Quote Originally Posted by irving2008 View Post
Incidentally, where did you get the 10v from? If you look at graph H55 on the spec for those relays, you will see that the 4PCO version is rated at 30v 6A. At 70v its derated to 0.5A... but thats only to meet the contact lifetime figures at 1800 cycles/hour. If you switch a dozen times a day it'll be a lot!!! On the AC side graph F55/1 shows that at 900VA the contact life is 200,000 cycles at 1800 cycles/hour so its not going to fail in your lifetime (about 45years at 12 cycles/day) lol.
The 10V was pulled out of the air for simplicity and example, I wasn't referring to any specific bit of kit.

As for the graphs, the issue for me is translating what I can see into usable information and that is where my lack of knowledge shines through. For example, you turn the supply on and run it for an hour. For that hour you're drawing a fairly constant 5A. My understanding was that, while the contact only switches once, it still has to carry 5A for that hour. My choices were made on that basis. Clearly that basis was wrong which is leading me to make some less-efficient choices.