50715 Air conditioning and heating concerns on 378 and 172 units

May 2012 in Train Operations

Equipment Rolling stock Work environment South East

Class 378 units:

• The air conditioning system can only be turned off for 20 minutes at a time.  This results in Drivers having to repeatedly turn if off when it restarts automatically.
• When the heating is on in the cab, the air conditioning is also on because it cannot be controlled independently.  This can result in the air conditioning creating a draft when trying to heat the cab.  If a Driver was to turn the air conditioning off, it would also turn the heating off.
• The air conditioning is very noisy, and comes on straight away when the cab is started up.  However, it takes a while for the computer system to boot up so Drivers cannot turn it off immediately.  The reporter states that the noise of the air conditioning can often make it difficult for Drivers to hear information over the radio.

Class 172 units:

• Drivers are able to stop the air conditioning for 60 seconds by using the 'damper' button which is independent of the system, but the reporter feels that this can be very distracting for Drivers.
• The air conditioning in the Driver's cab is linked to the system in the carriages, so if the Driver changes the temperature in the cab this also changes the temperature in the carriages.  This has previously caused complaints from passengers.
• As in the 378 units, the heating cannot be run without the air conditioning being on at the same time.

The reporter is concerned that the issues raised with the systems on these units could cause Drivers to become distracted and affect their ability to hear communications over the cab radio. 

Could LOROL:

• Consider separating the air conditioning and heating on the Class 378 and 172 units so they can be controlled independently by Drivers?
• Allow Drivers to have full control over the system, so that they can turn the system off and leave it off?
• State what regulations the current system adheres to?

 Response from London Overground

LOROL would like to thank the reporter for their concerns. 

Heating Ventilation and Air Conditioning (HVAC) systems installed into rolling stock are governed by the requirements set out byRailway Group StandardGM/RT2176 Issue 1, 'Air Quality and Lighting Environment For Train Crew Inside Railway Vehicles'. LOROL can confirm that both the 378 and 172 fleets comply with the requirements set out in the standard and are considered a climate control system. Of particular interest,section 5.1sets out a mandatory requirement to have at least 60 cubic meters fresh air delivered to the driving cab per hour.Section 5.2sets out the requirement for carbon monoxide levels to be kept to 'as near as practicable to the normal outdoor ambient levels and shall not exceed 0.01% (100 parts per million). This requires minimal ingestion of fumes and smoke generated by the train into the areas where Train Crew carry out their duties'.

In response to specific queries raised by this report.

Class 378

• LOROL notes that the reporter utilises the 20 minute 'turn off' function which is labelled 'smoke mode' and is a product of complying with the requirements set out byGM/RT2176 section 5.2. However, the repeated use of the 'smoke mode' does not allow the HVAC system to provide the required 60 cubic meters of fresh air per hour thus increasing the probability that the Driver who employs the repeated use of the smoke mode becoming drowsy - assuming emergency ventilation (drop lights) are kept closed. It is therefore a mandatory requirement to have the fans or the window open.
• Programmable logic controllers prevent the air conditioning from being on at the same time as heating. The reporter is mistaken on this point.
• As pointed out in point one above, the system is not designed to be turned off as it is a mandatory requirement to the system operative or the window open. In terms of noise, LOROL have trialled a noise insulation modification on 378255 and it was accepted as an improvement by the staff representatives.

 Class 172

• As with 378s, the damper button is provided with a view of preventing smoke ingress to the cab, it also closes the saloon dampers for the same period of time. For the avoidance of doubt, the damper button is not provided to turn off the fans for Driver comfort.
• The only shared functionality between saloon and cab is the damper switch. The saloon is independently controlled by a control panel in each of the body end cupboards. The reporter is mistaken as to the functionality of the system.
• As with 378s, programmable logic controllers prevent the air conditioning from being on at the same time as heating.

In conclusion, LOROL are in the process of addressing the noise issue which should then remove the practice of drivers repeatedly pressing smoke mode on 378s. It is quite clear that the HVAC system is designed to be compliant withGM/RT2176and turning the system off is not an option under consideration. Drivers currently have full control of the temperature and mode of operation; independent control of the system is not required as there is no evidence to suggest further control would be of benefit in light of the incorrectly perceived mode of operation reported.