The Brinsea plate has the 50F disclaimer(CYA),
the Premiere plate and the Sweeter Heater does not.
Not sure how cold of temps I've used my DIY Pseudo plate,
but it's been plenty colder than 50F and it's worked fine.
Folks have used the commercial plates at lower temps too.
Plates are way better than lamps, except if you have more the ~20 or so chicks.
The plates, like the prefab coops, exaggerate numbers of birds they will serve/fit.
the Premiere plate and the Sweeter Heater does not.
Not sure how cold of temps I've used my DIY Pseudo plate,
but it's been plenty colder than 50F and it's worked fine.
Folks have used the commercial plates at lower temps too.
Plates are way better than lamps, except if you have more the ~20 or so chicks.
The plates, like the prefab coops, exaggerate numbers of birds they will serve/fit.