NCB 175 settings

[92utownxh]

So, I figured I'd finally make my first post here. Been around for awhile though.

Back in October I installed a Natures Comfort NCB175 OWB to heat our 1400 sq ft house. An indoor stove wasn't an option. Its plumbed into our existing forced air furnace and duct work. The water to air heat exchanger is the biggest one I could fit in the plenum. It also heats our DHW with a sidearm. The well insulated 1" PEX is buried 3-4 feet. It works well and is good quality, but when the temp gets below the 20s I can only get about a 7-8 hour burn with seasoned oak. I go through at least 2 wheel barrow loads of wood a day.

This OWB has several different adjustments on it. I've experimented and right now the water temp is 140 on 150 off. It seems like the higher the temp it just eats more wood. The house furnace only runs about 7-8 minutes then it's off 7-8 minutes. I don't think that's too bad. I can adjust the setpoint and the temp spread for when the blower kicks on. One of the things I can't figure out is the blower has a selonoid to open and close. It also has a slide damper to control how much air goes into the firebox through the grates. It can be completely closed, completely open, or adjusted infinately in between. Right now I have it set about a quarter of the way open and the fire acts like a normally burning fire. Is it better to have a roaring fire instead and have a short recover time? What is more efficient? Any ideas on how to get a longer burn time or what adjustments to change? Thanks!

 

[motoman3b]

I'd say keep the manual damper closed that way the fire can choke out more on the off cycles... My OWB is similar to the woodmaster (built by a fabricator) and it didnt come with any damper on the blower but a manual positioned flap.... I modified the blower with a laundry vent backdraft valve so it stays shut completely when the fan is off and this really increased my burn times and I see much less creosote this year (hardly any!) The blower should be enough to get your fire roaring real quick when it needs to heat back up. You might increase your differental on the aquastat as well I'm on at 140 off at 160 and it works well

 

[92utownxh]

I see what you're saying. My blower does have a flap that completely closes during an off cycle to cut all the air to the fire. The damper I'm talking about is between the blower output and the ashpan. I can open and close that so the fire gets more or less air when the blower selonoid opens and turns on. Does that make sense? My thinking was to have a longer low burning fire so all the heat doesn't just go out the chimney. Maybe it's better to have a short, hot, roaring fire?

 

[motoman3b]

I see what your saying... My burner has a baffle along the top with waterlines running through the length of the firebox as well... hot air has to travel across this and then all the way back to the back to exit out the chimney if that makes sense so the heat and smoke take a S type route before exiting the chimney stack. I think this helps capture alot of heat that would otherwise go right out the chimney... not sure how yours is set up but I usually try to keep my coals near the back of the unit as well so the heat travels the farthest this seems to help.

I'd say run that damper wide open as a hot fire will be more efficient then a choked out one.

 

[92utownxh]

The way it's set up, the chimney is at the back of the firebox and extends down into the firebox to within 8 inches of the floor. That should keep the heat from exiting out the top.

 

[motoman3b]

I see yeah I'd keep the coals raked to the front of the wood burner damper wide open. I'd make sure your doors are sealed good and everything if everythings pretty air tight it should barely emit smoke and then be like a really faint blue smoke when its on. I know it took me 2 seasons to find out what worked best in mine. Right now I'm having no problem getting 12-15 hour burns with single digit temps using the same amount of wood I was only getting 8-10 hour burns in similar weather last year

 

[92utownxh]

Thanks for the help. The doors are sealed tight. I'll try opening up the damper and see what happens. I'll be around this weekend to watch it to see what it does.

 

[projectsho89]

I have an NCB-175 manufactured in late summer/early fall of 08 and it doesn't have the extra damper you described. It also came with a POS water heater thermostat that I replaced with a Ranco within 6 weeks.

My 175 is a wood-eating dragon. I'm heating quite a bit larger home (about 2700 sq ft) and I'm lucky if I can stuff enough wood in there to last 8 hours of 20°F weather.

