Will WYZE thermostat work if my old one only has two wires?

[bd0]

I have only a RH and W wire, and just bought a 24V AC Transformer that I use to power thermostat - see below on instructions:

Thermostat with external transformer

I’ve had to get one as well, but hasn’t came in yet. I have a radiant floor heat system that just has two wires running from the thermostat to the switch that turns on the water pumps.