Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: Bluegrass Wood Burner on January 17, 2018, 06:56:49 AM
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I had posted on the electronics section of this forums about the monitoring I'm doing with my meat probe thermometer. The findings have shocked me. When my boiler is in its burn cycle I'm getting 178 degree water at my heat exchangers, we have a split system , so they are about 4 feet apart. When the cycle is over the temps slowly start falling even though the boiler temp is 180 the inlet temp goes all the way down to 152 and stays that way until the next cycle starts. As the boiler temp rises from about 168 up to 182 approx. in its cycle the inlet temp starts coming up slowly until it gets to within 5 or 6 degrees of the high cycle temp of 180 ish. I'm worried that my boiler has been in constant shock since I started using it 3 years ago. I had never monitored any of these temps before except for the main boiler temp. Seems my water is nit mixing right. Just out the new Grundfos 26-99 pump on this year and am using speed 2 of the three. I tried switching to low speed and high speed and nothing changed. My supply line is coming from the top back and the return comes in at the bottom right. I have 1 inch pex the one that had 2 red 2 blue inside the insulated drain pipe. Loop is 150 feet total from start to finish 18 inches deep. I'm hoping all the info I'm leaving here will help you guys come up with solutions to help me with this. There's no doubt I'm losing efficiency here and at times my domestic water doesn't have that extreme feeling like it does other times. I'm heating 5400 sq ft with a boiler designed for up to 8000. Please chime in with your opinions please.
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I am guessing the aquastat is up higher in the stove than the water outlet?
Sounds like it is stratifying and you are only really heating the water at the top of the tank.
That is why most MFGs changed to the supply at the bottom and the return at the top.
The water at the bottom of the boiler is probably colder than the return water coming from the house.
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150 return temps with 180 setpoint won't hurt a thing. It's more than common. If you are concerned however, and have an extra set of ports available in the back of the stove, you can pipe between those two ports and just pump supply water directly to the return port. This will mix the water within the boiler and reduce stratification greatly. Heatmaster G200 come standard with this shunt pump, and I've added a few of them to other stoves with similar issues and it fixed them right up
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I think they used the same design as a Taylor, which was the first furnace I owned. If you notice where the outlet for the pump is, about a third of the way down from the top, and the return about a third of the way up from the bottom and has a internal pipe to the front of the furnace.The natural line of flow will be from the bottom front to the supply port. Your aquastat is on the upper front which is a dead spot in the water circulation rout as well as the fact that most of the heat is generated in the top of the furnace. You can put a shunt pump on but I doubt it will have a dramatic effect. This is just the way these these stoves have always done. If it heats your house I wouldn't worry.
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Would it be wise to up the hi temp to 190 and low at 175 or so?
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Where are you getting these numbers exactly? I've read the original post 20 times now and can't make heads or tails of what you're trying to say. Your aquastat cuts out at 180 I think, right? So boiler temp is theoretically 180. Inlet to the exchangers is 178 at this point and pulls down to 152 when the air handler starts and stays there indefinitely until the boiler cycle begins again, at which point it starts warming up the temps at the exchanger supply to 175ish again? I'm ever so confused. If your supply temp at the boiler is 180 and your supply water at the exchanger is only 152, your underground is not carrying any heat. What is the return temp at the boiler, with both exchangers in the house calling? As long as that temp stays above 140 degrees, there is nothing to worry about
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Maybe I misunderstand, but I thought he was saying; The water at the heatex is 178 with the aquastat saying 180 and the aquastat still says 180 after the airhandler runs awhile but the supply temp of the water drops. But I just reread it and maybe I'm wrong. A little confusing.
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I have 2 heat exchangers, they are in each of the split system, one for each end of my house. These two plenhums are side by side in center of my house. My probes are zip tied to the inlet pipe going into the exchangers. So im monitoring water going into the exchangers. The reason I'm monitoring both is I was curious if one was getting more heat than the other. Turns out they are real close. Also wanted to see if both my probes were together with each other in accuracy. That's seems to be good also. Im puzzled as to why the drop in the house at the exchangers and not outside on the boiler gauge. When it goes from 178 to 152 on both exchangers and the water in the boiler stays right on 180, that's a little puzzling to me.
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The 178-152 is before it goes thru the exchangers. Nothing in the house triggers this. The cycle I'm talking about is the aquastat telling combustion fan temp is below 170 and we need more heat and it blows until back up to 180. The idle time of the combustion fan when its dropping in the house at the exchangers.
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I haven't checked the return temps yet. Im out of town on my job, but plan on checking those when I get back home. I suspect the return temp at the boiler will be in the 140ish range when it gets down to 152 on the supply side.
