Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Plumbing => Topic started by: Scratch on February 02, 2009, 06:33:54 PM
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Gotta problem. Here is a quick sketch of my system...
(http://photos-d.ak.fbcdn.net/photos-ak-snc1/v2310/142/73/1090746934/n1090746934_30288691_9649.jpg)
My water comes in from the stove in the middle of the pic on 1" PEX
Goes through the green pump and "will" go through the domestic water heater. (for now it goes straight from the pump into that "Y" pipe.)
Then it splits and the left side goes into my home furnace water to air heat exchager. it's about 10 feet of 3/4" PEX.
On the right side, it travels through my house about 95 feet one way of 3/4" PEX to the other furnace which is a small furnace designed to heat a 16'X23' area on the other side of the garage. (one person hair salon).
It goes through the water to air heat exchager in that furnace, then travels back again about 95 feet of 3/4" PEX, and meets up with the other return line from the big furnace.
They both go into a manifold to warm 3 loops of radiant heat.
1. Basement floor,
2. 24'X24' garage floor,
3. 24'X24' floor under the garage
then it's back out to the OWB through 1" PEX.
Here's the problem. I just finalized my small furnace water to air heat exchager yesterday and it's not heating. When I turn the furnace fan off, the heat exchanger gets hot, and the in and out lines both get hot the entire length of the run. Hot enough that when I touch the brass fittings and valves, anywhere along the 95 foot run on either line, it burns my hand.
When I turn the furnace fan on, within 2 minutes, it cools down the return line a ton, and the vents blow cool air in just a couple of minutes.
I've tried shutting the valve to the main furnace and also 2 of the floor loops thinking that maybe the pump didn't have enough pressure but it's the same result. With the furnace fan on , it cools the heat exchanger so much that the water goes way down in temp and there's no heat from the vents.
I bought both exchangers at the same time from CB and the main furnace works great.
Any ideas...?
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What size pump do you have? Could it be possible that you're at the limits of the pump even without going through your first furnace? It kinda sounds to me like you just don't have enough volume of hot water running through your second heat exchanger. That sounds like a very complicated system that would possibly need a zone valve or multiple pumps/zones. I can't imagine you're running everything with a standard Taco 007, or even an 011.
If you go check out www.heatinghelp.com you can go to the wall and search for similar systems without the OWB and see what kind of flow they require.
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Thats alot pulling on one zone
Did you speed up the blower on the new furnace.
Can you shut off everything but the new furnace and see whats the temp does.
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i also dont see any mixing valve or zone valves on your system
i will venture a guess as to your problem....you 3/4 line to the home furnace is short...your 1/2 line to the shop is long the "friction head loss" on the small pipe is so great that the flow is likely way less than half of the short 3/4 line
your shop furnace is starved for more GPM
as long as your furnace pump can deliver the GPM needed if you had a larger pipe you could add a "booster pump" to the 1/2 inch line to increase GPM
if you added this pump and your furnace pump was not able to delive the GPM needed you may in fact starve the home furnace if both were running at the same time
i dont mean to be rude but your plumbing looks like it could be improved as OWB's go
most folks have two headers in the house a feed header and a return header...it takes more pipe but can come in a lot handier when needed to work on the system
you run seperate lines to each "appliance" from the feed header and seperate lines from each 'appliance" back to the return header..each and every line (both feed and return) are valved at the headers this way you can isolate any one "appliance" at any time to work on it if needed...also you can use the valves as "chokes" to adjust the GPM flow to each "appliance"
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I am running a standard Taco 007-F5 pump. But it worked great before I added the second excanger. Then to test out the small pump theory, I shut off the valves going to the first furnace and all but one floor loop, (the shortest) so the pump was pushing through the second exchanger, then through one floor loop and back to the OWB. It still cooled down.
I do have zone valves on the 3 floor zones hooked to seperate thermostats but I shut the valves to the 2 loops when I did that test.
I didn't do anything to the furnace blower, just switched the fan on and off.
I can't shut off everything but the furnace, as you can see in the picture, I have to leave one floor loop open to circulate back to the OWB.
I do have a mixing valve right before the floor valves, and I've playes with that. The small furnace still cools down the Xchanger.
Both lines to both furnaces are 3/4" PEX.
I'm up for either getting a stronger pump, or a "booster pump" or redoing my plumbing.
If anybody wants to attempt to sketch up a quick diagram now knowing what I have... I'd be real happy...
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I am running a standard Taco 007-F5 pump. But it worked great before I added the second excanger. Then to test out the small pump theory, I shut off the valves going to the first furnace and all but one floor loop, (the shortest) so the pump was pushing through the second exchanger, then through one floor loop and back to the OWB. It still cooled down.
