Finally Got my T8 Set Up

You are overcomplicating it. Just put one of the Acurites on the cool side and set the RHP with the T-stat till you get around 80F on the cool side the Acurite is on since you are using a UTH for a hot spot. In my PVC cage I don't even use a UTH, I just use a RHP on one side. I hung the probe about 3 inches to the left of the RHP and about 2 inches from the bottom so the snake doesn't sit on the probe. Then I just adjusted the T-stat until I got about an 87F hot spot as that seems to be what my snake likes. No snake needs belly heat as long as the ambient temp is correct. None of mine get belly heat and they all happy and growing like weeds.

Humidity will be higher since its fresh mixed Eco Earth. let it dry out a little bit. You generally don't want too much humidity as warmth+high humidity=mold/bacteria paradise. I never keep my humidity over 60% and I never have problem sheds. Since your snake isn't in there yet, just leave the doors cracked open "bleed" off some of the moisture. Personally when I used Eco Earth, I would mix it up in a bucket and let it sit a few days before I used it, stirring it once in a while. That helped dry it out a little before I tossed it in but after 1 year, I hate Eco Earth and just use aspen on all my snakes now and have no problem with humidity even in 2 temporary glass cages. Grats on the AP cage btw.

I never keep my humidity over 55% and I never have had a bad shed, but then I understand how temp and humidity are related. if the ambient temp is low 80% can be too low or 50% can be enough if they are spot on.

Sauzo did you find a huge difference in RH with or with out the RHP?

Not really. For me it seems to be about controlling the airflow. That's why even in glass tanks, I keep around 50-60% without trying too much. Honestly, my RHP seems to just be a safe and more efficient version of a CHE to me or at least that's how I really use them.

A CHE and RHP are completely different. CHEs heat the air RHP/UTH heat objects, they are radiant heat sources. This is evidenced by what you just said, they don't change the RH. If they heated the air it would increase the maximum saturation point and that would show a drop in RH. The math is super simple and very clear. 50% of 10 is 5. 50% of 20 is not 5 not can it ever be anything other than 10. You have just said you have 50% RH and then changed the air temp you must see a drop if it heated the air in any significant way. This is why you see a drop with a CHE it heats the air increases the max saturation point and the same humidity results in a lower %.

A few years ago I didn't understand RH, I spent 30 min reading and asked a couple of questions to a friendly meteorologist and now have a solid grasp of how humidity works and exactly how to control it. The math is super easy you just need a simple chart and you are done. RH is pointless with out the ambient air temp. Think about this example you want to buy a snake the breeder wants a 10% deposit, but never tells you how much the price is how much do you send? You must have the air temp to determine what the % is of.

The op might not have enough or way too much humidity. The evidence they have provided indicates the ambient temp reading is incorrect. It is easy, the dew point should be at the room temp, but yet there is no condensation. There is an error somewhere. RHPs mess with ambients they make it difficult to get a correct reading as they directly effect the thermometer. This is what the OP described.

Actually a CHE will heat objects too. Mine heat the tops of the RBI hides I use. Well its obvious he has too much humidity because it looks like the right door has condensation on it, or that is the lighting. Regardless though, I had the same problem with my Pro-Line cage when I put in fresh mixed Eco Earth back when I used that stuff. The problem is you have way too big of a water source and too small of airflow, thus my point of controlling the airflow being the key. That is why I get 50-60% and can even get higher with using a 36x18x12 glass tank. That's with just a water bowl. If I threw in a burlap craft bag with moist moss in it or a humid hide, I would get around 70%+. And this is all while running only a CHE. I even get the same with my 36x18x16 glass tank as well.

And yes a RHP does most of its heating from objects, the only object I got under my RHP is about 2 inches of aspen and that heats the whole cage fine. A UTH trying to use aspen as its object to heat fails miserably at heating the cage. So while I do agree they heat objects as their primary way of doing it, a RHP is much more efficient at heating air as well vs a UTH. That is why I don't ever use UTH. Snakes don't need belly heat as long as their ambient temp is good. The RHP can cover both of those like mine does with heating the aspen directly under it and heating the air. My CHE does the same thing, heats the RBI hide I put under it and also heating the air. Its just much more dangerous in that if I touch my CHE, I am going to get one heck of a burn where as I have touched and put my hand on my RHP while running full power and its fine, hot but nothing like a 600F CHE.

From what I read the Op was having humidity issues as in too much now. That isn't affected by the RHP. If he turned off the heating in the cage and closed the doors, he would still get condensation and humidty issues because like I said, the airflow vs water source is unbalanced. And this is because he is using freshly soaked Eco Earth which has crazy humidity until it dries out some. He will have really high humidity probably for a week or 2. He needs to air out the cage or pull the Eco Earth out and dry it some, otherwise so much humidity that is makes condensation will be a breeding ground for bacteria and mold/fungus. Like I said, I had that issue and my boa packed the wet Eco Earth down and it actually started growing these weird mold balls under the substrate. I noticed because I smelled the mildew and when I sifted through the Eco Earth I found these weird white slimy balls, they weren't snake urate either. That's when I quit using Eco Earth and tore the whole cage down, scrubbed it all, threw away all the wood, scrubbed the hides and went to aspen.

And as for the whole RH deal, I never really looked into how that all works. I just am saying what I have learned from my experience with keeping reptiles over the years in glass tanks since back when I was a teenager, a fancy cage was one built from 2x2 studs as a frame, then plywood sheets as walls and all painted lol. Heating was done with lights in metal cages so the snakes/lizards couldn't get to them. Heck I don't even think there were even Herpstats back then...about 25-30 years ago :weirdface Anyways, I defer to you on the whole RH deal and how that works as like I said, I never looked into how that all works.

That is the point actually, RH is linked exactly to temperature. The first problem you have said your RHP did not change the RH, there fore it has not altered the ambient air temp. Simple physics RH is a % of the saturation point.

A chart for you.
78ºF can have a max of 23.8 gm/m3 of water vapour
80ºF can have a max of 25.4 gm/m3
83ºF can have a max of 27.9 gm/m3

60% RH would be 14.28,15.24, and 16.74gm/m3

Royals need basically 15.24 gm/m3 to shed so 60% is too low just right and more than you need all at once. A CHE changes the ambient air temp very easily so therefor it alters the RH very quickly. It principally is a convection heater, You have stated the RHPs do not significantly change the RH and we know they heat with radiant heat, so the do not significantly heat the air. You have given your own proof. The demonstration the OP has an issue is the lack of condensation. The figures they have provided is a huge amount of humidity. 80/80 is 20.4gm/m3 absolute humidity. The glass of the from based on the cool room temp must condense water. It is not. HOWEVER if the ambient air temp is lower like closer to the room temp lets use 71ºF (three degrees ambient lift to the RHP is the average I get with the three of mine)

71/80 is actually only 15gm/m3 and is actually a touch low, but at this point you don't see condensation (you need 64ºF to get that) That is the point. The OP is not measuring ambient air temp, but surface temps because the thermometer placement is off.

Where the myth RHP heat air came from I don't know, but the belief they do is proved out all the time. They don't change the RH nobody talks of them sucking out the water (which is also untrue they change the figure the % is of) If they did heat the air, they would do exactly that.

Think on this,
In winter, heating your house tends to make the air excessively dry. Your degree of comfort depends upon the relative humidity. The outside air has a relative humidity is about 70%. Then presume you take that air into your house and heat it to 20°C without changing the actual humidity. What will that do to the relative humidity?