I wish I could get longer burn times...

My next experiment will be to upgrade from a single-stage to a dual-stage Ranco so I can control the blower and damper separately. I'm also going to re-do the system so the pump only runs on demand from the house while the Ranco controls the boiler temp without regard to the house blower's status.

Since I'm now wired up to monitor the boiler temp and the HVAC's blower (indirectly) and to log the operation to a graph, I'll be able to see what's going on as far as HVAC blower cycle time relative to the boiler temp.

Last night, I didn't get the door closed tight, so the boiler ran hot (180-185) all night due to the extra air. The furnace blower's cycle times were much shorter overnight and I still ended up with an 8-hour burn...

The experiment continues...

 

[applefarmer]

Can you guys totaly isolate you hx's and just let the water loop for a day. This will tell you how much heat you are losing to the ground. I was ready to give up on my boiler last year until I installed the required valves to loop it. Needless to say I got the backhoe out last summer and got to buy my underground pipe twice. As much as it hurt to admit my mistake, my boiler is a totaly different animal this year. We just went through a cold spell here with highs in the low teens lows around 0. I fill the boiler with large splits and full rounds once in 20-24 hrs. My house is 2800 sq ft. plus unfinished basement. 68 when we are gone 74 when we are here plus dhw. Boiler is similar to yours in size hawkin, 150 gals of water, forced draft with damper gate to restrict air flow. I know every house and boiler is a different situation but I was experencing very similar burn times to you last year. I hope this helps.

 

[projectsho89]

Yeah, I'm probably in the same situation. I've got earthworms that don't have to hibernate....

 

[applefarmer]

Trust me that is where ALOT of your heat is going. I really think logster pipe is alot of the reason cb owners always seem satisfied with their setup. Don't get me wrong cb makes a really nice high quality boiler, but if you can keep the heat out of the ground you just gained huge!

 

[92utownxh]

I can't isolate the heat exchanger. I don't remember the brand of underground pex I used, but I know it was high dollar stuff. I don't have thermometers in the lines, but that's probably not where I have heat loss. There is one spot where the line had to go within a foot of the surface by the foundation and the snow never melts off. Last weekend it warmed up a bit and got into the 40s during the day. I could go about 24 hours then with the ground still frozen. It's just when the outside temperature gets into the 20s and below that the wood usage goes way up. Part of the problem could be I have about a foot or so of the insulated pex exposed from the ground to the back of the owb. I need to box it in with some more insulation then what the pex has. I think I just need to figure out all the different adjustments on it. It's the 2009 model and the changed and improved a few things. We'll see how it goes this weekend with it. It's going to stay cold and I'll be around to watch it.

 

[atlarge54]

I'm located in northern Indiana so we've had similar weather for comparison purposes. I'm heating about 1000sq. ft. of a 1250 sq. ft. home which was built in 1953. The attic and crawl space are pretty well insulated. The walls aren't very well insulated and the windows and doors aren't super.

My OWB is based on a scrap Global Hydronics unit. The firebox was wrapped in copper coils the original water jacket area filled with pea gravel. The OWB feeds a sidearm for DHW and floor radiant plus a water to air HX with thermostatically operated fan for the colder periods. With floor radiant low 70's is comfortable, I turn the thermostat down 2 degrees at bedtime.

I believe the Global Hydronics has an air supply similar to yours, on a call for heat a solenoid opens a port to supply air and at the same time turns on a blower. The first time I saw this unit kick on I about SH*T, talk about heat being wasted. I immediately unhooked the blower and now on a call for heat it just opens the port for combustion air.

I've been operating this unit for over five years both winter and summer. A couple days ago my neighbor asked how often I have to load the stove with the weather we've had. I told him the truth is I really don't know since I mess with it more than I need to. So I decided to find out. For the past two days my burn times have exceeded 24 hours. I was really surprised. I'm not stuffing it to the gills either. A typical load might be three 10"-12" rounds (Hard maple and mulberry) and maybe 3 or 4 pieces of 4" diameter dead elm (red?). The wood lengths are about 16" to 18", longer wood just seems too heavy for me.

