# Question for Radiant Floor Heat Specialists



## BEI (Oct 27, 2008)

We installed the Tagaki TK Jr LP gas tankless boiler to heat the water for our radiant floor heating system. This thing never shuts off at night and we are burning about 20 gallon of propane per day (it's been very cold here, Northern Illinois). Is this normal? That system and the water heaters for the rest of the home are all that require propane; all electric 3800 sf home with a cathedral ceiling and a loft in the center of the home. 

The house is fairly warm at night, tho we are losing about 4 degrees each night, so a bit chilly in some areas in the morning. We are trying to keep the thermostats set at 68 degrees which is comfortable. The water lines in the floors make really wierd popping noises at times, too. Thanks in advance for any advice offered.


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## beenthere (Mar 5, 2009)

How are the loops installed?

How cold has your area been?


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## JohnFRWhipple (Oct 20, 2009)

*How many zones do you have?*

How many zones do you have?

What is the water temperature set to?

Did you alter or change the amount of windows?

Who spec'd the system? Did a Heat Loss Engineer get involved?

Where are your thermostats located?

A million variables are involved in this....

JW


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## Mr Latone (Jan 8, 2011)

JohnFRWhipple said:


> How many zones do you have?
> 
> What is the water temperature set to?
> 
> ...


some more ......

how many zones are calling for heat?
what is the return water temp?
what is your transfer medium?
what about floor coverings?


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## BEI (Oct 27, 2008)

For starters... we have 5 zones (3/4" copper feeds and returns to each zone) w/thermostats on center walls, away from drafts and windows. 6000 LF of Tek (sp) tubing was stapled in between wood floor joists with aluminum foil heat reflectors. Floor coverings are glued down engineered wood on main floor, plywood still remains in soon-to-be carpeted bedrooms (3), loft and stairs, and tile in bathrooms (4).

Boiler temp set at 180 degrees max and water temp at return is around 90 degrees. 

We do have a heat loss data sheet (all greek to me). The tech spent many hours designing the system. It would seem that the TK Jr cannot keep up with the demand. Would a regular boiler be better?


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## DuMass (Feb 6, 2008)

Well, I’m no radiant heating expert, but with a 180 supply temp, it sure sounds like your return water temp of 90 is way too low. That could mean maybe the loops are too long or the pump is too small or possibly something else is going on. 
The manual for that little T-K Jr. says the maximum flow rate is 5.8GPM, but according to their output chart, it’s only about 2.25GPM at 180 degrees.
So, I’m really wondering if maybe it’s just too small for the amount of heating required, especially if it’s been exceptionally cold where you for several days in a row.


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## BEI (Oct 27, 2008)

Our tech has done his due diligence and feels the propane in and of itself is the culprit... three times as expensive as NG, bit we still would have seen a $450 bill for December, that's expensive! It wasn't that cold.


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## Mr Latone (Jan 8, 2011)

I don't think I would put my whole house on an on demand water heater. I might if it was maybe half the size of what you said you have.

Do you think the TK Jr can put up with the required duty cycle?

You said the tank was set for 180 output temp, with its running is it putting out that temp during high demand? (like three or more zones calling for heat)

Just some thoughts. I have a five zone radiant to cover 3200 sf. I use LP with a condensing boiler Monitor 25C, 10 years old. Since then I have seen condensing boilers I would probably favor, but mine is still working fine. The boiler has a circulator and I have one adjunct circulator. My output water temp is 117 deg F. The boiler always keeps up with demand, but there are certain floor coverings (carpet) which inhibit heat transfer, so during the coldest (or longest cold) the return water is still carrying more heat than I would like.

I would just suggest you check you actual output temp during high demand paying particular attention to more demanding zones.


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## BEI (Oct 27, 2008)

Tech's coming out Saturday to go over things... thanks for all your help! Any other ideas appreciated!


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## beenthere (Mar 5, 2009)

Do you only have 1 circulator?


