I hear that hydronic in floor heat does take a long time to warm up a room, however mine seems to take an especially long time. The boiler will run for 3 to 4 hours to heat the room one degree. When I put a thermometer on the floor it only seems to read 1F warmer than the air 7' off the floor. Also, in MN when an especially chilly cold front moves in, I've seen the room temperature actually drop while the boiler is running. Is all of this all normal and to be expected of in floor?

I am running a pretty high heating bill so I'm trying to figure out if the cause of it is due to poor insulation in the walls or under the slab. (I have no loss of snow around that slab.) If this is not normal for in floor heat, is there anything else that may be causing the such slow generation of warmth like air in the tubing, poor pump, or what not? Any trouble shooting or feedback would be greatly appreciated. Also, I do have a combination of sheet good flooring and carpeting.

Thanks much!

Many times in water heated floors The contractor forgets or just doesn't know to have a good thermal brake from the outside slab which is very close to the water loops and that gets them chilled That's one issue
Also the contractor forgets or gets cheap and doesn't put in a min 3" 2x8 polystyrene under the outer edges of the contract slab and uses a less thickness of foam board insul..
Sometimes the plummer sized the floor wrong for heat and his loop spacing in the concrete floor was to wide for the radiant heat to be effective.
The boiler may be undersized for the amount of radiant pipe in the concrete area its heating. This is a tuff one and there are many many variables.
What is your wall thickness and what type of wall is it and how high are the ceilings?
Sorry theses another variable that the plummer may not be aware of is if the slab is raised and the contractor forgot insulate behind the block that are above outside grade and then the cold gets past the upper insulation undernaeath the conc slab That that will greatly effect the outer and inner water loops and the boiler will struggle to keep up. Hydronic in floor heat Is wonderful heat done the right way the problem is the Block layer didn't put the insul behind the block and it really isn't his job. The excavator when backfilling forgot to put it in or say something or the builder ( which is his job to oversee this) Didn't catch it.
The plummer may have set the loop system to deep in the concrete and that is very important
Everything in insul concrete block walls has to done perfectly and the boiler needs to match the insul "R" s to the right height in placement of the hydronic loops and spread. And the size of room.

At this point there is really nothing to do but check the boiler and see if is running right and the circulator(s) are running correctly. If all is good then the boiler
may not be bug enough to keep up with the demand on it. I would start on seeing what the boiler BTU input and output is. And then determine the room(s) sizes for BTU required to heat that cubic feet and go from there. Have a couple of plumber's look at it. I just wanted to give you the ins and out here on the many major variables to effect the heating deficiencies
So recheck boiler Btus and circulator(s)

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In floor heat especially in concrete has a very slow temperature rise. The main reason is the concrete acts like a heat sink and slowly radiates the heat upwards. In floor heat also has to run a much lower temperature due to the materials that finish the floor. Some pretty nasty chemicals can be released from carpet especially if it is exposed to much extra temperatures and wood floor construction can also be damaged by a high heat factor.

In most cases unless the system was designed for fast recovery (additional loops of PEX or other pipe for the heat transfer mode) was installed the system will have a great lag in performance (as in temperature rise). On thing nice about in floor heat when it is properly installed you can operate your thermostat at a lower temperature and still feel comfortable. We have a great tool at the university that will allow us to actually see the heat lines under the concrete or other surfaces. In simple terms it is called a heat X-Ray machine. When you broadcast it across the floor then look at the monitor it will show the pipe layout under the covering and even form a grid of the heat surface. A few years ago we were doing experiments for a rather large corporation and they gave the machine to us to do part of the design work. When the project was over they told us to keep the machine for further work in the future. I mention this because someone in your area might have something similar and it could be used to allow you to see just how much pipe has been installed and then a calculation could be done to determine if it is sufficient for your heating area. While it will not cure your problem it will help to finally figure out what the exact problem really is.

[If all is good then the boiler may not be bug enough to keep up with the demand on it. I would start on seeing what the boiler BTU input and output is. And then determine the room(s) sizes for BTU required to heat that cubic feet and go from there. ]


The boilers btu/hr is rated at 31,717. My patio home is about 1,300sqft with vaulted ceilings. It looks like the boiler is too small, right?

Thanks for your trouble shooting advice!

Quote:

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Originally Posted by harwaaah

[If all is good then the boiler may not be bug enough to keep up with the demand on it. I would start on seeing what the boiler BTU input and output is. And then determine the room(s) sizes for BTU required to heat that cubic feet and go from there. ]


The boilers btu/hr is rated at 31,717. My patio home is about 1,300sqft with vaulted ceilings. It looks like the boiler is too small, right?

Thanks for your trouble shooting advice!

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In order to figure out weather the boiler is to small you will have to provide us with a complete manual J of your home or all else will be guess work.

Quote:

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Originally Posted by hvac1000

In order to figure out weather the boiler is to small you will have to provide us with a complete manual J of your home or all else will be guess work.

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Ahh, so its much more complex than simple square footage. I didn't realize I'd need a local HVAC service person to do a walk-through to determine its fit.

Thanks again for your input!

Actually it is not a walk through by any means. It is the only way to exactly calculate the heat loss of the structure and there by allowing an exact calculation of the requirements of the boiler. Most if not all failures to heat and cool properly or economically is caused by equipment sizing problems unless the equipment does not run to start with. The old rule of thumb will not work today due to more critical sizing requirements driven by economics and highly technical equipment controls. To big a unit wastes fuel and to small a unit will never keep up with the demand. Also many units especially high efficiency boilers do not come pre-adjusted from the factory and need to be fine tuned after the install. Many times this does not happen since the correct electronic instruments/tools are not affordable to the slap and clobber set of mechanics who do not know what they are doing to start with.

It is possible a quality mechanic skilled in the use of these tools could bring some new life to your system by making the proper adjustments and if not at least you will know that your system is operating at its best efficiency. The days of guessing in the HVAC industry is long past gone but there are still uneducated individuals playing the guessing game at the customers expense.