Author Topic: Hydronic (underfloor hot water) Heating (Read 9218 times)

Stan · « **on:** February 08, 2007, 11:39:28 PM »

I'm considering putting in hydronic heating in my house. My boiler will be gas powered but there still has to be at least a couple of water pumps to pump the hot water around though the house and the heater. Does anyone have such a system now? Is it compatible with 12 volt operation or are the pumps only available in 120V versions? If they are 120v, how many amps do they draw, both on start up and normal running.

This information would be good to know if I wanted to be able to power my home's heating source from Penelope or battery in case of winter power outages.

Stan

dkwflight · « **Reply #1 on:** February 09, 2007, 12:02:14 AM »

Hi
I have some experience with a couple of different systems, different houses.
My brothers house works well. The house is very comfortable and economical to heat.

To begin with make sure the house and windows are well insulated. If the house is not very well insulated the floor can be too warm.
The system includes a tempering devise to control the tempreture of the water circulating in the under floor circuit. you will have two pumps. one to bring hot water from the boiler to the tempering thermostat. Another pump to move water through the loops under the floor.

The advantage of this kind of heat is you are circulating a low temp water. and if your feet are warm then the rest of you is comfortable at a lower temp.

Good luck
Dennis

GIII · « **Reply #2 on:** February 09, 2007, 01:22:31 AM »

All the above!
I have had three houses with in floor heat. Insulation is your friend; you can't have too much. Also, the floor HAS to have enough tubing to supply all the heat losses at a low water temperatures, say in the order of 100 degrees F, or the water temperature will need to be high enough for the floor to feel hot, which is bad. The answer is to put in more feet of tubing than the calculations call for; space it closer together so the gradient between tubes will be less. Run several parallel paths of about the same length instead of one long loop and space the tubes about 3 inches apart no matter what anybody says about saving money by using a larger spacing. If you need to save money that badly, get another job until you can afford to do this correctly because it is nealy impossible to make up for too little tubing after the fact.

Plan on setting the boiler temp at a modest temperature, maybe 140 F, and use a three port temperature regulating valve to mix the boiler water with some return water to get the 100 F for the floor loop. I used a Watts valve that cost about $35. A single pump can do the job if selection is made VERY carefully, but for the cost of another pump, it is not worth worrying about. Valves and themometers are handy to sort out startup.

To do a real first class job consider reflective bubble insulation under the tubing and gypsum concrete about 1.25 inches above the whole thing to level the temperature gradient. I have used concrete and gypsum and have heard all the horror stories about both, but find both cost about the same and both work very well. The weight savings of gypsum is substantial if this is over a wooden subfloor.

The pumps typically are permanent split capacitor motors and draw very little amps at 120vac. I've never looked for a dc circulator but I'm sure they can be had. The cheapest pumps don't generat enough head to work well pushing through a few hundred feet of tubing so check the specs carefully.

Right now it is 22 out side and I have the floor of my sunroom at 95 F and the air is 68 F, the garage floor is at 75 and the air is at 45. I'm using a propane hot water heater for the main source of heat, with a coil in my wood stove sucking up some 'free' heat. In floor heating can't be beat for my money.

George

chug · « **Reply #3 on:** February 09, 2007, 02:42:23 AM »

I use bronze taco pumps in my outdoor wood boiler. They work great. I push water 195' to the house and 75' to my shop in a 1" pex line. My big pump is 1/8 hp, 1.76amp,60hz, 115volts.

I'm not sure if this is going to hyper link or not, but here is there web site.

http://www.taco-hvac.com/

Tim

rmchambers · « **Reply #4 on:** February 09, 2007, 04:33:42 AM »

Stan,
Were you considering using penelope's heat to heat the water for the subfloor or just use the electrical energy to move the otherwise heated water around?

If you wanted to use the mechanical energy from the Lister to move the water around I'd think the losses would be less than converting motion to electricity and then from there back into a separate electric pump motor. If the lister is out in the barn somewhere then it doesn't make sense.

Robert

Doug · « **Reply #5 on:** February 09, 2007, 04:58:16 AM »

See if you can get one of these little Indian water pumps from your engine vender....

Should be the cheapest thing going...

http://www.putfile.com/pic.php?img=4071037

Lower left, its not top of the line but I can't see them selling for more than 20 bucks

Elk County Dutch · « **Reply #6 on:** February 09, 2007, 08:54:24 AM »

Stan, My wood fired system uses taco pumps. one is 110 volt ac and the other 24 volt dc. they will take the 180 F degree average heat with no problems. My 110 volt taco has several thousand hours so far. Gene

Rod · « **Reply #7 on:** February 09, 2007, 02:54:13 PM »

