You connect it across the solenoid coil so it is normally not conducting. It is there to "catch" the rather large inductive voltage kick a solenioid gives off when the power is removed.

Put it in there and the voltage seen by the relay contacts is small and controlled.

Leave it out and the relay will fail sooner rather than later.

 

Here is a visual.
http://www.industrial-electronics.com/articles/article_title/Solenoid-Valves.html
Max.

 

So this http://uk.rs-online.com/web/p/produ...Phrase-_-313cc500-9da4-7789-cbaa-00007800cd76

Would be suffeicnet for the applicaton. Where would i wire this, ie on the positve wire or the negative wire? And also would i put one on each solenoid to relay circuit and would i just solder it?

 

Place one on each and every solenoid. Best place is right at the solenoid itself.

It goes between the positive (banded end of diode) and the negative wires.

 

If you are using the proper stake-on terminals for the intended solenoid, you could place the diode lead into the stak-on with the DC conductor.
With these types of connector it does pay to get the proper crimp tool.
Max.

 

Would I simply be able to use a high value resistors wired in series?

 

Would I simply be able to use a high value resistors wired in series?

No. If a use a high value resistors wired in series would do the job I would have said "use a high value resistors wired in series."