After installing a skuttle spray type humidifier and testing it o.k. I closed the panels and went to the thermostat to retest. When I call for heat from the thermostat, nothing happens. The blower fan won't even turn on.

Is possible you fried the transformer during the new install,, does anything work,, the ac maybe?

The doesn't work either.

The ac doesn't work either.

I would check the transformer for power output after checking to make sure there is power to the furnace, check all fuses and breakers

Transformer has 110 going in but 000 on the 24vac output side.

I don't understand why the blower (operates off 110vac) doesn't work. If the transformer is fried then only the 24vac side shouldn't work.

24 volts tells the blower relay to work. Are you sure you got your humidistat wired right?

I replaced an old one with a new one and wired it the same.