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Do you have a gauge on the supply line at the boiler or are you going by what the aquastat says? They are often located in places that are drastically different than what the actual temp is. Just last week I had a brand new Central 6048 reading 185 on the digital controller but only 173 on the supply line. I had piped in a primary/secondary type fashion with a second pump within the boiler cavity due to undersized underground to keep return temps up which didn't seem to change the difference, still 12 degrees. I looped the second set of ports together with hoses and a transfer pump and it evened right out. Some of em just need more mixing. I need a solid 175 minimum in that building so I turned it up to 200 with a 10 degree diff and it's fine now. Still 12 degrees off from what the controller reads, but my actually supply temps are 178 at the very bottom of the cycle and it doesn't boil within the unit.
In your case however, if you read 152 and 178 both in the same spot while the boiler only has a 10 degree diff, that doesn't work. Sounds like your aquatstat is goofy or your probes need calibrating. When you're seeing 152 at the exchangers, the boiler still reads 180??
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Sounds to me like ht mixing is poor in the boiler, you have extra ports, take another pump and pull from the bottom and return to the top. I built my waste oil boiler this way, all four pumps pull from the bottom and return to the top, maybe a degree difference between the Ranco which is in a thermowell at the top and the differential controller that has a probe on a lower supply pipe.
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I have a large round Gauge on the front of my boiler. Its on the right hand side about a foot down from top. The Aquastat is on opposite side on from about a foot down.
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Just some kind of cheap pump I assume would work for that? Any suggestions? Should it be on a timer or run all the time? Should I consider flipping my supply line and return line? Some of the advice I'm getting is if its heating your house just leave it alone. I do have times when its below zero at night when my heat is set on 73 on both ends and its 71 and duct blowers running solid. The difference in 178 and 152 no doubt would make a change in that. Thanks for all your advice.
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If you have the space for it, I would certainly try the shunt pump route. Any small, cheap circulator will help. Check Liquidus pumps on eBay, or I think Badger has their line (pretty sure they are the same thing with different labels) also for in the $65 range. I've used a few Liquidus and a local dealer has used exclusively Liquidus for several years now with no callbacks. They seem to be a high quality pump, plus they're 3 speed! I really think before you do anything though, you would benefit from getting a thermometer in the supply line at the boiler so you know exactly what's leaving the boiler and compare it to the other boiler thermometer
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Ok That's what I will do. I have plenty of room on back of my boiler. Ill check the return temps first. I'm in Detroit for next couple days. My wife and 25 year old son are taking turns manning the boiler while I'm gone.
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My return temps are good. I'm loosing around 8 degrees in my exchanger. The problems I have been having are indeed caused by poor mixing of water inside my boiler. I bought an Armstrong pump today and am gonna mount it to pump water from bottom to top. I'm wandering if I should let that pump be controlled by a aquastat that is monitoring water temps of the supply water. If supply water drops to a set temp let the pump kick in and run until temps come back up on supply side. This would save some electricity and save life of a second pump. What's your thoughts on this? Should I just let it run constantly? Also I'm thing of putting a filter on with this pump so water can be filtered while circulating.
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Personally I'd just let it run. Or just plug it in during cold weather when you need max temp supply water. Starting and stopping is harder on a pump than running. But it'll work either way. An aquastat would take several years to pay for in electricity savings.
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Good point yoder. Thanks
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I'd also let it run. Just low speed will be fine with no head. Any reason behind pumping return into supply though and not the other way around? I always do it the other way but only did it because that's how they want the load piped so figured it'd be the same with a shunt
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You know I have played with fans and ex changers and baseboards .. I have 152-160f degree water going to 60,000 btus exchanger
and about 1200 cfm on exchanger temp drop is 10-13 degrees at -21f keeps the house 76f 28x48 house what part am I missing that everyone need that water temp at 175 f I also have a 100,000 btu exchanger with a 500cfm fan heating shop 32x32 keeps what ever I set it pull as much as 19 degrees off water . my boiler does same thing top of tank can be from 165-185f when im burning slabs
you just -10 degrees and thats what lower output temp is in the house .. Baseboards you cant get a enough heat to them there for slow small room heating in my book . ( bedrooms bathrooms etc.) I think ductwork and fan air flow is a bigger deal . 150f air coming off a exchanger when water 175f will take your breath away stinking nasty hot . don't like fan noise get quiter fan there's nice ones out there . Last thought check your in ground lines and see how much heat there robing . :thumbup:
this my findings with heatmor 400 and 200 . and older houses 1976 and 1991
heat550
looked on the website ozark there pulling water out the of top of the tanks this give you wild temps . mixing would be totally different then my setup.
