I just read that with baseboard heat, any stored heat has to remain at 150. Is this true, and is it not worth the effort to install storage?
Storage with baseboard heat
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trehugr said:
Baseboards lose capacity quickly as the water temperature drops. I run mine on stored water down to 120 degrees, but I'm really not getting much out of them at that temperature. If you have plenty of baseboard length, you can get enough heat at lower water temps. At some point, though, the baseboards can't keep up with your heat loss to the outside.
Basically, baseboards require more storage than radiant to get the same amount of usable heat. I'm planning on adding a radiant zone for that reason.
trehugr said:
I'm a fan of storage. I just posted a graph on another thread showing my storage system at work, allowing me to skip building a fire yesterday. With baseboards, you need more storage, but it's still a good idea. More civilized, more efficient, and most important, better WAF.
You can run without as I did my first year, but I think most people consider storage to be worth the effort. Most who have done it are fairly hardcore DIY types, though.
AFAIK, pressure only helps if you're running really close to boiling. I run at 15-20psi, and never intentionally above 190 degrees.
Nofossil, Trehugr,
Good question, then what is your feeling on an air exchanger. Would you say that if you were to rate these, would you order them:
3. Air Exchanger
2. Baseboard
1. Radiant
#1 being easiest on btu's and stretching out a charged storage bank?
Good question, then what is your feeling on an air exchanger. Would you say that if you were to rate these, would you order them:
3. Air Exchanger
2. Baseboard
1. Radiant
#1 being easiest on btu's and stretching out a charged storage bank?
barnartist said:
I would rate them exactly that way, though I would have put #1 at the top of the list rather than the other way around. I think they're all equally efficient - none of them wastes BTUs to the outside, but there's a lot of advantage in getting usable heat from water that's at lower temps.
Everyone I have asked have told me that you have to maintain high heat 135 degree F. and above too support water to air plenum heating. In our previous home we heated the house using a ground source heat pump with an air plenum. The air temperature coming directly off the plenum never was more than 90 degrees F. and the house was always warm and comfortable even in the coldest weather. How come?
Don L said:
I'm venturing outside my actual experience here, but that's never stopped me....
I suspect that liquid-to-air heat exchangers have a higher delta between the liquid and the air than you would have with liquid-to-liquid. Perhaps 135 degree water is necessary to get 90 degree air. The working fluid in your heat pump might well be 135 or so in order to get the 90 degree air. In any event, the net result is that there is less usable heat in a storage tank if you're using a water-to-air heat exchanger to extract it.
Now someone is going to point out that baseboards are in fact water-to-air heat exchangers, and that their uncle Louie had a heat exchanger where the output temperature exceeded the input temperature, and this will spiral off into the weeds. In the meantime, I hope this helps.
The figure I recall from Dave at cozyheat to run thru the exchanger was 130 degrees but I assume there are some exceptions.
It was always my understanding that if you use some sort of forced hot air system you actually can get to lower temps. You may not be getting the same BTU/hr but you do get usable heat from the unit. I find that with my baseboard once I get down to below 160 it seems useless because it won't convect or circulate well.
Steve
Steve
Im was wandering whether to switch to radiant or baseboard. I do remember a chart showing something like 180=120k...170=100k....160=80k
Something like that.
I dont like the fact of running a big electric fan LONGER though to get it warmer.
Something like that.
I dont like the fact of running a big electric fan LONGER though to get it warmer.
The figure of 130 was with a pump circulating the water thru an exchanger in a forced air furnace.
This is something I am still working on, and not at a stage where I think it is ready for use. So if you mess up you WAF by trying this not my fault
But..
The most efficient way that I have found to sqeeze out the heat so far has been with small heat pump. Of course I didn't buy one
but made one out of a 8000 BTU window AC.
I tried not to reinivent the wheel. it seemed to me that you either had to use an in floor radiant run
Or, use the same principes we use in AC. -- a heat pump
I choose AC, but I learned alot about how to blow up AC units too. So like I said watch your WAF. I used all old systems for this. And, I tried to "overmaximize" my gains
I still think I can do better, but I am certain I can work with water down to 70 F, I just don't think I can use a small circ if I do that.
