setting up radiant floor heating with HOT WATER HEATER
Yes, I have searched the archives and I am reading them. One person mentioned doing a system as I am proposing (Maura at http://www.homesteadingtoday.com/pri...d.php?t=105288) so hopefully she will post here again with more details or PM me. Here's what I have, folks.
I am in Southcentral Alaska. I live in a rural area. I am off-grid on a solar system with back-up generator and batteries. The house is about 2,000sf on 2 levels, with all modern amenities. We have oil heat in the house now using two Toyostoves. They work but they don't put heat where we want it so we are always running ceiling fans, etc. and having to leave bedroom doors open. In anticipation of this, we planned for a supplemental or secondary heat system (if it works well, it may end up as our primary heating system).
So, we ran hot water capable PEX and separate thermostat wires in several different zones under the subfloor as a staple up system and insulated with reflective bubble sheets to reflect the heat up and then used bat insulation to fill the voids before drywalling. We have a very deep basement-like crawlspace so we terminated all the PEX runs there. We have plenty of room to install a system here and all of our mechanical components are here except the electrical breaker box. it is high and dry and vapor barriered so no issues there. We also ran power from the electrical breaker box to the same area in the crawl to power the system on a dedicated circuit. I believe we have 6 zones.
We would be using either a propane or an oil-fired hot water heater, NOT a boiler (unless you guys talk me out of it, lol). We were going to put in a fairly small HWH along the lines of 20 gallons or so but not sure what size is needed for sure. Whatever we use, it can't be electric (I don't think) as we are off-grid with pretty high usage already. So then the non-electric HWH would be vented directly out of the crawlspace above the foundation, of course. We only have to worry about national basic life/safety and plumbing codes for bank financing, there are no local building codes. To date, everything we've done has been inspected and approved.
We would be using WATER (probably distilled to keep it from being contaminated or high in mineral content), not glycol, in the system. I already have some parts on hand from a guy that engineered a system (without the how-tos of course) using black iron pipes (which I think is a BAD idea for water pipes long-term) and a big, expensive boiler that I found out right quick was a model with a bad reliability history. We took back the boiler before ever unwrapping it and haven't done any work on the system since. We got a bid for an oil-fired boiler from another company that was WAY TOO HIGH and then I started reading about hot water heaters and how and why they work better, especially for closed-loop systems as we plan to use.
What we need to do now is figure out how to build a manifold type system and set it up for a closed-loop system with a hot water heater. I've read a lot on this but seen no real diagrams and shopping lists of parts with a good how-to. I've been to the book stores and the libraries and I can't find the two books that have been recommended in the past on other websites. Don't ask me what they're called now as I have forgotten since it's been a while.
What I am looking for are some caveats and info. from people that have done this using a hot water heater for this application or from those that know about this sort of set-up. I would also like a diagram or even some step-by-steps of how this is supposed to look and work and what materials I need to get the system running.
Have seen it done several times, but it will have to have water feed, expansion tank, back flow preventer, pump/s, bleeders and generally the most of the same components as a small boiler.
Might want to price it both ways.
Since I can get a HWH very inexpensively compared to the boiler, and since they are supposed to handle this system better, that's where we were leaning. The boilers alone are upwards of $4K here. I would get the best HWH I could find and afford (recommendations or warnings of ones to avoid?). I don't mind setting up all the extra components you mention hunter63, just need to see some diagrams and a few comments on how tos.
On a tankless, wouldn't it always be running since the circulation pumps would always be pushing water in/out of it and thus triggering the heating mechanism?
mtman - I've heard this concern before but keep reading from people that have done it that that isn't true. ??? They all advocate for lower water temps (like 100F instead of 130F) but most water heaters I've seen *can* go as high as 140F. I think the other thread to which I linked talked a bit about this too - something about it's not necessary to have the water so hot and may make the floor uncomfortable?? Not sure that would be the case here though, where we have subfloor, underlayment, then flooring on top of the PEX.
My buddy just put in PEX in his cabin on KGB (mile 10). The boiler was set low and it would not heat. He called out one of the senior plumbers from Gold Star and the guy said that it had to be set higher. I believe it is at 180 degrees. I do not know how you could set it up with a hot water heater. His pump was more expensive but I believe that it is much more energy effecient.
My neighbor created a radiant heating system that works good. He uses clear plastic pipe under the subfloor, held in place with aluminum reflector sheets. His operating temperature is around 100 degrees F. That's a lot cooler than I'd expected. His system has a hot water storage of 20,000 gallons, so he doesn't have to fire up his wod boiler often. So, based on that, I'd say you could run your propane water heater at a low setting. Your system would have to be non-pressure, open system, to prevent blowing your lines.
Our on demand propane water heater heats both our radiant floor and all domestic water. It is an open system that we installed and plumbed ourselves. We are on well water and installed a water softner.
Wirsbo is a maker of pex and heating systems.
Might want to get to their web site. Don't know if the publish them on line but,
there are calculations that have to do with length/ size of tubing vs sq ft, vs floor temp/flo rate/btu's given up etc.
mtman is correct water, heaters weren't made for this, but I have seen some in action, as supplemental heating
We're about to put in a system using a water heater. I went to Radiantec and they were very helpful. They have a system that uses your potable water for heat so there is never a chance of stale, bacteria laden nasty stagnant water gathering in the pipes. The water also can help cool the house a little in the summer.
He quickly steered me away from an on demand heater. His explanation was that they operate at a set, high btu. If you turn on a faucet to wash your hands, it blasts full power until you get done washing. Lots of heat just went up the flue. he told me to shop for the highest efficiency (within reason) propane heater I could find locally. 40 or 50 gallon will be plenty big enough. He will be supplying all the pex and fittings and pumps and controls. I checked locally and he beat the local tubing price.
The schematics and diagrams and instructions included in the quote package make it look very simple to hook up.
No, I don't work for them but I am about to be a customer.
As with any heating system, the source of the heat must meet or excede the demand. The BTU requirement for the house must be determined before proceeding with the selection of the device/size to be used.
"He quickly steered me away from an on demand heater. His explanation was that they operate at a set, high btu. If you turn on a faucet to wash your hands, it blasts full power until you get done washing"
Not quite correct. My on-demand only heats the water to the proper temp. It modulates the heat form a low of 17000 BTU's to 140,000 BTU's. The warmer the water coming back the less BTU's used.
If you use a regular hot water heater, you will be using the same water that you use in your faucets. The PEX is much smoother than metal pipes and you shouldn't have trouble with minerals. Many of them are lost at the bottom of the HWH anyway. We have a lot of minerals in our water also. Our local building inspector made us use a closed loop system. This required buying an expensive HWH, one in which the floor water passes through a loop inside the HWH, so that the potable and floor water never meet. It is not as efficient as using a normal HWH and an open loop. I think it is a 30 gallon tank, it's whatever size those monsters come in. Think about how much hot water your family needs for bathing and cooking, etc.
I don't know how cold it gets in south central Alaska, but in floor heat has been used in Scandanavia for a decade or too, and I believe it gets pretty cold there. We are in Michigan and the temp rarely drops below -10. Our house stays as toasty as we like, but we also have thick insulation and high quality windows.
If you go to Radiant Tec, they will send you a packet of information which diagrams everything. They will help you determine how much PEX you need for your location and at what temp the water should be. A normal hot water heater should be able to supply enough heat for any installation.
__________________ Nothing is as strong as gentleness, nothing so gentle as real strength - St. Francis de Sales