Hotwater Heating

I want to install underfloor hotwater heating in my family room, tried every contractor in the yellow pages, none would even bother to give me a price, so I am going to try and do it myself. I am an electrician by trade and have soldered copper pipe before, so I am fairly handy.
The house is 30yrs old so the insulation is average. The room approx 340sq ft, with a 4' crawl space below, so I have access to the joists above.
I plan to use a closed system with 1/2 pex in between the joists approx 500' of pipe. I am thinking 2 loops off a 3/4 manifold, I can't use a gas heater, so it will have to be an elec water heater. Anyone have any comments on what Iv'e said so far, also how do I work out the size of the hotwater tank I need, my thought is a 23 gallon with one 3000w element. the spec on the heater is GPH@100f 12.4
Also what would be the specs on the pump, I have no idea on that one.
Thanks in advance for your help.
tel

What's on the floor? WOod, tile, carpet? That makes a difference. If you can't use gas, have you looked at electric mats? These work especially well under tile.

You are going to a lot of trouble to convert kilowatt-hours to BTUs to put it where it will have poor heat transfer to the floor and a lot of it will leak out to the atmosphere even through the thick insulation that you will have to put under the pipes.

The only place I would put heat in a floor is if the heat leaking down was going to some place I wanted to keep warm, or maybe in a bathroom where I want to keep my feet warm when I jump out of the shower. Otherwise, I would wear socks or slippers.

You would get the same effect by putting some heat lamps or radiant heating elements in your ceiling, and would not have to learn to solder pipes.

http://www.eere.energy.gov/consumer/your_home/space_heating_cooling/index.cfm/mytopic=12590

http://www.orbitmfg.com/html/hotwater.html

I am not pushing electric vs. hot water for heating a floor, but the links above give you something to consider.

The reason I want to install underfloor heating is because my familyroom is so far away from the warm air furnace the room is always 4 or 5 degrees cooler than the rest of the house, I have checked the return air ducts, also the room has a very large window. I will be using heat transfer plates and insulation, I dont mind some heat leakage into the crawl space as I use it for storage.
tel

tel said:

I want to install underfloor hotwater heating in my family room ... I am going to try and do it myself ...

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How is that project coming along? I have a bathroom to do and I wonder what you might be learning.

If I were going to do anything like that I'd be using double bubble insulation for sure!

What I have is a 5x10 bathroom on the main floor (heated basement below and 2nd floor above), and with only one 5' wall (behind the tub/shower) being an outside wall with our attached garage beyond that. So, I am not concerned about much heat loss here. But by the time you deduct the areas of the fixtures and a closet, less that 30 sq. ft. remain for heating area.

My first thought quite some time ago was to at least lay some copper tubing in the floor in front of the tub so the hot water going to the tub would warm that part of the floor while the water was running, then I realized the effect would likely be quite minimal. So, my next thought was for copper tubing laid in the entire area and fed in a more usual hydronic way. Then electric floor heat was brought to my attention, and now I am pondering the best way to do either. But as to double bubble wrap, I have learned that a havey layer of SLC or whatever can help keep the floor (and more?) warm without the source always being on.

as to double bubble wrap, I have learned that a havey layer of SLC or whatever can help keep the floor (and more?) warm without the source always being on.

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Not really following you. Double Bubble/e-foil would reflect the heat back up to the floor. Some people put a layer of pink panther under it then seal it all up with plastic sheeting (visqueen). If you use self leveling concrete in a heavy layer then you are increasing the time to get the heat going (which is fine if you continuously heat it) but you gain the effect of it being a heat bank. Regardless of what you go with, controlling heat loss is the key to efficiency. It would be easy to drop a good bit of money into the project just tweeking it....adding circulation pump, thermostats, etc...but if I had the money it would be really nice to step on that warm floor and not have a heater to deal with.

heat in the floor is great to have.

hi tel,

Underfloor heat is great ! Electric heat is far more trouble-free.

All the negatives about hydronic are true when the system is large. Your space is small, so hydronic heat under the floor could be done off a single home HW heater. If you enjoy being in your crawl space, and if you plan to seal it off later with rigid foam and a lot of sprayed airtight polyurethane or polyisocyanurate foam .. But I get the feeling that you are undersizing your HW heater, underestimating the importance of insulation, and idealizing what hydronic will do compared to electric-generated heat. It is bit of a leap of faith to convert electricity to heat in warm water and then run that warm water under the floor to heat it, AND to expect that there is a gain or some other good reason to do it that way. There is no proof that it will be more efficient, and every reason to expect it to be less efficient. Bob already pointed out ("kWh to BTU") what I can paraphrase as "it is not as efficient to warm water up as just to warm the floor directly with your electricity. It's a different story if you are starting with gas." Gas heats efficiently. Electricity is not bad.

