Outdoor Wood Furnace Info

Outdoor Furnaces - Manufacturers with NON EPA-Certified Models Only => Home Made => Topic started by: MarkP on December 10, 2021, 09:18:28 AM

Title: Correct pump and heat exchanger for house and garage
Post by: MarkP on December 10, 2021, 09:18:28 AM
I have some questions regarding my homebuilt boiler, and the best combination of pump/heat exchanger.   I built the stove about 4 years ago, and only built it for my garage, but decided to add the house to it this week.  Here's what I have:
180 gallon boiler with a 24"W X 28"H X 36" L firebox. 75 cfm draft fan on the door, and 6" stack out the top.
20X20 heat exchanger with Taco 009 in the garage 1000 sq. ft with 10' ceilings.... well insulated.
12X15 heat exchanger with Taco007 for the house 1680 sq ft built in 2004.. also well insulated.

Does this combination seem adequate?  I know the garage is working great, and it's only 15 feet from 009 pump on the back of the stove to the heat exchanger.  My question is more around the house.  Is 12X15 heat exchanger enough for a 1680 sq ft house, and is the Taco 007 enough to keep the hot water there?  I have a total of 100 feet of 1" pipe from the pump to the heat exchanger, with 25 feet of that in the crawlspace. Both pumps are approx. 48" above the ground, and both heat exchangers are at ground level.   Lines on each are insulated, and buried 30", inside a 6" pipe.  The pipe is covered in sand, and 4" hard foam insulation on top of that, then the dirt.   Also.... will a 180 gallon stove keep up with both.  Water temperature is set at 170 on the stove.

thanks!!

Mark

Title: Re: Correct pump and heat exchanger for house and garage
Post by: RSI on December 10, 2021, 09:29:17 PM
The pumps should be swapped opposite of what you have them. The 009 should be on the long run and the 007 on the short run.
Title: Re: Correct pump and heat exchanger for house and garage
Post by: MarkP on December 11, 2021, 09:13:31 AM
I was thinking that, but then I saw the GPM for each.  The 007 has 0-23 GPM and the 009 has 0-10 GPM.  I'm not sure how the head range affects each of those.  Common sense tells me that a 15 foot run would get the smaller pump.

thanks!!
Title: Re: Correct pump and heat exchanger for house and garage
Post by: shepherd boy on December 11, 2021, 04:46:52 PM
The head on a 007 is low, head = pressure, so you can have a lot of gpm if you don't have to have pressure to push it down a pipe. The 009 is probably pushing more gpm down the pipe than the 007, but 100 ft. is not a long way so if it is working let it go. if you need to replace a pump at some point I'd look for a pump with head a little stronger than the 007 and less gpm, split the difference between those two pumps, like the 008 although I like a different brand.
Title: Re: Correct pump and heat exchanger for house and garage
Post by: RSI on December 11, 2021, 10:29:04 PM
250' round trip is a lot for a 007. Might get 5 gpm if you are lucky. The 009 should get around 7 gpm on the same loop.
The short loop the 007 would probably do about 10 gpm and the 009 would do a little over 9gpm.
Title: Re: Correct pump and heat exchanger for house and garage
Post by: MarkP on December 12, 2021, 02:34:56 AM
Thanks for the input.   I understand it a little better now, and I kind of expected the relationship between GPM and head.  I have it all running now, and with 30 degrees outside, it's keeping up, but barely.  The air temperature at the registers is around 85-88. It should be higher than that...... possibly the 007 not quite keeping up?   I'll be swapping pumps today, and see how it does.  I have my garage turned down to 60 degrees at night, and the house is 71. I just checked the boiler, and it's on 171 degrees.  I'll find out how it goes with the pumps swapped, and I'll report back.  Thanks!!
Title: Re: Correct pump and heat exchanger for house and garage
Post by: shepherd boy on December 12, 2021, 02:09:35 PM
Sorry, misunderstood your pipe length. Thought you were saying total round trip 100'. Totally agree with RSI.
Title: Re: Correct pump and heat exchanger for house and garage
Post by: MarkP on December 12, 2021, 04:45:09 PM
Total round trip to the house and back is 200 feet exactly.  I've had the OWB off all day, and was using the furnace.  I just changed it to boiler, and the heat coming from the registers was 95-105 degrees, with the higher temperature being the registers, closest to the heat exchanger.  It brought the temperature up 2 degrees very quickly.  It seemed the longer it ran, the cooler the temperature got. Even by turning it off, it took quite a while for the heat exchanger to get hot again.  This makes me think as RSI stated, that the 007 isn't strong enough to keep the heat exchanger supplied with hot water.  Today was my family Christmas dinner, so I didn't get the chance to swap pumps yet.  I think the flanges are the same size, so it is a quick and easy swap.  I'll get it done tomorrow morning and report back. 

