Pump monitoring (again)

["Benfield, John \(Penta\)" <john.benfield-eds@xxxxxxx>]

I need someone to confirm my understanding of how relays work and will
do what I am expecting.

In my quest to monitoring my central heating I am looking at a way of
monitoring when the various pumps come on. I already have a hardwired
controller that links all of the timers/thermostats/pumps together. The
controller has a screw terminal block within it and I have worked out
which terminals go live for each pump. What I *think* I now need it a
230v relay attached to these.

My really really basic understanding of a relay (such as this
http://tinyurl.com/kwtd2) is that when
a voltage is applied across one
set of contacts, the pair on the other side of the relay either open or
close. Am I correct in assuming that the 230v does not get passed
through the relay to the second contacts - this will destroy my 1-wire
sensors.

Looking at the various relays out there I guess I need a DPDT 5a 230v,
does this sound correct?

JB



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