Recommended Max Input Temp for Entran II in Concrete Floor

Entran_II_Owner

We have recently purchased a home that was built in 1993. It has Entran II tubing in the concrete floors. I have looked and do not see any date codes on the visible part of the tubing. The tubing is still looking good and seems to be appropriately flexible.

My impression from what I have read on this website is that one does not want to subject the tubing to extremely hot water.

I am trying to find what the consensus is for what the maximum setting should be for the water coming out of the boiler into the floor. The boiler is a Navien (installed in 2018) and I can set the temp of the water going into the floor separately from the temp of the domestic hot water.

Any advice is appreciated.

Zman

You want to go as low as you can while still maintaining room temp. Your boiler likely has a feature called outdoor reset that varies the water temp based on outdoor temp. The outdoor sensor would need to be installed.
You can probably run between 120 and 130 degrees on the coldest day and 70-80 degrees on the warmest.
Keeping an eye on your water chemistry is also a good idea.

pecmsg

110 - 120°F supply. You can go higher if needed but start low.

GroundUp

That's going to depend largely on the heat load of the building and the under-slab insulation values. I average probably 80-100 radiant systems a year and have never once needed more than 100 degree SWT at design (-30F here) in any new building with proper insulation values above and below grade. Even those with huge heat losses and cubic footage like farm shops. Like Zman said, as low as you can get it while maintaining setpoint is ideal. I usually set my ODR to 100 degrees at design and let it go for new builds, very seldom does that need to be adjusted. Something like yours I'd probably try 110-115 in my climate but again, your heat load is going to dictate quite a bit.

Entran_II_Owner

We are in New Mexico at 7100' so it does get (and is getting) cold.

Since this is the first cold weather since we arrived, I will have to see if the system can keep the house warm with the boiler output to the floor set at 115. We do have a couple of mini-split systems in the main rooms and a gas fireplace in a converted garage that I could use to back up the radiant floor if necessary. I want to do whatever I can to ensure that the Entran II lasts as long as possible.

A local contractor said that he would flush the system, but I was hesitant to do that as I didn't know if introducing fresh water would be a benefit or a detriment to the tubing. (Would introducing fresh water cause more problems with the oxygen it contains?) If I were to check the water chemistry as Zman suggested, what particular issues should I be aware of considering that this is the infamous Entran II?

hot_rod

while it’s true flushing will remove the black magnetite sludge caused by the lack of an O2 barrier. It can also flush the plasticizers that are keeping the hose from hardening.

Watch the the connections, they were prone to leaking as the years went by.

If ever you replace the boiler, I would separate it from the tube with a plate HX, keeping everything non ferrous

If the tube lasted this long, you may have a good batch. When it went bad it was in very random locations along the hose, really no way to predict.
As other mentioned, as low as possible, the higher the SWT, the higher the O2 ingress.
Check the pump volutes, those are most prone to corrosion and blockage 

Entran_II_Owner

Thanks for the responses. Your time and experience is appreciated.

Nick