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On the left side of back of the boiler there are two ports not being used. I'm just gonna run a pipe from the bottom one up to the top one. Mount the pump between them. So I'll be bringing water from bottom of boiler and pushing up to the top. Hoping that will solve my issues.
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On the left side of back of the boiler there are two ports not being used. I'm just gonna run a pipe from the bottom one up to the top one. Mount the pump between them. So I'll be bringing water from bottom of boiler and pushing up to the top. Hoping that will solve my issues.
Why backwards? I feel like that may introduce colder water to your supply line to the house and not help a lot. Any reason not to go from supply to return like the MFG wants? Unless you swap the house loop to bottom supply also, I feel like they might fight each other
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One more question for you all. I have Grundfos 26-99 3 speed pump as my main pump. I bought this pump yesterday and it's a single speed. Which would you run where? Should I make the Armstrong my main pump and use the Grundfos as the shunt or the opposite. I got a really good deal on the Armstrong so I couldn't turn it down. Probably overkill either with pump as the shunt. Do any of you know anything about this new pump I bought. It's like new hardly used at all and I gave 25.00 for it. 250.00-300.00 on eBay
armstrong-s-25-bf-in-line-circulator-1-12-hp-pump-174031-013-cast-iron
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That one is really low head. I'd put it on the shunt side if you're deadset on using it and leave the Grundfos where it is. Personally I would've spent another $40 and bought a 15-58 sized for the application but that's just me. I'm going to ask one more time, what your reasoning is behind pumping from return to supply with the shunt?
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I'm not really sure why I was gonna go in that direction, I think just to be opposite of the other side. So you say pump from top down to the bottom like I'm doing on the right side ? I will take your advice on that. Thanks for doing the double take and getting my attention on that. I really had not intended to buy a pump the size of the Armstrong but I couldn't pass up that kinda deal. What about putting a water filter I this small loop. Put a pressure gauge on it and when the pressure starts rising I'll know it needs replacing My water seems to have a lot of sediment. Might prevent exchangers from clogging down the road.
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I'm not really sure why I was gonna go in that direction, I think just to be opposite of the other side. So you say pump from top down to the bottom like I'm doing on the right side ? I will take your advice on that. Thanks for doing the double take and getting my attention on that. I really had not intended to buy a pump the size of the Armstrong but I couldn't pass up that kinda deal. What about putting a water filter I this small loop. Put a pressure gauge on it and when the pressure starts rising I'll know it needs replacing My water seems to have a lot of sediment. Might prevent exchangers from clogging down the road.
Triple take, actually lol. I may be out in left field here, but I feel like bringing constant cold water from the bottom and dumping it in the top near the supply to the house is going to cool your outgoing supply water to the house. Just seems to me the flow should be in the same direction in each set of ports. As far as the filter, are you thinking like a whole-house type filter with the clear housing so you can keep an eye on it? Otherwise a regular old $20 cast iron y-strainer with a ball valve on the outlet works well also. No pressure gauge needed, you can just open the valve once in awhile to blow down the crap caught in the screen without having to change anything else, only takes a few seconds and they catch a lot more than one might expect them to. The canister style seems to be the way to go but I don't know if I'd want that in the boiler to be changing filters when it's below zero. Most put them in the house loop somewhere
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I believe your goal is to equalize the temperature in your boiler, correct? Just try it one way or the other and see if it works.
Also, have you measured your supply water temp as it leaves the boiler toward the house, and then compared it with what you have at your heat exchanger? Such as using an infared heat temp gun? Meaning, are you sure you are not losing a bunch of heat to the ground?
Let us know what you find.
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When the boiler cycles with combustion fan on and begins to really blaze the whole unit vibrates a little and I feel this vibration mixes the water a bit and that's when the temp goes up on the exchangers inlets at my air handler. When its sitting their in idle very quiet and calm with very little coming out the stack that's when the temps start dropping inside at the exchanger inlets. I have 178 temps on supply side when its right, then that drops to 150 when I still have 180 at the boiler. There's no way I'm getting the maximum efficiency out of my boiler when the water is not mixing and my return water is going back out without getting heated back up. I'm losing around 18-22 degrees in my loop when the blowers in my air handlers are running. I have two exchangers side by side. When the blowers are not running I'm losing about 4-6 degrees from one end of exchangers to the other. I believe all those numbers are pretty good. However when I'm trying to heat my house with the 150-155 inlet temps and 130-135 return temps its laboring a bit. At times when its in 0-5 degree range outside my temp on my thermostat my be set at 173, but the actual temp in house is 171. This has happened quite a bit this year. I'm heating 5400 sq. ft. of well insulated with good windows. I feel the only way my boiler will give me all it can with my setup is if my water temps are from 165-175 on supply side in air handler at exchanger, and 145-165 return temp.
