ok thanks guys thats makes sense but would i not be switching the NO to the run contact of the VFD instead of the common? is the common not 0 volts?

 

If you ref the pic in post #14 you will see it just requires a contact closure as 7 is common 9 is 24vdc and 8 is digital common.
The input contact of the relay just connects 9 which is the 24vdc source to 2 input.
IOW it it is a sinking input that just requires the 24vdc.
No external voltage needed.
Max.

 

Hi Max,
I think you are running out of different ways to describe how to connect a pair of relay contacts to two terminals on the VFD.

Les.

 

Hi Max,
I think you are running out of different ways to describe how to connect a pair of relay contacts to two terminals on the VFD.
Les.

Don't make me come over there!
Max.

 

....cont post #13

Before I go on, just know this: Max's 1-relay solution is the simplest to implement. I don't even know why I'm still here talking, other than I don't like systems becoming overly discombobulated over time. I've worked on machines that had 120v going to relay, switching 24v to another relay, switching 120v to its final destination. Why not just take the original 120v output to its final destination? Because the panel had so many hands in over the years and so many undocumented and unsanctioned modifications that nobody knew what was going on in there. I spent a lot of time cleaning up crap like that and rebuilding panels to the state they should have been, had everything been done right over the years.

Using an extraneous 120v supply when the VFD has its own supply, is the first step down that road. Maybe I'm just being dramatic, but whatever, this is how I would do it:



I'm making a lot of assumptions here, like for example: everything. Sorry, just working with the information I have. Assuming your PLC has relay outputs (most common for 120v control), you can do away with the 120v entirely and run the VFD's own 24v to the PLC and pushbuttons.

 

The reason I gave my solution I thought may be the easiest for the OP @BENCASEY83 to follow, the PLC I was referring to was the logic I/O of the VFD which most commonly use this expression for the low voltage I/O control.
Max.

 

The reason I gave my solution I thought may be the easiest for the OP @BENCASEY83 to follow,

yes I agree. This is probably one of those times where the simplest advice is the best advice. Now that I've said my piece, I'm casting my vote for your solution.