Fin Tube Low temp Possible?

Louis_3

fin tube low water temp

1st:

Is it possible to install sufficient copper tube & fin baseboard, sized correctly for heat loss, to run at a low temp with a condensating boiler? (perhaps a Viessman Vitoden 100 or a Munchkin- as the max temp on these boiliers are only 176) Will convection actually work at 140 or does it need to be a 170 to heat a 2500 sq ft house on a concrete slab? the mfg. tables show BTU output at 140-150 but will heat come? will the convection work as there is no 'mass' such as a panel or cast iron?

Or should i just keep it simple & install sufficient amount of BB at 180 and get a convential boiler?

2nd:
there are many heat-loss calcs out there- which one is good and not too complicated? heatload.com?

Everybody i ask gives me a different answer- no kidding!

ALH_4

mod/con and baseboard

I think you will get a resounding yes from everyone here when it comes to low temperature fin tube baseboard with a mod/con. Slant/Fin offers their heat loss software for download. They also publish low temperature output charts for their baseboard.

Brad White

Another Resounding Yes

With enough of any kind of radiation sized to any available water temperature with output which in turn will match your heat loss, yes, absolutely.

A study by the Brookhaven National Laboratory (attached) pretty well settled that you could even have baseboard sized for 180 F and install a ModCon in a retrofit application and still have enough hours of the year when condensing occurs to make it worthwhile. This naturally figured that the very coldest weather would require boiler operation outside of the condensing mode but rapidly went back to condensing when the outdoor temperature rose and the water temperature accordingly dropped.

This was a way to determine the efficacy of retrofit only, to an existing system. If you are going in anew, by all means lay out the baseboard on as low a water temperature as you can fit and afford. I find a 130 degree average water temperature (140 F entering, 120F out) to be ideal. You can even go to 40 degree drop (140 to 100 out) but the low flow rates may lead to loss of output due to laminar flow. Like you should worry....

If you maximize your radiation this way, you can still be condensing even on the coldest day. You will also minimize that "scorched" smell of hot dust during first start-up each season.

What is key to the approach in any case is outdoor reset- index the water temperature from your "lowest high temperature that will heat the house on the coldest design day" and reduce it to "near room temperature when outdoor temperatures and indoor temperatures nearly coincide". This will assure you of the maximum number of hours during which you will get most efficiency.

Mike T., Swampeast MO

A Third Resounding \"YES\"!

Slant-fin is the first (and perhaps the only) fin baseboard manufacturer to rate their products at lower temperatures. See this example

You can find similar for all of their baseboard products by choosing "click for specificications and additional information" and then selecting the "ratings chart" from the pop-up menu.

I can only assume that these are certified ratings and somewhat to my surprise you'll find that the output curve with regards to supply temperature IS NOT LINEAR. Output drops greater in the "typical" hot water range (say 160F - 180F) than it does below 140F!!! I say "somewhat" surprised only because to the best of my abilities I've found that decreasing temperature below "typical" with iron radiators actually increases relative output...

My only reservation with Slant Fin's (an MANY other mfgrs.) outputs comes from the 15% addition for "heating effect factor". Such "heating effect (or is that affect) factor" comes from placement of the emitters on outside walls. I can agree if the outside walls are essentially filled with baseboard, but be darned careful if you're working with a highly efficient shell! Granted this is an extreme, but there's no freaking way I'll add the "heating effect" factor in a room with 40' of exposed walls and only 5' of baseboard required at 150F design water temp when it's -20F outside!

As to heat loss calculation programs: Most are based on Manual-J. Nothing at all wrong with that, but just be aware that Manual-J (like ANY well-proven standard) WILL result in somewhat overstated heat loss, ESPECIALLY with a true hydronic system driven by a mod-con. Design your system based on Manual-J requirements at 150-160F supply temp I can nearly guarantee you that the system will never need more than 140F in any reasonably insulated/weatherized shell.