I have my Armstrong pump ready to install as a shunt. I know its much more pump than I need for this situation. Will the 30gpm be Ok for the mixing effect. Is the overkill gonna cause me any other problems. I'm just gonna put a galvanized pipe from bottom to top on the side of my boiler that's not being used at all and mount this pump at the top of that pipe. Therefore taking from one port and send to another. I feel this extra circulation will solve these inconsistencies.
Several have said if it heats your house just be satisfied. I just don't look at it that way. Its like using a chainsaw that doesn't cut straight. It will cut and eventually get the tree cut up. I cut wood with sharp straight chains and I want my boiler to be what's its supposed to be. My wood usage is up this year. It has been around 12 cords but this year more like 15-16. Its been cold, but some of it may be the mixing.
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DO NOT USE GALVANIZED PIPE in a hot water heating system, you will be disappointed. The galvanizing will flake off and eventually corrode to a point of pinholes and paper thin pipe walls. Use black pipe for anything requiring the rigidity. As for the overkill on the pump, there is no such thing as too much mixing. Depending on the design, you may find some turbulence inside but if you have isolation valves at the boiler, which you should, you can easily throttle the one on the pump discharge to slow flow down if it causes any issues.
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Thanks for advice on Black pipe. I assume the same one we use for propane and natural gas?
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Yes, a schedule 40 black pipe with malleable or cast iron fittings. I prefer malleable myself, both cheaper and easier to handle. The cast is typically only for steam and condensate
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[quote author=Bluegrass Wood Burner link=topic=9530.msg82168#msg82168 date=15
Several have said if it heats your house just be satisfied. I just don't look at it that way.
[/quote]
After this further discussion sounds like it's not, so I wouldn't be satisfied either.
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I got my Armstrong pump installed to circulate my boiler water. The pump is very quiet and it solved my temperature drops in the house at the exchanger. I'm very pleased at how consistent my supply temps are now coming in the house. Hopefully I'll notice a drop in wood usage. Thanks to everyone who helped me figure all this out.
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It will be interesting to hear if wood usage goes up, down or stays the same.
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I'll let you know. I'll probably use a little more electricity with the two pumps running constant. I really was bugged to look and see 150-155 temps going in to my heat exchanger on these 0 degree nights like we had couple weeks ago. Ever since I turned the pump on after I got it in my inlet temps have not dropped below 172. I'm only losing couple degree in my loop which makes me real happy. House is bound to have shorter heat cycles with that much more temp consistency.
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Here we had 0 for the high a few times.
Good circulation is key for heating on extremely cold days/nights. I have about a 16 degree drop when my heat kicks on.
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Glad to hear the results of the changes made to your system.
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Thats awesome it fixed the issue .. I was thinking on mine I might be getting luckyer then I thought . dumb luck having 3 loops mine must be super mixing it might be why Im getting by with lower boiler temps 7 GPM x3 21 GPM in tank . I never thought of it that way . Im having set point of 165f and everything stays nice and warm even at -21f . hot burning oak slabs might be a key point also . thanks for letting us know the out come . :thumbup:
Heat550
6600 sqft heating
175 gallons
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Mostly the ability to heat with lower water temps has a lot to do with heat exchanger sizing in the house and airflow (with forced air).
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Mostly the ability to heat with lower water temps has a lot to do with heat exchanger sizing in the house and airflow (with forced air).
Interesting In house 28x48 I have a 60,000 btus exchanger 1197 cfm fan mounted In a closet thats at the top of the valted ceiling pointed in to the living room
It gets nice and toasty in there keeps house 76f average in whole house . and in shop I have 100,000BTU air exchanger pointing straight up with a 500 cfm fan 32x32ft heats up to what ever I want 50-70f
there is zero duct back pressure on both of these . I will keep this Idea in mind when i put air exchangers in my other house . thanks for the info.
heat550
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Well it turns out the temps stayed more consistent however I felt like I used more wood and my electric bill was around 30-40.00 more running the pump. I'm wandering if I can switch supply and return lines on my main pump and fix the problem and do away with the extra pump.
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Did you use that big Armstrong pump for the recirculation pump? What's the amp rating? A small circ like a 15-58, NRF-22 would use way less electric and stir the furnace fine I would think.
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Yes I used the Armstrong. I may need to find me a smaller pump. I'm wandering if switch my supply and return would help?
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I would use an ecm pump for the recirc. Unless your power rate is really high, would only be $3-$5 per month to run.