Garage Slab Mixing Temp

Unknown

it'll take a while for the slab to warm up, like 2-3 days AND you will probably never experience a "warm" slab. A slab that feels warm will probably overheat the space. Don't go by how the slab feels, go by room temp. My feeling on water temp is go with the lowest you can that still satisfies the room setting.

Rob_42

Ultra Oil Weil McLain AFM - Mixing Temp for Garage Slab

Hi All, I just had what I consider a "expensive" boiler system installed, where I had to pull teeth to get my boiler guy to install what I wanted. He had no experience with the new Ultra Oil only the old style WGO WM boilers.

So I come to HH for some help. I am running a Ultra Oil UO3 with .65 nozzle. It supplies a WM Gold Plus 60 DHW tank, two Hi-Velocity Fan Coils for house heat, and an infloor loop for the garage slab.

I had him hook the slab headers up yesterday and get the system going. The Garage Slab loop supply heads into a Tekmar 741 Actuating Motor which is mounted to what I can see is a 3-way valve (3 way intersection). The supply then get circulated by a Taco 007 pump. The pump ran for about 5 hours but the mixing supply temp never got over 65F (18C) (hence cold floor). The AFM (Advanced features module) was set to Mixing type "VAR" for variable injection pump. I suspect this was wrong so I changed it to "FLOT" Floating Action. Here the boiler fired and mixing temp rose up to 104F (40C) right way and varied in the low to mid forties C. I turned it on about midnight and checked again at 8am and still a cold slab. Now it is -23F (-31C) outside, but the room temp in the garage is 55F (13C) just from the boiler heat alone. The slab has 2" foil backed insulation under it and the garage is constructed with 6" walls. Rough heat loss calcs show about 15,000 BTU requirement at -41C design.

On the AFM, Mix Max is set to 140F (60C), Mix Min is set to 68F (20C), Mix Room is set to 66F (19C) and the target based on the outdoor reset is about 115 based on the outside outside temperature (which is off by about 7 degrees (warm) due to location but thats another story).

So is the problem that I do have hot enough water hitting the slab? Or do I have my boiler setup wrong? What temperature is safe to put into a slab? My slab is only about 2 weeks old, but it is about 18 to 20 Mpa based on comprerssive strength at 7-days. It is a 25 Mpa mix. I don't want to dry it out with heat, but would like the room to be in the 55F to 65F range for the next couple weeks while the slab is still curing.

Another note: I can feel the supply header is warm (as per boiler target of 46F), and the return header is cool, not cold, but I suspect about 55F or so.

Thanks so much, sorry for being long winded, but wanted to explain well. This is the first of many questions I have.

Unknown

What exactly is the problem? the room is where you want it to be?

Slab startup is an "all bets are off" proposition as MPF noted; nothing is sure for a few days. But after a few days if you have a problem, then you might actually have a problem

You don't want to run more than 140 in a slab though.

Rob_42

Well my unknown problem was if I had changed my boiler AFM properly to FLOT from VAR. It seemed to do the trick, but was unsure if I did the right thing.

Anyway, once it seemed to be working, maybe I was expecting too much out of the slab (as in heat the room more quickly). I noticed at lunch today (now running for about 12 hours with a mix temp of 114F) that the slab is beginning to feel warm. Now from what I mean warm is standing on it with bare feet doesn't make you dance... it feels comfortable. So the slab is heating up ok. Room temp is now at 61F. I'll give it a few days and see how it seems to be going then.

Also thank you for the Max Mix temp of 140 (120 was the default in the control) and the tip that I should run the lowest possible temp to achieve the heated result. I'll have to crunch some numbers to figure out my Mix Maximum setting based on heat loss design at -42F. But should I set a Mix Min? Default on the unit is OFF. But it would seem to me if the room is typically set to say 65F, would you not want the mix to me a minimum of 65F?

Unknown

Mix temp...

That number will be determined by the lowest setting you can get away with. If 65* works than it is OK. Keep in mind though, the lower the water temp the more the pump will run. FYI some around here consider constant circulation to be a viable option.