How to wire a modern contactor to a Mk1 Bantam

[wilson logan 1Participant @wilsonlogan1]

Hi All,

I want to change the old contactor on my Bantam to something more modern (Siemens 3RT2015-1AF02).

I’m reasonably happy with the connections to be made other than the black wire (top right).

I believe this is the e-stop connection for the foot brake switch (and possibly the chuck guard & end stop).

Normally e-stops are wired across the NC positions of the contactor (21NC & 22NC) but I have only one wire.

What should I wire the other side of the NC contact to? Earth?

Cheers,

Wilson Logan.

[noel shelleyParticipant @noelshelley55608]

Assuming that the coil circuit is on the live side then what coil voltage 240v or 415v ? If 240 then wire Phase to neutral, if 415v Then wire across 2 phases. Taking it to earth sounds very wrong and likely to cause alsorts of trouble. The various stop switches will all be parallel across this circuit, breaking the circuit will drop the coil. UNLESS you have a low voltage control system with a 24v coil, that’s another ball game ! Noel

[Robert Atkinson 2Participant @robertatkinson2]

An E-Stop should not be wired in parallel (across) a normally closed contact on the contactor they control. If you do the contactor will effectively return the E-Stop to the released state when the contactor is de-energised.
Normally an E-Stop would be wired in SERIES with a Normally Open contact. This circuit latches the contractor on when the start button is pushed.

Robert.

[noel shelleyParticipant @noelshelley55608]

Not thinking properly ! Robert is right, series in a NO circuit. Sorry Noel.

[wilson logan 1Participant @wilsonlogan1]

Thanks chaps!

[EmgeeParticipant @emgee]

Looks like you are short of a pair of NO contacts to maintain the coil connection when energised,

21-22 are labelled NC so can’t be used to maintain the cct.

 

Emgee

[Robert Atkinson 2Participant @robertatkinson2]

As Emgee says that contactor does not look suitable.  Also it has a 110V coil which would be unusual for a small lathe. The Bantam diagrams I can find do not have a control transformer.
Did you select that contactor or was it just “available”?

Do you have a wiring diagram for your lathe?

Any pictures of the old contactor? Ideally installed and one of the part number / rating plate.

Robert.

[wilson logan 1Participant @wilsonlogan1]

Here’s the old contactor.   I am not sure of the make/model as I didn’t photograph the name plate.

[noel shelleyParticipant @noelshelley55608]

IF the old unit works why change it ? IF you don’t understand the wiring and as Robert has pointed out it has 110v coil then my advice would be to find a competent person to do the job for you as it is NOT as simple as you think. Noel

[Pete RimmerParticipant @peterimmer30576]

You could use that new contactor if you fitted an auxiliary to the top, but then it probably wouldn’t fit inside the original button box.

[Robert Atkinson 2Participant @robertatkinson2]

Sorry but there is not enough information to give accurate advice.

[EmgeeParticipant @emgee]

The starter is a Crabtree B15 with an oil filled dashpot adjustable overload at the top left corner.

Both the fixed and moving contacts are replaceable, I have some spares in the depths of a cupboard.

The external control buttons as follows : stop button operates on the top right red shaft and the start operates the bottom contact block which has the contactor hold circuit connected.

Standard fitting on most Colchester lathes during many years.

Looing at your top picture it looks like the suds pump supply is linked to the motor feed but there may be a separate suds pump starter for control as you don’t always want coolant flow.

Emgee

 

[EmgeeParticipant @emgee]

Had 2nd thoughts about the overload type on the B15 starter, delete the oil filled dashpot comment, now believe it is a thermal type with fine adjustment.

Emgee

[Les Jones 1Participant @lesjones1]

As well as the new contactor not having a NO maintainer contact it does not have any motor overload protection. If you insist on replacing your existing contactor you need to buy a SUITABLE new one.

Les.

[Anonymous]

All the contactors on my Harrison M300 have 110VAC coils, and one side of the 110VAC supply is connected to ground.

Since the control voltage transformer, no-volt contactor and the main reverse contactor have failed I am in the process of throwing everything away, buying new items, and re-wiring based on the original schematic.

Andrew

[Author]

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