floor radiant heat

Mark Hunt

if he gets the hardwood floor surface temp to 97* everything will be better.

HB!! You just keep on doin what you do!! It all comes out in the wash.

Regards!!

Mark H

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allen

floor radiant heat

Last month I installed 1/2 pex tubing with aluminum plates against subfloor. And then aluminum foil and insulation and a vapor barrier beneath it as the manufacturer said...

The manufacturer told me to place one aluminum plate, skip one, install one... basically skipping every other one & they are maybe 8".

Does anyone know if I add more aluminum plates will I increase the amount of heat into the floor thus generating more btus? I am making contact with about half of pex tubing with aluminum plates.

I am running the hot tubes in basement header at 135 degrees and getting the return side at 123 degrees - thus a 12 degree drop or btu xfer to hardwood floors. The floor was between 72 & 76 when I was outputting at 135 on hot side.

The manufacturer said if thermistat on wall says 70 that the floor should be around 75 degrees.?

So I just adjusted the hot side up to 148 (from 135) and left hoping that I will get more btus out of it. I am concerned about going too high and warping the newly installed hardwood floor. Its about 25 degrees outside and it could go down to 0 in the middle of the winter - so this ain't looking too good to me.

TIA,

Allen

chuck shaw

couple of things...

First, who did your heat loss calculation? A floor temp of 75*F is no gaurentee of any room temperature, there are too many variables, if you have a lot of glass, it may not work. I have installed under hardwood, without plates, and have had great luck. It depends on what the heat loss tells you. And skiping every other plate....I have never heard of that (not saying it isnt done) but most people will either use plates or not. And, you are approaching the upper limit of what most people would say you should have for a water temperature under hardwood.

Chuck Shaw

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Mark Eatherton1

Whose system...

did you install? I agree with all that the Chuckster said.

Did they want you to maintain a 2" air gap between the insulation and the bottom of the floor, or is the foil in contact with the tube/plates?

ME


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allen

You guys are f-a-s-t !

I installed it all according to Radiantec. There is about 1 to 2 inches under the tubes / aluminum plates and aluminum foil. Then the insulation is under that and under that is a similar product to tyvec.

I am concerned, as Chuck mentioned, about warping the floor.

Allen

Mark Eatherton1

I'm sorry to hear that you \"bought\" the system.

These websters are less than helpful when a problem arises. For me and my money, I'd recommend you install the plates along every accesible foot of tubing. In my opinion, you also want the plates in direct contact with the wood floor, not suspended below it. In doing it suspended, you're basically dealing with a poor convective system which probably won't work real well when it gets cold outside.

Your concerns about warping and cupping the floor are valid.

Will they stand behind their product if it doesn't work?

How many BTUs per square foot per hour do they claim their system will put out?

Did they even perform a heat loss calculation?

What recourse do you have if it doesn't work?

Are you using a water heater to heat the house, AND your domestic hot water?

Is that legal in your state/city?

There ought to be a law...


ME


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allen

Whoops. Miswrote that. The plates are touching the 1/2 pex tubing. They are holding the tubing up. Being an older house with floor joists varying - the tubes are about every 8 inches, or one tube on one side and the return on other side of the joist.

This zone is off a 207 Burnham gas boiler which has plenty of extra btus as its around 230k output just running an indirect and another 3 room apartment. The boiler will run maybe once every 10 minutes for a minute.

Soooo I will R.T.M. and figure out heat load and see if this is undersized. They came up with 25k for load which seems low for a 4 room first floor apartment in Boston area of the country.

But my question is still: if I add more plates in the floor will this increase heat disappated out and produce more btus? I want to know this before I yank down vapor barrier, insulation, aluminum foil in a 120 year old house. Its not exactly a clean pleasant job. FWIW the temp was around 75 at top of floor, under 3/4 hardwood and another 3/4 subfloor about 110 degrees, and at header 135. I cranked it up about 12 degrees yesterday so everything should be hotter right now. I do know that the apt got warmer last night from cranking it up.

TIA.

Allen

Mark Eatherton1

Yes...

adding more plates will deliver more heat and give a greater differential in fluid temperature and cause the boiler to have longer on cycles.

I hope your boiler is out of warranty, because the tubing they sell is a non oxygen barrier tube and the warranty on the boiler is now void. Did they mention this?

Now your boiler will be continuously exposed to raw, metal hungry oxygen, unless of course you installed a heat exchanger to isolate the two systems, or are willing to do an annual fluid corrosion inhibitor update package. Did they mention that?

If your system is typical, you're using 3/4" poly potable water rated tube installed at 16" on center. And although you might be seeing a high floor temperature in the area directly above the tube/plate assembly, there are areas between the tubes that are substantially lower in temperature, thereby lowering the average floor surface temperature and lowering the BTUH output per square foot factor. Works OK as a floor conditioning systems, but falls short of a true radiant floor heating system.

We'll help you as much as we can, even though they (internet DIY heating companies) are taking money from our businesses...

ME

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Michael B

BRAVO

Mark, as a wholesaler I struggle with this stuff every day. "Customers" come to me and say how we are 3 cents higher per foot then the internet suppliers. I ask them the same questions and voice the same concerns. At the end of the day when they have a leak or need a heat loss calculation or help troubleshooting a problem they end up paying for it if you know what I mean.

