OWB Water temps

[AIM]

+1 on this. You don't want your return coming back below 140° or the condensation will bring an early death to your owb. Just because you are running at hotter temp doesn't mean you'll burn more wood. The fire is only going to burn to bring temp back up to set point, to reheat water the 10-15° between differentials. Myself, I prefer 180° with a 165° low for a little safety net on the bottom in case it gets hit with a load right at the kick on point so the fire can get going in time.

I know my boiler doesn't go this route. Hotter water = more wood.

 

[sam-tip]

175 to 195. Heating 5000 sft plus. Only used 3 cord so far this season.

Sent from my SCH-R950 using Tapatalk

 

[Speed]

I don't know anything about a Mahoning first-hand, but chances are it has some return protection built-in? Somehow mixes some hot supply water into the cold return water just before the return water enters the bottom of the boiler?

If not, it's a poor design & you've been lucky. It's pretty well known that water below 140° entering into the bottom of a wood boiler will cause increased creosote condensation inside the boiler & lead to premature corrosion. Even my old inefficient indoor boiler I got 18 years ago had a recirc pump on it that kept the return-in warm by mixing via a bypass.

Thank you, NSMaple. I'm one of three to mention this so far. I'm not making this up on my own for my entertainment. I've talked to several dealers in this business and they all have said the same thing. Just passing along what I have learned to someone that asked a question.

Showrguy, If I remember correctly the exact return temp that condensation starts at is 136°. I'm not a scientist or a metallurgist, I don't know how or why. Just passing along what i have learned.

 

[John R]

+1 on this. You don't want your return coming back below 140° or the condensation will bring an early death to your owb. Just because you are running at hotter temp doesn't mean you'll burn more wood. The fire is only going to burn to bring temp back up to set point, to reheat water the 10-15° between differentials. Myself, I prefer 180° with a 165° low for a little safety net on the bottom in case it gets hit with a load right at the kick on point so the fire can get going in time.

Condensation where?

 

[Cbird14]

Condensation where?

I'm guessing inside the firebox

 

[NSMaple1]

Yes, in the firebox.

I think most all reputable manufacturers these days have some sort of return temp protection built-in. Or at least have an option for it that should be discussed on purchase.

 

[sam-tip]

Mine stops sending hot water to heat exchanger at 150. Full open at 175. It is just a auto thermostat in a chase. Opens when hot enough then water goes to heat exchanger. If cold it just bypasses the exchanger keeping the boiler water hot. The fire can go out and the boiler will stay warm for days.

The hotter the water the more heat to the house.

 

[John R]

Yes, in the firebox.

I think most all reputable manufacturers these days have some sort of return temp protection built-in. Or at least have an option for it that should be discussed on purchase.

Guess I don't understand condensation in the fire box with hot coals in there smolderingly all the time.
Not saying your wrong, just don't get it.

 

[showrguy]

my owb holds 352 gal and has a circulator pump that runs 24/7 so the return water is mixiing as soon as it enters the unit...
i think this condensation discussion might be more of a sales pitch than anything else ??

 

[NSMaple1]

Who's selling something? And what?

Firebox condensation is real, under the right (wrong) conditions. Those conditions may or may not apply to whoever & wherever. Manufacturers aren't building return temp protection in just for something to do. There's also a reason for some people having their OWBs become sieves after a few short years - they started out watertight, something ate them away. Friend of mine had to junk his WoodDoctor after 5 years, sure there's lots more stories like that. Lots of info on it on the net - believe it or not, doesn't make much difference to me.

 

[motoman3b]

I'm not buying the condensation argument, as long as you keep the coals stirred up and monitor your water conditions I think a stove should last just as long as someones running 160 or 180 degree water. If this was the case you could open your wood burner in the down season and see lots of condensation right? I like getting longer burn times and cooler water isnt as hard on the water pumps as well. My hot water is hot and my house is warm why would I need to run the water hotter then it needs to be?

 

[John R]

I'm not buying the condensation argument, as long as you keep the coals stirred up and monitor your water conditions I think a stove should last just as long as someones running 160 or 180 degree water. If this was the case you could open your wood burner in the down season and see lots of condensation right? I like getting longer burn times and cooler water isnt as hard on the water pumps as well. My hot water is hot and my house is warm why would I need to run the water hotter then it needs to be?

Kind of what I was thinking.

 

[Speed]

If it was a sales pitch to make money, I would think the salesmen would be telling you to run them at 125° so they WON'T last. And I haven't made a dime off this topic, nor did I pay for the advice that I received. Heck, I dont even sell firewood. Run'em where it makes you feel warm and fuzzy. It affects me not.

 

[NSMaple1]

If this was the case you could open your wood burner in the down season and see lots of condensation right?

No, because in the down season everything is the same temp & you're not producing gases or water vapour in your firebox.

Nobody gets any creosote in their firebox?

Think I'm out of this one - everyone can believe what they want.

 

[showrguy]

i ain't arguing with you guys about this...
but i will say, my stove don't give a **** what my return temps are...
and since my return temps are so low (125-135) i should have so much condensation forming in my firebox that it'll likely put itself out ??
i'm gonna post this quick so i can run out in the woods to make sure i still have fire ...........

 

[lefturnfreek]

I heat a 1800 sqft house and a 1600 sqft shop with a locally made boiler and vary the water temp to the weather. So 130 - 175 or so and that's from 28 to -40 below. I'd be very surprised my return water temp during my burning season would even average 140, then I leave the pumps on all year to cool the house in summer.

 

[Richard@PM]

Wow I cant believe this thread, I do represent a manufacturer and I will say, do as the manufacturer asks with the water temps, if they don't tell you then by all means do as you wish but I will tell you that if you run one of my units at below 140 degrees on a regular basis then you can kiss that boiler and it's warranty good bye. todays boilers have way more built into them than the old smoke dragons of yesteryear, it may be time for some of you to wake up and realize that a lot of money / research went into these new boilers and running them at those temps is like buying a new truck and expecting it to last without changing the oil, Wake up and listen to the new generation of manufacturers

 

[blackdogon57]

Wow I cant believe this thread, I do represent a manufacturer and I will say, do as the manufacturer asks with the water temps, if they don't tell you then by all means do as you wish but I will tell you that if you run one of my units at below 140 degrees on a regular basis then you can kiss that boiler and it's warranty good bye. todays boilers have way more built into them than the old smoke dragons of yesteryear, it may be time for some of you to wake up and realize that a lot of money / research went into these new boilers and running them at those temps is like buying a new truck and expecting it to last without changing the oil, Wake up and listen to the new generation of manufacturers

If you work in the industry maybe you can explain the science behind what causes the condensation. No one else here really has.

 

[Richard@PM]

If you work in the industry maybe you can explain the science behind what causes the condensation. No one else here really has.

I don't need a lot of science, todays stoves are far more efficient with much cooler exhaust temps, my Optimizer 250 has an exhaust temp of 270 degrees running full speed with a water temp of 190 degrees, you can actually see the moisture develop in the heat exchanger tubes at below about 230 degrees with higher moisture content fuel, the old smoke dragons run an exhaust temp of over 1000 degrees. can you see the difference, you can get away with more in the old tecnology but it will cost you more in wood consumption, bottom line, the manufacturers should and in most cases do know thier units best, you would do well to take thier advice.

 

[Cbird14]

Glad I brought this up. The guy I bought mine from never said a word about keeping the return temp above 140°. And I really don't wanna send mine to a early grave!!