Radiant Floor

I just finished up the install of a keystoker k-6 boiler and radiant floor application ---- question???

my layout is 7 zones of anywhere from 250-300 foor loops 7 loops total
mixing valve set at 130 degreese
tyvek as vapor barrier
1inch foam under slab
tubing 12 inch on center(i know overkill) so I thought
20 yards of concrete 24x40 garage 5 to 6 inch depth
i just fired this up and it is now running for 48 hours, temps during day 65-70 overnight 40-50 garage is at 86 degreese(but hold on) my question is I t expected this thing to feel warmer than it does! I used a thermal gun that shoots the laser light at an object and it gives you a reading of the object the overall estimated temp of the floor from just walking around is anywhere from 74 to 85 degreese does this sound right!!!!

things I do know is that the tubing is pretty much in the middle of the slab so the heat is not pushing into the ground
and the system is not airlocked and garage is insulated well

or does it need to be cooler out to really see the benefit of radiant heat, becaus 86 degreese seems high i'm only overcoming 16 degrees over the day temperature i'm just wondering what the winter effects will have on the slab still only a 16 degree increase??? remeber this is only a trial run just wanted some input

It might take some time to get the floor's mass up to temp, once up there it will take nothing to keep it there. When the temps drop, the Keystoker just has to add a little more to maintain temp. How hard was the boiler running? If it has been eating a few 100# of coal in two days, you may have a problem. If it was loafing along, you are going to be extremely happy all winter.

Lsfarm has a big shop heated this way and loves it, I'm sure he will chime in.

A floor target temperature of less that 85* is normal.. any hotter and your feet get uncomfortably hot. I maintain my floor at 55*, and that nets me air temp of35-45* depending on the wind and outside temp.

You will probably find that a floor temp minus 10* will be your air temp.. it might be equal if you have low 8' ceilings and good insulation.

You really only need about 65* to be comfortable, if your feet are warm, you are warm.. the rest of the body usually is comfortable at cooler temps, and our head usually doesn't like to be in high temps.

I'd turn it back and keep the floor at 65*-70* and just leave it there,, you will love as December and January come along.

Greg L

When we did radiant floors we did 12" on center on the outside edge for the first 3 feet, then 16" on center for the rest of the floor. In concrete, water temp around 120, floor temp 80 will give air temp of about 68 and you'll feel very comfy. It can take more than 2 days to bring a big slab up to temp the first time. No loops should be over 200 feet as the water will spend all of it's BTUs in that distance.

One thing to look at is what the temperature of the water in the return manifold is at before going back into your boiler? If there is a huge temperature drop then try turning the pump up to see if you can get a little more even coat of heat through out your slab.

Radiant floor systems will throw off approx. 35 BTU per sq. ft, with a surface temp of 85 max, (minmize expansion for wood flooring) but keep in mind that radiant floor systems are approx 30% more efficient when compared to hydronic baseboard. The overall effect is a cooler (temp) room with all flooring, furnishings etc. being heated to 80 deg or so then the temp cools as you go higher in the room, thus fooling your body into comfort by applying heat where we get cold, lower extremities and minimizing temps at our core (chest). Just remember once the slab is fully heated, do not mess with the thermostat, set it and forget it, if you turn it down, even just a few degrees, you boiler will play catch-up (thermal mass) and negate the efficiency savings. I have found 68 deg. quite comfortable. set in october and off in may.

Freddy wrote: No loops should be over 200 feet as the water will spend all of it's BTUs in that distance.

The maxmimum loop length depends on the diameter of the tubing used. I think the 200 foot rule applies to 3/8" tubing.

I'm not an expert on this at all, but I was told 200' and this was with 3/4" tubing burried in a 6" concrete slab.. my loops are all 180'-200', the return water is rarely more that 5* cooler than the supply water temp.

If I raised the floor temp, the differential may be a lot greater.

Greg L

tubing diameter, media to which heat is transferred (wet or dry application), flow rate and water temp will dictate loop length, usuall not more than 300' per loop. looking for a 8-10 degree temp differential supply vs. return.

frank