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## GettingBy (Aug 19, 2010)

BEI said:


> 20 gallon of propane per day
> Boiler temp set at 180 degrees max and water temp at return is around 90 degrees.
> We do have a heat loss data sheet (all greek to me).


Propane gives off 22,000 BTU per pound but I can't find the pounds to gallons conversion.
2 GPM of water dropping 90 F is giving up 90,000 BTU/hr. Does this sound right?
Post your heat loss sheet.


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## beenthere (Mar 5, 2009)

1 gallon of propane is 92,000 BTUs.

2 GPM at 90°F delta is 88,776 BTUs an hour.


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## TimNJ (Sep 7, 2005)

How many loops are on each zone and what are the lengths of the loops? What diameter is your tubing?


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## dakzaag (Jan 6, 2009)

I had the same problem ten years ago. What I found was the radiant was too slow to adjust to our temp. fluctuations. I live about 40 miles south of the lake, so not much different than you.

I made my own solution by adding a hot water loop through my air exchanger (for the AC) I have two A frame coils stacked on top of each other. One circulates hot water in the winter and one circulates freon for the summer. 

The fan helps the house recover when the sun goes down and the pump has been off all day cause it was warm. The fan doesn't run much, but it is just what we need to keep up with the temp. swings.

By the way, it has been colder than you think, Dec. I used more gas in one month than any month since I built this place in 01. 

Your tech will not like this idea, but I am telling you a little hot air will go a long way.


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## BEI (Oct 27, 2008)

beenthere said:


> Do you only have 1 circulator?


 
We have 5. The biggest question we have... do you think a regular boiler would be better than the on-demand TK Jr?


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## BEI (Oct 27, 2008)

dakzaag said:


> I had the same problem ten years ago. What I found was the radiant was too slow to adjust to our temp. fluctuations. I live about 40 miles south of the lake, so not much different than you.
> 
> I made my own solution by adding a hot water loop through my air exchanger (for the AC) I have two A frame coils stacked on top of each other. One circulates hot water in the winter and one circulates freon for the summer.
> 
> ...


We have 3 SpacePak Units for our AC... I think now we may add the heat ($3000.00). It may be well worth the money!


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## GettingBy (Aug 19, 2010)

BEI said:


> We have 5. The biggest question we have... do you think a regular boiler would be better than the on-demand TK Jr?


The on demand should be slightly more efficient. 
With the thermal inertia of your floor I doubt that you'd notice a difference in comfort level between on demand and a tank system.


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## dakzaag (Jan 6, 2009)

The guy who introduced me to radiant heat over twenty years ago told me something that I think is very true. Radiant heat is an excellent heat source to establish a base temperature. For example 60 to 64 degrees. Then use hot air to fine tune your needs and react to quick temperature changes. 

Our basement zone is set at 65 and the pump runs maybe two times a day after the initial startup in the fall. Upstairs the demand is much higher and variable. The zones for upstairs and the forced air are constantly circulating as needed.

BTW I have a boiler, but have often thought that I could have gotten by with a water heater. The HVAC guy setting up my system wanted more capacity to cover high demand situations. 

Running on Propane sucks, but it is part of the price we pay for living out in the country. The longer NG stays cheap, the lower propane will have to drop to remain competitive.


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## GettingBy (Aug 19, 2010)

dakzaag said:


> For example 60 to 64 degrees. Then use hot air to fine tune your needs and react to quick temperature changes.


Did your floor suck heat to the tune of 0.9 therm per hour? 

Is there a rule of thumb for how many watts per sq. ft. floor radiant heating is supposed to use?

I guess not - see below

". . . we can estimate the average output of a radiant floor at 18-25 BTU's per square foot but windows, doors, insulation, and degree days all make a major impact on getting you just what you need. Remember, Heat Losses can vary from house to house, city to city and state to state. We have seen heat losses range from 10 Btu per square foot to as high of 120 Bty per square foot for 2 houses in the same area. "


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## BEI (Oct 27, 2008)

dakzaag said:


> The guy who introduced me to radiant heat over twenty years ago told me something that I think is very true. Radiant heat is an excellent heat source to establish a base temperature. For example 60 to 64 degrees. Then use hot air to fine tune your needs and react to quick temperature changes.
> 
> Our basement zone is set at 65 and the pump runs maybe two times a day after the initial startup in the fall. Upstairs the demand is much higher and variable. The zones for upstairs and the forced air are constantly circulating as needed.
> 
> ...


