conventional hot water heater for radient flooring
terranova
| Posted in Energy, Heating & Insulation on
Hello Heaters and Coolers.
Has anybody out there successfully used a conventional gas-fired water heater for radient floor heating ?
I’m looking at an 840 square foot well insulated space in New England as a possible candidate, but 3000+ bucks for a Polaris water heater gives me heartburn.
I’ll get a professional to do the study and make the reccomendation but I need real world non-profit advice before I start that song and dance.
Thank you all.
Replies
least expensive hot water heat
hey terranova,
There are some very inexpensive self contained electric hot water heat systems that hang on a wall space about the size of a small bulletin board. I am sure you can substitute gas/oil for electricity.
Really most people approach your building idea with the heat system first, then add in the hot water storage system as a side benefit of the radiant installation. The radiant system is just a simple circuit, but with a lack of familiarity you can fall into some really confusing pitfalls.
Some things to watch out for: the radiant systems have to provide for the returning water temperature to be mixed near the return port of the boiler, so that the boiler jacket is not stressed beyond its mechanical property limits (this is actually the most complex part of the system); the control implementation of the system looks very confusing, but like I said some of the systems offered are self contained on a space the size of a small bulletin board; protect the radiant fluid from problems like fastener penetrations, back flow into the potable water source; and last but not least look closely at your desire to have radiant heat.
Radiant heat dries out every stick of wood inside the conditioned building envelope (it actually works rather well). Radiant heat might be very comfortable (it really is), but unless you have a pretty darn good complete building envelope you will have a very expensive to operate heating system.
I am pro radiant heat, (a metal roof cover is actually an enhancement to a really good system), but unless you find out about th drying out problem early, it can be a very expensive learning experience.
Douglas
I find your "radiant heat
I find your "radiant heat dries out every stick of wood" statement as ridiculous as the claim that hot water heat is "moist heat", and doesn't "dry the air" as much as forced air. Heat is heat.
comparative heat sources for radiant floor heating.
Good Morning Dan.
Thank you for your reply.
Do you have background in radiant floor heating systems?
I could sure use some pointers regarding reliable and cost-effective heat sources.
Thank you, Sir.
t'nova.
Maybe you also didn't know that food cooked on a wood burning stove tastes better than if cooked on gas or electric.
well maybe a little
DanH wrote:
I find your "radiant heat dries out every stick of wood" statement as ridiculous as the claim that hot water heat is "moist heat", and doesn't "dry the air" as much as forced air. Heat is heat.
Well, radiant heat does dry out wood floors and type of flooring should be part of the overall plan. I also have an issue with winter time squeaks as it seems my floor joists shrunk which I didn't anticipate. If you do a decent job sealing and insulating each joist bay then it gets pretty warm in there. I probably should have screwed the subfloor down instead of using some adhesive and a nail gun. Even better would have been engineered lumber (TJI's). But I do get what you mean as the wood in the rest of the house is not effected.
One last comment on relying on 1st floor radiant to cast enough ambient heat to warm the second floor. Don't count on it. Radiant heat is just that-radiant. It warms the floor , furniture etc. and does not warm the air per se. It does some of course, but not nearly as well as other types of heat. The stack effect in houses is minimized with radiant . Its true what they say about heat not rising, but hot air does.
Yeah, any time you put a heating source right next to wood, that wood will dry out. Put an electric heater next to some wood paneling, and the paneling will dry out, because it's being maintained several degrees warmer than its surroundings. That's simple physics.
Dan,
As you mention, I have heard it said that hot water heat is nice because it is moist. But I know the water stays inside the system and cannot contribute to the moistness of the condidioned space.
Raising the temperature in a space permits it to hold more vapor, so it sucks the moisture up wherever it finds it. So I don't see any difference in that effect from one heat source to another. I agree with your observation "that heat is heat".
But I do see that materials nearer the heat hydronic loop will be subjected to higer temperatures compared to the balance of the living space. So those materials that abosorb and release water vapor will be relatively drier on average.
So, if you add a hydronic loop into a building that has become establised at a cycle of moisture, it would shrink wood in that vicinity. My sense is that if you added a hydronic loop under a seasoned and established hardwood floor, it might open all the joints.
But that is just because of the fact that what people tend to call "radiant heat" is in the floor, and so it places the floor directly into a higher temperature zone. I would say that "Radiant heat" per se is not fundamentally more "drying" that any other type of heat. It is just that the elevated temperature of the heat souce near wood is going to dry that wood more than average.
I am very interested in radiant heat. I am intrigued that the term has almost univerally come to mean in-floor heat. I am very interested in the concept of slab hydronic wall panel type radiators. One thing about hydronic in a slab is that you have a lot of thermal flywheel in the slab mass.
radiant heat pitfalls.
Thank you for your reply, Douglas.
Some specifics which apply here:
The roof system is R-32 SIP, with an airgap between the SIP surface and the 5/8" plywood roof decking.