Mark
Title: Re: Correct pump and heat exchanger for house and garage
Post by: MarkP on December 14, 2021, 07:48:50 AM
Yesterday, I swapped the pumps on the boiler.  I put the 007 on the very short run (30 total feet) to the garage, and what I thought was a 009, turned out to be a 011, to the 200 foot run to the house.  As for the house, it has improved with the pump swap, but it's still not where I think it should be.  We had a 25 degree night, and it kept up through the night, but if I want to move it up a couple degrees, it has a hard time, and lengthy run time, reaching the new set point.  I kept it at 71 in the night, and this morning, I changed the set point to 73, and it struggled to get there.  Again.. much better than it was, but not quite what I expected.  Bottom line... I haven't fired the propane furnace up since I swapped pumps!!   :thumbup:

My thoughts are going to 2 things:

1)    The house heat exchanger is 12" X 15" and rated at 72,000 BTUs.  The one I had used about 5 years ago, with a different boiler, was 130,000 BTU,  Is the current heat exchanger adequate???

2)    I have a 2 stage ArcoAire furnace/AC, and the fan is set initially to the lowest speed.  Minimal air movement.  Once the furnace kicks into the 2nd stage, it goes to a high fan speed.  On low, you can't
       hear it run.  I need to check, but I think it has the capability to run at a medium speed on start up, instead of low, but it can't be controlled through the thermostat.  I would need to make that change
       on the PC board inside the furnace.  Possibly a higher fan speed initially would make a quicker increase in temperature??

Your thoughts......
 
Title: Re: Correct pump and heat exchanger for house and garage
Post by: shepherd boy on December 14, 2021, 05:36:03 PM
Definitely enough pump. What temp is the water coming to the house? Not boiler temp but actual water temp at the coil. Reverse water flow to air flow at coil? Yes, get the fan speed up but if it goes to high and stays on high should work.  gallons of water in stove means little, can the stove maintain 170 at the heat exchanger during a long pull.
Title: Re: Correct pump and heat exchanger for house and garage
Post by: MarkP on December 14, 2021, 06:31:52 PM
I'm not sure of the water temperature at the coil, but I'll check tomorrow.  What is meant by "reverse water flow to air flow at coil"??  I have the water going in the bottom of the coil.  I have a friend that is a CB dealer, and he told this is the preferred inlet.   I'll get the fan speed up to "medium" speed on the PC board.  Not sure if the stove can keep 170 at the coil for an extended period of time or not.  I checked it yesterday at the registers, and at 25 minutes, air temperature had dropped an average of 3 degrees at all the registers. 

Also.. the ductwork and all piping, including the heat exchanger are in an unheated crawlspace.  I have foam tubes on the 1" plastic, but the  copper of the heat exchanger is open to the crawlspace atmosphere.  May be a good idea to insulate that as well. Easily done.

I appreciate everyone's input.  I'll keep you posted! 
Title: Re: Correct pump and heat exchanger for house and garage
Post by: shepherd boy on December 14, 2021, 06:42:59 PM
If your air is flowing up you want your water flowing down.  In at top out at bottom.so your air hits the hottest water as it leaves the coil.
Title: Re: Correct pump and heat exchanger for house and garage
Post by: MarkP on December 15, 2021, 05:41:07 AM
The heat exchanger is mounted vertically, in the ductwork, and the ductwork is running horizontally across the bottom of the floor joists.  That shouldn't be an issue, EXCEPT.... I have a section of ductwork broke to accept the heat exchanger.  The bottom of the ductwork is expanded down to fit the heat exchanger into the ductwork.  It could possibly cause a disruption in the airflow where it goes down into the area that is extended.  I could see where the hottest area, the bottom, isn't getting the direct air flow like the top is.  Never gave that a thought.  Easy swap.  I'll give that a try tomorrow.  I appreciate the suggestion!! 
Title: Re: Correct pump and heat exchanger for house and garage
Post by: shepherd boy on December 15, 2021, 09:34:53 AM
Don't see where that would be a problem. water should go in the port furthest from the air handler and return from the port closet to the air handler. putting a 'v' in the duck is fine. Unless I'm not understanding you.
Title: Re: Correct pump and heat exchanger for house and garage
Post by: RSI on December 15, 2021, 04:15:22 PM
Is the supply pipe at the heat exchanger as hot as the boiler? If so, how much cooler is the return out of the heat exchanger?
Do you have the water flowing opposite of the airflow as mentioned by Shepherd Boy?
Do you hear and noise in the heat exchanger? If so, try closing a valve on the return line and open back up instantly. Usually that will purge trapped air. If you hear air gurgle out then repeat till there is no more air.
Title: Re: Correct pump and heat exchanger for house and garage
Post by: MarkP on December 16, 2021, 07:37:36 AM
I stopped at Harbor Freight Tools yesterday and bought a infrared thermometer.  I'm not sure how accurate they are, but they claim to be */- 1 degree.  I went under the house and reversed the lines on the heat exchanger.  Heat goes in the top, and out the bottom now, but that made it going in the port closest to the furnace fan.  I let it circulate about 5 minutes, and checked temperatures.  I have the boiler set on 180 degrees now, but using the infrared thermometer, the hottest part of the back of the boiler, pump, lines, etc, was 155 degrees.  I have an Emerson digital aquastat on the boiler, and I expected it to be fairly accurate.  Could it be 25 degrees less than water temperature, being exposed to outside air?  When I went under the house to check the temperate at the heat exchanger, it shows 98 degrees on any copper surface, and the pex tubing was indicating 130 degrees.  Maybe getting a reflection from the copper causing it to read wrong??  I'm more confused now than ever.  I'll try it again tonight with a Snap On thermometer.  The air temperature coming out of the registers in the house was 110 degrees, measured with a regular thermometer that uses a liquid inside a tube.  I'm not sure if they still use mercury or not, but anyways....  Assuming that the thermometer is "somewhat accurate", that is a huge drop from the boiler to the HE.  What can cause such a drop?  I have 6" -12" of fiberglass insulation around the boiler, so I'm sure it's getting little to no heat loss there.  We had a snow last week, and it didn't melt the snow off the top of the boiler.

