defective in 30c heat...

 

[captainbigun]

A Mk3 coach has 2 x MA (Motor Alternators) and one of these powers the aircon. They are old now and do fail on a regular basis.

Only the RFMs have two MA sets. FOs and TSOs only have one.

 

[cjmillsnun]

at least with a MKiii you can stick your head out f it gets to hot

As long as it isn't a Chiltern modified one

 

[ryan125hst]

A Mk3 coach has 2 x MA (Motor Alternators) and one of these powers the aircon. They are old now and do fail on a regular basis.

Only the RFMs have two MA sets. FOs and TSOs only have one.

As far as I understand, you are both incorrect. The loco hauled Mark 3's do have Motor Alternators, but the HST power cars provide 415v three phase power to the coaches directly, so a MA failure wouldn't be responsible for the lack of air conditioning on a HST.

I'm guessing it is the air conditioning modules that are failing on the HST's as it is unlikely that the ETS would be down: There is one ETS generator in each power car and if it was down, there would be no lighting or catering either.

I should point out that I have learnt all of the above from the internet, so I might not be 100% correct on everything.

 

[VP185]

I think a lot has to do with the fact all the AC equipment is located in the under carriage of the vehicle.
When it sits at a platform there is very little airflow and as its exhausting hot air out underneath the coach I presume the AC equipment then runs hot and somehow trips out. I'm not 100% on that, but you'll note that modern trains have roof equipment nowadays.

 

[Temple Meads]

at least with a MKiii you can stick your head out f it gets to hot

Yep, natures great air conditioner

(And also decapitator if you're stupid)

 

[BestWestern]

As far as I understand, you are both incorrect. The loco hauled Mark 3's do have Motor Alternators, but the HST power cars provide 415v three phase power to the coaches directly, so a MA failure wouldn't be responsible for the lack of air conditioning on a HST.

I'm guessing it is the air conditioning modules that are failing on the HST's as it is unlikely that the ETS would be down: There is one ETS generator in each power car and if it was down, there would be no lighting or catering either.

I should point out that I have learnt all of the above from the internet, so I might not be 100% correct on everything.

If I can remember my traction bumpf, I think you're pretty much spot on

The a/c is powered both by the ETS directly (fans & equipment) and by the coach batteries (control systems), which in turn are charged continuously by the ETS supply. The lighting also comes off the batteries, as do the control systems for door operation and buzzers etc. As you say, catering is ETS directly, as are the plug sockets in the luggage racks (but the at-seat is battery). In normal operation the rear power car provides the supply, if it fails for any reason the Driver will switch to the front. The voltage actually varies depending on the engine speed, but 415 is the maximum output, 270 being the minimum. Unless both power cars or their ETS supplies fail, there will always be a power supply to the a/c and the system should be 'on' (unless it has been isolated for maintenance reasons of course).

In most cases there will be coaches within a set which are suitably cool, and others which aren't. Whilst the electrical supply is common throughout the train, obviously the a/c equipment is individual per coach and so will vary in condition and operation. Coach D tends to be warmer to begin with as it is full of televisions, which do generate a fair bit of heat between them. Obviously the area around the buffet kitchen can also be particularly toasty. I've seen defect sheets where Fleet have suspected a simple lack of coolant gas, and others where major a/c components have failed. It's a common problem, and of course the need to have working air conditioning has to be balanced against the need to have trains out in service when the fleet allocation is permanently tight.

It does seem in general that the specification for air conditioning systems supplied to the UK needs to be re-examined, as failure even of fairly new kit is far too widespread.

 

[Flying Snail]

If I can remember my traction bumpf, I think you're pretty much spot on

The a/c is powered both by the ETS directly (fans & equipment) and by the coach batteries (control systems), which in turn are charged continuously by the ETS supply. The lighting also comes off the batteries, as do the control systems for door operation and buzzers etc. As you say, catering is ETS directly, as are the plug sockets in the luggage racks (but the at-seat is battery). In normal operation the rear power car provides the supply, if it fails for any reason the Driver will switch to the front. The voltage actually varies depending on the engine speed, but 415 is the maximum output, 270 being the minimum. Unless both power cars or their ETS supplies fail, there will always be a power supply to the a/c and the system should be 'on' (unless it has been isolated for maintenance reasons of course).

In most cases there will be coaches within a set which are suitably cool, and others which aren't. Whilst the electrical supply is common throughout the train, obviously the a/c equipment is individual per coach and so will vary in condition and operation. Coach D tends to be warmer to begin with as it is full of televisions, which do generate a fair bit of heat between them. Obviously the area around the buffet kitchen can also be particularly toasty. I've seen defect sheets where Fleet have suspected a simple lack of coolant gas, and others where major a/c components have failed. It's a common problem, and of course the need to have working air conditioning has to be balanced against the need to have trains out in service when the fleet allocation is permanently tight.

It does seem in general that the specification for air conditioning systems supplied to the UK needs to be re-examined, as failure even of fairly new kit is far too widespread.

My experience of road coaches is similar, the units fail on a regular basis no matter what manufacturer. Of the new coaches we got early in 2012 at least 1/3 have registered low pressure faults on the modules by now and around a quarter have failed completely.

It seems to me that AC systems are just quite fragile in general and require a regular maintenance regime to keep them in any way reliable. In this part of the world we can easily get by without it for 7-8 months which may explain why they seem so unreliable. If one leaks and looses refrigerant in October does anyone care? I highly doubt it will be a priority to fix it so it could end up running around for months pumping air rather than refrigerant around the system which does it no good at all.


