Hydronic radiant floor - floor doesn't feel warm...

Brad White_19

Jim,
Putting aside the technical questions of what was done and how, I would like to address the larger picture of expectations and specifically the conflict within them.

Firstly, your spouse has the expectation that the floors should feel warm. Her view is one of a perceptable floor temperature.

Secondly, the general purpose of a radiant floor is to heat the house (which it seems to be doing, almost too well).
Given that, the floor temperature becomes almost incidental.

These two expectations are in conflict.

From the sounds of things, the system is doing what it is supposed to do but perhaps the reverse of what you intended (that the floor be supplemental and the furnace would do the base heating). It is the other way around and that is not a bad thing either!

A floor at 85F or approaching that is usually enough to heat most spaces. A bathroom might tolerate a warmer temperature but that is an exception. Warmer than that, physiologically, a person might feel too warm.

The body cannot radiate heat to a surface warmer than itself, and your skin temperature can easily be in the mid-80's, sometimes higher such as when you just pull off a sweater and sometimes cooler such as your hands or feet might be.

Yes you might be able to get the floor to 85 but your energy costs go to waste and the spaces would over-heat. Cannot have it both ways. I do not see the system as needing fixing. But I would set up the controls to make best use of the floor as the primary and set the force hot air as a back-up by putting that on a lower setpoint. When the floor cannot keep up, the FAH kicks in. It may never happen you know.

Jim_76

Hydronic radiant floor heat - floor is not warm....

I recently put radiant floor heating in my new house. The system heats fine but the complaint is the floor is not warm enough (hot). Dual use Polaris 130kBTU water heater directly heats potable water. Flat plate heat exchanger off heating ports for floor loops. Two zones - one in basement, one in garage. Thermostats trigger motorized valves to open. Switch on valves runs pumps when open. Just two pumps, one on each side of heat exchanger. 25% glycol for freeze protection because of garage. Main goal was floor warming rather than complete space heating - have a forced air furnace/AC for space heating/cooling. Seems like a good fit as lower level needs more heat in the winter and less cooling in the summer so the radiant fills those needs nicely.

Here is the problem: Spouse thinks the floors should be warm (over 85F) to the touch. After several complaints of wanting the floor warmer I just turned it way up and said tell me when its warm enough. Basement got up to about 80F. Upper level was at about 74F. Furnace didn't come on for days although it wasn't particularly cold outside (about 40F average). But complaint is floor is still not hot enough. She wants to walk around in bare feet and have the floor feel realy warm. Floor material is tile over concrete slab. Floor temp was measured to be about 84F when room was at 80. She now wants me to call in an expert to fix the system. It seems like it is working fine to me as it can heat the whole house and I don't know of any way to make the floor hot without heating up the rooms. Only way I know to make the floor radiate less heat is to paint it with a radiant barrier coating which I doubt would be acceptable either.

Am I missing something? I would appreciate any comments on if the system is working right, what changes might help, how to explain it if system is working right, etc.

As a somewhat seperate issue, I want to give priority to domestic hot water. Since the floor heat comes from the same tank I cannot do this in the manner used for indirect water heater. Any suggestions on how to do this simply? I am thinking of putting a temperature sensor on the hot water pipe out of the heater about 3 feet from the tank. This is about 80F with no hot water use but rises rapidly to over 115F with use. A control which disables the circulation pumps when the temp is above 90F seems like it should work (at least until most of the hot water is used up)

ChasMan

You could add in a skylight and leave it open. That would warm up the floor.

Sorry, I could not resist, I envy your problem.

kevin coppinger_4

if the floor..

temp is 84F you should be in good shape. Is it really 80 inside? Sounds to me as if you have the age old problem that the wife can never be warm enough....I would be in shorts! kpc

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Unknown

I would suspect that the load the radiant is meeting is low.

You could do two-stage heating, radiant then triggerring FHA for backup if needed... though not if the FHA zoning won't allow this, probably.

You could use PWM thermostats to make the zones cycle more consistently, which would work if the floors are warm enough when the zones are heating regularly, but are just cold for long periods between cycles. But if the floors are just never warm enough, then it may not do the trick.

You could use a slab sensor to maintain a minimum floor temp... would be interesting to see what a warm enough floor really does to your room temp if you control it from that end.

But ultimately, floor surface temp is room temp plus half the BTU/sq ft load. If that BTU/sq ft load or room temp setpoint is low, the floor is cooler, and heating it up further results in a hotter room. That's the low down.

Ericjeeper

wow.. My house is soley heated by radiant inslab

If I crank my floors up to anywhere above 75 the house would be over 75 degrees.
If you really wish to have warm floors and not be overheated in the space.. The only way to ever achieve this will be, to either open a window all the way, or remove all the insulation from the attic.. That should pretty much gaurantee you warm feet and tolerable living space temps..
I know my envelope is very well insulated and very air tight.. to tight actually.. That is a problem I am adressing next HRV.
Buy her some slippers.

Gordy

Shoulder season temps.

With the outside temps averaging 40*, It just sounds like a shoulder season issue. Outside temps are not cold enough to really work the radiant floor much. Your envelope sounds well insulated. Low heatloss. Wait till outside temps get down to teens or below. Set up your system like some have suggested. Or buy her radiant sandles/slippers. Hmmmm, new product for the radiant market. Women would die for them.

Gordy

Jamie_6

Jim,

Everyone is correct! If the room is warm the floor is doing its job. When the temperature outside gets down to design conditions I'm sure it will be much more noticable that you have radiant heating.

Anna Conda

I think part of the problem is marketing. So many radiant manufacturers advertise "toasty warm floors" as a selling point... but I've yet to encounter an in-floor system that had 'toasty floors'. Unless something was akilter with the boiler.

Ed Lentz_2

IN my place (also in floor pex) if the temp outside is 40 the floor is very cool, but if the outside temp is 10 then the floor is really toasty. That is life with a radiant floor, as I see it.