You are truly a voice for the rest of us.

Michael

hr

Lotta boiler!

230,000 BTU for that 700 sq. ft. floor plan? Tell me there is a lot more load somewhere. (25,000 BTU/hr. MAY be close for the plan you show)

A 1 minute boiler run time! I doubt those boiler sections ever get above condensing temperature in on minute, much less the flue pipe.

You may want to have an experienced radiant contractor stop by, it may be the best money you spend on that system

hot rod

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GH

radiant heat

placing radiant heat under the sub-floor ?

allen

Its Radiantec. I called them and they were in on Saturday & gave me good advice. I need more btus. I was told that adding more aluminum plates to the pex tubing will not increase btus transferred. It would raise the temperature and that I would then lower the output temp on the header so in the end it would be the same temp on the top of floor = same btus out. (I remember doing another manufacturer a few years ago that used just staples.)

I installed it. The tubing is tight to the floor being held by their little aluminum plates. Then there is an inch or two of air and continuouse aluminum foil. Then r-19 underneath. And then a material similar to tyvec that forces the heat up.

It appears that the entire problem is the lack of insulation within exterior walls so I am going to add some baseboard heat this week. This is a rental unit and I do not want problems when it gets down near zero F. I am on the upper limit for heat as I cannot twirl floor temp up any more - I cranked it up another 10 degrees and will check it this week. I was at 135 at my header to run the heat, under subfloor was 110, and top of hardwood floor was 75 but I did add another 10 degrees to it on Friday. So I have to check it this week - but it was warm in there last night when I called.

I just cannot install wall insulation as the unit is occupied with a tenant and I am not about to have insulation blown in this time of year and then have to paint the place. So its easier to add another heat loop. Right now off this boiler there is a 3 room apt., a one room addition, a 40 gallon indirect, and this apartment. And there is yet another 3 room apt to be added in a few months. The boiler cycles up to its own high limit for all zones and then the boiler shuts down so I am getting it to temperature.

I just calculated the btus and came out with 16k on walls and another 7 k for windows. The floor beneath is insulated and heat is coming from there so I figured no heat loss there. The ceiling above has an apt where I am paying the heat - so that is probably on at 70 all the time. This system is spec'd to produce 23.5 k btus. I came out with what they came out for heat load (22.5 k btus). The actual blue print is in another post.

I will install a heat exchanger to the indirect zone this week. I missed that entirely. Hope that I didn't damage the boiler over the last 6 weeks without it.

Would I do this in another rental unit? Yup - I have one after this one. And that one has lots of wall insulation so this shouldn't happen.

BTW - am I wrong to say this? The floor is the heating element and thus can only produce so many btu's per sq foot. I am getting around 35 btus per foot. Thus, a radiant heat system needs a well insulated building to work.

Allen

heatboy

I should stay far away from this.........

since I'm not looking for a fight. But I must tell you that you have been taken advantage of. Were there any local contractors you could have met with? Did anyone from Radiantec actually visit with you face to face before they "designed" your heating system? I already know the answer because this company and others have a one size fits all attitude when it comes to the widgets they sell. I believe these are the same people that have told me I have priced myself out of range of most people. That may be so, but there is nothing wrong with fin tube baseboard or even forced air if the "budget" won't allow a radiant system that actually works. "The floor should be 72° to 75° if the thermostat is set at 70°." Did they really say that? I had no idea that every room was the same. And to think, all this time I put into meeting my clients and designing...............My head hurts.

Warm Regards,

hb

"Expert in Silent Warmth"™

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Mark Eatherton1

Sounds to me like...

someone is blowing smoke in your ears and blaming the deficiencies on you. You said,"I was told that adding more aluminum plates to the pex tubing will not increase btus transferred."

If this is the case, why don't you take ALL the plates out and see how many btu's it'll transfer.

Why do they sell plates if adding more won't deliver more heat. You are installed at 16" on center are you not?

You may not have toasted the interior of the boiler in such a short period of time, but if the boiler was new, you did toast the warranty...

A professional hydronic heating company would have performed a complete heat loss and you'd have been aware of the heating system deficiency long before you started the job.

Being short 1,000 btus isn't squat. Consider that each person at rest produces 500 btu/hr and you realize it's no big deal. A 100 watt bulb would produce 342 btu/hr, so when it it gets real cold outside, just have your tenant leave the lights on, or invite a couple of friends over to spend the night.

I hate being brash, but it sounds like you got what you paid for, a cheap internet system. Now you're scrambling trying to make it work. I seriously doubt that we'll ever get the whole story, or the bottom line on the story. In any case, hopefully you've learned something that you can carry forward on your next radiant project with you.

DO A HEAT LOSS BEFORE YOU START THE JOB. We do.

Maybe another coat of Tyvek will convince the btus to jump out of the joist bays faster.

Good luck in your endeavors.

ME


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John Jr

Heatboy

Didn't we just discuss this at Wetstock? Boy how fast they come out and hold on because there will be more!!!! How can these systems be sold? And then we try to tell them the problems and were still wrong! You can lead a horse to water but you can't make him drink!

John Jr