# OWB water temperature question?



## Canton (Dec 11, 2012)

New to the OWB thing. Wondering what temp (water) you guys run your OWB at. The more interesting question might be why? So far where I live (NE PA), it hasn't been very cold. I've been running my OWB at 150 without any noticable issues. Any reason to turn it up?

Jeff.


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## OH_Varmntr (Dec 11, 2012)

190* is where my Central Boiler runs. Few reasons...

1. 155* is the temp where my thermostatic valve begins to open to allow boiler water to circulate through the heat exchangers in my house. Anything below that and the water is diverted back to the boiler. 

2. Water-to-air heat exchangers used in forced air heating need higher water temps to be more efficient. This is because higher inlet water temps mean higher outlet air temps which is used to heat your home. 

3. Higher water temps entering my home means the water will stay hotter throughout the PEX lines. The water will still lose some heat through the PEX, but if it's hotter when it comes into my home, it's hotter as it reaches and circulates between the heat exchangers.

As far as reasons to turn it up, it all depends on your setup.


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## memory (Dec 11, 2012)

Our OWB is burning 24/7 since we have two water heaters hooked up to it. During the warmer months, we set it to 170, maybe 175. When it gets cold, we bump it up to 190 to 195. One reason we set it so high in the warmer months is because we own a dairy farm and you need really warm water to keep things clean.

I see no reason to turn yours up. Now if you were running out of hot water, then I would turn it up.


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## Stihl310 (Dec 11, 2012)

150, run that temp all winter and my house stays just fine.


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## jh35 (Dec 11, 2012)

The blower on my Heatmor comes on at 160 and goes off at 180.


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## upsnake (Dec 11, 2012)

There is the whole condensation angle from CB.. To the point that they have their special valve that will just send water back to the boiler if it below 160 ish


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## Canton (Dec 11, 2012)

upsnake said:


> There is the whole condensation angle from CB.. To the point that they have their special valve that will just send water back to the boiler if it below 160 ish




Can someone explain the condensation issue? I've heard this referenced before, but I'm not sure what they are referring to. Condensation where?


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## OH_Varmntr (Dec 11, 2012)

Inside the firebox. Supposedly the inside of the firebox starts to heavily condense water once the boiler water hits 145-150*. I have not seen it in my 6048, but a friend of mine with an older CB said he thought his waterjacket sprung a leak but when he called CB about it they said it was condensation. He fired it up again and once the water temps got higher it stopped. 

But I've only heard of it, never witnessed it myself.


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## memory (Dec 11, 2012)

Our 6048 did that when we fired it up for the first time. Luckily, the CB guy was still there just making sure nothing happened and said that is normal. It has not done it again since it rarely gets shut down.


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## Dusty Rhodes (Dec 11, 2012)

I think we need to know your make of OWB. They differ in how they operate and the controls that are in place varies from manufacturer to manufacturer. My Heatmore constantly circulates the water through my system wether it is calling for heat or not at the house thermostat. I do not know if that is typical for all Heatmore furnaces of if that is just the way my dealer set mine up. My boiler it is set to keep the water temperature at the boiler from 160 to 180F. In other words the blower comes on when the aquastat at the furnace registers the water has cooled to 160 degrees. With the air blower now on to the firebox, the wood comes to full combustion again and the temperature rises in the water jacket. When the water temperature reaches the 180 degree mark at the aquastat on the boiler the blower shuts off, the fire dies down and the cycle will repeat itself once the water gives up its heat. I would think that I would want higher than 150 degrees flowing to my house. I would not want higher than 180 at the furnace as I believe the pex is rated to 180 degrees. While I think it would take a higher temperature I do not push it. My aquastat is designed to be adjustable to a lower than 180 max temperature and it has a differential setting as well. If I set the max at 180 f and then set the differential to 15 degrees then my aquastat will operate from 165 to 180. If I set the high at 180 and the differential at 12 degrees then it will operate from 168 to 180. If there is a malfunction and the furnace after the blower shuts down and for some reason the firebox continues to draw enough air to continue combustion of the wood the water temp could continue to rise an approach or reach boiling. That would be a major problem me thinks. Get a manual for your furnace or contact a dealer and get some knowledge of how your boiler operates.


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## OH_Varmntr (Dec 11, 2012)

My CB operates in a similar manner. It also circulates water through the system constantly regardless of heat requirements inside the home unless the water is under 150ish degrees. Lower than that it circulates only from the boiler to the basement where the thermostat is then back to the boiler. I think I read in the instructions that this is because if the water temp is too low, it can lead to more deposits in the circulation system inside the house.

The CB digital controller has a 10 degree swing. Setpoint adjustable from 180-195*, controller opens damper door in the loading door once water temp drops 10* below the setpoint, closes damper door once water temp reaches setpoint.

For the water temp setpoint, like said above it all depends on how you are using the water to conduct the heat into the house. 