I do have zone valves on the 3 floor zones hooked to seperate thermostats but I shut the valves to the 2 loops when I did that test.
I didn't do anything to the furnace blower, just switched the fan on and off.
I can't shut off everything but the furnace, as you can see in the picture, I have to leave one floor loop open to circulate back to the OWB.
I do have a mixing valve right before the floor valves, and I've playes with that. The small furnace still cools down the Xchanger.
Both lines to both furnaces are 3/4" PEX.
I'm up for either getting a stronger pump, or a "booster pump" or redoing my plumbing.
If anybody wants to attempt to sketch up a quick diagram now knowing what I have... I'd be real happy...
add a booster pump but I think the 3/4" line is the problem going that distance
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Can you slow down the blower o the new furnace
I messed around with my blower to see what worked best I can change from low ,med,high
on high it cools it way down I have mine on medium now and it works good if you can switch to low speed it might not cool it down and allow the pump to keep up
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I can try the blower speed easily enough, but you think 3/4" is too small for that distance?
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correct meif i am wrong (as i ahve been about your line sizes, i apologize) how does your return water get back to the furnace, it almost looks like from your diagram that the return water has to pass through your mixing valve to the radiant header?
if this is the case then you are resticting the flow rate of the return water?
i am almost sure i can't be seeing this right but i have to ask
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pardon my bad spelling in the last post but when i look at your drawing again it looks as though your mixing valve (if that is what is to the left of the top valve in your radiant drawing) may be hooked up wrong. it looks as though your return from your home furnaces must pass through this valve to get back to the OWB. if this is true this is where you are restricting your flow.
if what i am describing is true then your fix looks simple
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One thing I don't see mentioned is the elevation of the furnaces, plus the depth of the lines underground. Is any of this run into a basement and back up to ground level or above? The 007 ony has a head of just less than 11 feet, per the Taco spec. sheet, but even at 4 feet, the GPM is cut to about 12, from 23 at ground zero.
I am using a Taco 007 to transfer water to my house with no problems. The lines are 38" deep, and the HX is about ground level in the ductwork under my house. No problems.
3 weeks ago, I installed a furnace in my garage. I purchased a second 007 for the garage, and installed a HX/blower hanging from my ceiling. The total run to the garage is only about 15 feet total. I turned on the pump, and the HX was hot in a matter of seconds. I turned on the blower, and had heat for about 30 seconds. I tried this several times, but no change. The total height of the furnace in the garage, plus the depth of lines underground pushed the height to around 11 feet. I either had to buy a larger pump, or lower the furnace. I remounted the furnace under the stairway in the garage, and have had no problems since.
The Taco website has an easy to read chart on the GPM curve at all heights. These are calculated at no resistance. Now, add in other appliances, smaller lines, etc., Do you think the 007 is capable of keeping up?
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OK my two cents, don't know if it matters but I to have two air exchangers but I didn't split off the lines fearing the water would flow unevenly because of different run lengths so it took more line but I ran everything in series so there was no doubt the water went the right direction.
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Well,
Are you sure there is no blockage? ::)
Can you test your new heat exchanger to ensure there is no flow restriction? :bash:
Leaky :bag:
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The return from both furnaces, go into the mixing valve which is wide open, then into the rad heat manifolds. I went off from this drawing which shows the hot going into the water heater, then into the HX then into the manifold and out.
http://www.centralboiler.com/Tech/C190.pdf (http://www.centralboiler.com/Tech/C190.pdf)
I just realized now though that it shows a note where the hot water splits and goes directly out to the OWB "and" to the rad heat manifolds. Really? I would think that since the rad heat lines are 1/2" and the return to the OWB is 1", the hot water would want to skip right past the rad heat manifold.
As far as height goes, my pump is about 5 feet below the ground my OWB is sitting on. the HX's are about 2-3 feet at most above the pump but the 3/4" PEX that feeds both HX goes up to the ceiling which is about 4' above the pump.
I do remember blowing through the second HX before I hooked it up, but didn't notice any restriction... of course I was just using my mouth.
The reason I split the two lines was I figured that the longer run would cool down faster than the shorter run, so if I ran them in series, the water would be alot cooler going into the floor lines. This way there would be a mix of hot water and really hot water going into the floor lines.
But again... I shut everything else down remember. Here's what I have for loops, approximate lengths:
1 main furnace run, 3/4", 20 feet total
1 second furnace run, 3/4", 190 feet total
1 garage rad heat loop, 1/2", 560 feet total
1 under garage rad heat loop, 1/2" 560 feet total
1 basement bedrooms rad heat loop, 1/2", 400 feet total
And it's been working great on all but the second furnace. The main HX stays hot, the floor lines stay hot, no problems.
