Hydronic In floor heat - is this normal

Brad White_191

If not, there is another person living in your house with the same question... a few posts down.

:)

Kara

radiant heat - is this normal?

I recently purchased a patio home with hydronic in floor heat warmed by an electric boiler. Recently I set a thermometer on the floor and compared it to the air temperature 6 feet above the floor. The floor was only 2 degrees F warmer than the air temperature.

Is this normal???

If not what is a normal range of temperature from floor to air??

Thanks, for your input.

Unknown

was it running at the time?

that's about 4 BTUs/sq ft of output. not much. but if you were at room temperature at the time, obviously it's doing the job... just might not be after a full heating demand or something...

Kara

radiant heat - is this normal?

The boiler had already been running for an hour before I took the temperature and got the 2 degree difference. Only after bumping up the thermostat a degree did I get a 3 degree difference. The system does keep up for the most part, except when the outdoor temperature drops very rapidly.

But, according to you it sounds like the range is normal and that there are tons of variables which affect how much warmer a floor will be.

Ha, ha. The "Frank" post was from my house, but hopefully "Frank" is not hiding in a closet somewhere. The post was mine - after checking back to the site I noticed that "Frank" was listed as the author so I sent a second message and made sure that I was listed as the author - I'm not sure why "Frank" appeared!

Brad White_203

\"No, I'll be Frank\"

as the punchline to an old joke goes... and speaking of closets..

N-E-Way....

If the house is comfortable, you are well ahead. If the temperature drops off when the outside air temperature drops off then I would look to improve your control- what is known as PI or PID control, whereby the outside air temperature is taken into account as well as space and floor temperature.

For example, if a cold front comes through, the control system would take stock of that, the room temperature and the history of what temperature floor is required when it gets that cold out, in order to heat the house.

Basically, the "deviation from setpoint" is key. If the system sees potential catching up to do, it ramps up the response. If that gap narrows, so does the response.

The response, (all in very simplistic terms), is to increase the floor temperature ahead of the perceived cooling of the space, so that no determinable space temperature drop occurs.

Absent this kind of control, the house gets cool then catches up when it can.

Hope this helps.

CMadatMe

What was the sufrace

temp of the floor? What is your supply water temp going to the floor? What is the finished floor?

Uni R_2

Does the boiler have an outside temp sensor?

I experienced the lag effect when temperatures suddenly dropped when I was running an ODR boiler purely off the reset curve. Whenever the temp would drop suddenly, you could notice a cooling effect until the house finally caught up.

I was curious about the cause of this so I took an IR gun outside and shot the sensor location and sure enough it was several degrees warmer there than the outside temps due to all the stored thermal mass of the bricks it was mounted to and its by the book sheltered location. The bricks were fooling the sensor. The solution was to move it out a bit so that it was getting a better sample of the true outdoor temperatures.

Kara

radiant heat - is this normal?

I'm not sure what affect the especially cold weather, which dropped from -8 to -26F overnight, has on the data I took, but here goes. (I REALLY appreciate your time!!! Thanks SO much!)

As far as I can tell I only have an air sensing thermostat (no slab stat nor outdoor reset). In addition this thermostat is located on the back side of the wall that contains all of the boiler piping, causing it to get reading that is 2F warmer than the rest of the house. Furthermore, because my home gains about 7-8F from the sun, my boiler is off all day.

That being said, when the boiler turned on last evening at 7PM the floor read 66F while 4' above the air was 65F. Additionally the water exiting the boiler was 80F. I believe the boiler shut off around 3AM (8hrs later), at that time the floor read 70F, while the air read 66. Additionally, the water exiting the boiler at this time was 100F.

I also took a look at my electric mini-boiler, it is rated at 30,717btu/h. My patio home is 1,300 sq.ft. - isn't that a bit small? An article I found on the web seemed to recommend 27-40 btu/sq.ft., which would imply 34,722 - 51,400 btu's for my home???

Could the boiler size, in addition to the lack of an slab thermostat & outdoor reset be the source of my cool floor and lagging temperature or could it possibly be faulty slab insulation or piping depth?

Kara

PID control

Can this PID control be installed in a home that has currently has no sensor in the slab? I assume I'd have to drill a hole into the concrete, right?

Kara

PID control

Can this PID control be installed in a home that has currently has no sensor in the slab? I assume I'd have to drill a hole into the concrete, right?

ScottMP

Kara

After the drop in temperature does the house recover ? Do you eventually get to the set temp. on the thermostat ?

This may be more a problem with the building envelope and what you need are new windows and insualtion.

Scott

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Kara

Yes, the space does return to temperature. Its just that it'll drop below the programmed temperature during the night.

ml_4

Kara

Radiant heat does not stratify to the degree that most heating systems do. Look at the following link for a graphic that pretty well explains this.

http://www.wattsradiant.com/homeowner/aboutradiantheat.asp

If the room is not coming up to temp. then there are other issues that need to be remedied... insulation, water temp, pump output, etc

Mike