An under-the-floor heater

[Sam Takoy]

Hi,

I have a very small room on the first floor and the hot water radiator takes way too much space. I'm not considering a baseboard.

Here's how I would like to heat it?

Place fin tubing between the joists in the basement. Insulate the subflooring to protect the hardwood floors (and I am not looking for a warm floor). Install two registers through the floor at either end of the way between the joists. Install a slow rotating fan somewhere along the bay. Box the whole thing in.

My idea is that the air will get heated by the fin tubing and enter the room.

Would something like this work? Where does one buy fin tubing?

Thanks in advance,

Sam

[hrhofmann]

Are proposing to heat the air and push it up through both floor registers, or move it horizontally sucking air in at one floor register and pushing it out the other floor register??

[Sam Takoy]

The latter: sucking air in away from the window and pushing it out right under a window.

[ransley]

Did you ever hear of Radiant heating, no fan needed and a warm floor is great, but there are total output of Btu isssues. A fan is also going to pull alot of electricity, maybe equal to what the whole boiler uses now and will be noisy. Cast iron radiators put out alot of Btus and continue to release heat for hours where any fin tube will cool off in maybe 10% of the time as a cast iron radiator, net result you will be cold just from the inbalance you have just entered into the equation, even if your new "experiment" has the same Btu output. A radiator in a room releases radiant heat and convective heat, how are you going to rate and make two different sources equal. Something like that would need a seperate loop , pump, and thermostat to have any chance of giving you equal heat. I bet the rating of Btus between cast iron and any fin tube will also vary as the boiler reaches its operating temp. Bottom line I think it wont make you happy when its real cold out, you might get it to work at maybe 40f outside but not on the coldest days.

[jamesgangnc]

To meet fire safety code you will need to box it in with metal. And you will need to figure out how to have access it all for repair/ replacement purposes. If you really want to make a small forced air heat exchanger try the junk yard for an automotive heat exchanger. They tend to be about the size you'd be looking for. You need your fan to be more that slow moving. And you need to work a thermostat control into it as well.

Or install an in floor radiant heating system instead.

[Art Todesco]

I wonder about that. Around here, in NC, most of the builders run a feed duct right under a kitchen or bathroom vanity cabinet and let the warm air just fill the cabinet base. A register is mounted on the kick plate of the cabinet. I wondered about fire safety.

[jamesgangnc]

It's not the heated air that causes the requirement. It's the fan motor.

[beecrofter]

A small low voltage computer fan could be built right into the register and powered with a wall wart , cheap and quiet. Can't speak about code issues.

[jamesgangnc]

Any fan built into the house should be enclosed in a fire proof housing of some sort. A 5 inch computer fan could be adapted to work but generally your talking about a 1 to 1.5 amps for one of those big enough. And I'd be tempted to go with two fans of those sort myself. Either way that's a fairly big wall wart.

[Art Todesco]

Thanks, that makes sense and makes me feel better about that situation.

[hrhofmann]

Are you sure the 200 watts wasn't to heat the water itself????

[ransley]

e quoted text -

That statement shows just how little you know.