Depending on the manufacture the ratings vary. My Sharkbite PEX is rated for 200*F at 80PSI. CB circulating systems are designed to be non-pressurized.


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## cre10 (Dec 11, 2012)

I would think there would be a lot of heat loss my continuously running the pump unless you have an interior storage tank or buffer tank, but even then continuous flow through the ground would have heat loss.


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## MNJake (Dec 12, 2012)

I'm running my Crown Royal 7400 at 180-190 now. I had it in the 145-155 range this summer for the two hot water heaters in my house, but had a lot of creosote problems by the end of the summer. Now that I've been running consistently hotter for the last couple weeks, I'm finally getting the creosote to burn off and it just seems to run better when I'm running it hotter.


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## AIM (Dec 12, 2012)

I start the burning season at 120 and go up to 160 as the outside cools down. My house could be adequately heated at 140 but 160 gets my shop through the coldest of temps.

With my homemade OWB there is a direct relationship between water temp and wood consumption. If I try to get 170-190 it eats wood like CRAZY.


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## Kemper (Dec 12, 2012)

*water temp*

I have mine set at 140 and it will heat the house with ease, I know my neighbor runs his at 180 and I'm not sure why?

I know his is 100 gallon capacity and mine is 250 so I guess i have more as far as volume is concerned.

It seems to me that at 180 it would just eat more wood, mine is on at 125 and off at 140.


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## Boydz (Dec 12, 2012)

Borrowed from another thread - Seems to make sense to me why CB and many others are doing this now to avoid early failures within the fireboxes.

If you run your stove at 150-160 and you pull off 20-30 degrees at times, your return water comes back to cold and it really impacts the life of the boiler, because, moisture from burning wood will gather on steel cooler than 140. If u have a spot on your stove where the return water is cooling the steel down to below 140, moisture will develop there, and run down into the ashes

Its not recommended for anyone to run less than 175

It's scientific fact that moisture will gather on steel that's cooler than 136 degrees, some links from the candaian govt I beleive about to never slow your boiler to see temps that low..

So if you have return water coming back at 110-120 or whatever where that water encounters the firebox it makes a cool spot where moisture can gather and thus corrosion can occur over the long haul.

Central and Empyre aren't making folks install boiler protection because they want to, it's because it's very important, they don't want to have to add cost to there products but by doing so, there protecting the boiler from future claims and replacments.


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## Canton (Dec 12, 2012)

Boydz said:


> Borrowed from another thread - Seems to make sense to me why CB and many others are doing this now to avoid early failures within the fireboxes.
> 
> If you run your stove at 150-160 and you pull off 20-30 degrees at times, your return water comes back to cold and it really impacts the life of the boiler, because, moisture from burning wood will gather on steel cooler than 140. If u have a spot on your stove where the return water is cooling the steel down to below 140, moisture will develop there, and run down into the ashes
> 
> ...



This is actually the statement that I heard before, and I found it in this article - https://greenwood.zendesk.com/attachments/token/swhhiibf6bhz8uj/?name=Condensation.pdf. It's still confusing to me. Water is going to condense at whatever the dew point is - could be 1 degree below its boiling point. Creosote is going to condense at temps below 250. I have read that below 150 it is more likely that cresote will form a sticky tar like substance. Is this maybe what they are referring to?


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## Stihl310 (Dec 13, 2012)

After reading this I may try bumping mine up slightly. The problem I find in warmer temps is my house is so well insulated that the furnace blower will barely run all day and the hot coals just set there and heat up a bunch of water that is not having the heat drawn off. I've seen some pretty high temps in the evenings when I get home after a warm day. That being said, I clean my firebox out each spring and oil it, I've not seen a single sign of corrosion as of yet.

A guy I work w built his own as well and had premature failure, he's not certain whether it was bad steel or the temps he was running. He said when he was forming the metal something just didn't seem right about the structure of the steel. Who knows though. 

I've yet to notice any condensation in my box, and I feel as though I watch it pretty closely.


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## artbaldoni (Dec 13, 2012)

Isn't there a correlation between dissolved oxygen and water temperatures? Lower temps mean more dissolved oxygen...which in turn means more corrosion.


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## Guswhit (Dec 14, 2012)

Without knowing what type of burner you have and how your system is plumbed, the only thing I can do is tell you what I run mine at. I have a C.B. 5036 and run my set point at 170 until mid January when the coldest part of the year comes and then I bump it up to 180, unless we are in a mild winter. I would like to point out that if your system is not plumbed correctly it can cause alot of problems, for instance, I have a (stubborn) friend who has the exact same stove as myself and he had someone hook it up on the cheap. Now his house is smaller than mine by around 300 sq. ft. His home is an older brick 1 1/2 that has been remodeled and insulated. When it came time for updating the furnace and air system, he put 2 small units in the house, one in the basement for the downstairs and one in the attic because the heating guy told him it would be less expensive. Getting back to my point, when they hooked up his C.B. they ran one loop into the house and it goes through the downstairs furnace, the water heater and the upstairs furnce and on the return line he is usually losing somewhere between 26-30 degrees. Now that may not sound like a lot but on a system that holds less than 300 gals that you are turning over 26-30 degrees temperature on 20-25 gal a minute that turns into quite the btu usage. He burns double the wood I do and I can not make him understand the problem. Last year I offered to rehook his loop from the garage to one of the furnaces for no charge until he could see the differance in his wood consumption and he turned me down, so I just let him keep whining. Bottom line is you are going to have to take the MFg's suggested parameters and then see what produces the best results for you.