With any in-floor heat, it's a good idea to ensure the heat warms your floor, above the cables, and does not spread out in all directions. A heat break is a VERY good idea. That is a thermal insulator. Wood is a so-so insulator, not the best by far, but also not the best heat conductor either. Any membrane sold as a waterproofing or soundproofing membrane under tiles will be a good heat break too, under electric heat cables in a tiled floor.

You have the perfect situation for electric cables. Warmth from electric cables is more trouble-free.

david

Randyj said:

Not really following you. Double Bubble/e-foil would reflect the heat back up to the floor ...

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Ah! The bumkin sitting here in my seat at that particular time had never before heard of "Double Bubble/e-foil" and thought you were talking/joking about those blister sheets my grandchildren and I like to step on!

Randyj said:

Some people put a layer of pink panther under it then seal it all up with plastic sheeting (visqueen). If you use self leveling concrete in a heavy layer then you are increasing the time to get the heat going (which is fine if you continuously heat it) but you gain the effect of it being a heat bank.

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Somewhere I read it can be a good idea to have a heavy layer of concrete as that "heat bank" to absorb from an off-peak cycle and give it back over a longer time. But, I have also heard how difficult or even impossible it can be to anticipate need in that scenario (as when the outside temperature changes greatly) and/or to ever quickly stop the heat altogether. We are planning to install ceramic tile, and I suspect we are talking about a grand total of less than an inch here ... but at the moment I am still pondering and sorting what to do with that.

a little hydronic loop

hi lee,

i have often wondered why there are not more DIY perfectionists putting a couple runs of their HW back and forth around their tub, so that the floor (and maybe more) gets warmed up too, at a minimal cost.

I wanted to do this, but a couple significant people nixed the idea of me finagling and finessing, when finishing was their most desired goal.

A short loop of any Hot Water isn't going to hurt the HW heater or stress anything else. Back and forth a couple times. I have even wondered why people don't do this to go up a wall and into a shelf or a 1.5" chrome bar, for a towel warmer!

I'll start a new thread on this, in a few days.

david

Leejo... it's harder to heat up an ice cube than it is to heat up water... that's the idea of using a material which will isolate the heat bank. The big advantage of the slab is that it gives the floor a more constant temperature which I find very attractive. I'm not experienced with it but I'd bet that the floor will dry quicker too and be a little less problem with mildew... just my speculation without much thought and zero research.

Electric heat is 100% efficient, and most gas heat isn't. Gas heat is currently cheaper than electirc heat. That is why we don't use electric heat all the time. You need to evaluate your energy costs gas vs. electric when making decisions on heat. e.g. do you have off-peak electric rates? do you live in a city/village with a cheaper electricity supply, what's going to happen to natural gas prices 5 years from now? These ahould be your intitial considerations. Imagine the possibilities if we could find affordable ways to generate electricity for independent households. Especially here in the North!

Molo

geniescience said:

... a couple significant people nixed the idea of me finagling and finessing, when finishing was their most desired goal.

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Personally, I often find “getting there†the most exciting part of just about anything! And when you are working out of a jar of pocket change, the overall challenge is even greater.

geniescience said:

I'll start a new thread on this, in a few days.

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I will be watching!

Randyj said:

I'd bet that the floor will dry quicker too and be a little less problem with mildew... just my speculation without much thought and zero research.

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Sounds right to me, but I have read that at least the electric radiants need moisture protection, like maybe in the case of grout or tile crackings? Then, I have also read just a little about radiant wire in bathroom floors needing an integral copper sheathing, maybe like a ground in case they do happen to get wet?

I think I know where I can get a large amount of heating wire for pennies on the dollar, and one thought I have had is to run 3/8 copper tubing around in the floor and put that wire in it ... then if anything ever happens to the wire later and the house is still here, I can simply abandon it and run hot water through the tubing. But, I certainly do know I dare not approach that kind of thing casually.

molo said:

You need to evaluate your energy costs gas vs. electric when making decisions on heat ...

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Last year our gas went up quite a bit here and electric was actually cheaper for a while. But overall, my first thought is usually about all those gas nickels floating up and away out of our chimney. Ultimately, it would sure be nice to be able to run hot water through the floor from any of several possible sources for heat. Many years ago I once saw a monstrous “pellet stove†that burned chipped wood and heated an entire factory via forced air, and if I ever get the opportunity, I am going to play around with a small version of something like that in conjunction with an electric water heater containing an auxiliary heat exchanger.

cables already have sheathed and grounding.

leejosepho said:

.... need moisture protection, like maybe in the case of grout or tile crackings? .... needing an integral copper sheathing, maybe like a ground in case they do happen to get wet? ....

