OWB blower fan thermostat setting

[bitzer]

Just wondering what a good setting is for when the blower kicks on to stoke the fire on an OWB. My boss has an OWB that heats his 3500sq ft house plus a 600 sq ft shop. I cut all the wood and do most of the filling of the burner. We burn a mix of hardwood, some green some dry. The temp we have the boiler set at is 180 deg. and the fan kicks on at 160 deg. Our local dealer told that if we set it any closer say like 170 deg. we will be burning more wood. My thoughts are if we keep the water temp more constant there will be less fluctuation and a more consistant burn. At the current setting when the blower kicks on the temp is continuing to drop and usually reaches about 150 deg. which causes the blower to run for an extended period before it finally shuts off near 175 or so. I think the fire is getting too cold causing extended blower durations which in turn is blowing more heat out of the chimney. Anyone have any thoughts? My local dealer is not helpful and many of the things he has told us have turned out to be untrue. Thanks again!

 

[yodayoda]

Currently i have mine set at 160, with a 5 degree differential.(off at 160, on at 155) seems to be working well, I am anticipating having to bump it up to 170, 180ish, when it gets colder.
20 degree differential sounds like alot to me, how hard is it to change the setting? If it's easy I would try experimenting with different temps and differentials, see what works best.

In my brain, it seems the lower the water temp, the less wood you will use, as long as you don't go so low it can't keep up with demand.

Last winter when it got really cold, if my water temp got below about 150, it couldnt keep up with demand.

 

[oneoldbanjo]

My Woodmaster came from the factory with the off temp set at 170 and the blower on temp at 160. The blower would come on when the temperature dropped to 160 and the fire would barely get to burning cleanly before the temperature would reach 170 again and the blower would shut off. I changed the spread to 150 and 170 and there is much less smoke as the fire has a chance to burn a little longer and burn cleanly for a while. My house is very well insulated and it doesn't take very much heat from the boiler to heat my house and I don't need to have my boiler going to 180 degrees ever.

I may try setting it back to the 10 spread again and see if the wood consumption is less - but there is much less smoke if I only put enough wood in to burn 12 hours and load morning and night (and with the 20 degree spread).

 

[Paul61]

Bit,
180 sounds high but, it's a setting you're gonna have to experiment a little with as each stove is different?
My Heatmaster was factory set to 170 but, I found 160 was better for wood usage.
Mine is extremely air tight, if I set the diff. to more than 7 degrees, the fire goes out. I set it @ 5 degs. in the cold weather, change it to 3 for the warmer stuff.
The water capacity will also effect the diff. setting, mine is 300 gals.

Paul

 

[bitzer]

Thanks for the info guys! I would say the boiler never reaches 180 even though the dial for the thermostat is set at it. It usually cuts out at about 175. We often have a problem when it gets real cold out that the blower will run for long periods (6-8 hrs) trying to get up to temp. The entire time the blower is running I think it is blowing heat out of the chimney and it is pointlessly overburning the wood while not reaching the shutoff temp. It seems that the fan setting should be closer to the shutoff and by your posts and hopefully others will confirm that. Thanks again!

 

[AIM]

Every boiler and setup is different. Mine is a set 5° differential that I run at about 140 or 150 depending on my mood. My suggestion would be to set the differential as close as possible and the water temp as low as possible and start from there. If it seems that it isn't keeping up well then just bump the temp up 10° or so. If your fire isn't burning well. widen out the differential a bit.
Like I said. Every setup is different.

 

[applefarmer]

What is the benifit to having the off/on set so close? Are you guys saving wood by doing this? I have my boiler set with a 30 degree spread. On at 140 off at 170. It takes about 15 minutes for the fan to run to reach its upper limit. My stove holds about 150 gallons of water, depending on how cold it is it usually cycles once every 3-4 hours. I guess if I changed it to a 10 degree spread it would cycle once per hour but only run for 5 minutes? Would this decrease wood consumption?

 

[traestree]

Mine is set at 135 and seems to work great in keeping up, will have to raise im sure when it starts to get cold, I think it is all about the demand and ability to keep it smoldering when not in use.

 

[mtfallsmikey]

As far as I know, my CB 5036 and all other CB models have a fixed 10 deg. differential. I've got mine at 150/160 for now, weather is still fairly mild, don't need 180 deg. water to run the HX in the house now. That's why I oversized my HX in the ductwork, to be able to heat the house at a lower temp. than 180.

 

[ghitch75]

i keep mine set at a 40 degree spread in the summer and 20 degree in the winter.....never have trouble with it goin' out.....anything closer than 20 degrees wood use goes up....off and on like a yo-yo....120 to 160 summer...160 to 180 in winter