You made the point that fixing AC has to be balanced against providing the required service fleet but IMO that is a big part of the problem. If it is acceptable to release carriages into service without AC working then that is exactly what is going to happen.

With a single carriage on a HST out then it would seem extreme to ground the whole set but when you look at the likes of the ATW, EMT and Northern 158 fleet the current policy of allowing defective units out into service means the majority of these trains are running day after day with no working AC and no real pressure on maintenance or management to fix them. If it was made compulsory for the AC to be in working order before leaving depots then the necessary inspections, maintenance and servicing regime would have to be put in place and that would be that. The odd carriage would fail in service but you wouldn't see the widespread failures there are at present.

What I am surprised about is the on board staff and their unions apparent willingness to put up with this ongoing issue. As bad as it is for passengers the traincrew are on these units for entire shifts, they shouldn't have to work in these conditions.

 

[BestWestern]

What I am surprised about is the on board staff and their unions apparent willingness to put up with this ongoing issue. As bad as it is for passengers the traincrew are on these units for entire shifts, they shouldn't have to work in these conditions.

The issue there is that the affected trains (158s, MK3s etc) all have some form of alternative ventilation available, through droplights or hopper vents, which means that on paper they are acceptable even with failed a/c systems. The Guard has the option of failing a train if he feels that the inside temperature is excessive to the point of being a safety hazard, and that does happen sometimes, though not very often. But that doesn't solve the problem from the point of view of the passenger, who then has to wait for the next service which is likely to be just as bad and will now be twice as busy. The Driver can do the same if the cab is too hot to work safely in, but again in practice it is pretty rare that it happens. FGW's Sprinter and Pacer fleets have cab a/c units fitted, but failure of the kit is not generally deemed a unit failure because they have managed 20 - 30 years without them!

If the stock concerned was of the newer variety and completely sealed, then I would imagine crew would fail them routinely as such conditions would be entirely unacceptable and very likely dangerous. That would be my view anyhow.

 

[Bushy]

It was certainly b***** hot on an HST from Swindon to Paddington yesterday lunchtime. Makes me appreciate the A/C on 375s on my normal commuting route.

Regards

Bushy

Wrote that too soon. Short stock, hence packed, and no A/C on our 375 this evening.

Regards

Bushy

 

[cjmillsnun]

I think a lot has to do with the fact all the AC equipment is located in the under carriage of the vehicle.
When it sits at a platform there is very little airflow and as its exhausting hot air out underneath the coach I presume the AC equipment then runs hot and somehow trips out. I'm not 100% on that, but you'll note that modern trains have roof equipment nowadays.

I suspect that is more to do with how much they have managed to shrink the systems down.

Mk3 A/C technology was probably designed 3-4 years before the first coaches were built (Prototype Mk3 coaches were built in '72) so we're talking 60's technology compared with late 90's early 00's for the roof mounted units.

 

[ryan125hst]

If I can remember my traction bumpf, I think you're pretty much spot on

The a/c is powered both by the ETS directly (fans & equipment) and by the coach batteries (control systems), which in turn are charged continuously by the ETS supply. The lighting also comes off the batteries, as do the control systems for door operation and buzzers etc. As you say, catering is ETS directly, as are the plug sockets in the luggage racks (but the at-seat is battery). In normal operation the rear power car provides the supply, if it fails for any reason the Driver will switch to the front. The voltage actually varies depending on the engine speed, but 415 is the maximum output, 270 being the minimum. Unless both power cars or their ETS supplies fail, there will always be a power supply to the a/c and the system should be 'on' (unless it has been isolated for maintenance reasons of course).

In most cases there will be coaches within a set which are suitably cool, and others which aren't. Whilst the electrical supply is common throughout the train, obviously the a/c equipment is individual per coach and so will vary in condition and operation. Coach D tends to be warmer to begin with as it is full of televisions, which do generate a fair bit of heat between them. Obviously the area around the buffet kitchen can also be particularly toasty. I've seen defect sheets where Fleet have suspected a simple lack of coolant gas, and others where major a/c components have failed. It's a common problem, and of course the need to have working air conditioning has to be balanced against the need to have trains out in service when the fleet allocation is permanently tight.

It does seem in general that the specification for air conditioning systems supplied to the UK needs to be re-examined, as failure even of fairly new kit is far too widespread.

I didn't realise that the voltage could vary that much: I thought it was just a standard three phase 415v supply.

Taking it a bit further, I'm guessing that the electrical system works like this:

• 415v supply directly powers the higher load items, such as the a/c compressor, heaters, catering equipment
• 230v for the lighting is taken off the three phase supply. Presumably, this also powers sockets in the kitchen, air conditioning fans, toilet water heater ect.
• 110v battery charged from the ETS and supplies the emergency lighting and control circuits. This would also supply the inverters for the at seat power sockets.

I might be slightly wrong as I am working on what I have read online about ETS more generally. You mention that the lights run off the batteries, so is this the whole system and not just the emergency lights?

Going back on topic to the air conditioning, is everything located under the coach (compressor, condenser, evaporator and fans) with the cold (or heated) air sent via ducts to the passenger saloon? I've seen diagrams that suggest this is the case. However, diagrams for other trains show the compressor and condenser under the floor with the evaporator and fans located in the roof. Are HST's different in this respect?

Finally, is heating provided by electric heaters only or can the air conditioning work in reverse to provide heating (heat pump mode)? Most a/c systems for buildings now have a heat pump mode, and I was surprised to see that a website with information about the class 442's mentioned that they had a heat pump, so I was wondering if the HST's were the same.

Thanks

Ryan