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no, no special needs. The sheathing supplied with electric heat cables is already insulated and grounded, and the thermostat can be a GFCI that shuts off with any microcurrent leak. And nothing special is needed against moisture.

in other words, you just lay them down (glue or thinset) and lay tile on them.

david

cables already sheathed and grounded.

leejosepho said:

.... need moisture protection, like maybe in the case of grout or tile crackings? .... needing an integral copper sheathing, maybe like a ground in case they do happen to get wet? ....

Click to expand...

no, no special needs. The sheathing supplied with electric heat cables is already insulated and grounded, and the thermostat can be a GFCI that shuts off with any microcurrent leak. And nothing special is needed against moisture.

in other words, you just lay them down (glue or thinset) and lay tile on them. It's numbskull simple.

david

electric floor heating

geniescience said:

no, no special needs. The sheathing supplied with electric heat cables is already insulated and grounded, and the thermostat can be a GFCI that shuts off with any microcurrent leak. And nothing special is needed against moisture.

in other words, you just lay them down (glue or thinset) and lay tile on them. It's numbskull simple.

david

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Which might be better: Single wire or dual wire?

I am doing my homework and finally learning some of the techs and specs.

i don'T mean to be flip, but i do want to direct you the right way.

They all work. Think of a toaster. It isn't high tech; it's a heater. There are design constraints and considerations but very few. So the cable itself is low level technology.

You could get the cheapest available, and spend on the thermostat.

If you believe in paying for service, advice, guarantees and honesty, order from Warmly Yours. Follow their advice on insulation too! Most places have no idea what to tell you about insulation and they will always underplay it just to make the sale and get it over with. It saves a lot of time and trouble to have someone else lay out the cables in a mat for you in advance. Otherwise you spend days calculating, laying cable back and forth and then adjusting it. I say days since you are a first timer. With a mat you can still place a section of cable where you want (by reshaping the mat, slicing around the cables) but 98% of the calculating and placement is already done.

you asked about single or double wire, i believe. Is there such a thing as a single wire that goes out from a power source but does not return current...? No. Instead of redefining the question more clearly now, take the attitude that it isn't relevant. There are hundreds of heat cable firms out there now, and they all create their own special marketing "talk" so they make you believe there is something great about what they do. You may read and read and keep on getting more and more informatoin about truly minor concepts that they build up to make them sound magnificent.

It's a toaster. The big cost is the work involved in planning and installing. The management of it all is in the thermostat. The cost of operation is from 5 cents to a dollar a day, depending on the insulation or lack thereof.

david

geniescience said:

They all work. Think of a toaster ... design constraints and considerations but very few ... the cable itself is low level technology.

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Would the cable from a mat intended for a concrete pour be okay between ceramic tile and a wood-frame floor? My thought is that it would be since it is likely designed to withstand rougher handling during installation, and I intend to do my own layout so I can heat just as much floor as possible while going around the fixtures in a small bathroom.

The web site you mentioned has no information about insulation, but I believe Randy has already made mention of what he would use.

geniescience said:

It saves a lot of time and trouble to have someone else lay out the cables in a mat for you in advance.

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For some folks, maybe, but not for me! I seldom use anything “out of the box†without some kind of modification or customization, and a certain company’s “custom layout†I have just received does not impress me at all.

What do you mean by “days calculating, laying cable back and forth and then adjusting it� If you are talking about configuration on the floor, that will not take long at all. But if you are talking about something technical, maybe I am looking at all of this too simply. My plan is to lay the cable and crimp it to lead wires wherever it ends, and to then learn whatever I must to figure out what kind of control I need.

geniescience said:

you asked about single or double wire, i believe. Is there such a thing as a single wire that goes out from a power source but does not return current...? No. Instead of redefining the question more clearly now, take the attitude that it isn't relevant.

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Well, in my mind it is. A single wire cannot short against another, and two running together while producing heat just does not sound good to me. Then, my son-in-law wonders whether a single might produce a magnetic field that could be therapeutic ...

Yes, I will forget about all of that within six months, but only because I will be into something else!

leejosepho said:

....My plan is to lay the cable and crimp it to lead wires wherever it ends, and to then learn whatever ....

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a single wire begins & ends at the thermostat, and that long long loop is what you lay out on the floor to heat the various spots you want to heat. If you lay it out once and then don't modify your layout, it will not take days, only hours.

it is true that you could buy two wires (making two long loops) so that the micro magnetic field might be canceled out, but i don't recommend it. A wire carrying AC and spread out going back and forth on your floor isn't going to make the kind of magnetic field that would worry me. It's also not close to you on a long term basis, not like a clock radio on your bedside table.

i'm not sure if i got what you mean by "crimp it to lead wires", so i'll saythis, just to be sure we are on the same page: you use only the wire they sell you and no more and no less, in order for the GFCI thermostat to work, since it is matched for resistance and impedance. No modification can be made to the circuit, not in the least.

you can also have a system with NO thermostat, and just a switch. That is even cheaper.

david