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## Canton (Dec 14, 2012)

Guswhit said:


> Without knowing what type of burner you have and how your system is plumbed, the only thing I can do is tell you what I run mine at. I have a C.B. 5036 and run my set point at 170 until mid January when the coldest part of the year comes and then I bump it up to 180, unless we are in a mild winter. I would like to point out that if your system is not plumbed correctly it can cause alot of problems, for instance, I have a (stubborn) friend who has the exact same stove as myself and he had someone hook it up on the cheap. Now his house is smaller than mine by around 300 sq. ft. His home is an older brick 1 1/2 that has been remodeled and insulated. When it came time for updating the furnace and air system, he put 2 small units in the house, one in the basement for the downstairs and one in the attic because the heating guy told him it would be less expensive. Getting back to my point, when they hooked up his C.B. they ran one loop into the house and it goes through the downstairs furnace, the water heater and the upstairs furnce and on the return line he is usually losing somewhere between 26-30 degrees. Now that may not sound like a lot but on a system that holds less than 300 gals that you are turning over 26-30 degrees temperature on 20-25 gal a minute that turns into quite the btu usage. He burns double the wood I do and I can not make him understand the problem. Last year I offered to rehook his loop from the garage to one of the furnaces for no charge until he could see the differance in his wood consumption and he turned me down, so I just let him keep whining. Bottom line is you are going to have to take the MFg's suggested parameters and then see what produces the best results for you.



Yes, you are correct. I should have included my setup in this. Currenlty I'm running a shaver 250 (230 gallons) with one circulator pump running 24/7. It runs into the house through a 3 port manifold, through the water to air heatexchanger in my furnace plenum and back out to the stove. Also off the manifold is a seperate pump that runs to a small (22K BTU) water to air htxch with fan setup to heat my basement. With my OWB pump, I'm getting around 10-12 GPM at the furnace and, best I can tell with the crappy gauges I have, I lose about 6 degrees when the fan in the plenum runs. This seems a little low to me, but my incoming temp is fairly low. I can't notice much of a loss with the small basement heater. My boiler is running at 150 right now with a 5 degree differential on the t-stat. I can't see any difference in temp in the line set - less than a degree, possibly 1 degree.

I can't believe your friend is pushing 20-25 gpm through his system. That must either be one hell of a pump or an awful big line set. I'm no expert on this, but I think that's like 20 psi through 1" copper - very impressive.

Back to my original question - any reason to run higher temps in the boiler other than the fact that your delta over the heat exchanger should be greater resulting im more heat output? I've seen the condensation issue stated and I think it has some merit, but I'm not sure I'm a believer yet.


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## darren_nh (Dec 22, 2012)

I may have missed it but if your system is hot water and not air, keep in mind that the baseboard heating lenths and zones in your house are sized for 180 degree water. If my water was at 150, the zone pumps in the basement would be running a lot more than at 175 keeping the house at the thermometer setting.

I have a hot water system with oil backup. I don't think my OWB would go down to 150.


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## russhd1997 (Dec 22, 2012)

darren_nh said:


> I may have missed it but if your system is hot water and not air, keep in mind that the baseboard heating lenths and zones in your house are sized for 180 degree water. If my water was at 150, the zone pumps in the basement would be running a lot more than at 175 keeping the house at the thermometer setting.
> 
> I have a hot water system with oil backup. I don't think my OWB would go down to 150.



I have a similar set up in both of the houses that I heat with my OWB. I have a Central Classic 6048. I leave mine at the default setting of 185 degrees year round. It can be adjusted up to 195 but I don't know what the lower limit is. Our hot water is heated by the OWB too and I don't like the "cold shower" complaints.


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## Canton (Dec 22, 2012)

darren_nh said:


> I may have missed it but if your system is hot water and not air, keep in mind that the baseboard heating lenths and zones in your house are sized for 180 degree water. If my water was at 150, the zone pumps in the basement would be running a lot more than at 175 keeping the house at the thermometer setting.
> 
> I have a hot water system with oil backup. I don't think my OWB would go down to 150.




I'm not sure where this thread went south, but my only question was whether or not there was any factual reason to keep your water temperature above 140. I have no problems with my system. I'm not trying to solve any issues. I'm only wondering if there is any advantage to increase the water temp in my OWB. My apologies if this was unclear.


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