So then I shut the valves to the main furnace and 2 of the long floor loops so now, all it was going through was:
1 second furnace run, 3/4", 190 feet total
1 basement bedrooms rad heat loop, 1/2", 400 feet total
and the fan cooled it down right away.
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So if you shut other lines down and still not enough heat recovery, you need to increase volume of heated water go 1" lines which might require bigger pump. That's what I got going with no probelms and like I mention earlier in series or you might need a back flow preventer on the longer line . I've been monitoring my line temp and losing about 10-13 deg. when blower kicks on. if that helps any
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So you run your two HX's in series huh? Don't you get so much heat loss that by the time it gets to your floor lines, it's pretty cool?
Or do you not have any floor lines.
Does anybody here have 2 HX's and floor lines? If so can you draw up what you did.
Here's another thought...I could easily pull everything off the system but the 2nd HX. So it would run in from the OWB on 1" PEX, then reduce down to 3/4" PEX go through the smaller HX, then back, go back up to 1" PEX and out to the OWB.
That would shouldn't lose much temp with the furnace fan on right? I'm just trying to figure out a way to use all that 3/4" PEX I got ran through my basement now....
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Humor me i think that when you had only nuimber one furnace hooked up, when it was running the return water was cool enough to go right through your mixing valve and that let the house warm perfectly and when the house did not call for heat the mixing valve worked as it should and let the water only trickle through as needed but when you added the line to the second furnace you now have (when one furnace is not calling for heat) at leas one line at the mixing valve delivering water hot enough to shut the mixing valve and only let it trickle through
also when you said you shut all you could off to test the shop furnace you didnt say it you shut the first furnace off and you did say you shut part of your radiant heat off..again this caused the mixing valve to choke the system down
you need to take number one furnace off the mixing valve and go directly to the boiler return..then take number 2 furnace and tee it at the mixing valve with one line entering the mixing valve and one line to the boiler return..this way your return water goes full speed to your boiler and when the mixing valve calls for water it opens and let the water mix by adding a little hot and if the hot has to go in then some cold has to come out of the radiant lines...this cold will travel up the mixing valve and thus..mix with the hot and everything will work as it should and have NO effect on choking the two furnaces down
as long as the pump is of sufficeant size the problem is solved
Take the mixing valve out of the loop for testing purposes and see what happens
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just a note scratch...in the drawing you posted form CB if you look close you will see the mixing valve has nothing to do with the return water from the furnace to the boiler..as it should be
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Scratch- I don't have floor heat but would have plenty left to do so. The reason for in series you're pushing water not pressurized so when you wyed the line, the water split it's energy and because the first line is shorter it'll have more push when the two return lines meet back up and that might put back pressure on the second line slowing the flow more. I'm thinking if you shut everything else down and the 2nd still blowing cold air you probably need a bigger pump for faster recovery.
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Re did the plumbing layout today... I went from the OWB inside on 1" PEX to the pump, then to the water heater, then to 3/4" PEX and to the main HX, then to the second HX, and back to the OWB. Right before it goes back out to the OWB... it T's off to go to a second pump where it pulls the water through my floor lines manifold. Then that water T's back into the main return line back outside to the OWB.
So far it seems to work great. The fans from both furnaces does cool it down some but not much and not nearly as much as it did before. I think this solved the problem.
The only thing I think I would improve upon would be using 1" PEX for the furnace lines instead of 3/4". But I already had the 3/4" ran so I figured I'd try it anyways. Would it even help though... because both HX's are 3/4" so there would be restriction there anyways wouldn't there be?
As long as my house stays warm and I don't gotta pay for LP...
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scratch, i'm not entirely sure what you did but even if it is wrong and it is working...it is right
happy heads in the hair shop now!
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Here's my new layout. Obviously not all the valves are closed...
(http://photos-c.ak.fbcdn.net/photos-ak-sf2p/v648/142/73/1090746934/n1090746934_30309378_2736.jpg)
I forgot to draw the zone valves for the floor lines but they and the second pump are controlled by thermostats. Also there's a mixing valve right after the second pump there too.
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Here's my new layout. Obviously not all the valves are closed...
(http://photos-c.ak.fbcdn.net/photos-ak-sf2p/v648/142/73/1090746934/n1090746934_30309378_2736.jpg)
I forgot to draw the zone valves for the floor lines but they and the second pump are controlled by thermostats. Also there's a mixing valve right after the second pump there too.
scratch, i see you have added a bunch of valves that let you isolate your "appliances" from the system at will..good idea i think you should maybe include another set on the radiant heat, one on the inlet side of the pump and one on the return side of the mixing vavle..this will lwt you isolate the radiant system without shutting down the entire system should you need to replace the pump for your radiant heating or the mixing valve (if you can put the valve on the feed line so it also isolates your zone valve)