High infloor temps in concrete...(175 degrees)

Tim Schram_2

Hello all,

Just wanted to get some opinions. I have a high mass system with onix tubing in concrete. The floors are bare concrete with a sealer over them to give it a semi gloss type finish. We replaced a failed boiler and so had no previous information on the old system performance. I did find the aquastat on the old boiler set to 190 degrees which I thought very excessive. After installation I set the outdoor reset to 125 degrees. This definitely proved to not be enough as the cold weather set in. I was continually upping the curve. I finally was able to achieve the desired comfort levels at 175 degrees. He does not set back the thermostat on the system. My thoughts are that we don't have enough tubing, it's too deep, not insulated etc.. but I'd like to get some more opinions.

Thanks

Tim Schram_2

I should also probably mention that the tubing is NOT losing water and leaking and this is POST recall tubing with aluminum barrier.

Radix

What is the return water temperature ? If you have the right temp and delta t, it should show the only remaining variable ( flow) is in the ballpark... Leaving the issues you mentioned - not enough tube or insulation.

Tim Schram_2

We have about 150 return water give or take.

hot_rod

Any way to get a flow rate in the loop? Any flow setters or meters. If so you can calculate the btus being transferred into the floor.

If the heat being transferred matches the load then it's getting away from you

Tim Schram_2

Not without some modifications to the system. We did have some major issues coming from the existing system tubing with fouling. Originally had a wye strainer, but I kept having to clean crap out of my pump impellers, then went to a spirovent dirt separator and ended up using a braze plate heat exchanger with a bronze pump on the system side to separate my boiler from the nasty in those tubes. Once I did that I didn't need to clean out my pump impellers every month. It actually got so bad I had to change out the boiler's heat exchanger because my attempt to clean it was unsuccessful. This was in October. Since the separation no problems other than the concerns with high loop temps.

Paul Pollets

Excessive temps for a slab. Either there's little or no insulation under the slab (R10 required for slab on grade, with R5 min. on perimeter edge) or the tubing is not 12" on center. Most slabs will heat adequately with 90-110 degree water. You may need water treatment as well.

Gordy

Is it slab on grade? Or a sub grade basement?


Wondering how much gunk is still in the loops to decrease heat transfer, and flow rates. Deltas don't lie 15 is pretty good so no doubt the btu's are being unloaded. Tubing centers, or the lack of would be a direction I would pursue. Use an IR thermometer to track tube centers.

While insulation is important there are plenty of old slabs before the use of insulation that heated structures well maybe at higher temps, and more cost, but they worked.

icesailor

The problem with floor heat in concrete is you never know what is under the floor.

I found a big floor, all nicely done in a nice house, where I turned on the water and heat, and turned on the floor. 24 hours later, there still was no hot water coming back to the boiler on the return side. There was cold coming back, but it appeared that there was so much under floor heat loss, that the flow just couldn't catch up with it. So I shut it off. It never did get hot, and the customer didn't want a warm floor in July and August.

tjorn

175 is to high of temp to run that at, it will take its toll on the concrete.