Relay To Prevent Loop?

[washcroft]

Hello,
What would I use to stop the following, a relay of sorts?

Simplified:
Switch A - Gives Live to Appliance A
Switch B - Gives Live to Appliance A and B

The problem is that when Switch A is used, Live gets to Appliance B through its connection with Application A on Switch B.

I have no control over the switches so they can't be changed, I just have two feeds coming from them to make this work.

Cheers,
Warren

 

[ericmark]

Change switch A for a two way switch appliance to common and line to L1 and switch B to L2. Of course must be of correct rating likely a grid switch would do the job.

Using a change over relay controlled by switch A would do same thing of course.

 

[washcroft]

Change switch A for a two way switch appliance to common and line to L1 and switch B to L2. Of course must be of correct rating likely a grid switch would do the job.

Thank you, but I can't replace the "switches" - that term was used to simplify the scenario. Basically I have two lives which are switched digitally.

 

[Alarm]

What are you doing then?
What are you switching?
Can a contactor/relay be inserted?

 

[EFLImpudence]

Unless Appliance B is dependent on Appliance A being on first and as well I do not see the need for your desired arrangement.

If as above, have both wired from Switch A but Appliance B going through switch B.

If not as above, just have two separate switches as you will have to manipulate both anyway depending on what you want.

 

[sparkiemike]

If I understand you correctly you can use a 2pole relay on switch B if loads are less than 10A then IMO RL01C ( http://c613539.r39.cf3.rackcdn.com/rs.pdf ) will do the job. Most wholesalers sell them

Use switch B to energise the coil on the relay, you will need to feed a live through both poles of the relay ( terminals 1 & 8 ) - you can use the same switch live from the coil.

Put one load on one set of relay contacts and the other load on the other set of relay contacts.

Wire switch A to the load as you would normally.

 

[washcroft]

Unless Appliance B is dependent on Appliance A being on first and as well I do not see the need for your desired arrangement.

It is dependant, consider Appliance B as a booster for Appliance A - there would be times when you wouldn't need Application B.

If I understand you correctly you can use a 2pole relay on switch B if loads are less than 10A then IMO RL01C ( http://c613539.r39.cf3.rackcdn.com/rs.pdf ) will do the job. Most wholesalers sell them

Use switch B to energise the coil on the relay, you will need to feed a live through both poles of the relay ( terminals 1 & 8 ) - you can use the same switch live from the coil.

Put one load on one set of relay contacts and the other load on the other set of relay contacts.

Wire switch A to the load as you would normally.

That is exactly what I need, do they come in other forms - something with terminals I can mount somewhere?

 

[sparkiemike]

That is exactly what I need, do they come in other forms - something with terminals I can mount somewhere?

You have to purchase the base and this is din rail mounted, and the base has screw terminals

Check out rs components for other types

 

[EFLImpudence]

have both wired from Switch A but Appliance B going through switch B.

Is this not the simplest solution?

Switch B only works if switch A is on.

 

[333rocky333]

you could use something like merlin gerin CT contactors, they are 20 amp rated and these clip on din rail and fit most, off the shelf plastic enclosures.

 

[washcroft]

have both wired from Switch A but Appliance B going through switch B.

Is this not the simplest solution?

Switch B only works if switch A is on.

It would be, except they are both independently controlled - either one of two lives will be live, never both.

 

[washcroft]

That is exactly what I need, do they come in other forms - something with terminals I can mount somewhere?

You have to purchase the base and this is din rail mounted, and the base has screw terminals

Check out rs components for other types

I'll have a look, cheers.

you could use something like merlin gerin CT contactors, they are 20 amp rated and these clip on din rail and fit most, off the shelf plastic enclosures.

Also look like they will do what I need, thanks.

 

[EFLImpudence]

have both wired from Switch A but Appliance B going through switch B.

Is this not the simplest solution?

Switch B only works if switch A is on.

It would be, except they are both independently controlled - either one of two lives will be live, never both.

That's not what you said.

Two switches then.

 

[sparkiemike]

MK also do contactors (6220 & 6420) that might be more readily available, only downside is they make quite a "clunk" when energised.

 

[Alarm]

That's not what you said.

Two switches then.

Why I asked again.