Very interesting information! and to the price we pay for peace and quiet... our vendors have the market... no NG for many miles. We're locked at $1.89. It's a good price for these parts.


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## beenthere (Mar 5, 2009)

I think you have improper water flow(not enough), and too small of a boiler.


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## TimNJ (Sep 7, 2005)

BEI said:


> For starters... we have 5 zones (3/4" copper feeds and returns to each zone) w/thermostats on center walls, away from drafts and windows. 6000 LF of Tek (sp) tubing was stapled in between wood floor joists with aluminum foil heat reflectors. Floor coverings are glued down engineered wood on main floor, plywood still remains in soon-to-be carpeted bedrooms (3), loft and stairs, and tile in bathrooms (4).
> 
> Boiler temp set at 180 degrees max and water temp at return is around 90 degrees.


What is the spacing of your tubing in the joist bays? Is the tubing backed up with insulation as well as the aluminum reflectors? 3/4" seems too small for a manifold depending on what diamaeter your tubing is and how many loops are coming off each manifold per zone.


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## BEI (Oct 27, 2008)

Well, we have likely figured out what was wrong with the system... faulty propane tank regulator. Guess when we discovered this... during the blizzard! We ran out of propane :furious: We also discovered that the thing had been set at 11" when 12 is preferred... that setting may have screwed up our TK-Jr, it's making all kinds of racket now (fan). Whose fault would this be? Our system installer, or the propane co? What a wicked couple of weeks we have had! We truly won't know for sure until we get our next monthly propane bill...


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## BadgerBoilerMN (Sep 10, 2010)

Tankless water heaters are not boilers.

First, a room-by-room heat load analysis. Next, the type of radiant emitter "panel" is chosen according to the requirements of each room. If you have decided on radiant floors, you next have to consider the floor coverings, which in turn dictate the type of top-floor or sub-floor system. If you must install a sub-floor system (the one with the lowest efficiency and slowest response time) you will need a computer program specific to the product you are using or much design experience (few contractors have either). The program will tell you if the sub-floor radiant system you chose would overcome the heat load you have. It will also tell you how much insulation you will need below the tubing. 

The tubing should be placed in aluminum emission plates. Bare tube will require higher water temperatures, may have more trouble with response time, total output and will always burn more fuel then a plated system.

_None of the manufacturers of radiant floor heating products recommend bubble wrap below their floors, as it is a very poor insulator and a waste of money as a radiant barrier._

 A condensing boiler, sized to the load, will have outdoor reset matching burner output to load and negating some the negative effects of sub-floor systems, condensing and burning fuel at 95% AFUE.


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## dakzaag (Jan 6, 2009)

BEI said:


> Very interesting information! and to the price we pay for peace and quiet... our vendors have the market... no NG for many miles. We're locked at $1.89. It's a good price for these parts.


 
I just filled for the first time since it turned cold. $2.15 a gallon .

I'm really ticked at my supplier as I just wanted about 250 gallons to see if I could make it to spring. Once it warms up, I will only use about 50 gallons till fall. Summer fill is always the cheapest and I usually try to buy about 65% of my needs in summer. He delivered almost 600 gallons :furious::furious:. I am tempted to make him come and take it out. I will carry close to 350 gallons through the summer and be limited on how much I can buy in July/august because of limited capacity. 

IMHO you’re temp. drop is way too high from input temp to outlet. I go in at 130 and out at 115 to 120. I have half inch pex running about 350 feet per loop. I didn't buy all the fancy fittings and conductor plates, just fastened the tubing to the bottom of the floor at about 10" centers. Then I insulated the crap out of it attempting to force the heat up. (I used foil/bubble/ foil and in retrospec, I wish I would have added 4" of bat in some areas. I drywalled the ceiling of the basement so it would be a major mess to go back and add it now. )The hardwood and linoleum floors are super comfortable (actually the temp is just a little high for the hardwood per manufacturer specs) and the carpet areas are slightly cooler. 

