>You don't need two, the 12VAC is isolated and two won't help. The voltage
>losses will be significant enough from just one. Why don't you use a
>relay? No voltage loss to speak of, and at 2 operations per day, a relay
>rated at 50,000 operations (tungsten load) should last the rest of your
life.
>
>(Do be sure to get one with a suitable 'tungsten' rating, otherwise
>there's a risk of contacts welding "on" or short life)

You could always use a triac to soft start the lamp, then use relay contacts
across the triac when close to 100% current. Bit complex perhaps, but would
cut the losses, while being gentler on relay contacts.

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