Stan, It's too bad you don't live around here, I was born into the plumbing & heating business. If your doing a multi-room house you need to do a "heat loss" for each seperate room in order to get even heat throughout the house whether or not you build seperate zones. The floor heat is by far the cheapest to run and the most comfortable but it takes all day to make a 10* temp change so if you don't have the right footage in a room it's either gonna be too cool or to hot and impossible to ballance. What you need is an I.B.R. manual to do the heat loss, if you know a good plumbing contractor he should have one. I just loaned mine out to a guy that changing form (scorched) hot air heat to hot water. If you do it right you end up using the least material and having the most comfort. Depending on where you live you might be able to get a Wholesaler to do the heat loss in trade for buying the material from him, this isn't something to guess about, I've seen real disasters because of someone with a little knowlage thinking he could build a system.
A real heat loss is done with something like a big mathamatical formula using the square footage of each room, size & type of each window, weather or not there is a door in the room, the R value of the insulation in the walls the R value in the ceiling, the design temp of the water etc. when you're done, you end up with the number of BTU loss and therefore the footage of pipe for each room.
If you google I.B.R. School you may be able to buy the book. The school was great fun, those guys have done some crazy experiments in test houses.
Rod

adhall · « **Reply #8 on:** February 09, 2007, 03:57:00 PM »

Stan:

To veer the discussion back to your original question:
Yes, there are 12 VDC powered circulator pumps available. I haven't used any myself, so I can't recommend a brand, but I've seen them advertised on web sites that deal with solar heating and radiant heating. I just did a quick web search for "circulator pump DC" and found a bunch of options. There are also electronic controls available the vary the speed of the pump to control the temperature.

By the way, I'm researching a radient heat system for my house, too.

Best regards,
Andy Hall

Stan · « **Reply #9 on:** February 09, 2007, 04:09:13 PM »

Thanks for all the great info guys! I've planned to use 120v pumps, as they appear to draw so little current Penelope or even my emergency battery bank could handle the load. I'm greatful for the advice from George and Rob for the info on insulation. I've gutted the house and added good insulation/vapour barrier in all the walls but the ceilings are another story. It's a flat roofed house and I can't get at the space which just has the really old fashioned 2" black "rock wool" batts with heavy brown paper on both sides of it. Not the best in any situation but after 65 years, it's terrible insulation. Possibly I'll have to blow fiberfill in on top of it to get an acceptable level of insulation.
Stan

rmchambers · « **Reply #10 on:** February 09, 2007, 04:22:05 PM »

Stan,
Since most of your heat tends to rise up and escape, the ceiling/roof insulation is your primary concern now. My house (built in the 50's) had the same rockwool insulation you speak of in the walls and loose rockwood in the attic. Talk about messy, I suited up and cleaned it out by hand then shopvac-ed between the joists to get all the dust/fiber/glass beads out and then re-insulated with some modern insulation. It was a messy job but I felt the improvements right away. Do you have any sort of attic egress or would you have to cut a hole somewhere to do this work?

Blown in insulation would be an improvement over what you have. It would be nicer still if you could get the old non-performing insulation out first though.

Good luck with the project.

Robert

ronmar · « **Reply #11 on:** February 09, 2007, 09:15:51 PM »

Some of this http://outdoorpipeinsulation.com/ might be handy if you were trying to incorporate the wast heat from a genset out in the hut, into the floor heating or domestic water system. Pretty low thermal loss figures over pretty large distances.

Has anyone here seen or heard of a metal hydronic floor heating system? I came across one installed in a home during the local solar tour we had here this past fall. It is low mass and uses NO concrete. Precut foam insulation about 2" thick is layed down over a vapor barrier onto the subfloor. This insulation has channels milled into it which accept the corrigations from a thin stamped sheet of aluminum. The shape of the stamping is designed to accept a PEX tube. Over this metal plate is placed a floating wood floor or carpet pad/carpet. The aluminum conducts and distributes the heat from the water in the tube to evenly radiate the heat up into the room. I can't remember the link to the manufacturer. If I find it I will post it.

Stan · « **Reply #12 on:** February 09, 2007, 11:45:21 PM »

Robert...Nope, can't get at it unless I rip the ceilings out of the house. My project manager has nixed that

Stan

dkwflight · « **Reply #13 on:** February 10, 2007, 12:09:26 AM »

Hi
Many older homes have a small hatch cut into a closet ceiling or an opening on the end of the house acessed from a ladder. Find a way,it will be worth it.

One '60s house had copper pipe in the poured floor. It worked fine except the insulation was nor up to snuff and the floors were too warm. Today the cost of copper will kill the job.

There are comanies that do spray foam insulation. This works well because the small openings that allow air to infiltrate into the house are sealed.

I have been around several very old houses that had laid up stone walls for the cellar. Plastering these stone foundations is worth while to seal them.

Dennis

Stan · « **Reply #14 on:** February 10, 2007, 04:15:22 AM »

This is a flat roofed house, it's got 12" of space between the ceiling and the roof. I'm not that skinny any more, (never was!). Funny they'd build a flat roofed house in a ski resort where we have 4 feet of snow in the yard (not on the roof though $:-\$
Stan

btw...they use PEX plastic pipe now for hydronic piping, it's good the pumps only draw a couple of amps apiece, it makes it much easier planning for alternate power sources, like a 6/1.

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