You would not believe the reduction in run time the forced air option gives the whole system. I know some would say if you’re going to have forced air anyway, then why bother with the radiant heat in the first place. I disagree, the comfort and low cost of radiant is superior, but it does struggle to keep up with large temp. swings. Since your forcing air with the AC system, I found it very economical to add a heated forced air option to help the system be more efficient. Remember I use hot water for the forced air, not electric coils.

I am not a hvac guy at all, as these other guys will tell you, but your numbers tell me there is insufficient insulation, most likely in the attic. I don't know if you have a basement or not, but if you do, don't be afraid to run that quite a bit warmer than the upstairs as that heat will make if upstairs eventually and really make the basement more usable. (Assuming a finished basement.) 

Here's hoping the prognosticator from puxwanty knows what he is talking about. :clap:


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## BadgerBoilerMN (Sep 10, 2010)

dakzaag said:


> The guy who introduced me to radiant heat over twenty years ago told me something that I think is very true. Radiant heat is an excellent heat source to establish a base temperature. For example 60 to 64 degrees. Then use hot air to fine tune your needs and react to quick temperature changes.
> 
> Our basement zone is set at 65 and the pump runs maybe two times a day after the initial startup in the fall. Upstairs the demand is much higher and variable. The zones for upstairs and the forced air are constantly circulating as needed.
> 
> ...


The "guy" was mistaken.

It is certainly possible to radiate a floor, wall or ceiling and design for second-stage air especially in high load (walls of glass) applications or in commercial applications where large "people" loads are anticipated; but this less than optimal. 

The most efficient and comfortable heating systems start with a room-by-room heat load, followed by floor covering considerations, radiant panel, heat source and control selection.

Efficiency is best optimized in two ways, first to size the radiation for lowest design operating temperature and second to using outdoor reset control, which should be added to every residential boiler system regardless of the fuel source, this includes electric boilers.

All condensing gas boilers have outdoor reset built-in.

As for tankless water heaters...they are not boilers and do not have the fuel saving features of space heating boilers. Expect to have less comfort, higher fuel bills plus maintenance for a product designed for intermittent use.


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## BadgerBoilerMN (Sep 10, 2010)

It is certainly possible to radiate a floor, wall or ceiling and design for second-stage air especially in high load (walls of glass) applications or in commercial applications where large "people" loads are anticipated; but this less than optimal. A properly designed radiant floor heating system will heat any well constructed space efficiently without suffering from lead or lag. If your heating system won't satisfy the thermostat it is a poor design, installation or maintenance.

The most efficient and comfortable heating systems start with a room-by-room heat load, followed by floor covering considerations, radiant panel, heat source and control selection.

Efficiency is best optimized in two ways, first to size the radiation for lowest design operating temperature and second to using outdoor reset control, which should be added to every residential boiler system regardless of the fuel source, this includes electric boilers.

All condensing gas boilers have outdoor reset built-in.

As for tankless water heaters...they are not boilers and do not have the fuel saving features of space heating boilers. Expect to have less comfort, higher fuel bills plus maintenance for a product designed for intermittent use.


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## BEI (Oct 27, 2008)

Thanks for the input!!! All advice much appreciated! We have a consultant scheduled to come over and give us a second opinion, so this additional knowledge will keep us from believing _everything_ he says:whistling The TK Jr was made specifically as a tankless boiler. I've been pretty impressed with unit now that it appears to be working, even with the noisy fan.


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## BEI (Oct 27, 2008)

Well, we are finally installing a boiler... $5000 worth of propane for one season is beyond ridiculous. Consultant was right on with this... but he wanted 15K to rework the system... and $8500 for the boiler install :laughing: My husband, the carpenter, is so pissed he's going to do the work himself. Wish us luck.


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