adding baseboard

chuck172

In Europe I understand that the maximum temperature legally allowed in hydronic heating systems is about 167*. They do this by using using mixing valves and low temp. heat emitters like panel radiators.

Fintube-baseboard hydronic systems here are designed to use 180* water with 20*delta T. Heating systems are designed around heat loss calculators which size the length of baseboards.

My question is would it be more efficient to install more fintube, enough to allow lets say 160* boiler water temps and lower the design temperature?

CMadatMe

Baseboard Ouput

Is based on a combination of  flowrate and water temp. Providing you do a heat loss of the home and break out the loss of each zone you can run what ever temp you want as long as the board is sized correctly. I posted about a job the other day, Fin tube board with mod-con. Temp outside was 27 degrees, the boiler temp 108 and a system supply water temp of 98 through the board and the house was 70 in all 5 zones.  Thursday night here is was 7 degrees. Boiler temp was 135 and system supply temp 128. It all comes down to design.  There is a de-rating chart that Meztek, the makers of SunTemp, Embassy and other boards gave me. It' will give you the factors to calculate the output of board all the way down to 100 degree water at a 1gpm flow rate. You then use the flow rate correction factors to get your output.



If you are deciding to try this. I would also use a high output board. It will give you much more flexability in water temps.

chuck172

fin tube temp

I looked up your post refering to lowering baseboard temps.



"This has my brain asking the question. If I can design/do this in a baseboard application properly controlled with a Mod/Con is it a bigger bang for the buck for the customer than installing a complete radiant system? Is the money/efficiency savings for radiant truly any better than what is being experienced here?"



I've been playing around with my slantfin hydronic explorer heat loss calculator. I can add sufficient amounts of fintube to get me "radiant like" temperature performance.

Will this really improve my overall efficiency?

CMadatMe

Rule of Thumb

The basic rule of thumb for savings. For every 3 degrees I can run my system under 180 degree water I can save 1 percent of fuel. If I design properly and my boiler supply water temp max is 140 degrees that is a 12% fuel savings if that was constant. Now think about how many heating days your at design. Maybe 5 if your lucky in my area. In the system in my previous post  I'm betting on an average water temp of 125 or so. That equates to almost a 20% savings. Plus I'm condensing the whole season so my efficiency rating stays alot closer to that 95% rating versus a boiler designed for 180 or so. At 180 your really only running at around 87 to 90 percent. It boils down to system efficiency. Everyone gets caught up in AFUE. I feel that system efficiency is more important. It's what you do with the energy produced by your fuel dollars that counts.

chuck172

In my case

In my particular case, I use a Tarm wood boiler with 500 gallons of storage. Five hundred gallons seems like a lot but it's really on the low side of what is more beneficial.

I'm trying to stretch this storage to utilize the heat for a longer period of time. I usually get the tank up to aprox. 195* max.

I'm thinking if I can lower the load temp. by increasing the amount of fintube per zone. I will increase the amount of time my storage lasts.

CMadatMe

You may want to consider

Using a modulating mixing valve that gives you outdoor reset. Viessmann makes a nice control for this and you could also add indoor feedback. You could do the same with Tekmar controls.  You could really finetune. Of course it all depends on budget. 

[Deleted User]

Adding and oversizing baseboard

We bought our house 5yrs ago, boiler in the 35 year old house was Weil Mclain gas boiler of 140K-btu’s , no zoning.   After the 1st year, performed a heat load calculation on 1900sqft 2-story house which is 48K-btu’s.  I installed a WM-Ultra 105 and an indirect water heater. I throttled the boiler down to 50K-btu’s, max water temp 140 deg at 18 deg oat, zoned the house, 2-zones, upstairs/downstairs.   Replaced the old baseboards with high output baseboards, and added a few extra sections!  The boiler runs steady at 18 deg oat and it keeps it a comfy 70 degs.  It almost feels like radiant floor heat when it runs at 18 deg oat, a wall of warmth.  Doing all the above I saw about a 35% drop in CCF of gas and the house feels a little warmer!





Mike

Bruce Marshall

Low temp baseboard

Take a look at this product. It will produce more btu/ft at 120 degrees than conventional baseboard will at 180 degrees. The condensing boiler will operate as it was designed to when connected to this system. Works for solar and geothermal applications too.

CMadatMe

Interesting

Thanks for the post. Interesting. I'd like to get my hands on a sample.