DOL with external e-stop and auto-start timer

Aaron b · Jan 28, 2022

Hello, I have recently designed a system including a pump. It is only 4amp and it is controlled using a crompton DOL. An external twist to reset estop has been incorporated in the circuit in series with the stop button. The client has requested the addition timer to autorun the pump daily.

I don't want the pump to be started automatically and bypass the estop and want it as simple as possible. I can add a 2 pole relay and a estop reset button and break the line conductor to the push buttons but I was wondering if there was a simpler way that I may have overlooked?

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Aaron b · Jan 28, 2022

I missed that I would need to have a normally closed contact from the timer too, to stop the aux contact on the contactor latching.

David Prosser · Jan 28, 2022

Post this on the trainee forum. Is this really for a client or for a college question?

Aaron b · Jan 28, 2022

David Prosser said:
Post this on the trainee forum. Is this really for a client or for a college question?

Thanks, it's a real job. I joined the trainee section of the forum as I never completed my apprenticeship so I am going back through the experienced worker route. I don't have any experienced peers so I was just wondering if it was anything others have come across and if there was another method I might have overlooked.

David Prosser · Jan 28, 2022

Use an on off 8 or 11 pin timer relay in parallel with start button and the latch for the contactor.

Spoon · Jan 28, 2022

Do you require E-stops or just stop buttons?
If E-stops then you need to do a risk assessment to determine what category of stop you need.
Also when designing things like this, it have to comply with EN60204 along with other regs.

Aaron b · Jan 28, 2022

Spoon said:
Do you require E-stops or just stop buttons?
If E-stops then you need to do a risk assessment to determine what category of stop you need.
Also when designing things like this, it have to comply with EN60204 along with other regs.

The client requested a separate estop and their engineering specifications require that its in an enclosure with a isolator. Personally I think it should have been waivered as the stop button is raised on the starter. I have enough room to add some components in that enclosure now but will have to replace the front as I haven't laid it out for a reset button. Thanks for the prompt, it's a fully enclosed pump with no accessable rotating parts so the risk is minimal but I'll have another look at the standards as it's been a while.