Hmmm, on our Doorbell I found the hottest section to be around the Lens area and the temp. lowered as I went down the Doorbell from Lens area to PIR section then Button section being the lowest. Your middle PIR area is hotter than your Lens area, interesting...Did another outdoor with cover on temperatures test post installation of the 16VAC / 10VA transformer. Here mine is in the basement about 5 feet below the chime on the main floor and a short run of maybe 25 feet to the doorbell on the front door. I've switched the tranformer a few times now in the last few weeks so it now takes about 15 minutes to swap it out.
Here in the midwest.
Ambient temps outside a few minutes ago are 50 ° F.
Tested temps on sides and top cover.
All side plastic temps were around 60 ° F except for front face.
Front face / cover camera section was around 62°F. Middle PIR section was around 68 °F and bottom button section was around 60° F.
I am fine with these temps and not concerned any more.
My 16v/10va worked fine with our Mech. Chime while pressing the Doorbell button. Only reason I changed it out was my thought of running two to three 24/7 streams may bring on more load on the Doorbell. I stayed with 16v not to push more voltage to the Chime (Making it louder) and figured 30va should be able to handle any extra load. So now you got me thinking, which this has been brought up several times in this forum, if the range on these Doorbells is 8-24 volts, operating at the lowest voltage in theory should produce the least amount of heat, kinda like it does with CPUs. Chadsturgill posted message #32 & message #33 here stating 12va would probably be minimum load needed for this Doorbell. I do know each transformer will give off different voltage/amperage readings, usually higher than labeled, see video below...
Funny but the guy's name on this video is Chad too
16V 10va VS 16V 30va Doorbell Transformer