I've heated with wood most of my life and the only fire I've ever seen that needed a blower was at the blacksmith shop.

 

[magnumhntr]

So how do you control the temps with no water in the water jacket? I know a guy that did the same thing but used sand instead of pea gravel. I am going to call him this weekend to see how he controlled his burns.

Chris

 

[atlarge54]

So how do you control the temps with no water in the water jacket? I know a guy that did the same thing but used sand instead of pea gravel. I am going to call him this weekend to see how he controlled his burns.

Chris

Just like if it was a boiler an aquastat controls when the fire does and doesn't get air. The aquastat monitors the water temp coming out of the boiler.

It really isn't a boiler maybe a heat exchanger would be a better term. One nice thing is it's a pressurized closed system so water and oxygen problems are greatly reduced.

 

[92utownxh]

I opened the damper on the blower so its burning really good. I checked it this morning after 10 hours and there was nothing left. It was a bit better but not much. My dealer, who has been very helpful, has no idea whats going on either. Our crawlspace and floor are not insulated, so that could affect it too. The duct work is not insulated either, but it seems to do fine. I plan to insulate the crawlspace this spring. Anymore ideas let me know. Time to go haul out a bunch of wood for next year since the ground's frozen.

 

[92utownxh]

Still no improvement

I tried turning the set point to 140 on 155 off. Seemed to use more wood. It only lasted about 8 hours today. How long does it take your owb to recover? Any other ideas on things to try?

 

[atlarge54]

I tried turning the set point to 140 on 155 off. Seemed to use more wood. It only lasted about 8 hours today. How long does it take your owb to recover? Any other ideas on things to try?

Uninsulated crawl space and duct work, ouch. When I moved into this house thats what I was facing. There was no way I was going to insulate that floor without putting in floor radiant first.
I don't know how young you are, can you spend a few days wallowing in your crawl space? The materials are actually pretty inexpensive, the labor involved is nasty. Leave your forced air in place and let the floor radiant handle the base load. I don't even have a thermostat on my floor system, running full time in the winter, optional on or off during shoulder season.

I just stuffed my boiler full today just as an experiment. I don't intend to open it for 48 hours. If I backed off the thermostat and just left the floor on a 3 day weekend away from home would be a no brainer. Current temps are 5-10 deg F night and 20's daytime.

You'll never regret having floor radiant heat. You'll find higher comfort at lower temps.

 

[atlarge54]

I tried turning the set point to 140 on 155 off. Seemed to use more wood. It only lasted about 8 hours today. How long does it take your owb to recover? Any other ideas on things to try?

Why not experiment? Disconnect your blower, it's just a couple wire nuts. If you don't like it hook em back up.

What are you burning for wood ? Just because green wood will burn doesn't mean it'll make good heat. Moisture in wood can be a absolute killer. I mean burn really dry wood not just well seasoned, I mean seasoned and kept OUT OF THE ELEMENTS. No rain snow and ice BS.

Real estate: location, location, location

Wood burning: DRY WOOD, DRY WOOD, DRY WOOD

 

[applefarmer]

How warm are you keeping your house? I have a programable thermost set during the week at 72 from 5:30am till 8:30am, 68 till 5:00 pm, 74 from 5 till 11:30pm then back to 68. During the weekend we keep it from 72-74 during the day, 68 at night. I was working near it this afternoon when it cycled on, I didn't time it but I would guess 15-20 minutes to cycle off.

Is your crawl space vented so it is the same temp as outside?

How well is your house insulated?

I don't know why you would use more wood at a lower set point?

My floors and ductwork are not insulated.

This is bothering me when you say 8 hours. You mean you filled it how full then 8 hours later nothing was left?

How big are the pieces you are putting in? My boiler will eat small splits fast!