Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Plumbing => Topic started by: rsv101 on October 16, 2014, 09:05:13 AM
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Any ideas would be great. I have a Johnson outdoor wood burner. All pipe coming from stove to house is new and insulated well in last 2 years. I have a 50 plate flat plate heat exchanger that was put in at the same time. I am getting great heat to the house. It is pumped to the house with a bell and gossett pl-36 pump. On the house side I have a viessmann gas boiler and viessmann 53 gallon water storage tank. I dont seem to have good heat on house side. I have baseboard hot water, it is all on one zone and is approx 2000 square foot on the zone with 15 baseboards. Even when I am not calling for heat I cannot produce enough hot water from the wood burner to recover my domestic hot water even though the hot water coming into the house is 160. It will take hours for the wood stove to recover the domestic hot water tank. The domestic hot water zone and baseboard hot water zone are both on seperate zone pumps and each pump is a taco 007-F5. My baseboards never truly get hot even after running for hours. I am kind of thinking flow is not enough and i am wondering if a bigger pumps would help and what kind? This system was in the house when i moved there and i have been trying to improve it. Any ideas or suggestions would be much appreciated.
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Sounds to me that either your circ on the gas boiler has quit or it is airlocked
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The water does not circulate on the house side until the system is calling for heat or domestic hot water. Both domestic hot water and baseboard taco 007-f5 pumps are new. On the house side there is good pressure in the system and air has been bled.
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I would say that they are not plumbed properly or you have 2 bad flow checks and that is highly unlikely, could you draw us a picture of how it's plumbed?
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Thank you for your input, please see attachment for diagram of layout.
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Ok I'm not seeing anything stopping the circs from pulling water through the gas boiler instead of the plate exchanger!
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I have the ability to shut the boiler off so it does not fire and the water just can then move through it. Which i have shut it down but it just takes forever for the dhw water to recover.
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On the house side of the flat plate exchanger when either pump is running the pipes are not very warm. You can grab any pump and hold it no problem
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Clogged or airlocked plate exchanger.
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i did isolate the short loop of the exchanger on the house side , about 4 feet on both hot and cold and drain and refill the short loop. Water drained clean. I did that twice.
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That will work but there is a better way, if you give me the evening I'll post a drawing of what I would do because your gas boiler is a cold start unit and should not need to be heated!
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I have attached some real photos of my system.
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I truly hate to say it but whomever put that together should try again because it ain't right, I'll be home in about an hour and try to draw something up for you! I think your issue is that the water from your zones is going through the gas boiler and not the plate exchanger, let me guess if you are burning gas all works fine right?
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OK the wife has had me doing THE honey dew list, look at your original drawing, as I see it the plate exchanger has more resistance than the boiler loop, really look at the piping and determine if the circs might be pulling water through the gas boiler instead of the plate exchanger, remember , water will always take the path of least resistance, can you close a ball valve on the gas boiler loop to stop the flow there? if you can and then the system works OK then it needs to be re plumbed, I suspect that the water on your loops is simply flowing through the gas boiler and not the heat exchanger, there are several ways to fix it!
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Ok my thought is to plumb the hot line from the flat plate heat exchanger into the return line of the gas boiler and plumb the return cold line from the baseboard and domestic water into the cold of the flat plate exchanger. That way the water is hot going into the boiler and coming out hot. I am thinking that should help with proper flow and i can shut the gas off and just let the water flow through the boiler, then when summer comes isolate the plate exchanger and turn the gas on for domestic hot water.
Do you think the taco 007-f5 pumps are the proper pumps for the job?
At one point someone had a pump running 24-7 on the house side it is now gutted, would it be necessary to have water flowing on the house side if nothing is calling for heat?
Should the hot water coming from the wood stove be about the same temp as the water coming out of the hot side of the flat plate heat exchanger?
Thanks for the help again!
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What do you mean gutted? are you saying that there used to be a circ running constant, keeping the gas boiler hot, if so put the circ back on line and your issue is solved
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Where in your original drawing?
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I can't tell what it was doing from the picture, could you draw it into your first drawing and re post
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That would work but if you put the circ back in, it will also work and that will be a heck of a lot less work, look at your original drawing, your zone circs were pulling through the gas boiler and very little water was forced through your plate exchanger, that is what the abandoned circ was for!
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It should not ghost flow but if it does then lets work on the wiring then! lets get your heat going first!
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:post: :post: :post: beers to slim!! what a helper!!
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So is it working?
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I think you will find that it will !
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I gather that no news is good news!
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It did not seem to make a noticeable difference with the extra pump in place. Not sure what to do.
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OK , now after reviewing your original drawing and first post, I see your wood boiler water is entering the plate exchanger at 160 degrees,This is not hot enough to satisfy your heating demand, baseboard heat needs to have 180 degrees minimum to function properly. Please turn up the temp on the wood boiler to at least 180, next are you sure of the direction of flow in the plate exchanger as it is wrong in the drawing, all plate exchangers should be plumbed with counter current flow, this means if your wood boiler water is entering in the bottom of the plate exchanger then the oil boiler water should enter at the top, this will help with the transfer of heat! Is the wood boiler water being supplied to the heat exchanger from the top of the boiler or bottom, hottest water in the wood boiler will be at the top, if you are pulling from the bottom of your wood boiler, this would be an easy fix to simply reverse the circulator on the wood boiler, is the circ at the wood boiler or inside at the heat exchanger?
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The circ is inside at the heat exchanger. The hot line from outdoor wood boiler comes into bottom left of heat exchanger. The hot line on the oil boiler is on the top right side of the exchanger. My hot line on the back of the outdoor wood furnace is at the top. So it looks like my house side is backwards going in and out of the plate heat exchanger?
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When you say hot line on the oil boiler, follow it back to the boiler is it coming from the bottom or top and which way is the circ pumping?
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Reverse your circ on the oil boiler!
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Or are you suggesting I reverse only the wrap around circ pump and leave the other two alone?
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Sorry, I missed your last post for some reason, yes reverse the main circ and leave the zone circs alone!
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Ok i will give that a try. I have attached a drawing on how it will flow with the pump reversed. Does the drawing look correct and how it should operate? It doesn't seem like the return flow from the dhw and baseboard zone will be re-heated by the flat plate heat exchanger because it will just flow into the return of gas boiler. I dont know how else you could make it work though. Maybe this way will work just fine.
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Yes that works,do you see how the check valves on the heat loops will force circulation through the reurn on the gas boiler?
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Thanks Slim. Everything appears to be working great now.
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Awesome, Glad we could help! :thumbup: