Do E Stops Need a manual reset or not

[TailSpin]

Hi All,

This is an issue with air handing units that have E stops fitted to stop the supply fan and main fan unit. At the moment on most AHU,s there is no manual reset on these units. So once the E stop has been activated the unit will re start when the stop is reset.

It seems that there is a lot of discussion on this type of question.

I know in the 17th reg : 537.4.2.6 at the bottom of the text it stats :

The release of an emergency switching device shall not be re-energize the relevant part of the installation.

Also are AHU's covered under machine law if so this is some text from it :

Once active operation of the emergency stop control has ceased following
a stop command, that command must be sustained by engagement of the
emergency stop device until that engagement is specifically overridden; it
must not be possible to engage the device without triggering a stop
command; it must be possible to disengage the device only by an
appropriate operation, and disengaging the device must not restart the
Machinery but only permit restarting.

Risk assessments and categories are also mentioned but I am not sure if this changes the out come.

Any Help on this would be appreciated.

Regards

Tail Spin

 

[silva.foxx]

I worked on AHUs back in the day and also recall the local e/stop, that would allow the fan to restart upon release! Scary. To think I used to change out drive belts with just this e/stop, as no local isolation.

You need to risk assess the situation really. In this day I would definitely have the e/stop circuit requiring reset and needing the AHU to be restarted also.

.

 

[jpmiff]

how do you reset the E stop?

 

[xraytek]

I am not familiar with AHU's but wonder if the fans are driven by contactors?
If they are, are the contactors monitored by the safety circuit via an N/C contact?
If it is then you can stick a N/O reset button in series with the N/C of the contactor.

Whether its required or not is all down to risk assessment, but if the reset button is a simple addition then no reason not to add one.

 

[TailSpin]

Thanks For all your replies.

I look after a lot of Air Handling Units all with E stops. They all have a mixture of contactors overloads,soft start or inverter control systems. On these AHU's very few have a manual re sets, so in other words when the stop is re energised the unit will just re start. This just seems wrong as I have known E stops to fail. So I was just trying to clarify if the manual re set is a must or not .

Regards

Tail Spin

 

[telectrix]

agree with previous posts. E/stops are Emergency Stops. Suppose some clown comes along and resets it. Nothing to do with IEE in my opinion, just common sense and safety. Restart of any machinery should only be undertaken by a competent person, once he/she deems it safe to do so.

 

[Guest123]

IMO it's always been a big no no. Releasing the EM stop should not result in that piece of equipment re-starting automatically, it must be physically re-started via another method.

All IMO.

 

[davelerave]

i think an additional key-start or similar is needed

not too familiar with them


not allowed anyhow for sure

 

[telectrix]

wouldn't like my lily whites in the workings if it were possible for somebody else to click a button and switch it on

 

[Guest123]

I believe Puwer98 would apply here also.

Puwer