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Author Topic: baseboard heat system with a wood boiler..  (Read 3571 times)

911c4dave

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baseboard heat system with a wood boiler..
« on: December 31, 2010, 12:09:25 AM »

Hello everyone, i am new to the site but not new to burning wood ;D
I have installed a few wood boiler heating systems in my past but only one of them was in a baseboard heat system all the others were central air. This is at my father-in-laws home so I was safe using him as the guini pig for my first install in a baseboard heat system. First off He has a home made wood boiler and it runs at 170*  the fan cycles once every 2-4 hours. I set the the system with 2 plate heat exchangers, a 20 for the hot water tank and a 50 plate with 1" nipples for the basebord boiler. The wood boiler is placed right next to the house where thier boiler room is so the 1" pex lines i used only travel 15' so there is pratically no heat wasted through the small distance.
The system has been up and running for a few months and produces a average of 73*-76* in the home even though the t-stat is set at 80*.  Now My question is what is holding the system back from acheiving the set 80* on the t-stat? (Not complaining that 73*-76* is'nt hot just curious why it don't reach 80*) And yes both pumps are working fine on the boiler system and the wood boiler.
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911c4dave

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Re: baseboard heat system with a wood boiler..
« Reply #1 on: December 31, 2010, 12:13:02 AM »

By the way it is a 1600 sq ft. ranch with a finnished basement, so right around 3000 sq ft...
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willieG

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Re: baseboard heat system with a wood boiler..
« Reply #2 on: December 31, 2010, 04:56:47 AM »

Dave, how many feet (in total) of baseboard heaters are in teh home? and are the pipes in them 3/4 or 1/2 inch and what size pipe feeds them from your plate exchanger?
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911c4dave

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Re: baseboard heat system with a wood boiler..
« Reply #3 on: January 01, 2011, 08:48:08 AM »

willie the piping is 3/4" in the basebords, the heat exchanger has a 1" nipple then from there it is a 1 1/4" which feeds the existing home boiler. As for as how many feet in his house?? I was told that the existing home boiler could've reached an 80*temperature in the house on the gas...
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911c4dave

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Re: baseboard heat system with a wood boiler..
« Reply #4 on: January 01, 2011, 08:56:10 AM »

I was thinking if there was a way i could tap directly in to the house boiler without the plate exchanger.. Only problem is that the wood boiler is a non pressurized unit.. like i said originally this is my 1st time ever dealing with any type of hydronic house boilers..
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MattyNH

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Re: baseboard heat system with a wood boiler..
« Reply #5 on: January 01, 2011, 03:30:37 PM »

You can hook it up directly..Just make sure the boiler isnt down hill from your house..If its down hill youll drain the pipes in your house.... I have a friend that had that prob..Only one prob too is youll be exposing all of your pipes to the atmosphere..
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willieG

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Re: baseboard heat system with a wood boiler..
« Reply #6 on: January 01, 2011, 03:49:50 PM »

your peoblem may be quite simple.. you say you were told that with the baseboards you nwo have that your gas boiler could get yout to 80 degrees. OK lets say that is true...also it is normal for a gas boiler to produce 180 degree water, you say your boiler is only at 170

at 180 degrees your baseboards are (supposed to) putting out 600 btu per foot of basebaord
at 170 degree water it will be much less. you either need to add more baseboard or up your boiler temps

that is one reason i would ask what temp is the water going back to your OWB after it exits the palte exchanger and also what temp is the water going to yoru baseboards after it leaves the exchanger.

your water temp going to the baseboards should be the same as the OWB. if not you need a bigger plate exchanger (within a degree or two)
If you are going to continue heating with lower than 180 degree water in your baseboards....you need more baseboards
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willieG

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Re: baseboard heat system with a wood boiler..
« Reply #7 on: January 01, 2011, 04:04:29 PM »

here are some numbers from the net

for single pipe aluminum fin baseboards:

160 degree water (likley what your low temp water is before OWB kicks in) 570 BTU per foot of baseboard
170"   "      "        "  your high temp of your OWB 650 BTU per foot of basebaord
180 "     "      "     "  your normal gas boiler feed water temps 740 BTU per foot of baseaord

so compared to your gas boiler you are looking at an average of about 140 BTU less per foot of basebaord and the only way to make that up is hotter water or more feet of baseboard
it is my belief that this difference in btu per foot of heater could very well be why you can not get your home any hotter than you have been able to

there could be other reasons but you seem to have ruled them out by saying that your boiler gets to temp and the fan shuts off (that means OWB can easily deliver the heat needed) this is why i would suggest finding out the temps of the water entering the baseboards and the temps of the water exiting the exchanger and returning to the OWB (this will give you your delta and can be helpful in pinpointing problems
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maine owb

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Re: baseboard heat system with a wood boiler..
« Reply #8 on: January 03, 2011, 08:31:33 AM »

you need o know first of all how much baseboard is in the house and can it put out enough btu's on the coldest day of the year and then can the heat exchanger match that heat output. More often than not there is not enough baseboard in the house for the coldest days of the year. for a standard baseboard (3/4") between 1 and 4 gallons per minute flow 1 lineal foot can put out about 480-510 btus per hour at 150 degrees, at 160 degrees it is between 570 and 600 btu's and at 170 degrees it is between 660 and 700 btu's per hour. If the boiler is at 170 degrees the water will be less by the time it gets to the baseboard in most cases between 10 and 15 degrees less. Add up how many feet of baseboard you have and what the btu's are and see if the heat exchanger can match that at the temp you are running it at. If the oil fired boiler can heat the house to 80 degrees than the wood side is not hot enough. Most houses are designed to be heated to 72 degrees on the coldest day of the year and not 80 unless the heat guy was told to do so when first building the house.
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