Control Of 1/2hp Motor Using 20a Sp Switch

[marconi]

This morning I have put a query to Honeywell/MK electric technical desk asking for them to provide the inductive switching rating of their grid switch MK4896N and to confirm its neutral pole is first make and last break. I thought of a grid switch so you could put a neon beside it all in the space of a standard switch plate.
I will let you have MK's response when I receive it. Enjoy the sunny weather.

 

[marconi]

Lucien, here is the response from Honeywell/MK on my query. Helpfully, they have given a contact number and invitation for further clarification. I cannot quickly turn up what is the definition of the AX rating - something for me to do in a quieter moment later.

We confirm that DP K4896N switch is specifically designed to make first / break last on the Neutral pole. In regard to Inductive loads the switch is AX rated and therefore meets the requirements of the standard BS EN 60669-1 which includes loads for Fluorescent lamps but not specifically motor loads having much higher start currents. For any further clarification please call our help line on 01268 563720 and one of our engineers would be happy to assist further with your query. Assuring you of our best attention at all times. (E&OE)

Stephen Cocks

Technical Sales & Service Department

Honeywell ED&S Ltd

The Arnold Centre, Paycocke Road, Basildon, Essex, SS14 3EA

Telephone 01268 563720

 

[Lucien Nunes]

Thanks for doing the spade work and forwarding that info. X-rated switches are those that do not have to be derated below their Ith rating for discharge lamp duty.

I did the job this afternoon and things were easier than expected. The motor was in pristine condition and newer than I thought - I tried to date it from the start capacitor but the date code was unintelligible - mid 1980s anyhow. The insulation resistance was >99MΩ both cold and hot and the leakage was <0.1mA starting and running. I fitted a motor circuit breaker / manual starter in an enclosure adjacent to the motor but left it as a standalone device with a 13A plug. There was enough room to add a separate enclosure in which I placed a small 20A contactor rated for 1.1kW motor load at 230V, to control the socket outlets like a glorified remote-controlled 13A strip. The cable to the switch had been successfully freed off and was replaced with 4-core, as the switch itself was replaced with a new decorative finish metal one that needed the earth. This overcame the colour code guilt with only the grey core needing to be sleeved blue for neutral.

The result is that the switch and indicator are normally wired, the motor and transformer are controlled by a contactor expressly rated for the duty, convenient local isolation and the ability to separate the parts remain by way of the 13A sockets, and the whole was completed in a few hours.

Cheers also to DW for the suggestions and ideas above!