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Maximum safe hot water supply temperature to a concrete floor with tile surface

I am in the process of building a new house. I have hydronic heating in 5 different zones. One zone is dedicated to a towel bar. I have a 110kBTU Crown Phantom boiler. The subfloor is 1 inch plywood with the 5/8 PEX stapled to the plywood with 1.5 inch of dry pack and the red mat with red sealer (forget name) for anti crack and then a 1/4 inch motar with 3/8 inch porcelain tile. The boiler is currently set at a maximum temperature of 130 with a declining temperature depending on the outdoor temperature. The system typically provides water at 123 to the floor and subsequently to the towel bar. The towels are not all that warm I would like to increase the maximum operating temperature to at least 135 and tighten up the temperature curve so it does not go below 125. Does anyone have experience operating a hydronic system with a 135 to maybe a 140 setpoint. An additional 10 degrees to the towel bar will make a big difference because I ran it at 135 and it felt great but concerned about the main floor system.
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Comments
The radiant doesn't need or want to run any warmer that what is required to cover the load. Was there a design done on the system before it was installed? It should indicate the SWT required to cover the design condition. Sounds like the 130 SWT is the design day condition?
Warming the surface above maybe 80- 82 starts to get uncomfortable, and the floor will tend to overshoot after the stat turns off, if it runs too warm.
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me
just my .02
I found with my electric towel bar, closing the door, allows the bar to warm towels and the room and power down. Mine is a tiny 5X6 bathroom in the shop.
DHW is another option the bar should be made of non ferrous, low lead material.
Depending on if the recirc line is well insulated, running that loop 24/7 may cost more $$ than the electric bar?
I start the towel bar before I start the heating system for warm towels as I use an outdoor shower as late into the fall as I can stand it.
In fact this may be the weekend to fire up the towels
trainer for Caleffi NA
The magic is in hydronics, and hydronics is in me