When I ran the lines, I used coils of pex, and used foam sleeves on each, and all joints are taped.  Probably not the best way to insulate, but that's what I went with.  I already had a 6 inch pipe underground, as I had used this in the past with a different boiler.  I was able to slide the new pex inside the 6" pipe.  After I sold my last boiler, I kept the open ends of the 6" pipes covered.  If rain water had gotten inside the pipe underground, could this cause a large drop in temperature.  No evidence that it has water in it, but I'm grasping at straws now.   We are having above normal temperatures now, so it's not a good test of heating the home now, but it is to drop this weekend.

I've never had any issues with the last couple boilers I've had, and this one is testing me.   And people ask me why I drink....... :bash:
Title: Re: Correct pump and heat exchanger for house and garage
Post by: RSI on December 16, 2021, 10:24:40 PM
Those infrared thermometers never seem to work on pipes.
Can you hold your hand on the line at the heat exchanger? If you can keep your hand on it at all you probably are not near 180. Can you feel a big temperature difference between supply and return pipes?
Title: Re: Correct pump and heat exchanger for house and garage
Post by: MarkP on December 17, 2021, 09:15:18 AM
I've used several of the infrared thermometers, and while working as a diesel mechanic, the Snap On was the best I've used for detecting a weak cylinder on a truck engine.  It seemed to be pretty accurate.  I have no doubt that mine is a piece of crap.  As for holding my hand on the heat exchanger lines... I can't keep it there for more than a bump.  The pex doesn't seem to hold the heat like the copper does, but  that's understandable.  I can't feel a difference from supply to return, even on the pex line.  I use some dial type temperature gauges on a "craft" that I make here in WV, and I may add a "T" to the line, and screw one of those in.  With the 110 degree air temperature coming from the registers, even with the fan still set to low speed, I'm pretty satisfied that I have a high temperature at the exchanger, but I want to make sure that I don't have an excessive temperature drop.  Our temperature is to drop this weekend, so that will be a good test.  In the meantime, I'll try to get an accurate temperature reading from the exchanger.  I'm trying to knock out all the variables one at a time. 

Thanks again, and I'll keep you posted!!
Title: Re: Correct pump and heat exchanger for house and garage
Post by: RSI on December 17, 2021, 12:32:34 PM
If you can't feel a difference between the supply and return pipes with the blower running then it is an exchanger issue. Did you confirm that the water inlet is on the side of the heat exchanger that the our blows out of? (flow opposite directions)
If so then I would guess either it is partially air locked, you don't have enough air flow or it is just too small.
Title: Re: Correct pump and heat exchanger for house and garage
Post by: MarkP on January 30, 2022, 12:11:43 PM
Sorry I haven't checked in for a while.  I have some health issues, which includes 3 spine surgeries, and I've had a bit of a setback with the lumbar surgeries.  Procedures are scheduled for next month, and I haven't been able to get under the house and check much of anything, but with the recent snow we've had, I can see where the snow melts over the buried lines.  I can see a definite problem within 12 feet of the wood boiler.  The 6 inch snowfall we've had recently hasn't even covered the ground above the line, even with temperatures in the single digits..  That tells me I have a major heat loss in that area.  The stove can't keep up with heating the 1050 sq. ft. garage, and the 1680 sq. ft house at the same time.  I didn't have that issue when I was heating both about 4 years ago.  I'm guessing that the 6" pipe that I buried, that I run the water lines through, has water in it.  I had sold my last stove several years ago, and had tried to keep the pipe covered, in case I was ever to put new lines in with a new stove.  I think if the 6" pipe has water in it, it would create a heat loss/transfer that would melt the snow above it.  This is just theory, and my wife mentioned when she pulled the lines through, there was a little moisture on the lines.  That first 12 feet was buried about 12" deeper than the rest of the pipe, as I had to come up on the house end, to get over the footer.  This is all theory, but for me, it makes sense. 

Now...with my current health, and the first of February around the corner, I've decided that I can't make corrections at this time.  I'll just live with the heat loss to the house, and be glad I have heat in the shop.  Once good weather moves in, I'll decided what my options are to get the water out of the pipe, if that is the case.  Being that close to the boiler end, I may be able to use a shop vac and suck it out.  If not, I'll figure something else out.

As always.... I'm open to, and appreciate your suggestions.  Thanks for the help!!