Low Temp. Emitters

[chuck172]

Seems like everyone is in agreement that the best way to efficient hydronic heating with wood boilers is through low temperature emitters. Be it adding more fintube, replacing fintube with panel radiators, adding panel radiators to existing heating systems, or installing in floor radiant heat.
Pressurized or non-pressurized storage will both benefit on utilizing lower temperatures
Like gooserider says, maybe we can get some real pros in this field to help us out.
Slantfin's hydronic explorer program can easily tell you how many feet of fintube is required per room (to add) at the desired boiler temperature.

 

[in hot water]

Here are some cheat sheets to help determine various emitters output at various supply temperatures.

Panel rads are typically rated at 180 °F This graph shows you how to de-rate their output at lower supply temperatures. It is intended for solar assisted hydronics, but works the same with low supply temperatures regardless of the 'generator."

Radiant ceilings and walls are another way to install or retrofit heat. With walls and ceilings you get more output than floors due to the ability to run much higher surface temperatures. And no furniture or floor coverings are installed on walls and ceilings. Typically Most installers do the lower 3 feet to stay away from wall hanging anchors.

And also a graph showing the output of concrete slabs with various floor covering r-values. It also show how tightening the tube spacing changes the output.

All these, with explanations can be found in Caleffi I-dronics 6 technical journal.
Used by permission.

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[DaveBP]

Seems like everyone is in agreement that the best way to efficient hydronic heating with wood boilers is through low temperature emitters.

Not just wood boilers, chuck.

Fossil fuel boiler technology is moving to condensing systems that use low return temps to condense the water vapor in the flue gases to recover a large fraction of the heat than ordinarily goes up the flue. Lots of condensing gas boilers out there now but I think oil boilers, too.

For lots of reasons, I think wood boilers have the most to gain.

 

[chuck172]

My LR. now has 20 feet of fintube. It is set up for 10*outside@ 180* boiler temp.
According to slantfin's hydronic explorer, If I add 10' of fintube, which I can, I will lower the boiler temp needed to 155*.
This will cost me about $88.00.
Now 155* is much more sustainable with my 500 gallons of storage.
I have 4 heating zones, if I take them one at a time, over a period of time, I can improve my situation.

 

[DaveBP]

According to slantfin’s hydronic explorer, If I add 10’ of fintube, which I can, I will lower the boiler temp needed to 155*.

I think you are onto a solution more folks should explore. Getting more usable heat out of the same heat storage tank by adding more baseboard to an existing baseboard setup. It can be a sticky interior decorating issue, especially if more than one opinion is involved in making the decision.

I think it would be best to plumb them in parallel to the existing units. Lower head and lower flow rate for a greater deltaT (water in/water out) if no pumping changes are made.

How much does it degrade their performance if they are put in one above the other, I wonder. Doesn't it just becomes a panel radiator? The top one will be seeing higher ambient temps so less deltaT (water to air) but do the stacked baseboards produce more convection to help counteract that effect?Probably need a professional opinion on this.

But, then, people have been telling me I need professional help for years.

 

[chuck172]

In my situation I can just add 10' of fintube to the existing 20'. Simple enough.
My master bedroom already has the required footage of fintube to allow 155* water temps.
So that's two zones out of the way. I going to look into panel radiators for some other zonesl

 

[lawandorder]

Anyone have any experience with Runtal North America???? They look like they are whats needed but how do you work in panel radiators into a baseboard set up. I have one zone in my LR that I would like to try this in but unsure if its worth it. This zone has two loops off of one Grundfos Pump cirulator. Are these radiators easily adaptable and installable into this type of system????

 

[NHFarmer]

Looks like my old cast iron rads are coming back in style. I can run my storage down to 130* and still have usable heat as long as the outside temp is not too low. The one down side to my non pressurized storage is with copper coils, the most heat I can transfer to the tank is about 175*. With the rads this still works fine for me

 

[rickh1001]

chuck,

what a great idea! I have been searching craigslist and other places trying to find more cast iron radiators. The Runthal radiator panels look great, but are very expensive. However, even if only for the short term, installing way more (inexpensive) fin tubing than normal sounds like a great, low cost way to use lower water temps. I wonder if the ratio of radiative to convective heat doesn't shift over towards the radiative at lower temps, as there is less air flow over the fins? It may not be in-floor radiant heating, but it is easy to install and inexpensive.