On Sat, 12 Nov 2005 23:09:39 -0600, "Martin H. Eastburn"
wrote:

Read the doc - it says you have to order 1-4 output boards.
One could be mechanical relay another their opto isolated SSR.
Then they have voltage source - (that could do it easily - program the voltage
needed on the output power SSR and forget other output boards)
and ....

Not knowing what your outside SSR needs - likely 5-12v that is for a TRUE - ?
then the voltage source is zero or 7v for off and on. If a new BIG one is needed
and it was a low voltage input - new values could be done...



Martin Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
NRA LOH, NRA Life
NRA Second Amendment Task Force Charter Founder

snip
What Martin said. Get the ssr output board. A mechanical relay has a
life rated in number of contact closures, maybe a couple hundred
thousand. With the controller in time proportional mode, with a time
interval of 2 seconds (for instance), a mechanical relay would hit
200,000 cycles in 4.6 days. The ssr will run indefinitely. By the
way, for the big external ssr, I'd get it rated for at least 2-3X your
load. The higher rating usually won't cost any more, and is likely to
last much longer. Also, ssr's are now available which fail open, much
to be preferred. In addition, when I'm using ssr's on 230V resistance
heaters, I use two and break both legs. This prevents continued
heating if the heater develops a partial ground.

I also put a mechanical relay in front of the power side of the
control relay and control it with another high temp alarm controller
with separate temperature measuring device, or failing that, an alarm
relay (sometimes already there, sometimes an option) in the main
temperature controller. The separate high temp controller is required
where I work. It can be a much cheaper simple on-off controller. I
usually series an on-off switch with the high temp controller output
to the mechanical relay. The on-off switch must be switched on to
enable the heater and allow the mechanical relay to pull in.

Good luck. Let us know how it turns out.

Pete Keillor