All my problems were related to water being below 50F. The type of compressor this AC unit is old and doens't like cold on the cold side of the loop.
But..
The most efficient way that I have found to sqeeze out the heat so far has been with small heat pump. Of course I didn't buy one
but made one out of a 8000 BTU window AC.
I tried not to reinivent the wheel. it seemed to me that you either had to use an in floor radiant run
Or, use the same principes we use in AC. -- a heat pump
I choose AC, but I learned alot about how to blow up AC units too. So like I said watch your WAF. I used all old systems for this. And, I tried to "overmaximize" my gains
I still think I can do better, but I am certain I can work with water down to 70 F, I just don't think I can use a small circ if I do that.
All my problems were related to water being below 50F. The type of compressor this AC unit is old and doens't like cold on the cold side of the loop.
Well, once again, a plethora of ideas and suggestions. Thank you all again. I really want to start working on storage because I can do the work in the basement during the winter. My next big questions are what materials to use. I have a 6L X 4D X 6H space to put some sort of tank. That gives me a little over 1000 gallons assuming those are inside dimensions. Steel is about a dollar a pound right now. I don't mind welding, however, are there plastic alternatives ? I have seen some online but I'm not sure they are for heat storage. Obviously, steel offers flexibility in construction ( fittings, size of tank ect.) Whatever it takes to do the job that won't look like something a mad scientist created. ( Im sort of particular that way. ) I plan on using a Boilermate for DHW. Do I need to know what brand of wood boiler I will use before I install a tank ?
As far as I know, there's nothing about a storage tank that would affect your boiler choice or vice versa.
I would rate in the order.
1. Radiant (lowest temp required)
2. Heat Exchanger (2nd lowest temp required)
3. Hydronic Baseboard (highest heat required)
Usually temps of around 120F are considered ideal for radiant (duh, we all know that)
On all air handlers that I've installed heat exchangers on the aquastat on the return side of the hx was set at 140F to turn on fan and seems to be ideal for that.
When I first set up my heating system, my high limit was set @ 160F due to the radiant polybutylene tubing, I gradually bumped the high limit to 180F since my baseboards weren't keeping the house warm in colder temps.
1. Radiant (lowest temp required)
2. Heat Exchanger (2nd lowest temp required)
3. Hydronic Baseboard (highest heat required)
Usually temps of around 120F are considered ideal for radiant (duh, we all know that)
On all air handlers that I've installed heat exchangers on the aquastat on the return side of the hx was set at 140F to turn on fan and seems to be ideal for that.
When I first set up my heating system, my high limit was set @ 160F due to the radiant polybutylene tubing, I gradually bumped the high limit to 180F since my baseboards weren't keeping the house warm in colder temps.
I like cast iron radiators, which I believe would fall between infloor radiant and finned tube baseboard for efficient use of water temps. But you can't warm your butt on infloor radiant (other than parking it on the floor) or baseboards.....
Just a note on my experience with a water to air hx unit heater (Modine) in my shop which is fed from storage and alternatively on a direct bypass from the boiler.
I get usable heat from the hx with water feed temp as low as 100. If shop air temp is 60, a hour or so with water from storage at 100-110 will bring the shop up to 70. Poorly insulated shop; 20 x 40 x 10.
I get usable heat from the hx with water feed temp as low as 100. If shop air temp is 60, a hour or so with water from storage at 100-110 will bring the shop up to 70. Poorly insulated shop; 20 x 40 x 10.
jebatty said:
I was under the same impression when deciding to use a water to air hx, I believe that I can get my tank temp down low and still get some heat out of it. The set up I have with the water to air heat exchanger is only temporary until I have time and money to do the floor heat. When I am all done I will be able to heat the house with baseboard , or the forced hot air or the in floor heat, everything will be independant and if I want I can run them all at the same time.
Steve
Interesting Jebatty, How much storage do you have? I like my air EX OK, but it takes more juice (AC) too than baseboard or radiant. Also cooler water would make that fan have to run longer. But it seems like maybe its not worth the expence to put the radiant in. Just wondering how to easily keep the house warm when power ges out and using a small generator.
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