The building is 1 1/2 story, measuring 26' x 20', with 2/6" studs and fiberglass insulation. The 2nd story is framed with true post and beam Western Fir ( above average biomass?) It being a story and a half, the upstairs walls are only 4 feet high, which, I expect, reduces heat loss.
I do need an expert opinion regarding the possibility of radiant heating the bottom floor ,and say, the upstairs bath directly and letting ambient handle the rest of the second floor.
I prefer oil heat, but have not done a cost analysis of oil/gas/electric recently, so that is sublect to change.
Electric would certainly be the lowest cost installation, so I am tempted, but power outages during a New England winter could be disastrous.
Can you steer me toward proven manufacturers of wall heat units who would most likely survive the inevitable market peaks and valleys of what is still an emerging technology? I will educate myself accordingly, but experience and background are the major inputs at this point and caveat emptor always rules.
Once again, I thank you for assisting me here.
t'nova
Here ya go
http://www.jlconline.com/cgi-local/viewnew.pdf/0/2ea50ceb07b961e486b5f16d78842ece/www.jlconline.com/cgi-bin/jlconline.storefront/4fa009fd1c5f21eb27170a323cb40648
This is from JLC 1998 -- great article & all you need to know.
Radiant heat dries out wood? Damn, who knew?
Joe H
conventional water heater for radient floor heat
Joe,
Jackpot!
I don't come here all that often, but I find what I need whenever I do.
Thank you, Sir.
I had a conventional water heater serving a radiant floor in a house I lived in and recently sold. Seemed to work fine. One guy told me it was 'the wrong way to do it', but after thinking about it ... I've no idea why. You may need a bigger water heater, but heat is heat ...
used gas domestic water heaters (DWH) for small hydronic heating installations. Most, basic tank water heaters have an input of 40,000 btuh. All of the other ratings are not useful to heating applications. Whether is has a 40 gallon or a 50 gallon storage has no bearing on its ability to provide warm water for infloor heating.
I currently use a Bosch Aquastar tankless DWH for the heat source in my garage. Works well, but the heat load is low and the temperature requirement is low so a tank would be better, but this was a "left over" so thats what I used. I would not recommend buying a tankless to use for heat.
Understand that you cannot mix heating water and potable water. In many jurisdictions it is simply illegal, in all others very risky and unwise.
Typical 40 gal natural draft unit, in my neck of the woods can be had for under $700. Regardless of the source, the remainder of the hydonic system will have the same components: back flow preventer, pressure regulating/feed valve, expansion tank, circulator, air separator. Additional controls will include a thermostat for each zone (if multiple zones are in the plans) and potentially mixng valve(s).
The purists will scoff. But purchasing a "real" boiler for heat load of 20 to 25 MBH is less than thrifty.
I have done this in many installations and/or "helped" plumbers and homeowners doing the same. Never had a problem. Some of these installations have been up and running for 20 years without problem.
Same as Tim
I did the same as Tim in a poorly insulated lake house I lived in back in Wisconsin. It was a low-budget experiment of sorts that worked out very well.
The house originally had a gas water heater for DHW and an oil burner for forced hot air heating.
I added a heat exchanger to the existing water heater so the RFH would be a closed-loop setup. I did staple-up PEX with no plates on the underside of the subfloor for the RFH. Half-inch foil-faced polyiso tucked up against the PEX staples, then R-19 unfaced FG batts were added under the polyiso. A single Taco pump l=kicked off by a thermostat circulated the RFH water through the single manifold to the various loops of PEX.
The comfort of the entire house was improved by a huge margin, and it was a heckuva lot more economical to heat with too.
Hi Terranova,
You might want to look at a Vertex water Heater from AO Smith. It is a very efficient condensing 50 gallon water heater which has side taps and is "designed" for water and heating applications - whatever that means. It is not cheap, but much less expensive than a Polaris, and if you take care of the Anodes, should last a long time. It puts out 95,000 btus, so can handle quite a load. It is a direct vent (a big plus), therefore there is fan noise at the unit, and outside at the intake / exhaust.
I use mine for Hot Water and to run a small radiant loop. mine is an open loop, but could be closed with another pump and a heat exchanger.
Hi Albany Chris -
I realize this is a very old thread....but I'm seeing some similarities here and I'd like to ask how your system worked out in the end. I'm also plumbing an "Open Direct" system (designed by Radiantec) and am strongly leaning towards the AO Smith Vertex (the 76k BTU, 50 gallon tank). Its a small (1 bed 1 bath) home, well insulated and air sealed. I know that the open direct systems don't get a lot of love, but I also know there are thousands of success stories with them.
Anyway -- wanted to see if you had any regrets/advice/etc. regarding your system (and heater)?
I have read some mixed reviews as to the longevity of the Vertex. I suppose staying on top of maintenance (flushing, anode changes) is sorta the best one can do?